×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Tire Design: Hydroplane Resistance
2

Tire Design: Hydroplane Resistance

Tire Design: Hydroplane Resistance

(OP)
Ladies and gents:

I'm considering new tires for a large FWD vehicle.  I'm currently running Michelin Pilot XGT H4 tires with good success, but with poor treadwear.  I'm looking at a few of Michelin's newer tire designs to replace my current Pilots.

Michelin has a family of tires most commonly seen as the Harmony.  You can buy the Harmony anywhere Michelin tires are sold I understand.  However, they also have some retailer-specific tread designs found under different names.  For example, the Michelin Agility is sold only at Sears.  The Michelin X Radial is sold only at Sams Club.  The Michelin Destiny is sold only at Discount Tire.  All these tires are based on the same design, with slightly different tread patterns.

My question relates to the design of the outer edges of the tire tread, and how that affects hydroplane resistance.  I just purchased Michelin Agility tires for another one of my vehicles, and they perform well.  There are no lateral grooves in the tread that "connect" the outer circumferential grooves to the "outside".  In other words, if you ran your finger down one of the outer circumferential grooves, and tried to find your way to the outside of the tire, like running a maze, you couldn't do it.  It's a "closed" design.

The Michelin Pilots that I currently have and am considering replacing have lateral grooves that connect the outer circumferential grooves to the outside of the tire.  Intuitively, I would guess those grooves would enhance hydroplaning resistance.  But as I look around at different tires, some have those lateral grooves and some do not.  If those lateral grooves appreciably affected hydroplane resistance, wouldn't all tires have them?

My question, in more particular terms, is if I purchase the Agility as a replacement for the Pilot, will there be a noticeable difference in the tire's ability to evacuate water from the contact patch?  Again, intuitively I'd say yes, but there seems to be a sufficient number of tires out there that DON'T have these lateral grooves that tells me the answer may not be that simple.

Thanks very much in advance,

Jason Adcock

RE: Tire Design: Hydroplane Resistance

Try and find some product literature from Michelin for the two tyres you are considering. Hopefully it'll have a table comparing the two, probably giving them stars for various aspects. If they have the same rating for wet weather you should be OK.

FWIW I was told by another manufacturer that the main dispersal mechanism is longitudinal, and if you are running in deepish water or at very high speed then it is better to have straight deep wide circumferential grooves. I was not particularly advised for or against lateral grooves for hydroplaning. I suspect the loss in shoulder stability would outweight the advantage in pumping ability in my application.

However, to slightly contradict the above, I have a graph here showing that narrow tires are better than wide tires for hydroplaning risk.

As with all things to do with tires - it is a black art and the compromises are unknown for the end-user.

BTW I buy Michelins as well.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

(OP)
Greg, many thanks for your reply!  The Hydroedge is rated as "10" across the board.  I don't think that's really a realistic rating, and it's just Michelin self-rating their tires for marketing.  All the Harmony family tires score between 7 and 9 on Michelin's internal scale for "wet traction".  I understand that the actual rubber compound has as much to do with wet TRACTION than does the physical tread pattern.  I was more curious about the quick overloading situations where you might suddenly hit .5" or 1" of standing water...I don't know of their "wet traction" rating really applies to that -- but it might.

Any elaborative information you might have from that tire manufacturer regarding the statement about the importance of deep/wide circumferential grooves would be most appreciated.  If that contact is lost, no worries.

Thanks again,

Jason Adcock

RE: Tire Design: Hydroplane Resistance

I am not a tyre expert, but I strongly suspect that rubber compound has a significant effect on wet adhesion before the onset of aquaplane, but once aquaplane is established the rubber is not touching the road, and therefore cannot have an influence.

Anything that helps reduce the build up of water in front of the tyre as it rolls and squeezes the water from underneath it's leading edge must help.

The greater the width of that leading edge, the greater the lift generated for the same water dissipation efficiency.

A solid shoulder tread should be more stable when cornering, and quieter when running. These aspects will be more important on a dry road, but tyres must be designed for all likely conditions.


Greg

Are tyres a black art because they are black.  

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Tire Design: Hydroplane Resistance

Intuitively, it seems that the primary water path is longitudinal.  That is working with the general direction of travel whereas in my mind, for the water to come out the sides, it would have to turn 90 degrees and it doesn't seem this would be very effective at high speeds.

RE: Tire Design: Hydroplane Resistance

(OP)
"Intuitively, it seems that the primary water path is longitudinal.  That is working with the general direction of travel whereas in my mind, for the water to come out the sides, it would have to turn 90 degrees and it doesn't seem this would be very effective at high speeds."

Blacksmith, I understand what you're saying here, but let me offer up another thought (and I may be off-base here).

The standing puddle of water on the Interstate is stationary.  The tire contact patch, when it comes into contact with the puddle of water, is also stationary.  The tire rotates forward "through" the puddle, but the actual tire footprint is stationary in relation to the puddle, correct?

I think of when you step down into a small puddle with your shoe as an approximate equal to how a tire reacts with a puddle when it rolls through it.  When you step down into a puddle, the shoe has to displace the water, and many times it "squishes" out toward the sides and water splashes to the left and to the right (as well as fore and aft).

When I think of a tire, I think that if there are no lateral grooves connecting the circumferential grooves, the avenue for the water to be "squished" out the sides of the tire is closed.  That's why I intuitively thought that lateral grooves would assist in hydroplane resistance.  But I'm certainly no tire engineer, and if it's indeed true that lateral grooves neither help nor hinder hydroplane resistance, I'll accept that and proclaim my intuition misguided.  :)

Many thanks,
Jason Adcock

RE: Tire Design: Hydroplane Resistance

I agree, lateral grooves should help. I know that on damp roads the sipes (the small diagonal cuts) are very important.

But as I said, it is a compromise, and in our case the gain in wet weather performnace from any lateral grooves was outweighed by the rapid shoulder wear in other circumstances.

I really would trust the ratings on the Michelin data, they know their stuff.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

jadcock - good point.  However, my thinking is as you said, with your foot, you at stepping down into the puddle and all escape paths (unless you have a hole in your shoe) are at right angles to the foot movement.  However as you said, the tire rolls forward through the puddle, this is where my reasoning came from.  I do agree that side sipes help, but I think they are temporary reservoirs for the water to retreat into and then the water is thrown off the back of the tire - witness the large amount of spray following a F1 car with rain tires.  In the end, I go with Greg, Michelin knows they stuff and their tires perform as advertised.

RE: Tire Design: Hydroplane Resistance

(OP)
I can see that point...that as a tire rolls through a puddle, the sipes in the tread, regardless of whether there are connecting lateral grooves or not, absorb the water and then shed it as they rotate out of the puddle and into the air.  The Agility tires are plenty siped...there are actually a lot of sipes and grooves in the tread (which is what turned me on to it).  And for all intents and purposes, the large lateral grooves ARE there.  They're just blocked off from the larger circumferential channels by a thin sliver of rubber.  I think to myself, why in the world would they have blocked those off instead of connecting them?  I guess they DO know what they're doing.

Thanks again,
Jason Adcock

RE: Tire Design: Hydroplane Resistance

The water that's under any given tread rib has to be accelerated forward by some amount as the tire rolls, since it takes a finite amount of time for it to travel laterally to get to the adjacent circumferential grooves.  Meanwhile, the tire has rolled a little.  It's either that or it would pile up under the rib (and initiate hydroplaning a bit sooner).  Supposedly the unidirectional tread patterns encourage the lateral travel of the water better than purely lateral ones, by using that forward acceleration of the water to get the lateral water movement underway more effectively.  But in water deep enough to fill the circumferential grooves to capacity, I think only the diagonal channels in the shoulder blocks can give much additional help (by venting the water laterally off the tread entirely).

Norm

RE: Tire Design: Hydroplane Resistance

I can not speak to the engineering behind this tire, but I can specifically speak to the Michelin Agility.  I have put about 80,000 on my current set.  I do not shy away from water on the interstate and am prone to pass when the out of towners are traveling through Florida on a rainy day (see also 70 - 80), mostly to get around them to an open place on the road.  This tire, for whatever reason, has never hydroplaned.  At about 80,000 thousand miles, I appear to be about 2/3 the way through the tread.  I am a LONG way from the wearout strip.  I recently brought my car in for a balance and rotate, and was informed that one of my Agilities had six nails in it.  The contruction boom, no doubt!  I had to replace that tire (replaced two to keep them even), but otherwise I'd be looking at 100000 - 120000 before it would be time to replace them.  So, engineering or not, I'll tell you that this one is a solid bet.  They aren't cheap, but giving me the ability to get around "the afraid" and dangerous on the road to a safe place is worth every penny.

RE: Tire Design: Hydroplane Resistance

(OP)
Thanks for your input JohnJacksonville.  We have about 6-7k miles on a set we just put on our Grand Caravan and they haven't even started to show any wear yet.  The Pilots were great tires for my Cadillac (the large FWD car I mentioned above), but being performance tires on a large car, I understand and accept the quick treadwear.  I've always gotten about 100x the treadwear rating, in miles.  For the Pilots, that's 40,000 miles (400 treadwear), and that's about exactly what I'll get.  The Agilitys are rated 740, so I expect to get at least 75k miles out of them.  Thanks again for the reassurance.  We love them so far on the van.

RE: Tire Design: Hydroplane Resistance

I'm not a tire expert either but I am one on roll coaters that use rollers to coat fluid onto sheets. The hydraulics are that the tire rolling into the puddle generates a hydraulic pressure that cause the fluid to flow toward lower pressure areas. These lower pressure areas are to the front, sides and rear of the tire. The fluid the flows forward simply piles up in front of the tire and has not been removed from the problem of causing hydroplaning. Some of this bow-wave will leak out to the sides, this is only an edge effect. On infinitely wide tires and at high speeds the edge effect drops to zero but on very narrow tires it can be significant. So except for side leakage which declines with speed and tire width all water displaced by the tire must flow through the longitudinal groves to the rear of the tire. That is the water velocity through the grooves relative to the ground is in the reverse direction to the car movement. When the hydraulic pressure rises to the point where it can lift the weight of the car through the small area of the contact patch then hydroplaning is the result.

RE: Tire Design: Hydroplane Resistance

Hydroplaning is one of the dirty little secrets in highway safety.  Once the depth of water exceeds the tire groove depth, the lift off point is a function of forward speed and tire pressure.  

A few years ago, I had a close call with the grim reaper  during a hydroplaning incident.  This summer I came upon two separate multi-car/truck pileups with fatalities within 5 miles of one another on a level straight stretch of I40 in East Arkansas, obviously caused by hydroplaning.  

Mech.and Civil engr.s should do the motoring public a favor by educating them on the deadly hazards of hydroplaning --how to react when one realizes one's vehicle is hydroplaning, how to defend against hydroplaning, and new driver's test and demo of this phenomenon.

RE: Tire Design: Hydroplane Resistance

The hydroplaning phenomenon isn't all that secret, unless driver education instructors and those who accompany the driver-in-training during practice driving sessions haven't been giving it much attention lately.  Or unless some of the tire advertisements have unintentionally caused a false sense of security to develop with respect to currently available products.  Forty years ago, my high school driver ed course covered this topic, at least in general terms.  Both my parents (high school diplomas only, and neither has ever been a car enthusiast) understood it as well and made sure that I did.

There are those to whom you can present this information, complete with tech and examples, until you're blue in the face - and who won't remember any of it an hour later.  Those individuals *might* benefit from time spent driving a car equipped with wide tires of zero to minimal tread groove depth on a flooded skidpad.  

Norm

RE: Tire Design: Hydroplane Resistance

I agree. 30 years ago the motoring magazines discussed it, and the tire adverts concentrated on it. I'd guess that was about the time that tread wear indicators were introduced.

So, um, once your car is aquaplaning, what's the trick?

My fastest ever aquaplane was at 150 mph. nasty.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

I guess if front and rear track are about equal, you might get some braking effect on the rears, but being able to make any significant use of that in the time available is doubtful at best.

Apart from that, you can cross your fingers or pray or whatever, and hope you ski through the puddle and regain control before a collision becomes imminent.

As kissing your butt good by would require releasing the seat belt, I would not recommend it in these circumstances.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Tire Design: Hydroplane Resistance

I copied this from the Rubber Manufacturer's Association web page on tire care:
According to RMA survey data, nearly 82 percent of Arizona drivers do not know how to properly check their tire pressure.
Other RMA survey data showed:
Only 18 percent of Arizona drivers properly check their tire inflation pressure.
27 percent of Arizona drivers wrongly believe that the best time to check their tires is when they are warm after being driven at least a few miles.
Two out of three Arizona drivers don’t know how to tell if their tires are bald.
71 percent of Arizona drivers do not check their tire pressure in their spare tire.

This is not encouraging, if one is looking for evidence that the motoring public in Arizona or the rest of the U.S. know about hydroplaning.

I see on Michelin's web site that they offer 11 models of passenger car tires.  Notice how when you click through their models that the performance indicators for mileage and wet traction go hand in hand.   My theory on this is that deeper circumferential grooves (tread depth) result in higher mileage before you hit the wear indicators, and correspondingly, the "skid pad" standing water depth can be higher before hydroplane onset.

Also one wonders how their 1-10 performance parameters are established?  Is there a guru in the back room pronouncing "wet traction" ratings, or do they have some real objective tests?  Is this an ASTM published test?

In the U.S., when Mom and Pop take the family sedan down to the dealers for their first tire replacement, the salesman will gladly put them in discount 10/32" tread depth tires with one radial ply sidewalls to keep them from running out of the store in sticker shock.  

RE: Tire Design: Hydroplane Resistance

(OP)
ccw, I don't know how Michelin rates their tires.  It's all relative to other tires in their line (and not to an industry standard unfortunately), and while I'm sure it's based on SOME objective data, I believe it's pretty loose also.  For example, their brand new tire (the Hydroedge), makes a perfect 10 all across the board, including noise and ride comfort.  It's well known that Michelin does sell tires that are quieter and softer than the relatively "hard" Hydroedge tires (like the Agility).  For that reason, I think their internal tire ratings are as much marketing as anything else.

In addition, I don't believe treadwear is directly related to tread depth anymore (if it once was in the past).  Almost all new passenger car tires that I could find have a new tread depth of 10 or 11/32".  The Michelin Pilots had this initial tread depth that are on the car now, and they have a treadwear rating of 400.  The Michelin Agility Touring tires that I plan to replace them with have the same initial tread depth, but a treadwear rating of 740.  The Pilots are performance tires, with a soft/sticky tread compound that wears out quicker.  The Agility tires are all-season tires with a different rubber compound that lasts longer than the Pilots.  I imagine that in the past when rubber compounds were more rudimentary, tire life and wet performance could be directly correlated to tread depth, but it may not be the case anymore.

RE: Tire Design: Hydroplane Resistance

Hi jadcock,

Punch in "tire hydroplane test" in google.  There are some interesting articles that come up.  Here is a quote from one:

"The faster you drive, the greater the risk of hydroplaning, since higher speeds allow less time for water to escape through the tread grooves. Shallower tread worsens that situation by allowing more water to stay beneath the tire. Our half-tread (tire milled down to half of new tread depth remaining) tires began to skim over the water's surface at as slow as 40 mph in our hydroplane test, about 3 to 4 mph slower than the full-tread tires. As the chart in All-season-tire wear shows, that represents a nearly 8 percent drop in hydroplaning resistance compared with the same model tires when new.
 
Photos from beneath a moving tire show how even new tread is likelier to hydroplane as speed increases. At 20 mph tread has full contact with the road surface. Hydroplaning begins at 40 mph and gets worse by 60 mph. Shallow tread grooves increase the risk of hydroplaning."

I perused the U.S. NHTSA FMVSS's on tire testing.  There are some mandatory tests for light vehicle radial ply tires now, but deal mainly with dry pavement performance (underinflation, overinflation, bead/rim separation, etc.). I could not find hydroplane data there, but Consumer's Union may have some.
 


RE: Tire Design: Hydroplane Resistance

Have you tried plotting tread depth vs distance?

I am told it is non linear, that is, very deep grooves are relatively unstable, and wear rapidly.

Therefore there is no particular advantage in increasing the tread depth.

Of all the tire manufacturers I have dealt with Michelin have the best handle on objective methods, and since hydroplaning is a relatively straightforward issue, I'd be surprised if they weren't on top of it.

Bear in mind when looking at the ratings that there is far more to wet weather performance than aquaplaning.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

Hi Greg,

"...plotting tread depth vs. distance?"
1. I would if I could find the @#$% data!  The big spread sheet comparisions that were on the web a few years back seem to have dried up.

Here is some PepBoy data (OK no jokes please)

Model      Warranty   TdDep  O.D.     Weight (lbs)
Futura 775 55KMi.     10/32  25.28    19.3
Fut.2000LTE 70KMi.    11/32  25.28    20.6
Fut.Plus SE 80KMi.    11/32  26.32    24.0

So, you can see (if this does not get scrambled) that
based on the first two points it plots linear st.line
Oh, about the third point, notice the increase in OD and the increase in weight, eg. more rubber, more wear.

"...no particular advantage...."?? OK, Tomorrow or today as your case may be, I will take my trusty dial calipers and visit a few tire dealers, see if I can get some more data.

RE: Tire Design: Hydroplane Resistance

Hi again Greg,
 
Breaking a rule following my own post:

All tires in the three records above were P205/70R15.

"...dealt with Michelin..."??  The last time I visited their Spartinburg SC plant, I was told that since I was a consulting engineer that I would have to be blindfolded and escorted if I wanted to make my way to their engineering offices, otherwise we would have the meeting in their visitor center outside the plant.  The only way to remove the blindfold would be to have a contract, "a need to know", and sign a non-disclosure, non-competition agreement.  Of course, I got used to being thrown out of classy joints like this.

RE: Tire Design: Hydroplane Resistance

One more time:

Breaking a rule following my own post:

The tires in the previous PepBoy data were NOT P205/70R15.
They were P205/70R14.  AND I think PepBoys have a bad entry in the third record.  After staring at copious tire data the third record looks like a 15 not a 14.

Anyway, finally found the www.tirerack.com online database that I was looking for.  Here is the Michelin data and all P205/70R15.

Model      Warr   Thddep  O.D.  Weight(lbs)  Hydro Resis.
Symmetry   65K    10/32   26.1  23           6.4
Harmony    80K    11/32   26.1  24           8.4
HydroEdge  90K    11/32   26.1  24           9.4

Again, first two records (Warrnt vs Thddep): straight line.
The HydroEdge changes compound adding silica to boost mileage and has those trick "HydroChutes" in the tread design.

RE: Tire Design: Hydroplane Resistance

Understand that the ratings posted on the various tire model pages at tirerack.com are compiled almost exclusively from customer reviews as opposed to coming out of any sort of testing program.  If you read some of the individual reviews, you'll find a number of 10.000 (perfect score) overall ratings for each of those tires (based on 55 or possibly fewer miles).  As such, those scores and all the individual category scores posted on the overview pages represent anecdotal evidence at best.  While that may be good enough to help the online tire buyer make a decision, it's nowhere near rigorous enough to serve as the basis for any further analysis.

What the footprint looks like under the influence of vehicle control inputs is also important.  Give some thought to individual tread block deformations under lateral and longitudinal loading in addition to that which happens under the vertical weight loading of the vehicle, on how tread depth and pattern might affect that, and on what the ultimate effects on wear rates might be.  Keep in mind that for most people the majority of driving is done on dry roads.

Norm

RE: Tire Design: Hydroplane Resistance

Hi NormPeterson

Tire Rack claims they have a test track.  So does CU, including a hydroplane test section and a test fleet.  Are you saying they don't, or do but do not use it?  I guess I did not read the fine print.  The only column I think could be subjective in the records would be the hydroplane resistance score.  CU says they drive the same circuit, and gradually increase the water depth in the test section until the car no longer tracks, for constant speed passes, or constant depth with multi-speed passes.

My thoughts are that since most people drive straight and level most of the time, that should be the focus, not dry or wet pavement ralley sport maneuvering.  That gets you to the high performance tires, which have no mileage guarantee that I can see.  

I want to focus on the mom & pop drivers in wet conditions, straight and level, family sedan, wet and flooded pavement conditions, maybe a few milli-g's maneuvering.  Those people under the white sheets back in Arkansas were not ralley sport drivers.

Since Michelin probably outsells other brands 2:1 if you include their cross-branding products, they are now mass marketing.  They answer to the BOD, have no altruistic notions about protecting mom and pop.  Their LTX M/S light truck/suv tires have 15/32 tread depth, so apparently there is not tread instability up to that depth?.

RE: Tire Design: Hydroplane Resistance

I'm aware that tire rack has their own facility, and that they do use it, mostly for comparative testing.  Every so often, they e-mail out a notice of such testing if you're on their list for receiving such material.

But what has to be considered the "fine print" for the typical visitor to the site is that only those reviews tagged as "expert reviews" have been performed by Tire Rack's own drivers, presumably involving their facility for at least some of the basis for the write-up.

That means that most of it is simply customer feedback, typically from those who have recently replaced something that was either worn out, damaged, or out of season, and the new tires felt so much better by comparison.  Within the various all-season tire lines, you can expect a relatively greater percentage of these reviews to have been submitted by people who don't have a lot of experience at or near the limits of what the tires can do, or have much understanding relative to describing what they do notice.  Hence the results of the sample are skewed by the relative (in)experience of those submitting the reviews, and my caution in interpreting them.

Although most "average" drivers seldom wander beyond 0.25g or so (in any direction) intentionally, they do get out of the milli-g range.  Personal observation in dry weather with a really cheapie accelerometer (anecdotal, to be sure, but bear with me) puts most drivers in that range (laterally, anyway), a few up toward 0.4-ish, and virtually nobody above 0.5g.  In more demanding circumstances, as in the Arkansas incidents, I would have to believe that at least some of those involved had attempted to undertake maneuvers (including braking) well beyond that 0.25g figure.  

Perhaps the average driver needs to shift his/her tire buying priorities a bit, away from price and advertised tread life over everything else and more toward performance, under wet road conditions at least.  An extra 50,000 miles of promised treadlife is all but worthless when what you really need RIGHT NOW is another 0.05g of performance.  Michelin, et als, will follow.[/soapbox]

BTW, most of those LTXs are 13/32" - all of the Standard Load sizes are 13/32" - and the LTXs are relatively heavy for their nominal size.  Many are XL or Load Range C, D, or E tires with extra load capacity.  I suspect that the compromises made for them that are acceptable in the LT market would be unacceptable in the car market - after all, more than a few people griped about noise with the HydroEdges.

Norm

RE: Tire Design: Hydroplane Resistance

I've got live data from around 40 real people driving cars. Longitudinally nobody uses more than 0.7g

all but 2 counts, in a million seconds of data, were less than 0.5g



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

Visited the tire stores today.

Some salient points:

11/32 tread depth is the max. for passenger car tires.

Michelin states that the center circumferential grooves in its HydroEdge are there for hydroplaning resistance.

Also says put two new tires on the back, not the front.

In deference to OZ, Goodyear describes its chevron like groove tread in its HydroEdge look-alike as "aquachutes", where the continental-like Michelin says "hydrochutes". Go figure.

Kelley Springfield and others have HydroEdge look alikes in their premium passenger tire tread patterns now as well.

RE: Tire Design: Hydroplane Resistance

Hello all,

First of all, I test tires both objectively (I do most of the objective hydroplaning stuff at our facility) and subjectively for a living and have some insight to add. Most of this is from first hand knowledge. Some is from consulting with tire building (as opposed to tire testing) engineers regarding tread design and some is from training.

On the subject of grooves or void characteristics, longitudal void ratio is a main contributor to hydroplaning resistance. Lateral void ratio is a minor contributor to hydroplaning resistance but is a major player in aiding with snow traction. I don't do longidudal hydroplaning testing per se, unless it appears during a regular wet handling test. However, I do a lot of lateral hydroplaning testing (hydroplaning in a corner at various speeds) and I can say that the tires that evacuate water effectively in the forward direction perform better. Not only do they evacuate water more effectively, the pumping action has a bigger slowing effect on the vehicle.  

Wet traction is not the same as hydroplaning resistance and is mostly a function of compound and somewhat a function of construction.

With today's building techniques and materials (like silica), tire longevity is not necessarily dependent on compound. However, I would say that cost, longevity and wet traction are interrelated.

Norm is right about people's buying habits. The marketing types at this company cultivate ulcers about how to make the buying public pay more for a given tire. It's difficult to sell something you can't immediately see and most people just see round and black. Of course, at the same time, they approve idiotic marketing campaigns that reinforce the public's perception of tires as a commodity.

This is why it's so important for tire companies to get original oem fitments. Although they might be loss leaders, the odds are that once the tires wear out, the consumer will buy the same brand. People tend to be very brand loyal when it comes to tires.

Hope this helps.

Ramon Mendoza
 

RE: Tire Design: Hydroplane Resistance

Hi Ramon,

   Thanks for the insight.  I have been thinking about a warning system for the driver/car to use to react favorably to longitudinal hydroplane onset.  Let's assume for the moment that all future passenger car rolling gear have tone rings and pickups.  Since you probably have a good seat of the pants feel now about hydroplane onset, do you have any ideas on the subject?  Also been thinking about the tread features that prevent longitudinal hydroplaning (which in my experience, by the way, may start out longitudinal but does not stay longitudinal for long).

   It seems after the Firestone/Bridgestone SUV episode a few years back that the government, tire consumers, and tire manufacturers became more sensitive to safe tire design.  We have the new federal tire rating and safety tests from USDOT/NHTSA/FMVSS as a result.  But, that result did not address hydroplaning.  

   Having lived through a near miss a few years back and seeing two fatalities this summer obviously caused by hydroplaning, this old driver is a little sensitive to the phenomenon.

    I guess the burning question is this:  Are current passenger car tire tread designs presenting the best in longitudinal hydroplane safety, marketing forces and compromises to address other hazards not withstanding?

1.  If there is a best design, why are all tread designs not the same?
2.  I say 3/8 tread depth is safer than 11/32.  Why is it not?
3.  I say the 1/16 "bald" indicator should be increased to 3/32" or 1/8".  Why is it not?

RE: Tire Design: Hydroplane Resistance

Re: #3, I think the Law of Unintended Consequences might apply here.  If the wear bars were to indicate at too great a depth people might be more apt to ignore the earliest warnings entirely.  They will still be seeing significant tread depth elsewhere - 25% to 40% of the original tread depth.  That's a lot of apparent life to be throwing away, and I can't think offhand of any other consumable product that normally gets tossed when it is only slightly more than half worn out.  

And they'll continue to disregard the warning as the tread depth drops below the current 2/32", unless there's some sort of second warning given that has greater visible urgency.  In such cases, the earlier warning serves little purpose beyond possibly (and briefly at that) suggesting that wet driving be done with greater caution.

That said, I certainly agree with the idea of replacing tires before they reach today's legal minimum tread depth if you frequently encounter moderate to heavy rainfall.  Living in places like Florida, for example, would suggest that a more conservative tread depth based tire replacement philosophy be followed than living where there's only a few inches of annual rainfall.

Norm

RE: Tire Design: Hydroplane Resistance

ccw,

Tire tread design is usually an optimization arrived at by compromising several different performance aspects of a tire. There cannot be a single best design for hydroplaning unless other factors are completely ignored. And unless it's a competition tire, this rarely happens.

In all-season tires, tread characteristics that affect things like; snow traction, wet traction, hydroplaning, noise, tire life, ride and dry traction are all compromised to some degree. Burdening the iteration process further, stylists also may have a say in what happens with a tread design. This is all true but to a much lesser extent with dedicated application tires. That is, modern snow tires are fabulous in the snow and are built to at least a minimum of dry running ability. Likewise with summer tires.

As far as a warning system is concerned, I think modern stability control devices work great in this respect. They sense very small but undesired forces/motion and apply the proper controls to counter whatever is going wrong. Usually, this means power is cut off and brakes are selectively applied. Unless you drive very fast into a very long sheet of water with at least significant yaw already imparted into these vehicles, they'll catch it, slow and correct it very well.

I don't think moving the wear indicators in or out would change people's tendency to buy tires far into the wear cycle. How about this, instead of using the indicators we have now, we could use color coded or noise indicators. Would police be more likely to issue citations for exessive wear this way?

Ramon

RE: Tire Design: Hydroplane Resistance

(OP)
Ramon, thanks for your comments.  It's interesting that you point out the importance of getting OE fitments.  I bet it's true that a lot of folks out there stick with the same tires the vehicle came with.  There's also a danger there...as many of the OE tires are completely different (at least it seems that way) than the general market tire you may replace it with.

For example, and I only use this because I know of it personally, Michelin Symmetry tires have a horrible reputation on Honda Odyssey vans.  I know that from personal experience and from reading reviews on places like Tirerack.com.  Half of the reviews of the Symmetry tire are from Honda Odyssey owners who had them as OE tires, and bought something else because of their poor performance.  Not everybody knows that if they'd purchase a set of general market Symmetry tires for their vans, they'd ride and drive COMPLETELY different than the OE formulations do.

Another example is the the Goodyear Integrity tire on Dodge Caravans (which is the vehicle on which I installed my first set of Michelin Agilitys).  The OE Goodyear Integrity tires are horrible in many folks' opinion.  They're loosy-goosy on slick roads, and are loud and rough on broken pavement.  Only after I replaced them with Agilitys did I realize that the general market replacement Integrity that you can buy at a store is VASTLY different from the cheaper OE version on the van.  Had I realized that, I may have considered new Integrity tires instead of switching brands to my admitted favorite.

It's important for manufacturers to recognize the public's misconception that an OE tire fitment represents everything the company values and stands for, which really isn't the case at all.  That was my misconception until just recently...I thought that a Goodyear Integrity was a Goodyear Integrity, whether you bought it from Dodge on your Caravan or whether you bought it from Merchants Tire.  Honda Odyssey owners think Michelin tires are junk and won't last more than 20,000 miles...but only because their OE Symmetrys gave them poor performance.  They don't realize that the very same tire (only the general market version) would probably last 3 times as long, and give better performance doing it.  It's a tough place for a tire maker to be in for sure -- provide a tire priced right for the vehicle manufacturer to use it, but still be high quality enough to retain that customer when the OE tire wears out in 20-30k miles.

Ramon, can you further elaborate on how your company walks that balancing act (of cost vs. quality) in regards to OE tires.  I think it'd be fascinating (without knowing names) how one of the tire manufacturers approaches that challenge.

Thanks again,
Jason

RE: Tire Design: Hydroplane Resistance

How odd. While I'd agree that there are differences between OE tires and aftermarket ones, at least in Australia they are made on the same production line from the same components.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

In the states, Europe, Japan and South America most OE tires are not the same as the replacement tire of the same name with the exception of GM TPC tires which are the same thing till the vehicle is out of production.

The performance spec is written by the vehicle mfg with ride, fuel economy, wet & dry traction, noise and handling evaluated by very knowledgable engineers in head to head comparisons with tires from a competitor. It can take from 3 to 12 rounds of submittals to get the combination the vehicle mfg will accept and you may not get the business if someone else has a better balance.

Yes it is the tire companies name on the tire and the replacement tire may be made in the same plant and even in the same mold but not necessarily with the same construction or compounds. Usually the replacement tire will deliver better wear at the expense of fuel economy but there may be other trade offs depending on the performance on the the original OE spec.

35 yrs Tire Eng. Designed basic rain Firestone for CART. SCCA & IMSA Pro & Am. Set lap records at 6 different road courses in '89-91.

RE: Tire Design: Hydroplane Resistance

Jason,

In this day and age, there is no cost vs. quality issues. If an OEM's specs cannot be reached on budget, the business is given up. There is too much to loose by sacrificing quality.

There is also no real danger in using the general market tires available. As tireman9 said, the major differences are in tuning for individual OEM requirements. The overall capability of an OEM vs. market tire to do the job is basically the same. What you end up with though is likely larger compromises with the market tires.

I would say that your particular experience with market vs. OEM tires is more of the exeption rather than the rule. The tires that came on your vehicle from the factory should have been very good fits when compared to the store ones. But, this does happen at times. There are instances where factory fitted tires have some sort of customer issues.

The way you came to find out about other people's problems with the same type tires is also quite interesting. It seems that lately, there are more and more vehicle issues being discussed on internet sites. These sites tend to be model/brand specific and a good place to compare notes. But, understandably, bad news travels faster than good news and they're actually looked at by OEMs and suppliers as early warning sources. I would'nt doubt that someone at Michelin knows about the accelerated wear some owners are experiencing.

Cheers.

Ramon

RE: Tire Design: Hydroplane Resistance

Ah, we seem to be slightly at cross purposes.

My comments apply when the OE tyre is the same brand and /model/ as the aftermarket tyre. As I said, in Australia, they cannot help but be practically identical, it is only testing after they are built that decides which pile they get thrown on.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Tire Design: Hydroplane Resistance

(OP)
Ramon, thanks.  Yes, I do agree that bad news always travels faster than good, and often times, folks search out Internet sites to vent their frustrations rather than spread good cheer.  I also concede that tire reviews from the general public can be dreadfully inconsistent, given no objective baseline from which to judge two different tires.  New tires always ride better than old tires, so you also have to take the comments like "new brand XX tires ride so much better than the brand YY junk tires that the vehicle came with" with a grain of salt.

I do think that the OE tires are sufficiently different from the general market tires to consider them separately, but perhaps that's more the exception than the rule as you say.  I do know that although the Michelin Symmetry tires LOOK the same between the OE and market fitments, even Michelin's specs on the website indicate there are physical differences between the OE and market tires...and one has to assume that construction and compounds are also different based on the drastically varying reviews on places like Tirerack.com.

I appreciate your responses, and everyone's responses.  The thread veered a bit from the original subject, but seeing that the original query about hydroplaning was sufficiently addressed, I've deeply enjoyed the added discussion.  I'd love to keep it up if there is more to be said on this topic.

Thanks,
Jason

RE: Tire Design: Hydroplane Resistance

Hi jadcock,

  Thanks for the article.   There is at least one glaring error in the writeup:

 "But it's important to understand that hydroplaning is caused by a combination of factors; they include vehicle speed, tread design, tread depth, tread compound, tire width, vehicle weight and water depth".  and:

"In response to this trait, tire manufacturers go to great lengths to design tread patterns and compounds that will resist hydroplaning."


I hope here we all agree that hydroplaning has LITTLE to do with TREAD COMPOUND.  When you are skiing on a water film and have no contact with the road surface, how could tire compound affect that?

The article does stress the importance of keeping the tires inflated tight and hard so the foot print pressure is high and the center section does not tend to go concave.
The author uses the word "slicing" through the water.

In another place the article states:

"In order to better resist the effects of hydroplaning, many wide performance tires (especially where Plus-Two or greater fitments are used) feature a very distinct "V" shape tread channel design intended to efficiently "pump" water out from between the tire and road."

This distinct "V" or chevron pattern is, in my opinion, a good compromise, but the optimum pattern for hydroplaning resistance and that alone are deep circumferential grooves that provide straight through pass channels for the highspeed water to move around the tread/pavement contact and out the rear (see aircraft tires).
Turning the water channel in or out from the longitudinal is a fluid flow momentum change, increasing the flow channel pressure drop, just like the elbow pressure drop in pipe flow.  Notice that Michelin boldly states that the center circumferential groove is kept to assure hydroplane resistance in their Hydroedge tread design.

So what is the chevron pattern for?   I conclude (based on totally unsound fluid flow knowledge of course), that, as explained by others in the thread, this is a compromise. The chevrons offer a cleat action to grip mud, snow, ice, shallow wet pavement, etc., but the water channel angle to longitudinal angle is kept small to minimize impedance to the highspeed longitudinal water flow.

These type of tires are directional mounts.  If I visualize correctly, once the tire is up and skiing on the water wedge in severe hydroplane action, the Michelin hydrochutes or Goodyear's aquachutes at the impending contact patch seem to be channeling the water toward the center of the tire, not away from the center, which is the wrong direction for that particular condition (see the low pressure effect discussion). Perhaps I have it wrong. Comments please.



RE: Tire Design: Hydroplane Resistance

Wet traction is very much effected by tyre compound. Full hydroplaning is not affected at all.

I guess there is a transition period with greatly reduced weight on the ground where the effect of rubber compound progressively becomes more important as it is all we have up to the point of total loss of contact. For example, if the car was travelling in deep water at a speed where 90% of the weight was being supported by the lift of the water, and 10 was supported directly by the road, I would want very very soft compound, all other factors being equal.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Tire Design: Hydroplane Resistance

Jadcock
Sorry to burst your bubble but compound has a lot to do with wet traction. We use special compounds that allow the tread to accomidate the microscopic irregularities in the road even when wet. The article is a good explanation of what is probably happening at that level.

Re the "chevron" pattern. I hold the patten on the basic design used in the Firestone CART rain tire and can assure you that I have the data to refute your belief that circumferential is best. When we add circ. grooves to the chevron the wet performance at speed is worse.

Now befor you all go complaining remember that the rain race tires do not have to worry about very many compromises and we can even design the front to have an impact on what the rear has to accomplish. So if you want to address just increasing the speed at which you loose traction you need both a good design and a good compound.

37 yrs Tire Eng. Designed basic rain Firestone for CART. SCCA & IMSA Pro & Am. Set lap records at 6 different road courses in '89-91.

RE: Tire Design: Hydroplane Resistance

(OP)
tireman9, I don't believe you were speaking to me.  I never claimed that the tire compound doesn't have to do with wet traction (because I believe it does).  I also made no references for or against the chevron patterns.

Jason

RE: Tire Design: Hydroplane Resistance

Jadcock

I am sorry.   I mistook your name in bold in the message from ccw.
All my comments were concerning the 25 Aug at 17:33 post from ccw.

37 yrs Tire Eng. Designed basic rain Firestone for CART. SCCA & IMSA Pro & Am. Set lap records at 6 different road courses in '89-91.

RE: Tire Design: Hydroplane Resistance

Sorry tireman9,

  That was my post that formed the bubble.  I agree, as patprimmer suggests, that in the TRANSITION just before complete lift off (10% of tread still in contact with the tarmac) that wet pavement traction can be affected by tire compound.  

  In my assessment of hydroplaning characteristics of tread patterns, what I am thinking of is how to delay, or avoid the onset of complete lift off.

   Here is Michelin's direct quote regarding their HydroEdge tread design.

"Other features that emphasize performance and dependability include the:
 
angled HydroChutes, grooves that channel water away from the tire's contact patch with the road surface
 
dual, continuous center grooves that evacuate water offer superior hydroplaning resistance
 
<some other features statements omitted for brevity>."

Apparently Michelin thinks, or wants us to think, that circular grooves improve hydroplaning resistance.

Tireman9, it is intriguing that you can program the front tire characteristics to help the rear tire performance.  I had a hunch that might be the case.  Patprimmer had alluded to this earlier as well, with the front tires sweeping out a path of more shallow standing water for the rear tires to address.  The front-to-rear effect is probably influenced also by which set are driving and which set are carrying the most load.  In most FWD passenger cars the front axle load is considerably higher that the rear axle load (70%-30% normally?).    

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources