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Tire lateral properties
2

Tire lateral properties

Tire lateral properties

(OP)
Hello ,
is possible (helpful) to measure and compare the tire lateral stiffness in garage conditions?

Thank You for ideas and opinions

Radek

RE: Tire lateral properties

The proprietary tire modeller I use does use the radial and lateral stiffness of the tire as inputs. I suspect that this is linked to the Mz/steer angle stiffness of the tire itself, which you can imagine is directly important. I don't know any more than that, and await @cibachrome's contribution!

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Tire lateral properties

(OP)
Thank You Greg,
i await also smile

RE: Tire lateral properties

OK, I'm game. What properties would you like to know about? With the right 3M ScotchWalk 'sandpaper', (It's not actually 'sandpaper', it's a carefully controlled surface suitable for calibrating tire test machines), you can measure Scrub Torque. That's the values and rate of Mz buildup related to parking effort. But, careful there, brakes on or off makes a difference. You can measure scrub radius if you are detail oriented. Static spring rate is there. On an alignment machine you could do some Mz compliance measurements of the whole quarter.

Displacement inputs can be managed. Force measurements are the problem for you.

But, what do you need or want? I've done tire properties from the statistical treatment of a large population of tire tests But it's thin ice. Honda wrote a paper on it. Basically neural network analysis.

If you happen to have a mid '80's HP analyzer lying around [garage, estate sale, and university overflow scrap sale items, you can do normal modes analysis of the tire and obtain the Kz, Fx, Fy, Mx and Mz from the resulting modal assembly. Thats a way to match tires and get consistent sets from pit stop to pit stop. Turns out 'Build Date' is the key sort variable.

If you can get ahold of a wide table mounted belt sander for wood working, you can rig up a rotating tin on a fixed frame, run the belt and feel the lateral stiffness. Actually now that I recall, I've done that on a chassis dyno with fairly large drums. You can run a sine steer test on it at the same time. If positioned properly, you will get identical results as a road test, just without the noise and crap in the signals. check this out:

https://www.youtube.com/watch?v=S4O7b0-epBo

Plus we got the same results from the same car shipped from Opel to Detroit ! Not bad for comparing stuff, but you need to have the stuff.
What's in your wallet ?

RE: Tire lateral properties

Cool stuff. I imagine sierra4000 wants to pull sideways on the wheel with a spring balance (or push with a suitable scale) while measuring the deflection. The numbers may be useful for comparing different tyres, pressures etc. I would suggest the opposite wheel be resting on a roller skate and the force be applied at the bottom of the rim (to minimise camber change).

EDIT. It would be useful to load and unload several times to identify deflections associated with tread "squirm" and static/dynamic friction.

je suis charlie

RE: Tire lateral properties

Either air bearings or 'grease plates'. But it's not a rolling tire, so If you had rolling tire data, you might try to correlate rolling vs. stationary properties. What's the brand, size, construction no., rim width and pressure?

Why do I believe we've been here before... And what do you expect to do with the information ?

RE: Tire lateral properties

Well whad ya no... Check this out. I suppose that if you had nothing and needed something, Probability could be in your favor. This is just a slab of ~360 (only) Continentals. Shift upwards is probably due to plysteer (so our headlight aim stays useful, at night, no moon, no stars, no streetlights, and no fireflies.)

Did I really call this pic "KY Jelly" ???

RE: Tire lateral properties

(OP)
Yes, some like Gruntguru said,
my imagine was put rear wheel on plate and laterally push or rotate his contact patch

now i have simple compliance tool which shift one wheel contact patch to inward that i can see camber and toe changes and suspension parts deflections and here contact patch movement is quite significant.............but forces is not too high (around 2kN max) because grip is loosen early with only static car weight so now i try improve plate surface

RE: Tire lateral properties

If you are looking for suspension compliance, you can eliminate contact patch friction by loading the wheel perimeter directly like this.


je suis charlie

RE: Tire lateral properties

(OP)
I know this, in fact i have feel that "caster effect" can be influenced for correct toe reading
in the past i use load direct to wheel center, but toe results was inaccurate

RE: Tire lateral properties

(OP)
Of course I'm trying still to find some improvement for my racing car
some local reinforcement give nice handling gains (car is very accurate and fast in response and entries ) but still remain significant movement on tires
if different behavior with different rim or tread width can be find, it can be benefit
unfortunately i must hold same tire brand (AVON crossply)no exist alternative small diameter for final ratio

RE: Tire lateral properties

Racing slicks? Avon make some very compliant tyres for lightweight cars. Reducing lateral compliance may or may not be a benefit- there are many examples of stiffer tyres producing slower track times.

je suis charlie

RE: Tire lateral properties

Yeah but he's doing the rear of the car. Stiffer is always better there. Stiffer tires can cause slower lap times for reasons that would be pretty obvious to vehicle dynamics engineers who can analyze the whole car. It is rocket science.

There is no such thing as "Good" compliance as far as handling is concerned. If you have a ride problem or a durability problem, then you have to make a compromise.

RE: Tire lateral properties

From a steering feel perspective, camber stiffness of the wheel ( a lump of metal) is apparently detectable to those who claim to be able to feel such things. If we call that 9/10 bullshit, it still leaves drivers able to detect lozenging of the sidewalls. Plus one can actually work out the effect on linear range understeer. As a sort of estimate, the mechanical stiffness laterally of the contact patch due to the tire is about the same as the vertical stiffness, say 250 N/mm. So, with say 1200/800 kg weight distribution, the front deflects by 23 mm/g, and the rear by 16, so the understeer effect is 0.16 deg/g on a 2500mm wheelbase

That's the sort of number we do piss and moan about, when putting the budget together. It's not a program killer, but you don't want too many of those going the wrong way.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Tire lateral properties

(OP)
If really we take into account that all stiffness comes more or less together then i have simple idea

see scheme please


for clarification, i can use tire 10"/15" or 10,7/15" same diameter 21,5" but is different construction kevlar versus nylon
set 4 pieces around 1500 euro
i can put to 10"" or 11" rim both is in manufacturer range

RE: Tire lateral properties

(OP)
Or maybe only simple put two different tires for any each axle,then test front or rear change............so real understeer will tell everything about this tires??

Cibachrome, You said : "Stiffer is always better there" this rule also when car still is understeering?
is prefer rear stiffer tires and found balance n another place?
where? alignment?

again thanks for all comments

RE: Tire lateral properties

If you have both tire constructions, intermix front and rear, then reverse. Like eye doctor chart: "Better or worse?"

Understeering and rear is stiffened --> more understeer.

Rather than loosening the rear, stiffen the front: reduce Ackermann (Anti-Ackermann) to get more front grip. If power steering, increase pump flow rate/pressure. or change gear (torsion bar). Won't help at max lat but will feel more linear.
Wider front rim. Dynamic camber increase if tires have any camber grip left.

If tires are bigger than O.E.M., ADD more front bar because the high load capacity tires LIKE Fz and the pair with like the extra load transfer: Outside tire will increase more Fy and inside will give up less.

RE: Tire lateral properties

Quote (ciba)

Wider front rim.
This would be increasing the Mz/steer angle stiffness as well as lateral stiffness of the tire carcass, right?


Quote:

If tires are bigger than O.E.M., ADD more front bar because the high load capacity tires LIKE Fz and the pair with like the extra load transfer: Outside tire will increase more Fy and inside will give up less.
The main reason I've heard for increasing front bar stiffness was to limit the amount of front tire grip loss due to strut suspensions' poor camber recovery and/or soft front suspension springing.


Norm

RE: Tire lateral properties

Rim increase normally does increase tire Mz stiffness but that's all gone near max lat. Usually goes negative if the caster is not set properly to align the peak Mz with the peak Fy. This is a 'feel' ingredient. But if you can work through it (as in ignore the negative torque gradient in the steering wheel), the front bite will keep going. The wider wheel will help relaxation distance/time constant which is a perception ingredient.

The higher load sensitivity (yeah, its sounds wrong, but we're stuck with it) means that the tire is more than willing to provide more force. As opposed to a pair of 'regular' pass car tires, with 90 - 95% reserve, which give up net Fy with a bar. Corvette TLLTD management is always faced with this situation. (typically 40% tire reserve). BTW: That's the max rated load molded into the sidewall but using only 60% of it..

Nobody mentioned weight distribution to change an understeer/oversteer regimen but that's effective. As for caster induced camber, the steered wheels have to steer. If you are hanging on at 20 degrees steering wheel angle, then that might mean 1 to 1.5 degrees at the kingpins. 20 degrees static caster will look pretty funny in a parking lot and sound bad, too, as the tires chew out the wheel house liners. There are some Cup cars that do this, but usually on the (always) outside front wheel because that has the highest load but not the Mu. (Inside tire has the extra Mu. Outside 1.5, inside 2.5.

RE: Tire lateral properties

(OP)
"Rim increase normally does increase tire Mz stiffness but that's all gone near max lat."
that seems like good news for me
because just when car approach max lat. then transitioned to strong understeer ....................but ONLY when steering angles are low (vice versa in slow corners with more steering angles seems correct)

on low lat.g range and transitionals is perfect
is almost parallel steering
stiffer front bar or springs create more understeer
56% front weight
cannot get front more camber gain with McPherson
maybe again more caster will help (is 8,5 now)

RE: Tire lateral properties

Extra caster won't help much when steering angles are low. More static neg camber will probably help but at some detriment to tyre life and braking performance.

je suis charlie

RE: Tire lateral properties

Quote (sierra)

cannot get front more camber gain with McPherson

What about taller ball joints or relocated chassis-side pickup points (if class-legal)? Either way would involve a bumpsteer kit.


Norm

RE: Tire lateral properties

Even if the car rolled 10 degrees per g and you jacked the front 'bump steer' (i.e. steer by roll) up to 10%, the lateral mu-slip curve for both tires as a pair is, or should be, already flatten out. Shoving another degree of steer angle at the front end won't/can't build any more force.

A video of the INSIDE tire at max lat may show you that it's actually working against you. That's a static toe or Ackermann issue. But you'll pay for it in other ways.

Remove some heavy stuff from the chassis, motor, bumper, or driver. At max lat, the tires only listen to Fz, camber, and temperature for a fixed pressure and wheel size family. [ Bleeders allowed ??? ].

If your trick book is already used up to change the front, you'll have to loosen the rear and live with the extra pain that goes along with it. It WILL re-balance the car but introduce some other bad habits (like lessening 'social distancing' from other cars, walls, and barriers.)!

RE: Tire lateral properties

(OP)
Is done Norm,
other front camber gain is limited with RCH i think
probably i can get little more from damper inclination
so maybe more KPI can help but this works against caster
for example extra+4 Dg KPI and extra+2 Dg caster

Yes Cibachrome,
probably almost all front ideas already are exhausted,
(bumpsteer,ackerman,static toe,toe stiffness,camber stiffness)
and car always was little better
remains "tire tuning"

in the past i tried get balance with loosen rear end with rear toe tuning, but although car feeld balanced over steady state in fact car slown down due to braking instabilty and corner entrys
(car is hill climber so stability seems like priority before steady state)

RE: Tire lateral properties

Get some hydraulic rear bushings and plum them into your rear brake line. They will solidify when pressure loads them up. A little pedal hysteresis, but get used to it. In the front, use steering assist pressure (need hydraulic power steering) to do the same thing. Solid rack mounts, lower steer ratio (less compliance from lower rack tooth separation forces, better wheel bearings, less caster (lower net tierod force), if your steering wheel returnability is then poor, put a pair of coil springs on the column to force the steering wheel to zero heading. Then get used to steering wheel torque falling off. A glass of wine on the dash will help you gauge the g-level better. Only drink 1/2 of it. (Is the glass half full or half empty ?) !

RE: Tire lateral properties

(OP)
Excelent!!
you may not believe me, but I am had quite similar idea, but you gave me determination and direction in it!
I have to think how to get on semitrailing arm..........maybe extra toe link?
yes, steering rack is solid mount already, new wheel bearing units, stiff alloy knuckles (compliance improvement is significant improvement and measurable half value)
but really i love my high caster feel, although i know you reasons

if you are interest here my compliance tool in action smile
https://www.youtube.com/watch?v=3LPVXFKCMkk

" if your steering wheel returnability is then poor, put a pair of coil springs on the column to force the steering wheel to zero heading."
sorry i do not understand

RE: Tire lateral properties

(OP)
oh,i understand,selfcentering system

i think i can get some extra toe due to rear crossmember controlled bending by brake line
(1mm crossmember center deflection = cca +2mm extra total toe-in)
in fact i think this part deforms anyway when laterally loaded

RE: Tire lateral properties

What is the caster setting of the rear suspension. You might have to disconnect some parts to let toe free to steer to do this on an aligner, but changing it from negative caster to positive will add some lateral force (oversteer) to you rear axle mechanism. Better than any aligning moment compliance influence.

BTW: have you looked at shaved tires (on the front only)? That will increase your grip. Your best bet is still to get on a wheel alignment machine with a digital steer and camber readout Hunter makes one) and then apply a lateral force (in phase) couple and and aligning moment couple (anti-phase) inputs. Also you can pull the car down and read out the ride-toe (steer and camber) characteristics. Somebody around there must have a lawn mower with hydraulic taps coming out for attachment controls. Even a snow plow truck setup. Then you can use the hydraulic cylinder to active the inputs. A pressure gauge can give you a ballpark force level if you know the cylinder push and pull diameter(s). You can make use of this apparatus to tell "better" or "worse" for part changes without worrying about absolute force readings.

Necessity is the Mother of Invention !!!

RE: Tire lateral properties

I liked your video. Unfortunately everything is moving on that side of the car. Do you have a video of the other side?

Mounting those tyres to a wider rim might reduce lateral compliance. Might increase rear grip too which is a good thing but won't help your understeer problem.

I couldn't see a rear ARB in that video?

je suis charlie

RE: Tire lateral properties

Put 90 psi in the tire and repeat, but now with the camera on the control arm. You should then be able to see what the rear problem is here. Try to get a view from the front or rear.

RE: Tire lateral properties

(OP)



Cibachrome
Unfortunatelly no exist rear caster............ is semitrailing axle
traing arms with low angle axis rotation (low camber gain and toe changes,low RCH)
How way shaved tires increase grip?
With my tool i know loaded contact patch quite accurate and repetable,deflection read at rim against body movement

on Video is not my car , is BMW E30 my friend car (almost stock setup)
noticable bearing deflection, found arm and crossmember significant bending(camber loss and toe-out under loading)

Gruntguru
no exist video of the other side, for reading is body movement subtracted
on my car is fully adjustable ARB blade style...............this BMW suffers sudden oversteer

Greg
this BMW have +0,5Dg/kN camber and -0,1Dg/kN toe loss
now after arm and crossmember reinorcement +0,3 camber and -0,05 toe

my car (Ford Sierra) currently +0,2 camber and -0,015 toe

RE: Tire lateral properties

(OP)
some cars rear camber lateral stiffness
new tool = load to contact patch, old tool=load to wheelcenter

RE: Tire lateral properties

Plus and minus slip angle effect. Sorry, this calculation was a kluge/hack on my regular tire sniffer. But you can see an asymmetry. These are all tested as right front tires (rotation and dressed sidewall facing out.

RE: Tire lateral properties

I just checked. Our lateral compliance model is talking about the change of overturning moment with lateral force, and it does go negative for 4 tires that I have plots for. That is, the effective centre of vertical force at the CP can move outwards as an inward force is applied, at low vertical force loadings. At higher loads it goes the way that a simple structural model would expect, ie positive. maybe the lateral force is pushing the sidewall under the rim, so more of the vertical load is taken in the sidewall rather than pneumatically at low loads.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Tire lateral properties

Well we both learned something today. Good investigation Greg. Nice to see somebody able to check out these details. I actually never gave it a thought. Sorry I can no longer call up the F.E.M. guys and ask what the deformation pattern sequence is.!

As for the compliance, All the Porsche's I've ever seen were at the 0.12 --> 0.14 range at 1 kN. Other cars in the Honda class bucket (0.15) are Opel Zafira, Ferrari F-430, Lexus IS-350, and Suzuki Grand Vitara.

If I were you I'g go for a 911. Guys are falling all over the results from these Porsches on a few forums. They use a bunch or roll steer at each end (15% FR, 6% RR) apparently to give the cars some manners, but you know what the cars are notorious for when the tires go blind to steer: "Another Brick in the Wall". (BTW The Brit Floyd Live version is so much better than the OEM version. And NOT the REM version). If they did computer modeling, would they be the OEM FEM REM gems ?

Ya know, Claude bought a (used but cared for) BLACK 911. If you could latch on to a RED one, you'd be faster. Red cars are ALWAYS faster.

RE: Tire lateral properties

Quote (GregLocock)

I just checked. Our lateral compliance model is talking about the change of overturning moment with lateral force, and it does go negative for 4 tires that I have plots for. That is, the effective centre of vertical force at the CP can move outwards as an inward force is applied, at low vertical force loadings. . . . . maybe the lateral force is pushing the sidewall under the rim, so more of the vertical load is taken in the sidewall rather than pneumatically at low loads.
I would be interested to know if that behaviour reduces with increasing rim width.

je suis charlie

RE: Tire lateral properties

Judge for yourself. I believe its all construction based. When tires are designed or 'created', a specific rim width and pressure are the basis parameters for which tire stiffness, traction, grip, noise, rolling resistance, and noise are optimized.

Rare to find a single construction on 4 rim widths. Mz vs. Fy stiffness comparison on multiple rims is more 'analytic'.

RE: Tire lateral properties

Thanks Cibachrome. Any rim width data for your model Greg?

I recall a Holden HQ racer telling me that the spec size tyre performed better (lap times) when oversized on rim width.

je suis charlie

RE: Tire lateral properties

(OP)
from Cibachrome last post even seems that vertical stiffness is more sensitive with rim width change

how vertical stiffness affect performance?
what is benefit from vertical stiffness?

RE: Tire lateral properties

Yes which makes sense if you look at a cross section. As you bring the sidewalls vertical they'll be working in compression instead of bending. So I'd expect the radial rate to rise to a maximum as the rim width reached the nominal width of the tire (or a little less) and then fall away again if the rim is too wide.

Yes, I can have a look at the model tomorrow. Irritatingly I used to have some nice Goodyear training material that demonstrated the difference various parameters made to Flattrac results, but that seems to have been shredded, lost or stolen.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Tire lateral properties

Anonymous tire randomly disguised, it is a 195 50 . If you look in front view the overturning moment is SLR*Fy+PSR*Fz where PSR is pneumatic scrub radius, the effective offset of the vertical laod relative to the point directly beneath the wheel centre.

So I think by lateral compliance I am talking about d PSR/d Fy

here's a graph

So, it goes -ve when the vertical load is small, and the rim width is high.

Not very sure what this means in the context of the original question though!


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Tire lateral properties

(OP)
Thank you all, was useful discussion anyway
Happy Easter !

RE: Tire lateral properties

(OP)
Idea,
what pressure use? can less pressure will be shown more different deflections for better comparison?
please your comments,
Thank you


RE: Tire lateral properties

Well done sierra sounds like a useful gain for you. Thanks for the update.

It would be good to have some data that could be extended to other tyres. I wonder what is the trend for lateral stiffness as you progress from under-width rims to over-width on the same tyre.

je suis charlie

RE: Tire lateral properties

(OP)
three tests

same tire Avon crossply 10,7x21,5x15.........very low aspect ratio
recommended rim range 9,5 to 11 inch

1) 10,7 tire on 10 rim 1,5 bar average 3,08mm/kN
2) 10,7 tire on 10 rim 2 bar average 2,38mm /kN
3) 10,7 tire on 11 rim 2 bar average 2,04mm/kN

RE: Tire lateral properties

Thanks guys. Great info.

Sensitivity seems to be stronger than direct proportion. Roughly ^3 for sierra's data and ^1.6 for Greg's

je suis charlie

RE: Tire lateral properties

A cluster-fugk of ~100 tires different brands, pressures, rims, usage and markets. Mostly sizes that you are interested in.

Yes there is such a thing as Too Much Data. Sorry, it's all evaluated at 1 Fz (530 kg), that's easy to specify at some fraction of recommended load, but for your case your car weight is the only option you have.

BTW: That seems like a LOT of deflection of wheel and chassis. How is the car anchored laterally ? Not well enough I'd say. As Claude would say "That's a LOT of compliance. And no such thing as Good compliance".

RE: Tire lateral properties

(OP)
Cibachrome,
You are right of course,

But the test with all its errors was only to show how much the lateral stiffness of one particular tire on a different rim width is affected.

the results are repeatable and obtained on the same car (same vertical load and same chassis rigidity)

I think the results are interesting anyway

RE: Tire lateral properties

Quote (cibachrome)

BTW: That seems like a LOT of deflection of wheel and chassis. How is the car anchored laterally ? Not well enough I'd say. As Claude would say "That's a LOT of compliance. And no such thing as Good compliance".
The location of the dial indicator in the video suggests that only tyre deflection was measured. There may have been some movement of the contact patch relative to the plate (squirm?).

Edit. On second viewing - there is some amplification due to angle of the dial gauge and possibly the surface where the gauge contacts the rim (not visible) is angled and/or curved.

je suis charlie

RE: Tire lateral properties

(OP)
Gruntguru,
Yes,indicator is direct on loading plate, so other movements are more or less unimportant

RE: Tire lateral properties

(OP)
Good notice, indicator is better hold strictly horizontally to exclude mistake

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