Tire vertical stiffnes

[sierra4000]

Hello,
Following the previous thread,
What is tire vertical stiffness effect on handling, performance and cornering balance?
what effect on balance during lateral load transfer?
if vertical stiffness is affected with rim width,what tire load sensitivity?

Thanks,
Radek

 

[GregLocock]

As it happens vertical stiffness doesn't change as much with rim width as I'd thought it would so I didn't plot it out. That may be a problem with the model I am using rather than the truth.

Cheers

Greg Locock


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[sierra4000]

I understand and thank you Greg,
although
i am still interested reasons why some tires creates faster lap time

and also how current tires performance can be maximized

 

[GregLocock]

I doubt vertical rate of the tire directly affects lap times. For lap times the first you need is max peak grip, everything else, just about, gets sacrificed for that.

Cheers

Greg Locock


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[cibachrome]

No secret here. Higher stiffness, let's just say, from a wider wheel instead of thicker wire in the bead package (see attached) does get you some high cornering power but comes with a dark side: Tires are fundamentally damping elements. They respond to velocity states. (Try turning into your driveway without moving some time i.e SET SPEED= 0. ) As tire stiffness goes up, the need to maintain velocity control becomes more difficult, just to maintain the same level of damping (ground contact). This means tighter dampers and more friction and higher chassis loads and more discomfort. The goal is to get the best (optimal ?) lap friction contact versus the highest possible ground speed. The two curves cross over as they decline. Then its just traffic and line management. Ever heard the phrase "The slowest looking car is often the fastest." ? That one goes along with "Smooth is Fast". Same concept. Keep tire slip velocities low. vertically and laterally.

 

[GregLocock]

So I'd guess that vertical stiffness is a proxy for the carcase and balloon stiffness of the tire, not the contact patch. in other words you are steering, hence twisting , the tire structure less to get a given slip angle at the contact patch.

Or is that too simplistic? Does the bit of rubber at the road really see much difference?

Cheers

Greg Locock


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[NormPeterson]

Lateral load transfer combined with tire vertical stiffnesses sounds like roll of the car and its suspension as a single rigid body, a little camber change relative to the road, and a slight shift in TLLTD relative to not considering it. Could amount to half a degree per lateral g (or more) in a road car, which may or may not be significant.

There's probably some correlation with mechanical grip.


Norm

 

[sierra4000]

ok,
thanks
in real world, when different tires (or rims) is mounted on front axle and car become less understeer, then we can say for sure :
BETTER tire/rim combination was found?
So when will set all these on car, will be ALWAYS faster with original balance?

 

[sierra4000]

And how does the tire pressure fit into this whole?
less pressure decrease vertical and lateral stiffness?
but increase grip due to contactpatch area?

 

[NormPeterson]

Structurally, tire vertical stiffness is a spring in series with the suspension (taken as a spring/collection of springs).

Mechanical grip as a function of inflation pressure is a separate matter.


Norm

 

[GregLocock]

"BETTER tire/rim combination was found?
So when will set all these on car, will be ALWAYS faster with original balance?"

No. The race engineers job is a compromise between maximum grip and handling, biased towards the first. Whereas for road cars handling and steering are far more important than ultimate grip, except for journalists.

Cheers

Greg Locock


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[sierra4000]

Is same tires ,
rim used 10 inch width,
recommended range is 9 to 11 inch