Importance of Side wall height on traction?

GunMetalGrey · 01-21-2019, 06:06 PM

Hi, I’m wondering how much of an impact a taller side wall would have on a good cornering street tire like the Micheline PS4S when it comes to getting traction when accelerating in a straight line.

For example, changing from a 305/30/20 to a 325/30/20 or 345/30/20 (the latter tire after widening the wheel or getting a d fiiferent wider wheel of course) and assuming same/similar tire pressure

Like wise, would having a taller side wall on a track tire hurt cornering significantly on the track?
For example using a pilot Cup 2 in a 345/30/20 instead of a 305/30/20?

Does anyone have any first hand experience with this?

Rodan · 01-21-2019, 06:55 PM

It probably wouldn't make a difference in the sizes you're talking about.

In general, a softer sidewall allows the tire to flex and put down a larger contact patch longitudinally. Thus, wrinkle wall drag tires. That's a benefit you're only going to see by significantly increasing sidewall, and decreasing rigidity.

For the road course, you want the opposite... a stable sidewall to keep the contact patch on the road laterally. In general, a 30 series high performance tire is going to have a very stiff sidewall, so you shouldn't see much of a difference between 305/30 and 345/30. Mathematically, that works out to an additional 6mm of sidewall between the wheel rim and road.

GunMetalGrey · 01-22-2019, 02:08 PM

Good to know, that’s what I was wondering since drag radials and slicks have MUCH taller and flexible sidewalks and MUCH lower tire pressure.

The idea was taller side wall and lower pressure for the rear street tires, though interestingly when I was at the track recently one of the techs said one of the advantages of the Trofeo R over the Michelin PSC2 was the softer side wall, obviously that’s only relative to the that tire but interesting nonetheless, he said that was part of the reason the Trofeo R is 1 second faster on their 1 minute 25 second track. That’s not much faster in my opinion considering how much more they cost but that would add up lap after lap I guess

Rodan · 01-22-2019, 02:19 PM

"Softer sidewall" in terms of the difference between a Cup 2 and Trofeo R is going to be a very small difference, and more than likely the improvement comes from steering feel rather than outright grip. And feel is a subjective thing that may not appeal equally to different drivers.

On the other hand, 1 sec/ min of lap time is a significant delta for a single change, and on a ~ 1min lap amounts to an average of 1mph over the entire track.

01-21-2019, 06:06 PM	#1
GunMetalGrey Drives: Track prepped 2018 Camaro ZL1 (a10) Join Date: Aug 2013 Location: Victoria B.C. Canada Posts: 1,384	Importance of Side wall height on traction? Hi, I’m wondering how much of an impact a taller side wall would have on a good cornering street tire like the Micheline PS4S when it comes to getting traction when accelerating in a straight line. For example, changing from a 305/30/20 to a 325/30/20 or 345/30/20 (the latter tire after widening the wheel or getting a d fiiferent wider wheel of course) and assuming same/similar tire pressure Like wise, would having a taller side wall on a track tire hurt cornering significantly on the track? For example using a pilot Cup 2 in a 345/30/20 instead of a 305/30/20? Does anyone have any first hand experience with this? __________________ 2018 ZL1; Mag 2650 and 2 inch LT Headers , every SPL suspension upgrade, MCS 2 way coilovers, sway bars, square SC3R 325's all the way around, and multiple brake cooling upgrades

01-22-2019, 02:08 PM	#3
GunMetalGrey Drives: Track prepped 2018 Camaro ZL1 (a10) Join Date: Aug 2013 Location: Victoria B.C. Canada Posts: 1,384	Good to know, that’s what I was wondering since drag radials and slicks have MUCH taller and flexible sidewalks and MUCH lower tire pressure. The idea was taller side wall and lower pressure for the rear street tires, though interestingly when I was at the track recently one of the techs said one of the advantages of the Trofeo R over the Michelin PSC2 was the softer side wall, obviously that’s only relative to the that tire but interesting nonetheless, he said that was part of the reason the Trofeo R is 1 second faster on their 1 minute 25 second track. That’s not much faster in my opinion considering how much more they cost but that would add up lap after lap I guess __________________ 2018 ZL1; Mag 2650 and 2 inch LT Headers , every SPL suspension upgrade, MCS 2 way coilovers, sway bars, square SC3R 325's all the way around, and multiple brake cooling upgrades

01-21-2019, 06:55 PM	#2
Rodan Drives: 2018 ZL1 coupe Join Date: Nov 2018 Location: Prescott, Arizona Posts: 589	It probably wouldn't make a difference in the sizes you're talking about. In general, a softer sidewall allows the tire to flex and put down a larger contact patch longitudinally. Thus, wrinkle wall drag tires. That's a benefit you're only going to see by significantly increasing sidewall, and decreasing rigidity. For the road course, you want the opposite... a stable sidewall to keep the contact patch on the road laterally. In general, a 30 series high performance tire is going to have a very stiff sidewall, so you shouldn't see much of a difference between 305/30 and 345/30. Mathematically, that works out to an additional 6mm of sidewall between the wheel rim and road.

01-22-2019, 02:19 PM	#4
Rodan Drives: 2018 ZL1 coupe Join Date: Nov 2018 Location: Prescott, Arizona Posts: 589	"Softer sidewall" in terms of the difference between a Cup 2 and Trofeo R is going to be a very small difference, and more than likely the improvement comes from steering feel rather than outright grip. And feel is a subjective thing that may not appeal equally to different drivers. On the other hand, 1 sec/ min of lap time is a significant delta for a single change, and on a ~ 1min lap amounts to an average of 1mph over the entire track.

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