Tyre sidewall stiffness. Do you notice/care about it?
Discussion
Seems to be a point of contention in people this one. Some are adamant that they must have a stiff side wall on their tyre, and a soft one ruins the handling. Others say nonsense, it doesn't make a difference, anyone claiming they can feel a difference on the road is talking rubbish.
My personal experience is this: For the last 12 months my MX5 has run on Uniroyal RainExpert tyres. They are/were superb in everything but wear, it seems that they had an incredibly soft sidewall and it collapsed under hard cornering meaning the outer shoulders got annihilated. I am not exaggerating either, they were gone in about 12 minutes from new (12 runs at an autotest).
I've just replaced two of them with Vredstein Sportracs, and these have a much stiffer wall. Where the uniroyal could be collapsed between thumb and forefinger, the Vred's barely deform with a full hand grip. The Vreds went on the front.
My initial reaction was as I expected, they rode a bit harder and the car turned in much faster, with less steering lock required for any given turn. It's become apparent though that by keeping the URs on the back, I have screwed up the handling somewhat. It becomes apparent over about 40-50mph on a straight road, the back end just feels wandery, like it's going to oversteer constantly. It never does though, when turning an actual corner the back end feels like it's stepping out before snapping into line and gripping. To me this feels like there's a massive delay between the front a rear slip angles generating, that wasn't there when the front sidewalls were also soft.
I had this once before on my Civic, I swapped the tyres front to back and problem instantly went away. I think that sidewall stiffness is a very real concern, however only if you mismatch on the axles.
Anyone else notice the sidewall stiffness at all?
My personal experience is this: For the last 12 months my MX5 has run on Uniroyal RainExpert tyres. They are/were superb in everything but wear, it seems that they had an incredibly soft sidewall and it collapsed under hard cornering meaning the outer shoulders got annihilated. I am not exaggerating either, they were gone in about 12 minutes from new (12 runs at an autotest).
I've just replaced two of them with Vredstein Sportracs, and these have a much stiffer wall. Where the uniroyal could be collapsed between thumb and forefinger, the Vred's barely deform with a full hand grip. The Vreds went on the front.
My initial reaction was as I expected, they rode a bit harder and the car turned in much faster, with less steering lock required for any given turn. It's become apparent though that by keeping the URs on the back, I have screwed up the handling somewhat. It becomes apparent over about 40-50mph on a straight road, the back end just feels wandery, like it's going to oversteer constantly. It never does though, when turning an actual corner the back end feels like it's stepping out before snapping into line and gripping. To me this feels like there's a massive delay between the front a rear slip angles generating, that wasn't there when the front sidewalls were also soft.
I had this once before on my Civic, I swapped the tyres front to back and problem instantly went away. I think that sidewall stiffness is a very real concern, however only if you mismatch on the axles.
Anyone else notice the sidewall stiffness at all?
jon- said:
I noticed it so much I started www.tyrereviews.co.uk
There's more going on than just sidewall stiffness to give you the feel you talk about, but I agree it's a huge deal for me.
I actually prefer the Bridgestone S001s on my M3 to the Michelin Pilot Super Sport due to the feel, even though the raw grip is lower.
ETA: I've been trying to think of a good way of measuring sidewall stiffness and charting it for the public, I can't think of a good way of measuring it accurately though.
Fantastic website that is, bravo!There's more going on than just sidewall stiffness to give you the feel you talk about, but I agree it's a huge deal for me.
I actually prefer the Bridgestone S001s on my M3 to the Michelin Pilot Super Sport due to the feel, even though the raw grip is lower.
ETA: I've been trying to think of a good way of measuring sidewall stiffness and charting it for the public, I can't think of a good way of measuring it accurately though.
A sidewall stiffness rating would be fantastic. Can you not just measure the average spring rate with the tyre off the rim? Maybe an average rate and also a range?
iloveboost said:
Quote:
Where the uniroyal could be collapsed between thumb and forefinger, the Vred's barely deform with a full hand grip.
EH?! What the heck are you talking about?!
It's not hard. Take a tyre with no wheel rim.Where the uniroyal could be collapsed between thumb and forefinger, the Vred's barely deform with a full hand grip.
EH?! What the heck are you talking about?!
Pinch the sidewall between thumb and forefinger. You could collapse/compress the sidewall like this.
On the Vreds, you had to use all four fingers in a proper grip to get it to compress.
I've seen photos before of someone standing on an upright tyre and it not collapsing. I assume it must have been a run flat?
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