Sidewalls rubbing during track day—stock wheels and tire size

[thefleshrocket]

I took my ‘11 S4 Prestige to its first track day at Gateway (aka Worldwide Technology Raceway) on Tuesday. I discovered that the sidewalls of the front and rear tires are rubbing.. either on the fender liners or the insides of the fenders. I’m running non-replica Rotors with Pirelli P Zero summer tires in 255/35R19 (which stuck impressively well at the track). The car is at stock ride height with newish 034 / Meyle HD control arms. I’m pretty sure the springs and sway bars are stock. The shocks and struts are not factory, because VCDS says it can’t communicate with the suspension damping controller, but they are both comfortable (during street driving) and well-damped (good control during track driving).

If I was running different sized wheels or tires, I’d assume that I just needed to roll the fenders to make more clearance. Does the car just have too much body roll? Like, is it by design that the tires are rubbing if the car rolls too much?

And more importantly, how do I fix it? Do the factory dampers firm up as the car leans to prevent rubbing, so I need to go back to stock dampers? Or should I install stiffer sway bars? Or something else?

[ak-s4]

I'm suspicious, are you sure the tires are rubbing or is that due to the hard cornering? Might need to increase the tire pressure?

[poloshirt]

You aren't rubbing. The patterning you see on your sidewalls is caused by the sidewall flexing during hard cornering and picking up dirt. I see the same thing after autocross and I don't rub in the front with a far more aggressive suspension setup.

[SwankPeRFection]

Am I seeing things or do those fenders look rolled? Whomever had it before you probably lowered it a lot and rolled the fenders and then put it back to stock height with non-original shocks/springs, especially since the car apparently had adaptive dampening and that’s not happening anymore on whatever shocks are on there now.

[dbtong]

Did you actually hear it rub?
Are there any visible marks on the fender liner?
I'm more inclined to think that you're rolling your sidewalls as mentioned in an earlier reply.

[thefleshrocket]

I'm suspicious, are you sure the tires are rubbing or is that due to the hard cornering? Might need to increase the tire pressure?

I was running 35 PSI cold. That was 40 PSI after one session, and 42 PSI after the second. Surely that's enough pressure to keep the tires from rolling over onto the sidewalls?

Am I seeing things or do those fenders look rolled? Whomever had it before you probably lowered it a lot and rolled the fenders and then put it back to stock height with non-original shocks/springs, especially since the car apparently had adaptive dampening and that’s not happening anymore on whatever shocks are on there now.

I'm not sure if the fenders are already rolled. I'll take a look at the fenders on my GF's A4, which I know have never been rolled, and see how they look compared to the ones on my S4.

Did you actually hear it rub?
Are there any visible marks on the fender liner?

I think I did hear it rub at multiple points in the track, but not positive. Kind of a brief, high-pitched squeak? I need to pull a wheel and stick my head in the wheel well and see if I can see if there is any evidence of rubbing. I suspect it's rubbing the fender liner, not the fender itself.

[Mfryman1]

Just curious have you looked at the recommended pressure on your door sticker? Mine says 41 PSI cold. Underinflated tire will roll on the sidewall. I have noticed that when I lower the pressure on mine it introduces body roll which is flexing in the sidewall of the tires during cornering. I may drive them at 36 PSI cold for cruising highway but if I am going to be on a country road I pressure them up. Makes for a harsher ride but more responsive cornering with less body roll.

[bgoetz]

At least one of those pics are 100% rubbing on something, you can see the cut in the tire. My guess is a clip or screw from the fender liner or perhaps as someone else suggested a poor job rolling the fenders. In general the wear on the tires do suggest poor tire pressure and/or camber or you are trying to force the car to turn when it simply can’t, my guess is a combo of all 3.

[ak-s4]

I looked very closely again at the photos and do not see any cuts. There is a groove that is normally supposed to be there, but on the fronts it has been worn away due the sidewall making contact with the pavement.

Since you said 35PSI cold, that really solidifies in my mind that the low pressure is the issue. My door sticker says 41PSI as well, and that is the pressure I run for street use.

You could swap the tires F/R, then go with the factory pressure and report back after your next track day?

[thefleshrocket]

I have a hard time wrapping my head around 35 PSI being too low and the tire rolling over onto the sidewall--I thought most track day people ran between 30-35 PSI. I guess what I need to do is suction-cup a GoPro to the fender and take a couple of on-ramps under high-G and see what I see.

[svt]

I have a hard time wrapping my head around 35 PSI being too low and the tire rolling over onto the sidewall--I thought most track day people ran between 30-35 PSI. I guess what I need to do is suction-cup a GoPro to the fender and take a couple of on-ramps under high-G and see what I see.

Even on my '12 A4, the pressures were 38 and 42 cold, for the front and rear, respectfully. My '16 S4 says 41 cold all around. And both the wheel and tires sizes were the same on the cars, so Audi must presume folks with an S4 drive more aggressively hence the higher pressure.

[ak-s4]

Here is a nice tire POV of this happening: https://www.youtube.com/watch?v=m75xWB3Rnho&t=370s

[Slvrbul8]

I have a hard time wrapping my head around 35 PSI being too low and the tire rolling over onto the sidewall--I thought most track day people ran between 30-35 PSI. I guess what I need to do is suction-cup a GoPro to the fender and take a couple of on-ramps under high-G and see what I see.

I think this is accurate, but the S4 is no track car. It's simply too heavy, and a lot of that weight is over the front axle. The first time I pushed my S4 on some tight TN backroads I can remember the front tires screaming around every corner.

[SSMOKE-U]

I am clearly seeing rollover on sidewall. I mean it's clear as day... Even on the street with my tires at the recommended 41 PSI, I still see evidence of rollover when aggressively cornering. You can even see the road wear on the top of the sidewall in a couple photos. You are most likely not touching your fenders. If you heard squealing in hard corners it's likely the P Zeros screaming. They have a tendency to be noisy at the limit.

[thefleshrocket]

I got under my S4 this weekend. Sure enough, I can't find any signs of rubbing on the fender liner or the fender. Additionally, the inside edges of the front tires are also worn similarly, though not quite as far over. All of which seems to point to this indeed being the tires rolling over.

When I ran my '02 911 at the same track, I used 35PSI and had no roll-over issues. When I noticed the Pilot Sport 4S tires getting a little greasy at during the second or third session, I dropped the pressure. I think I was at around 29 PSI. After that session, when I inspected my tires, the outer edge of the passenger side rear tire had rolled over and chunked the sidewall. I called it quits for the day at that point, obviously. Point being, I didn't have any issues at 35 PSI and it wasn't until I got around 30 PSI that tire roll-over struck. The Pirellis must have softer sidewalls than the Pilots, resulting in the roll-over despite higher pressure.

Thanks for the input, everyone. Next time out, I'll start at 42 PSI cold, and put some shoe polish on the sidewalls to see how much roll-over there is. I tried finding a recommended pressure but most were either "35 PSI hot", or "whatever is on the sticker in your door jamb".

[SwankPeRFection]

Run whatever tire pressure is needed to do what you need it to do. What works for one person’s driving doesn’t work for everyone. Also, if it’s an older car, make sure your suspension bushings aren’t shot. One thing to go quick and it’s hard to tell are the swaybar ones and they’re generally overlooked. For those I wouldn’t even put back OEM rubber ones. Go poly if you’re not already going aftermarket sways that come with poly. It will help with compliance as you turn.

[thefleshrocket]

Run whatever tire pressure is needed to do what you need it to do. What works for one person’s driving doesn’t work for everyone. Also, if it’s an older car, make sure your suspension bushings aren’t shot. One thing to go quick and it’s hard to tell are the swaybar ones and they’re generally overlooked. For those I wouldn’t even put back OEM rubber ones. Go poly if you’re not already going aftermarket sways that come with poly. It will help with compliance as you turn.

The car has 034 control arms up front from the previous owner, they all seem to be in good shape with a visual inspection and "feel for play" test. I haven't checked the sway bar bushings, but body roll doesn't seem to be excessive. I'll have a look next time I'm under the car.

I am hesitant to install aftermarket sway bars because of the experience I had with my '15 S4--I think it had ECS swaybars from a PO, and it had a disconcerting way of pushing when I'd let out of the throttle. Like, if I backed off the throttle a little bit mid-corner because I was a bit too hot, instead of it tucking the nose and tightening its line, it would actually drift even wider.

[SwankPeRFection]

The car has 034 control arms up front from the previous owner, they all seem to be in good shape with a visual inspection and "feel for play" test. I haven't checked the sway bar bushings, but body roll doesn't seem to be excessive. I'll have a look next time I'm under the car.

I am hesitant to install aftermarket sway bars because of the experience I had with my '15 S4--I think it had ECS swaybars from a PO, and it had a disconcerting way of pushing when I'd let out of the throttle. Like, if I backed off the throttle a little bit mid-corner because I was a bit too hot, instead of it tucking the nose and tightening its line, it would actually drift even wider.

If you like how the stock bars feel and the car is on original 2011 bushings, grab yourself a set of front and rear bushings from Powerflex and install them. The stock rubber ones suck compared to these. They can be installed with the car still on the ground (ALL 4 WHEELS) without issue, you just undo the 4 bushing bracket retaining bolts and replace the bushings and put the bracket/bolts back on. Super easy and no fuss.