Autocrossing first time in M3P

[aspec818]

Going to be autocrossing for the first time in the P3 this weekend. I’ve done a few laps with a BMW before. What’s the optimal tire pressure for wear on the stock PS4’s? I’m more concerned with preserving the tire walls rather than setting records.

I’m lowered on coilovers so I have a tiny bit of camber.

 

[superflyrolla]

There's a wide variety of advice out there, but I ran 40psi on PS4s on stock suspension.

 

[SK360]

Start at 40 and see where rollover is. Not going to be much else you can do in saving the 4S's, they're going to get beat up.

 

[aspec818]

Start at 40 and see where rollover is. Not going to be much else you can do in saving the 4S's, they're going to get beat up.

Lol yea they did. Exposed the cords on my front tire from chunking and the shoulders were all chopped up. All from 8 runs. And i was even taking it somewhat easy on the corners
Def getting dedicated track tires if I go autocrossing again. These ps4’s cannot hold up to much track use.

 

[gearchruncher]

Def getting dedicated track tires if I go autocrossing again. These ps4’s cannot hold up to much track use.

This comes from lack of camber, and it can beat up dedicated tires too.
If you're going to spend money, front camber arms may be a better initial investment. Getting 2-3 degrees fixes tearing up the 4S's and also improves handling. But it does depend what class you are trying to stay in if that matters to you.

I just ran my 4S's this weekend because it was supposed to rain. It did in the very morning, but almost all runs were in the full dry (20 runs). This would have killed the front 4S's on the stock camber, but with 2.7 degrees they hardly look driven. And I set FTD raw on them, much to the annoyance of my next closest competitor on hoosiers The G-meter was still showing 1.3-1.4G peak turning and braking forces.

 

[aspec818]

This comes from lack of camber, and it can beat up dedicated tires too.
If you're going to spend money, front camber arms may be a better initial investment. Getting 2-3 degrees fixes tearing up the 4S's and also improves handling. But it does depend what class you are trying to stay in if that matters to you.

I just ran my 4S's this weekend because it was supposed to rain. It did in the very morning, but almost all runs were in the full dry (20 runs). This would have killed the front 4S's on the stock camber, but with 2.7 degrees they hardly look driven. And I set FTD raw on them, much to the annoyance of my next closest competitor on hoosiers The G-meter was still showing 1.3-1.4G peak turning and braking forces.

So do you pull the camber back in for street use or leave as is? How’s the wear for street at -2.7?

 

[SK360]

So do you pull the camber back in for street use or leave as is? How’s the wear for street at -2.7?

I used to change mine every time and now I’m lazy and like how the car drives with all the camber. I drove my Corvette with -3.5° up front and tire wear was fine, I typically run 0 toe all around

I need spacers though for my stock wheels… lowered plus no shims up front looks silly

 

[CorneliusRox]

When you say wear was fine, how many miles were you getting before you started running out of tread?

I had an Audi S4 on coilovers and adjustable upper control arms. I had it set at ~-2deg or so, toe was at about 0.05deg per side (zero felt too darty on bad roads), and after about 20,000 miles the tires were done.
I had read threads about BMW and Corvette owners getting away with 'acceptable wear' at those specs. I'm curious if they meant 20k on tires is acceptable, or if the fact that an S4 is basically a FWD car with some RWD assist played a big role in wear. I'm guessing a Model3 would be somewhere in the middle since it can be completely RWD until power is requested.

 

[SK360]

I haven’t gotten 20k miles out of a set of tires on a performance vehicle in 15 years. So I’d put 20k at more than acceptable

 

[CorneliusRox]

I haven’t gotten 20k miles out of a set of tires on a performance vehicle in 15 years. So I’d put 20k at more than acceptable

Fair enough.

That's just not enough for me. I'm not sure what @aspec818 had in mind when he asked about wear, but I think anything past ~1.8deg neg camber is going to wear quick (<20k) even with basically no toe.

 

[gearchruncher]

I used to change mine every time and now I’m lazy and like how the car drives with all the camber. I drove my Corvette with -3.5° up front and tire wear was fine, I typically run 0 toe all around

I'm the same. Adjusting is a pain because you have to touch the toe too. I'd say it has a lot to do with how much street driving you do between events. During the pandemic, I'm almost driving more on tracks than the street. I'd probably put it back if I was going to do >1K miles between events.

That's just not enough for me. I'm not sure what @aspec818 had in mind when he asked about wear, but I think anything past ~1.8deg neg camber is going to wear quick (<20k) even with basically no toe.

I'm with @SK360 - I think my current record over the last 10 years is about 5K for a set of tires. @aspec818 just killed a set in about 5 miles due to not enough camber. So if your option is killing them every time you go to the track in 5 miles or on the street in 10K instead of 20K, that's still much better.

If you actually go to the track, then your tires will last longer overall with more camber. If you're just building a street fighter and never actually track it, then yeah, more camber is suddenly a massive tradeoff. @aspec818 is considering tracking enough that a second set of tires might be a reasonable idea, and in that case, camber is absolutely a money saver even if it wears the street tires faster. Even on the street, if you actually corner hard very often, more camber can help tire wear if you do more wear in corners than straight lines.

 

[superflyrolla]

I've been daily driving since June with between -2.0° and -2.4° camber and between zero and -0.05° toe. My non-data based observation is tire wear has improved by removing all the rear toe in (0.1° to 0.7°) from factory alignment specs.

Following what you guys are doing with great interest though. After the last autoX of this season, I may set camber more positive and re-zero toe with toe plates for the winter.

 

[SK360]

Well I think swapping shims and constantly adjusting tie rods have finally bit me. RIP to my last 2 original tires lol.

I think next season I’m just going no shims and getting it aligned to 0 toe and not touching it.

 

[RacerChris]

I’ve been driving around all summer with my car at -3.5 in the front (on the primacy tire) and they show no signs of wear. A lot of the driving is around town making turns so that probably helps (compared to if I was doing 50 miles a day on the freeway). I definitely recommend the mountain pass performance front arms- they look awesome and are easy to install / adjust.

 

[CorneliusRox]

Well I think swapping shims and constantly adjusting tie rods have finally bit me. RIP to my last 2 original tires lol.

I think next season I’m just going no shims and getting it aligned to 0 toe and not touching it.

Let us know how that holds up. IMO, this type of wear creeps up on you quick. I used to check my tires all the time and they'd be fine, then one day there would be cords.