[DesertCoupe]

I have done two track days in May and June, both times I really ruined my stock front RFT's. The temps where very high then 105+ ambient, I do believe that the premature wear of the RFT's was due to crazy tire pressures (even though I did fill my tires with Nitrogen ) it was the side walls that actually got most of the wear.

Anyway, I have a Track day coming up on the 1st of Nov , I really don't want to ruin my new PS2's on the first track day of this season ( I want them to last at least 10000 miles and about 5 track days), this is the max I expect out of these tires.

I expect the ambient temps to be 85+ and about 100+ for track (except if it is cloudy)

Any ideas on tire pressures i should use?


Sorry for the long post, and thanks in advance.

[BeAmW335i]

What psi were you running when you did the track days in May and June? I'd say start in the upper 30's (maybe 38). Keep checking the tire pressure as you get the opportunity and keep it at that level. If you increase the front psi more than the rear psi, you will increase understeer...and you probably don't want that.

[DesertCoupe]

I have the failed to check the pressures before I went out, but when I came in they where about 44 PSI, and I had a a lot of understeer

[clark192]

Im not sure about the PS2's since I have Pirelli Euporia's, but I usually run about 40 PSI in my tires, and altho I don't track the car (yet) I don't notice tooo much rise in tire temps. The Nitrogen really didn't do much either when I had it in the tires, so I just switched back to air. Best thing you can do is to run a few good laps, pit, and measure the temps. And like the last post says, keep the PSI in the upper 30s, since the air will most definately expand and increase pressure in the tires. I would try to keep it below 45 PSI or so, but see how the tires feel on the track after they are warm, so don't forget to measure the PSI before and after so find out the pressure changes.

[clark192]

BTW, is that the Bahrain International Circuit as your avatar?

[2e9x's]

Generally speaking 44 psi hot is too high. What you want to shoot for is about 38 hot. After each session, go straight in and immediately check the pressures. Lower them to 38. Just remember to check the pressures the next morning before driving. You will find the cold pressures below 30 and may trip a low tire pressure warning.

[leftcoastman]

My suggestion would be to get some track tars (cue Nascar reference).

The staggered setup of the 335i is designed to cause tons of understeer and the only way you can avoid that is trail brake, come in really slow to avoid scrubbing speed on entry and be really easy on throttle at corner exit to avoid pushing wide.

Here's a setup I've used to just about eliminate understeer:

- Non-staggered 255 tires all around (on Kosei K1)
- TcKline camber plates

Even then, I have to dial up the rebound and compression on my rear shocks to allow the car to rotate a bit more.

Some may argue otherwise, but I wouldn't mess with anti-sway bars. I paid $150 for the bars...$500 to install and after one track event, $500 to remove them. The stock bars are more than sufficient, IMO.

If you want to stick with your tires, try getting your fronts to 40 hot and your rears to 38 hot. That should help you rotate a tiny bit more.

[Bubbles]

Originally Posted by leftcoastman

My suggestion would be to get some track tars (cue Nascar reference).

The staggered setup of the 335i is designed to cause tons of understeer and the only way you can avoid that is trail brake, come in really slow to avoid scrubbing speed on entry and be really easy on throttle at corner exit to avoid pushing wide.

Here's a setup I've used to just about eliminate understeer:

- Non-staggered 255 tires all around (on Kosei K1)
- TcKline camber plates

Even then, I have to dial up the rebound and compression on my rear shocks to allow the car to rotate a bit more.

Some may argue otherwise, but I wouldn't mess with anti-sway bars. I paid $150 for the bars...$500 to install and after one track event, $500 to remove them. The stock bars are more than sufficient, IMO.

If you want to stick with your tires, try getting your fronts to 40 hot and your rears to 38 hot. That should help you rotate a tiny bit more.

LCM, you gotta take a pic of your 255s on the Koseis. I'm curious to see how they look mounted. I want to move up from 245s.

[satakal]

I know this isn't a direct answer to your question but... as you get better as a driver, your tires will last longer. Here's a few pics...





These pics are good examples of getting into a turn too hot. Doing this punishes the front outside wheel soooooo much. You see how they're rolling over on the tire onto the sidewall?

Compare that to these pics of the fast way around the course of "slow in, fast out"

[satakal]

Originally Posted by Bubbles

LCM, you gotta take a pic of your 255s on the Koseis. I'm curious to see how they look mounted. I want to move up from 245s.

I think I have the same setup except I'm on Falken rt615 255/40/17. Same Kosei K1s. Offset in the rear looks silly. But, it works well.

[leftcoastman]

My Koseis and the track tars are like mopeds. Fun to ride, but wouldn't want your friends to see you on them.

That said, it looks slightly less silly on an E92.

[DesertCoupe]

Originally Posted by clark192

BTW, is that the Bahrain International Circuit as your avatar?

No that's Losail International Circuit in Qatar, where the first motorcycle (MOTOGP) night race took place, I tracked my car there twice, and hopefully the third time will be this Saturday. But I have been to BIC for all the F1 races, and thinking for going to one of those trackdays when you rent a Caterham in December.

Leftcoastman you are 100% correct with your suggestion, and these PS2's will cost too much to change them, but I have to order the tires and rims from the US which will double their price due to shipping, and I also have to order the tires since I can't find R-compounds here. or even my stock car tire size

Satakal you have the best answer for my problem, I braked way too late and threw my car into the corners, and when i took it easy I was 3 seconds faster on worn tires. I really need to learn how to be patient.

I will try keeping my temps at 40 when hot and see how that works.

Should I set my front and rear pressures differently to reduce understeer?

A bit off topic, but anyone run a JB3 on trackdays in high temps, will it increase the chance of overheating (lowboost only)? because I already got limp mode stock twice while on the track, should i take it out or just put it in Valet mode?

[satakal]

they guys that know what they're talking about tell me to aim for 38 front, 36rear for the stock wheels. Take note of, and adjust your tirepressures first thing after you're off the track.

1- don't rush, but get to your garage/pit area as soon as possible
2- measure all 4 tire pressures. (leave the valve stem caps off for your track days)
3- adjust the pressures down to what you want them to be.
4- hours later will be your next session. You tire pressures will be way way lower than where you adjusted them. Maybe even 10 psi lower. That's fine. Just have a gentle 1 or 2 warmup laps then your pressures will be right to where you adjusted them down to.

Its an all day game of measuring and adjusting. FYI, the higher quality the tire, the bigger difference between cold and hot pressure. A rental car usually has very low performance tires and therefore will see less of a relationship between heat and pressure. The PS2s are a good tire and transfer alot of that on track heat to the air in the tires. Which means, the PS2s will have noticable pressure fluctuations.

Edit: Oh and just reading this forum, the tuned guys have no increase in overheating issues when compared to the stock guys. Your car has tons of torque. If you're taking it easy, shift at 5k rpm. If you're trying to go fast, shift at 6200. If you want heating issues, shift at redline. I suggest "slowing down to go faster." (shift before 6k)

[cobradac]

One more thought for you:

Your first experience was on RFTs which have a very stiff sidewall. You probably could have run lower pressures and still had nice firm control and turn-in on tight corners. Now you say you are on PS2s. Those sidewalls will be considerable softer unless you dropped the tire profile ratio (40 to 35 or even 30 for example). Do not expect to have the same feel with these tires that you had with the RFTs. In fact, if too low a pressure you may feel like you are rolling off the front tires in a tight turn.

Post prior to mine is excellent advice, but be prepared for a different experience on your PS2s compared to your RFTs. Do measure and RECORD your pressures before and after (cold and hot) so you can come back later and start off right the next time. Plus in so doing you can add to the body of knowledge to pass along.

[Bubbles]

Originally Posted by satakal

I think I have the same setup except I'm on Falken rt615 255/40/17. Same Kosei K1s. Offset in the rear looks silly. But, it works well.

Thanks for the pics, I had second thoughts on whether 255s could fit securely on a 8.5 rim. (I like your color vs. the silver)

Originally Posted by leftcoastman

My Koseis and the track tars are like mopeds. Fun to ride, but wouldn't want your friends to see you on them.

That said, it looks slightly less silly on an E92.

So no rubbing for you with the 255s on a coupe?

OP, I try to shoot for 38-40 psi warm.

[DesertCoupe]

Thanks guys for the help. Now i know what to do with my tire pressures.

Its the tune that is a bit scary now

[satakal]

Originally Posted by DesertCoupe

Thanks guys for the help. Now i know what to do with my tire pressures.

Its the tune that is a bit scary now

I've talked to a lot of guys with a tune that also track their 335. They have no issues. Well, no more issues than the guys that are tune-less. Nothing wrong with pulling it for the weekend and driving with 70 less touques. They say that a high torque car is a hinderance to learning the lesson of momentum.

[DesertCoupe]

Satakal thanks man for the quick reply's, you've been a great help. It looks I wont go to redline this time around and shift at 5800-6300 and use the low end torque a bit more, Ive got a step, last time it shifted mid corner and caused a high speed spin, Ill try not doing that again.
Hopefully gonna run the JB3 setting at low boost (never actually turned on the highboost)
Thanks guys

[leftcoastman]

Originally Posted by Bubbles

So no rubbing for you with the 255s on a coupe?

On the front, I will get rub when doing parking lot maneuvers - full lock.

Never any rub on track. Then again, I run negative camber up front (-3.5 or so).

Guys who have the 255s with stock suspension don't have problems, I don't think.

[Bubbles]

Originally Posted by leftcoastman

On the front, I will get rub when doing parking lot maneuvers - full lock.

Never any rub on track. Then again, I run negative camber up front (-3.5 or so).

Guys who have the 255s with stock suspension don't have problems, I don't think.

Thanks for the info.

[nicknaz]

OP, I use 32psi cold front and rear, which is ~38psi hot (for me).. same as on the street

if the car starts to understeer I use this trick called entering corner slower... and then follow up with get back on the gas sooner.. seems like it is working ok so far. As the day goes on and the tires get hotter and the ambient temp gets hotter, I have to sometimes enter slower. No point in trying to push the tires more when they are already showing signs of heat

personally, i would return the engine to stock. seems like a tune is unnecessary at this point