Tire pressure advice

[Hairy]

I'm an old 911 driver and recently came over to the "1". I've been to the track several times and continue to have the same problem. I'm running the toyo 888's and I build tire pressure in the left front VERY quickly. If I start out at 35 PSI cold it will go to 46 within just a couple of laps.... I have coil overs so I run about 2.6 degrees of negative camber, yet I still get pretty substantial rollover on that left front tire!

I'm thinking about kicking up my cold pressure to 40 or 41 in the hopes that it will reduce the rollover and cause less pressure build up as the tire works, but I'm concerned that it could go up from there and cause me real problems.

Do any of you have any experience in this area or have any sage advice.

Thanks

[m3bs]

What size Toyos are you running? What suspension? Spring rates, bars, etc?

The car really needs more tire up front. I think starting with a higher pressure may only aggravate the understeer problem by reducing the size of the tire contact patch.

The pressure rise you are seeing is not surprising. I typically start at 27 psi on my E36M3 track car to achieve 37-39 psi hot. When I was running R888s, I found 35-36 hot was optimum for my setup.

I'm running spring rates around 500/675 on my 135 with a H&R front bar. With the stock tires, it still plowed like a pig. When I put my 235/40-17 R888 square setup on it, the understeer was dramatically reduced, but the front tires still went away pretty quickly.

[bradford]

There was an excellent article in Roundel about tire pressures a couple months ago. Try to dig it out.

Synopsis: Use the triangles that are molded into the side of the tire. The wear should come just to the tip of the triangles and not onto them.

[Groundpilot]

Originally Posted by Hairy

I'm an old 911 driver and recently came over to the "1". I've been to the track several times and continue to have the same problem. I'm running the toyo 888's and I build tire pressure in the left front VERY quickly. If I start out at 35 PSI cold it will go to 46 within just a couple of laps.... I have coil overs so I run about 2.6 degrees of negative camber, yet I still get pretty substantial rollover on that left front tire!

I'm thinking about kicking up my cold pressure to 40 or 41 in the hopes that it will reduce the rollover and cause less pressure build up as the tire works, but I'm concerned that it could go up from there and cause me real problems.

Do any of you have any experience in this area or have any sage advice.

Thanks

I have exactly the same problem but i am running only -1 camber(strut pins removed, m3 control arms, e92 front bar) with f/245 michelin ps2 tires. I was hoping that negative 2.5 would help. I know tire pressure is very important but there must be somthing else. Maybe suspension experts can give us some info. about this issue.

[Hairy]

I go to the track on Friday. I'm going to try pushing my cold pressure up to about 40 and then check pressures and tire temps after a few laps..... I've tried most every thing else....

[Groundpilot]

Be carefull with 40 cold. It could go up to 50 or more depending on the ambient temperature.

[bradford]

Originally Posted by M3 09 AND135I 11

Be carefull with 40 cold. It could go up to 50 or more depending on the ambient temperature.

2nd.

[msos]

I had the exact same issue with R888's and would like to know how the higher front pressures worked out for you as I am heading to the track this Saturday myself? I used 37 cold at my last outing on the front and also got excessive scrubbing on the sidewalls vs. rears........I have stock M Suspension (2011 135i). Any advise would be much appreciated....

[Groundpilot]

As i said before, i am having the same problem with ps2 front left tire. I have had 2 track days so far and i decided to install KW3 Coilovers with camber plates and rear subframe bushings for my next track day on coming monday. As a matter of fact they are being installed right now by a reputable shop. They told me that negative camber -2.5 should solve this issue. We will see. I will post my impression after the track event.

[Hairy]

Spent 3 days at Putnam Park with the Porsche club. I started out cold at 41 PSI. After about six hot laps I came in and checked pressures and tire temps. The pressure had risen to 50 lbs. The temps were about 200 degrees across the tread (which is where I wanted it). Rollover was substantially reduced. The car handled much better and the tires did not get greasy.

I was still concerned about the pressure as the sidewall shows a max pressure of 51 lbs. I spoke to a Hoosier rep at the track and he said he wouldn't be worried as there is a substantial safety factor built into the max pressure. He thought I should go up a couple of more lbs. I increased the pressures and then drove very hard for the rest of the weekend. My pressures topped out at 55 lbs, and the car handled very well.

FYI, very hot humid weather really sucks the power out of the car. The only way to go fast is to carry the speed through the corners. If you drop many RPMs it's hard to get them back.

[Groundpilot]

Your car handled well with front tires 55 psi hot? Very interesting. Looks like TrackRat was right when he was talking about tire pressure. But you said you have toyo tires. What about michelin PS2? Anyone uses these as track tires?

I agree about losing power in hot humid weather. I was running at WGI two weeks ago and ambient temp. was more than 90f. Oil temp. was between 270-280 at times and i had to short shift on cool down laps. Never went into a limp mode but felt that power was reduced coming out of corners. Probably due to engine heat soak. Maybe installing aftermarket oil cooler is a good idea after all

[Sk8fe]

Now that various people in this thread has had time on the track, what is the consensus for starting cold tire pressure for R888's front and rear?

[Hairy]

Well, I don't know about consensus.... but at my next event in Sept. I'll be starting at 43 lbs cold in the front and about 36 in the rear. I'll adjust from there depending on roll over and tire temps. I will be at a different track than I was for my last event.

[msos]

I feel you may have solved my dilemma! Also have the R888's and fronts are rolling onto their sidewalls.......so much so that I am losing traction. I was starting with cold 36-38 pressures and will like you now start in the 43+ range cold. I am running stock suspension and before my next event was going to add camber plates and sway bar so I hope that I am not making too many changes at one shot.

[Sk8fe]

For R888's what hot temp range works well for our 135's then?

[Hairy]

Toyo says they should be between 160 F and 210 F when hot.

[Sk8fe]

What hot PSI range for front & rear?

[Dackelone]

Maybe for you guys that do DE (track events) you might consider using nitrogen in your tires. Less expansion psi when the tires get hot/drievn.

Over here in Germany, almost every tire shop offers it. And it is fairly cheap, like 5 euros extra per tire. I always opt for it in my summer and snow tires.

[Hairy]

I'm not the guy to answer the question of what the hot pressures should be. I truly don't know enough about suspension and tire dynamics to give any sort of knowledgeable reply. But I can tell you my thought process...

My stock car tore up the outside edge of the left front tire, so I got camber plates.

My car pushed like crazy, so I got coilovers

My car rolled over on the sidewalls of the tires and the pressures went through the roof.... so I talked to a tire guy and a suspension guy. They both told me that more cold pressure would make the tire roll over less AND would cause less flex in the tire rubber. This would cause less heat which would cause the pressure to raise less. They also told me that a reasonably high hot pressure was OK if the tire temperatures were within the manufacturers recommended ranges.

I was coming off the track with a hot pressure of around 55 lbs in the front and 45 lbs in the rear.

But, since I really don't know what I'm talking about, I will not recommend that anyone else take this approach.

I'm going to do it again.

[Sk8fe]

Thanks for your input. All experiences (and data points) are appreciated.


Like you, I don't profess to be an expert, just trying not to murder/destroy my R888's to get some "return on investment" (a.k.a. Money's worth).