I have staggered M contours on my 5sp 328is. 225 40 17 front and 245 35 17 rear with Michelin Pilot Sports on. What PSI would you recommend them to be at (hot or cold?).

Any other things I should keep in mind for this autoX, it is a high speed course like 90 mph on the straight :eyecrazy

Thanks for any tips or info!
-Chris :alright

I have staggered M contours on my 5sp 328is. 225 40 17 front and 245 35 17 rear with Michelin Pilot Sports on. What PSI would you recommend them to be at (hot or cold?).

Any other things I should keep in mind for this autoX, it is a high speed course like 90 mph on the straight :eyecrazy

Thanks for any tips or info!
-Chris :alright

i have no idea what other people run, but i use 36 front, 38 rear and im pretty happy with it.

Are you taking that reading with the tires hot or cold?

Generally, with street tires, you'll find that more pressure will actually result in more grip (up to a point where you have way too much air). Given that, I would go with more air in the front tires to balance out the understeer a bit. With street tires, I'd recommend something around 40 for the front and 36 for the rear.

Like Brian said, higher pressures (to a point) usually improves grip with street tires. Here is my suggestion:

My specs:
M3/4
Stock M3 shocks in front and Bilstein Sports in the Rear
Stock Springs and swaybars
225/45/17 S03s up front and 245/40/17 Pilot Sports in the rear

I found 42F/40R (cold) to work really well.

I personally prefer corner-entry oversteer, and I feel that this setup worked particularly well with my car's setup and my driving style. Granted my car's current setup is a mix-and-match of parts (tires and shocks), but there was a reasonable balance in the car.

My suggestion is to just experiment. Add and subtract pressues from the front and rear and play with the balance of the car. I tried doing this every autocross and I've learn a lot.

Also, I highly recommend keeping the spare inside the car. What little you will lose in acceleration, you will gain massive amounts in the corners. With my setup, taking out the spare meant throttle oversteer on the exit of any corner, and as much fun as it was power sliding out of all the corners, it was also very slow. I gained almost .5-1 sec per run after leaving the spare inside the car was that much more stable.

Drive Safely,
Raza

So i've been running my tyres pretty damn low on 30 then eh? Thats everyday driving....

Shall i give em a try with 35 then? Like what the 'max pressure' till you overinflate? 225's and 245 17's here..

Like what the 'max pressure' till you overinflate?

Most higher performance street tires are good to about 50psi, but check your sidewalls for proper information.

The problem with the low of pressures is sidewall roll over- you are not maximizing the contact patch and you are literally driving on your sidewall. Only with a true racing tire, with rock hard sidewalls, can deal with pressure that low.

Drive Safely,
Raza

So that woulda been why my tyres were squealing like a mother on track day?

oooo I am so gonna see if theyre better with more pressure..before work. Bet ill be the only guy inflating his tyres at 6.30am on a sunday morning.. haha

I don't have the greatest amount of experience, so take my input with a bit of a grain of salt, but in my experience 40 in front 36 in the rear has been a nice feel.

So that woulda been why my tyres were squealing like a mother on track day?

30 would be WAY too low on the track. I ran 35 on the street back when I had my M3.

I use 2,05bar front (29,75psi), 2,25bar rear (32,625psi), with 205/60 15' tires. Yours should be more tho, as the pressures on my car's manual states higher values for smaller profile (sidewall) tires.

Despite what's been said, I find my tires to slide more with higher pressures. Doesn't know if it has to do with the roads around here in Portugal. I tried a few pressures before reaching the optimal balance between handling, mileage and treadwear.

The stock pressures for my car ate 1,8bar front, 2,0bar rear.

edit: front tires up to 35psi, much much grippier.

I use 2,05bar front (29,75psi), 2,25bar rear (32,625psi), with 205/60 15' tires. Yours should be more tho, as the pressures on my car's manual states higher values for smaller profile (sidewall) tires.

Despite what's been said, I find my tires to slide more with higher pressures. Doesn't know if it has to do with the roads around here in Portugal. I tried a few pressures before reaching the optimal balance between handling, mileage and treadwear.

The stock pressures for my car ate 1,8bar front, 2,0bar rear.

I have found that my tires slide too, but that is if I up the pressure into the stupidly high range. Anything above 40 PSI seems to excacerbate it on my car.

Anything above 40 PSI seems to excacerbate it on my car.

I havent tried it that high. When I said "slide", I mean larger trajectory lines, more than "skids" or drifts. But I can feel small pressure adjustments in understeer/oversteer balance (when I drive faster).

Of course, when driving slower, I all resumes to more pressure (within the normal range) equals more responsive steering.

I have staggered M contours on my 5sp 328is. 225 40 17 front and 245 35 17 rear with Michelin Pilot Sports on. What PSI would you recommend them to be at (hot or cold?).

Any other things I should keep in mind for this autoX, it is a high speed course like 90 mph on the straight :eyecrazy

Thanks for any tips or info!
-Chris :alright

What's up with the slightly odd tire sizing you're running??? 225/40/17 front? and 245/35/17 rear? I run the same tires w/stag. set-up on my 328i although. the traditional M3 sizing. 45/40 series fr/rear. Cold pressures for auto-x have been 38f/35r. And I find I still experiment. I generally use those pressures as a starting point. Due to the wider rears, I try to dial out as much understeer as possible.

I run 40/f and 37-40/r on my non-staggered 16" setup on a 318i. The balance is good and I adjust between runs.

From my xp, the mich PS are fairly soft, so high pressures are probably in order. Don't be afraid of 50 psi cold if that's where it needs to be.

Don't be afraid of 50 psi cold if that's where it needs to be.

50psi are normally the max safe pressure for tires. 50 psi cold = more than 50 psi hot. I would not do that...

I'm running Kumho MX tires on a '99 M3 convertible. At the autox, I run 42 f, 38 r mainly because that's what others running the MX suggested when I asked about it here.

Recently, I've started to experiment with pressures, here is what I'm learning:

Anything over 40 in the rear, and the back end starts to lose grip, especially at the end of a run. This past weekend, I started to experiment with lowering the rear pressure to see I could find more grip, but I was rolling the sidewall over too much at 36 psi. (So I don't have much of a window to work with.)

I've been measuring my pressures at the start of a run, not the end of a run. I don't know if that is the recommended way to do it, that is just the habit I got into. I continue to measure that way so I can compare my pressures to previous experiences. I've only been doing this for a year and a half, so I am by no means an expert. YMMV, TTATE, 3KDAS

Scott

50psi are normally the max safe pressure for tires. 50 psi cold = more than 50 psi hot. I would not do that...

In most cases, it'll be just fine. Those numbers are on the tire to give a guide to street cars. A tire will hold a lot more than 50 psi without blowing.

In most cases, it'll be just fine. Those numbers are on the tire to give a guide to street cars. A tire will hold a lot more than 50 psi without blowing.

Ok then. But wouldn't it become too slippery?

Ok then. But wouldn't it become too slippery?

Depends on 100's of things...tires, conditions, alignment, spring rates, etc, etc, etc...

I hear rumors that some of the top auto-xers are running Hoosiers at over 50 psi in some classes.

My Hankooks feel best at about 50/48 psi hot. (auto-x)

50psi are normally the max safe pressure for tires. 50 psi cold = more than 50 psi hot. I would not do that...

I know plenty of national level competitors running 50+, at least for testing purposes. too many variables to generalize.

i wouldn't drive around town with 55 psi, but for a/x runs i don't think it's a big deal.

Though, i haven't competitively a/x'd in a year or so.