Non standard tire sizes and MDM/DSC.

[1MORELAP]

OK, I will start with a recent experience on my Cayman. I lowered it, and installed new 10mm wider tires in the rear - 275 versus stock 265. I also bought, but did not yet install 245s for the front (again 10mm wider than stock 235.)

At the track I drive - Pacific Raceways in Auburn, WA, turn 1 is taken ON throttle at anywhere between 120 and 170 MPH (mostly dependent on size of your balls, and power of the car.) I take it anywhere from 120 to 130. Mor or less at the apex, there is a little bump, and you DEFINITELY want to have the car planted with throttle - no lifting or braking - or you are F...ed, someone else can find that You Tube video.

With the above described tire setup my traction control kicks in at the bump and cuts throttle, possibly brakes the car. In other words my car is truly trying to kill me. I have ONLY experienced that with the current tire setup. Of course, I turn stability off as I like to keep the shiny side shiny.

But that begs a M3 related question. Seems that everyone here drastically changes the wheels size ratios when they track their M3. Square setup is WAY off from stock and traction control computers must be going CRAZY. Do people with square setups just automatically disable traction / stability control? Or, not so on the M3?

[Gearhead999s]

Why do you run on the track with the traction control on?I have tried it with the MDM on track and it is way too intrusive even in the 100mph + corners.

[1MORELAP]

Ohh, I am getting ZCP, which claims to have stability tuned for track / aggressive use.

[elh0102]

If I decide to do any regular track stuff with this car, I'll probably use either 265 or 275 tires all around, using a set of appropriate wheels. I know this is a common practice so just a couple of questions:

If I do not use pressure monitors, will any warnings other than the small red icon appear? I just don't want to deal with an endlessly recurring message appearing (I do not have tech package or i-drive).

Second, since the OE wheel/tire setup has about 0.5" of OD stagger, does the use of identical tires create any issues? I will have DSC turned off, but in some cars, the change in f/r rpm bias will still cause problems with traction control and/or tire pressure warnings.

[Gearhead999s]

Originally Posted by elh0102

If I decide to do any regular track stuff with this car, I'll probably use either 265 or 275 tires all around, using a set of appropriate wheels. I know this is a common practice so just a couple of questions:

If I do not use pressure monitors, will any warnings other than the small red icon appear? I just don't want to deal with an endlessly recurring message appearing (I do not have tech package or i-drive).

Second, since the OE wheel/tire setup has about 0.5" of OD stagger, does the use of identical tires create any issues? I will have DSC turned off, but in some cars, the change in f/r rpm bias will still cause problems with traction control and/or tire pressure warnings.

I do not know about the pressure sensors as the Canadian cars use a different monitoring system.With the DSC off you will not have any issues.If you try to run with the DSC on on track,you will find it way too intrusive to have any fun.

[sandwood]

you get two yellow icons for the TPMS, and a warning each time you start the car. not too annoying.

[1MORELAP]

Mod please combine threads. (I just asked the same question couple days ago.)

http://www.m3post.com/forums/showthread.php?t=435596

[1MORELAP]

Originally Posted by sandwood

you get two yellow icons for the TPMS, and a warning each time you start the car. not too annoying.

Does the yellow TPMS warning go away after some time?

[elh0102]

Originally Posted by 1MORELAP

OK, I will start with a recent experience on my Cayman. I lowered it, and installed new 10mm wider tires in the rear - 275 versus stock 265. I also bought, but did not yet install 245s for the front (again 10mm wider than stock 235.)

At the track I drive - Pacific Raceways in Auburn, WA, turn 1 is taken ON throttle at anywhere between 120 and 170 MPH (mostly dependent on size of your balls, and power of the car.) I take it anywhere from 120 to 130. Mor or less at the apex, there is a little bump, and you DEFINITELY want to have the car planted with throttle - no lifting or braking - or you are F...ed, someone else can find that You Tube video.

With the above described tire setup my traction control kicks in at the bump and cuts throttle, possibly brakes the car. In other words my car is truly trying to kill me. I have ONLY experienced that with the current tire setup. Of course, I turn stability off as I like to keep the shiny side shiny.

But that begs a M3 related question. Seems that everyone here drastically changes the wheels size ratios when they track their M3. Square setup is WAY off from stock and traction control computers must be going CRAZY. Do people with square setups just automatically disable traction / stability control? Or, not so on the M3?

I had a Cayman S. One problem with that car, you cannot turn off its stability control, not completely, unless you do some wiring work. That can make it frustrating on track.

[elh0102]

Originally Posted by 1MORELAP

Ohh, I am getting ZCP, which claims to have stability tuned for track / aggressive use.

Nope, you'll have to cut it off for track.

[1MORELAP]

Originally Posted by sandwood

you get two yellow icons for the TPMS, and a warning each time you start the car. not too annoying.

Does the yellow TPMS warning go away after some time?

[LiM3y]

Originally Posted by 1MORELAP

Does the yellow TPMS warning go away after some time?

No

[david @ eas]

Well if this is for a track specific set of wheels, I wouldn't bother with TPMS, just let the error go off as you'll save just a tad bit of weight with them, and you'll obviously spend less money with it.

BUT if you are running these on the streets occasionally, then sure, I would spend the extra cash to get TPMS in them as well. So with that in mind, lets move to track set up wheels.

For an inexpensive set, with some super sticky tires, we can certainly set you up with those. I'm thinking a 18x9.5" ET22 set up all around, and running a 265 size tire all around to make it work out perfect.

If anybody is curious on that set, just PM me and I can give you details.

[dawgdog]

I have a square setup and take turn 1 at Pacific Raceways at approx 140 mph and there are no issues with traction control.

[Bubbles]

Originally Posted by Gearhead999s

Why do you run on the track with the traction control on?I have tried it with the MDM on track and it is way too intrusive even in the 100mph + corners.

+1 and I have the "tuned ZCP" MDM. However, traction control is a good thing if you are starting out (some may disagree).

Originally Posted by 1MORELAP

Ohh, I am getting ZCP, which claims to have stability tuned for track / aggressive use.

IT's ok, but as you get better and the car leans more, the traction control will kick in too earlier.

Originally Posted by elh0102

If I decide to do any regular track stuff with this car, I'll probably use either 265 or 275 tires all around, using a set of appropriate wheels. I know this is a common practice so just a couple of questions:

If I do not use pressure monitors, will any warnings other than the small red icon appear? I just don't want to deal with an endlessly recurring message appearing (I do not have tech package or i-drive).

Second, since the OE wheel/tire setup has about 0.5" of OD stagger, does the use of identical tires create any issues? I will have DSC turned off, but in some cars, the change in f/r rpm bias will still cause problems with traction control and/or tire pressure warnings.

I run a square setup with 275 all round easy to swap front to back. TPMS isn't needed, the warning stays but no issue.

[FrenchBoy]

Originally Posted by dawgdog

I have a square setup and take turn 1 at Pacific Raceways at approx 140 mph and there are no issues with traction control.

+1. I too have a square 275/35/18 set-up and take Turn 1 at PR at about 140MPH without any issue. I now run with the DSC off. It never kicked in with the DCS on though (Don't have MDM)

I bet you'll be fine.

[rzm3]

From personal experience M3's stability/traction control is pretty flexible in terms of tire sizes... at least it does not completely disable the car (although performance might be affected). I have 265/35/18 and 295/30/18 which is pretty off vs OE but it seems to work with the controls. However I cannot say the system is as effective as if you were to use the standard sizes.

If you are in a more advanced group I would recommend turning it off... depending on DSC limits your ability to grow as a driver.

[E90M3CDFR]

Originally Posted by rldzhao

From personal experience M3's stability/traction control is pretty flexible in terms of tire sizes... at least it does not completely disable the car (although performance might be affected).

To add to your comment, I suspect that the BMW system has some adaptability built in because it has to be able to compensate for the difference between tire circumference/width/traction for 19" stock and 18" winter (square setup)...especially significant since the winter tire setup has a much degraded braking capacity and grip level.

Seat-of-the-pants I sense that the DSC/ABS system needs some mileage to adjust the threshold for intervention when I replace the tires with the winters. It seems like when you first switch to the winter size setup, the DSC/traction control does not intervene as smoothly (allowing for much higher side-to-side slip) as it does after being driven for a while.

I wonder if the DSC has two (or maybe three) program options - for 18", 19" and 18" square winter. None of the BMW materials I have read address the issue, though. For sure, ABS and DSC systems are much more sophisticated/sensitive now - they can adapt to wear in tire tread much more so than in the past.

[Richbot]

+1 on the permissive DSC with respect to tire diameter on the M3. When my 275/40-18 rears were new and the (stock) fronts were at about 7/32", the DSC seemed a little more sensitive over bumps, now that the fronts and rears are both at about the same tread depth it seems to have settled down a little. The 1" diameter split front to rear might be a little too much for it to handle, now it's a little better as the new rears have of course worn faster than the fronts

It's probably looking at delta between wheel speeds so the DSC may be less intrusive the closer the tire diameters get. I wonder if the traction control on a car with a square setup is, in effect, running in a state similar to constant wheelspin, since the rear tires aren't supposed to turn at the same rate as the fronts with OE tires. This stuff is complicated I'm really impressed with every new generation of these systems I try, but I'm glad the M3 has the push-button off switch right next to the shifter, none of that holding a button down for 5 seconds "ARE YOU SURE YOU WANT TO TURN IT OFF YOU COULD DIE!!!" nonsense like my 335 has.