Re: ASC vs Tire size, was Early vs. Later E36 M3

["Ron Buchalski" <rbuchals@xxxxxxxxxxx>]

Dale,

Since all four of your tires are the same size, you won't experience the 
problem.

The people who have seen problems are those who put non-standard sized tires 
on the car, like 235/45ZR17 in front and 255/40ZR17 in rear.  In some of 
these cases, the diameter of the front and rear tires will differ 
sufficiently to cause the ASC problem.

I don't have exact numbers, as I have a '95 model with no ASC.  But I read 
about it on the E36 M3 Digest.  If I remember correctly, ASC will kick in if 
there's a speed differential of about 3% between front and rear tires.

For more reading (from the E36 M3 Digest), check out:

http://www.bmw-m.net/digest/archive%5F2000%5F09%20digest%20484%20584/digest531.htm#6


- -rb

>
>Date: Sun, 20 Jan 2002 09:40:33 -0800 (PST)
>From: Dale Nelson <dalenelson1952@domain.elided>
>Subject: ASC vs Tire size, was Early vs. Later E36 M3
>
>Ron Buchalski's reply to Early vs. Later E36 M3 said
>
> > > ASC+T measures speed variations between wheels, so
> > changing tire sizes
> > (from
> > > standard) can result in ASC+T mistakenly
> > activating at high speeds
> > (because
> > > the speed difference between front and rear wheels
> > makes ASC+T think that
> > > wheelspin is taking place).  Just something to be
> > mindful of.
> > >
>
>I modified the setup on my 98 E36 M3 to be that of the
>95 M3 - 235/40-17 on 17x8 on all corners. (Helps with
>understeer and turnin). I have not noticed any ASC
>kickin up to approx 100MPH. I have measured about a 2%
>difference in true speed vs indicated now (the speedo
>says 61 MPH at a true 60 MPH). Question is: normal
>tire diameter differences between manufacturers can
>easily produce this variation, it would be BAD for ASC
>to kick in at highway speed due to normal tire
>variation or slightly modified setup (such as mine).
>Do you know what the threshold for detecting wheelspin
>with ASC is? Is there a speed on the highway I should
>no exceed without ASC off?
>
>Thanks
>Dale
>98 E36 M3
>97 E36 M3
>72 2002tii
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