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Old 04-30-2003, 01:57 AM
rrf rrf is offline
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Join Date: Jun 2002
Posts: 15
Is true wheel diameter setable in the DAS software?

Hello, maybe a dumb question, but probably worth a thought,

W203 2002 C-class

Is there an internal DAS setting to accomodate the EXACT tire circumferences for the BAS/ESP system?
For example when tires from different manufacturers are used or when slightly different sizes are installed.

Let's use a basic C320 as a reference:
The C320 offers a range of tires as options from the factory options list.

From the MB website for just the C320 :

Style B 225/45/17F and 225/45/17R
AMG Style III 225/45/17F and 245/40/17R

The diameter of the 245 is 629mm the 225 is 637mm so there is a 1% physical difference.
(Add in some normal tire wear and these differences could get even higher).

I see there are some possible answers to how the BAS/ESP might accomodate these "small differences":
1) The C320 BAS/ESP system doesn't care about small 1-2% differences in circumference
2) The C320 BAS/ESP system is changed/replaced/different whenever optional tires are chosen
3) The C320 BAS/ESP system is reprogrammed or "told" about the new tire option

#1 may be true, which is likely, and apparently is everyone's assumption. (Nobody touches ESP when they go to aftermarket wheels/tires). However, even when when optional FACTORY tires are selected, we know circumferences are different. My feeling is the computer will be a little more "eager" to use the ABS than it should be.... it has no choice but to be thinking there is a little slippage going on, which in its mind is OK, but after a certain point it must start to intervene. right? Won't its calculations be "off" by the % error above?
#2 seems a little crazy, and I have never heard of anyone replacing the system with tires.
#3 seems logical, but never mentioned by anyone, either

Is there such a setting as #3, and which DAS menu would it be available in?
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