[s-cars] NAC: ABS MIL

[Igor Kessel]

The conclusion.

per my recommendation, in no small part reinforced by the collective 
wisdom of this great list my doctor friend replaced the half worn front 
205/55/16 all-season Conty crap with a couple of brand new 205/50/16 
SP9000. Yeah, I know it's a wrong size, but they are the same as the 
rear ones and the rears are summer only and are almost new.

The ABS problem has magically gone away. My friend is now pissed like 
hell at his Volvo dealership and is considering suing them for consumer 
fraud for wanting to sell him a new ABS unit.
:)

Gentlemen, thank you so much for your replies and advice, both on- and 
off-list.

-- 
Igor Kessel
two turbo quattros


Toborg Michael (AC-SM/ESC3) * wrote:
> In theory, ABS needs to have all wheels the same rolling radius, but the
> system should be able to compensate for the ~3% difference. If the
> difference were a little bit bigger (5-6% difference) there might be a
> problem. 3% is kind of near the border on what can cause a shutdown.
> So, that could be the problem yes. If the MIL comes on after some
> driving, it must be the difference in rolling radius, if the MIL comes
> on at key up, that would point to some electical problem.
> HTH
> Mike
> 
> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Igor Kessel
> Sent: Friday, July 08, 2005 12:52 AM
> To: Audi S-list; Audi Q-list
> Subject: [s-cars] NAC: ABS MIL
> 
> Folks,
> I am posting this on behalf of one mechanically challenged doctor friend
> 
> of mine.
> The patient is a 1996 Volvo 850, 20v turbo 5 cylinder, auto. An ABS MIL 
> in his car was interpreted by the dealer as "come on in and bend over, 
> we'll screw you good". As we all know, 99% of problems with car 
> electronics happen due to bad connections, yet the dealer wants to 
> replace the ABS controller. Surprise surprise...
> 
> Anyway, it has just occurred to me that the ABS controller may not like 
> the fact that his front tyres are stock (205/55/16, yeah, just like the 
> Audi :), whereas his rear tyres are smaller by 20mm (205/50/16) - did I 
> mention that my friend was a doctor and could hardly tell a steering 
> wheel from a spare wheel?
> 
> Methinks that the 3.3% of rolling circumference difference and 20 extra 
> rev/km are enough to trip the ABS MIL. Is it too far fetched or is there
> 
> any merit to this suspicion? I have a gut feeling that the ABS 
> controller is not his problem.
> 
> Any opinions? Thx in advance.
>