My unmodified 2006 231 has just failed a vehicle inspection for a private sale (don't worry, I'm not deserting, she's only going as I've just got an R3) as the NS wheelbase is 10 mm shorter than on the OS, all apparently due to the rear wheels as the distance to the front of the rear arch is 10 mm different between the 2 wheels.

The NS lower rear lateral link is slightly bent (only noticeable if you look closely) but IMO if anything it would move the NS wheel further back not forwards.

A full 4-wheel alignment was done 12 mths ago and I don't remember anything since then that might have knocked the alignment.

I've had a crawl around underneath and can't see anything different between the 2 sides and am now going to have a more detailed check.

I've just checked against another RX8 - my NS wheel has the same arch clearance as this car but the OS is 10 mm further back.

I've called the alignment centre (a recognized speciality alignment centre not a high street tyre place or garage) and their guru says:
(a) what I'm talking about is a negative rear setback of up to 10mm. (b) Mazda don't publish setback tolerances as they believe setback to be unimportant - as is the case for just about all manufacturers (c) he could zero the setback but in his opinion it would be a waste of time and money (he's an hour's drive away).

All I now need to do is convince the tester that he can take my guru's views as gospel and pass my car.......

Anyone any knowledge?

Cheers,

Ian