Citroen XM Forum

Maybe that's the spec for the later ones, never had one as new as that.

Peter

You are ALL right with this!!!

Mk2 XM 2.1TD have different tyre specs for manuals (195/65/15) and for autos (205/65/15).

John

ahh..so my summer tyres are the right size for my auto but my winter ones are for the manual.

Why the different sizes for manual and auto?

Citroen decision on what was correct to fit.
In the 1995 owners manual there is a similar difference for V6 petrols.
Auto's came out the factory on 205/65/15's while the Manuals got 205/60/15's.

John

There's different sizes depending on the engine too - mine's currently fitted with 195/60/15's, which according to the information I have were fitted to the 2.0 petrol cars at the time mine was built. Mine should have the 65 profile tyres as mentioned above, and while I'm sure it'll improve the ride, I'm also too stingy to replace the tyres before they need it! I will have to replace them all when I do it though, as although in theory legal if using the same size across an axle, different size tyres will upset the ABS.

The examples I quoted are for Mk2 XM's.
There is a further minefield of minor differences across the Mk1 models of different ages.
Tyre diameter can vary by up to 12mm between new and MOT limit wear.
The XM ABS is comparing measured time difference on one 48th of a wheel revolution.
It takes a fairly major difference error for the ABS to get upset.
Virtually all other cars use a one 29th of a wheel revolution for the ABS.
That would make them nearly twice as likely to produce ABS faults from tyre size differences.

In the past I have run new 205/65/15's on the front and 205/60/15's on the back for the residual life of the tyres without ABS problems.

John

White Exec wrote:Why the different sizes for manual and auto?

Two reasons.
1. the auto box is heavier,
2. to raise the gearing for better economy for the auto.

The reason I mentioned the ABS issue is that on of the BX Club members (I believe it was actually Ian, who started this thread) once owned an ABS equipped BX that would show an ABS fault at motorway speeds, which I believe went away once the car was fitted with a matching set of tyres.

It's not only the tread depth that makes a difference to rolling diameter. When checking tyres prior to getting them fitted to my GS I've found anything up to 10mm difference in diameter between new tyres of the same size from different manufacturers.

That's true. My TZD estate would throw the ABS light on at an indicated 80mph. No other time. I thought it was some sort of speed nanny!

I guess I may have to say goodbye to those lovely tyres then. Hoping someone will buy the Rover soon so I can finally grab a slice of XM ownership. Can't imagine why I'm thrilled at the prospect of a Mandarin 2.1TD manual...