Brake Disc min Thickness?
 

Does anyone know, or better still direct me to Volvo documentation that shows, the front and rear brake disc wear limits?
At 18k miles the rear discs on my MY2011 D5AWD (Geartronic) appear to be wearing excessively, they certainly have worn more than the front discs.

The car went to my supplying dealer today to check this out, the have just reassured me that the pads are less than 25% worn. Doh!

I will be going back to try to reason face to face, but I do need some facts first, the most obvious being what the wear limit is. If I also knew what the original disc thicknesses were I would be even more informed :-)

Any help appreciated.

not sure, but you could pop in somewhere like kwik fit. pretty sure they'd do a free check for you. they are brake specialists afterall. they'd probably find some kind of indicator on the disc.

Digging up an old thread :)

Has anyone found the minimum thickness for the brake discs?

Thanks.

Edit - I have been onto Volvo and they won't release this information as they say it is only available to their technicians!!!

Why will they not tell me, the owner, the information? And why do garages not provide the information for you to assess? It seems that we are meant to accept whet they say, pay up and be grateful.

A lot of discs have the minimum thickness stamped on the outer edge

Thanks for this. I will have a look at this when I swap the tyres at the end of the month for the winter wheels - something I guess that doesn't happen in your part of the world :)

It would still be useful to know what the Volvo specified minimum thickness is as it is tarting to appear that it is almost automatic for Volvo to say that the discs need renewing when a service is done.

I have even been told that you will fail MOT if the discs need renewing, which is strange as they are not measured as part of the MOT, and the starting thickness is different for every car ;)

Firstly the only MOT criteria regarding failing a brake discs are :
"a brake disc or drum in such a condition that it is seriously weakened or insecure" mainly all it has to do is pass the retardation test on the MOT ....

Secondly , it is general with volvo that the max wear is 1mm per face , on an XC60 this would make the minimum thickness 20mm on vented rear discs or 9 mm on solid rear discs .
Rear discs are wearing more than fronts , as there is a lot more braking going on at the rear these days compared to the old V70's 900's etc , mainly due to Electronic control going on , ie hard braking and rears do a lot less work , gentle braking and the rears do a lot of work . You also have DSTC which operates the brakes independantly of the pedal sometimes . So the brake life is now determined by how the user drives . Remember you can go 100000 miles and need never touch the brake depending on how you drive and where you drive to !
In general terms you should be able to get through 2 sets of pads per disc as long as you change the first set before they go much below 4mm .

Thank you for this, it provides the information that I need to hold an informed discussion tomorrow ( at least informed on my side ;)).

It is very difficult to hold such a discussion when you cannot find out what the parameters are that define 'worn'. I now know these parameters and I am sure that this will also help others.

another point ,
the above is the very minimum the discs can be safely used . There is a another minumum figure slightly thicker which is used to determine if the disc is safe to have a new set of pads fitted . So with a set of pads in use they can be allowed to wear down to the disc minimum thickness , but if fitting new pads , the discs must be thicker than this minimum figure . I havent this figure for the XC60 but for example the V70 with 12mm rear discs, the minimum thickness is 10 mm but the minimum thickness for fitting new pads is 10.7 mm , i would allow the same ratio for the XC60 ..

This makes sense. It would indicate that each set of pads will wear the disc by 0.7mm - assuming that a disc lasts two sets of pads (which i have seen documented in several places). Volvo are protecting themselves by ensuring that when the disc wears with the new pads it does not go below the absolute minimum allowance.

This would suggest that the minimum for Xc60 rears would be 20.7 mm when fittings new pads, given that they start at 22 mm.

The saga of the brake discs is resolved without any need to renew them :). It would appear that it is 'normal' practice to renew them at 3 years when they renew pads, there is more than enough on my discs to last until next year, and beyond.

Repeatable I don't have the car back as they have identified an oil leak behind the engine which has been dripping down onto the engine floor plate and it would appear to be a bit more serious than thought as they now want to keep the car until at least Friday (that will be 4 days) - good thing is that I have a very impressive v50 (goes like sh1t of a shovel) and Volvo are extending the warranty on the car :)

Didn't need the warranty direct after all ( if only ...)

Has anyone heard of an oil leak on the engine that they initially thought was a leaking oil plug?