06 XC70 rear rotor minimum thickness Topic is solved

Post by **scot850** » 09 May 2018, 16:59

I read elsewhere that the minimum rear brake rotor thickness is 10mm, but is that for a standard solid rear Volvo OE rotor? It also stated that the minimum thickness for replacement pads only is 10.7mm. Again is this a Volvo measurement? The new Brembo brakes have a minimum measurement stamped on them of 10mm, which would match the Volvo spec as I understand it. Volvo only give a combined minimum of 17mm of remaining pads and rotor which would be 10mm rotor and 3.5mm each pad.

If that is the case the rear rotors on our XC70 which I was finally able to access (as I couldn't wait any longer for the replacement rear rotor from FCP as Customs/UPS dropped one by the looks of the damage on the edge). Winter tires removed I measured one of the rear rotors and it measures at 11.4 to 11.5mm which would mean they have actually little wear. Hard to measure the rear pads without full disassembly but they look like 5mm approx. each.

I don't have a new rear pad to measure (Volvo OE) but the Akebono pads are 10-11mm approx. If the rotors have done 32,000km. Assuming an even wear rate and a minimum pad thickness of 3mm each, it theoretically would mean another 10,000km or so on the rears and still should be able to swap the pads. I appreciate the Akebono ceramics will wear the rotors faster, but it looks like the rear rotors can stay on for a lot longer. Would there be agreement on my reasoning?

Thanks,

Neil.

Post by **oragex** » 09 May 2018, 22:20

Quality pads should be good down to a few mm, 3-4 if they wear uniformly. The rotors I like to look at the non worn lip near the center of the rotor, if it's past 1mm tall I would think about a replacement in the near future.

Post by **scot850** » 09 May 2018, 23:00

These have very little lip either on the inner lip or outer lip.

Neil.

Post by **abscate** » 10 May 2018, 03:51

Isn’t 3 mm approaching rivet height? See below

Post by **scot850** » 10 May 2018, 08:22

Pads have no rivets, and nor do parking brake shoes...!

Neil.

Post by **oragex** » 10 May 2018, 09:38

If Brembo says 10mm min for the rotor, I would take that as a reference, at least when it comes to quality rotors, which the OEM is. Maybe for a cheaper rotor with softer metal I would replace sooner, but on a quality part I wouldn't be worried, even at 10mm they still have a safe margin on them.

Post by **scot850** » 10 May 2018, 11:37

Thanks oragex. I just got a copy of the Volvo repair manual that the dealers have with specification details. If I can copy the format I will post it for others, but it does mirror what I had found elsewhere, that new rotor has 12mm on rears, and 10mm minimum, and a minimum of 10.7mm for a 2nd set of pads. Not sure how much the Akebono ceramic pads will wear down the rotors relative to the OE pads, but with over 11.4mm remaining, they should hopefully be good for a long time to come. Assuming the same length of service the rears will double the life of the front. Weird as some have written they can wear faster than the fronts.

I think I will still remove the rear rotors and maybe file the small lip off and clean and check the parking brake assembly and replace the shoes if worn or signs of any delamination of the brake material.

Thanks to all, and I will close this out if/when I can find a way to post the official info for all.

Neil.

Post by **scot850** » 10 May 2018, 11:58

The promised 'official' information for the rear brake rotors on our 06 XC70 with standard rear brakes.

06 Volvo XC70 rear brake specifications.pdf: 06 XC70 rear rotor specifications; (4.95 MiB) Downloaded 456 times

Hopefully this helps and it will cover other years and models.

Neil.

Post by **oragex** » 10 May 2018, 15:40

Great info, thanks for sharing!