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Brake caliper retaining bolt size

9K views 7 replies 5 participants last post by  romanrob 
#1 ·
So mot just before Xmas threw up an advisory for brake pads being worn,, so £31.98 later a full 4 wheel set arrives from europarts. Near side front came off ok pads hardly worn.,, offside front came off and the friction material had separated from backing plate on 1 of the pads , a new 1 for me after 43 years of driving. Rears are 50% worn but I Cannot undo the caliper bolts. Looks like 12mm but loose enough for the ratchet ring spanner to slide off, 11mm too small.. is it an odd size and if so what, please
 
#3 ·
They are 12mm and an 8mm fine thread (1.0mm or 1.25mm). I've got a set you wall drive 6 point sockets, the ones that drive on the flats rather than the points, they get most things off. That or a set of the Irvin sockets when they are badly rounded or rusted.
 
#4 · (Edited)
The bolts are M12 fine, so you can lean on them, but they're thread-locked and v high torque, so I wd try and use heat. I wouldn't put 6 point sockets anywhere near them, they're 12 point, with a 12mm head ( edit:13mm head), unless someone's changed them (unlikely as they probably wouldn't have been able to find the right thread, and it's probably why they're so corroded in the first place). And use an impact driver /socket to shock the bolts out, ratchet ring spanners are useless (or at least mine are) Edit - or a v long breaker bar
In order of increased desperation, you could probably also try and weld a hex head on top of it, or grind flats onto it to turn it into a 10mm hex head. The bolts will come out, just buy some nice new ones to replace them with
 
#5 ·
For front driver's side I wound a G-clamp up with the handle of the socket set and the wheel/axle assembly clamped in, bit of a stretch for the lower bolt. Passenger front that wouldn't work (rhd, there is a reason I had the spanner behind the wheel, I think it was space or bits of car in the way) so that was a long bar out from under which undid them by standing on it sort of under the passenger door. (On axle stands and a jack, other 3 wheels on the ground).

Both my rear brakes were a right state, and due to space constrictions I got them off with a soak in duck oil, followed by a wooden ended (heavy) mallet on the socket bar. Pretty much had to hammer the socket onto the rear bolts but after getting them out and cleaning them up they aren't as bad as they looked. I thought they'd rusted down to size at first glance. Doing them back up was a case of as tight as possible. I did put a torque wrench up and under the front ones but at the angle and with the leverage available I'd have had to lower the car onto it or jack the handle up from underneath. It's something like 122 Lb/ft from memory, could be wrong. There's not a lot of access for air-spanners either really.
 
#6 · (Edited)
Bit of confusion here on which bolts you are talking about. I was referring to the ones that hold the caliper to the slide pins being 12mm hex head with an M8 fine thread. The ones holding the caliper carrier to the hub assembly are the M12 fine with a 13mm 12 point head. Which ones do you mean?
 
#8 ·
I guess we both made that assumption, and you're right about the head on the rear carrier bolts 13mm, not 12mm
 
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