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Hi - I have a pair of avid juicy 3's. All is ok, more or less but I have noticed that the rear brake is a bit odd.
When I eye the front caliper there looks maybe 1/2mm on each side of the disc and when I pull the brake I clearly see both sides of the pad moving in to the disc. All works bon.
However, on the rear I cannot see any daylight though as it were, also when I pull the brake it only looks like one side moves in. Further, the rear disc only contacts with about 3-5mm of the pad which is all worn (and the pad is quite new as I recently changed them). It is almost like the pads are not pushed back enough and are almost sitting on the disc. Or maybe when they first were in it was ok but then the pistons disnt pop them back? Certainly when I spin the wheel the disc friction causes it to stop after a few rotations.
They arent that old (around 6 months), though I suspect some kind of loss of fluid on the rear at some point as I have to pull the lever in much further to get a brake than the front and also the top cap on the lever got all corroded and the paint came off the brake (which was replaced by the shop, just havent fitted it yet)which I presume was from some kind of leak?
Any ideas? I am fine with road bikes but mtb are a whole new world to me (yes i did build it:)!)
Cheers
Andy
sounds like two issues - and incompatable disc size / calliper mount and a sticky piston or the brakes not centred. Folk will tell you to pull the lever with the mounts loose to centre the caliper than tighten them. However the hope video shows a far better method.
Set up a caliper and centralise pistons on this page
http://www.hopetech.com/page.aspx?itemID=SPG219
I'd recommend starting from scratch, remove the wheel and pads,and flush out the caliper with brake cleaner(muc off's stuff is good),wiggle the pistons all the way back using the ring end of a 10mm combination spanner, then get in there with a toothbrush and more brake cleaner to make sure it's as clean as possible(if you can't push them both all the way in, you'll have too much fluid/air in the system).Once clean,work the pistons out a bit, and clean them too, then use a kiddies paint brush and apply silicone oil to them(Hunters, from a plumbers supplier), and work them in and out until smooth and free. Fit new pads, fit the wheel, then align the caliper so the pads are perfectly square to the disc in all planes, and equally spaced side to side (involves much nipping of bolts, wiggling just a smidge, and cursing lots, but no squeezing of the lever and tightening the bolts).Spin the wheel and check the disc is straight, tweak it using a clean adjustable spanner if it isn't (highly likely),and then get your bleed kit out and perform a thorough bleed(will take at least twice as long as t'internet experts reckon if you do it thoroughly).Repeat for the front when you realise it hasn't been as good as it could have for the last 6 months 🙂 .
Hi - thanks for the reply I think the mount/disc size is right as it came as a kit from merlin. The mount feels a bit tricky as shown but I imagine nothing that unusual. The advice sounds sound though so I will try it out.
Just to clarrify - to do the pistons should I take the wheel out and pads then pull the brake or is this bad (I was told previously not to do this as would have to have a shop reset the pistons)
Cheers
Andy
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Look at teh two hope vids for brake setup.
do not pull the brake with the wheel out - you can pop apiston right out
As long as you're not a hamfisted numpty, then it's safe to pull the lever with the wheel out, but you will then need to push the pistons back in(which is what you'll be doing to work the lube into the seals, and what you'll need to do when fitting new pads).Problems will occur if you repeatedly pump the lever, as mentioned above, the piston may well pop out necessitating refitting and bleeding.
As TJ says the piston can pop out.
As I found out on Friday when adjusting hose length then bleeding (I knew I'd forgotten something at the time!
ok cool - i will be very careful of that!
Do you have the tugnut washers in? I couldn't get mine to set up properly until I spaced the caliper away from the frame with a couple of M6 washers.