stuart147 Posted July 21, 2014 Share Posted July 21, 2014 On my sons Trek Elite M/B he has always had a problem getting the front wheel to spin freely after putting it back in after cleaning or puncture repairs. Despite numerous trips to a bike shop, the problem has never been fixed satisfactorily. I have noticed tonight that the disc does not sit in the middle of the caliper. The only adjustment available in this area is on the caliper mounts. My question is "what is the best/correct method to adjust the caliper so that the disc does sit in the middle of it and therefore eliminating the dreadful squeal. I hope all of that makes sense. Stuart Link to comment Share on other sites More sharing options...
Wrightpayne Posted July 21, 2014 Share Posted July 21, 2014 There are videos on youtube on how to. I've used two methods:- Slacken off the caliper fixings (slightly slotted ones) pull on the brakes then re tighten fixings. More involved and possibly better is remove wheel, remove pads then refit wheel. Slacken off caliper fixings and centre the disc in the middle of the slot in the caliper. Re tighten ensuring square to disc. Refit pads and wheel. Pull brakes on and off a few times. Assuming twin piston - if one side out further than the other push it back in a little and pull on lever trying to hold it back a little to let the other side equalise IYSWIM Ian Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 21, 2014 Member Share Posted July 21, 2014 1 Are you sure that the only problem is the brake adjustment... does the rim spin true and are the bearings OK? 2 Links to the Park Tools and Sheldon Brown sites in this thread. Adjustments differ between models of brakes, but they'll show you the principles. 3 Where are you and which bike shop, please? Jonathan Link to comment Share on other sites More sharing options...
Wrightpayne Posted July 21, 2014 Share Posted July 21, 2014 Just thinking what type of calipers are they - hydraulic or cable. Cable ones tend to work on one side only and need regular adjustment to keep the non moving pad close to the disc. Ian Link to comment Share on other sites More sharing options...
Roger Ford Posted July 21, 2014 Share Posted July 21, 2014 My one has shims between the caliper and mounting post. It was supplied with a set of shims (basically thin washers) to get the disc centred correctly. Link to comment Share on other sites More sharing options...
stuart147 Posted July 21, 2014 Author Share Posted July 21, 2014 Thanks for all of the replies. There is certainly plenty to go at now. Forgot to say that they are hydraulic brakes. Pretty sure disc and caliper is the problem. Cycle shop is one in Lichfield, Staffs. Stuart. Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted July 21, 2014 Share Posted July 21, 2014 What brakes and hub please? Most brake are now post mount which are easy to set up. Whip the disc off the hub, make sure it's flat and the mating surfaces are clean. If it's not flat, replace or bend straight. You'll have more luck with one than the other! Whilst the disc is off, fit the wheel and make sure it spins freely. If the bearings are knackered, replace. If it's a cheapo cup and cone Shimano style hub, you might be able to adjust it out but I think it's best to fit a hub with sealed bearings. Much less hassle. Refit disc and centre the caliper properly. It's as easy as described above. Link to comment Share on other sites More sharing options...
keybaud Posted July 21, 2014 Share Posted July 21, 2014 It shouldn't matter if the disc isn't exactly in the middle of the calliper, as bike hydraulic brakes self adjust, the same way car brakes do. i.e. The pistons move out towards the disc when the lever is pulled, but only retract a small amount when the lever is released. If one piston moves further than the other until it contacts the disc, it should stay out further when the lever is released. This is why you have to push the pistons back in when you replace the pads. If you can spin the wheel and either the disc or wheel rim are warped, you may get a metallic 'chin, chin' sound. If you do, this is the disc rubbing on the brake. This needs to be fixed before you do anything with the brakes. Once the wheel rotates freely and the disc doesn't rub on the pads, spin the wheel and gently press the lever to see if the pistons and pads more evenly towards the disc. If one doesn't move, then it may have seized. To fix this you want to remove the calliper, gently push both pistons back in as far as they will go (follow manufacturers instructions on how to do this), place the calliper over the disc and squeeze the lever to move the pistons out again. Keep doing this until the pistons move freely. If you are brave, you can use a thinner sheet than the disc or remove the pads. This will also allow the pistons to move out further, so you can see if they have corroded, which would cause them to stick. Once you have got everything to move freely, bleed the brakes according to the manufacturers instructions, as you may have air trapped preventing the callipers from moving simultaneously. If this is done properly, it will also centre the pads on the disc. If you're ever near Malvern I'm happy to have a look, as I strip and rebuild my own brakes. /edit Having reread your post, I think the issue is the pads have been pushed out too far, possibly someone pressing the brake lever with the wheel off and they need resetting, but it's hard to say without seeing them. Also, never push a hydraulic brake lever when the bike is upside down, as you run the risk of getting air into the brake hose. What make and model are the brakes or what year and model is the bike? Edited by - keybaud on 21 Jul 2014 23:58:36 Link to comment Share on other sites More sharing options...
Guest Posted July 21, 2014 Share Posted July 21, 2014 Alternately, an easy fix that I have resorted to is to use washers to move the mount, where it bolts to the forks, one way or the other in order to centre things up. Buy a bunch of different thicknesses! Link to comment Share on other sites More sharing options...
stuart147 Posted July 22, 2014 Author Share Posted July 22, 2014 Thanks to everyone that contributed to this thread. I used a variety of methods to get the caliper to fit perfectly and it is certainly the best it has been. I did notice however that there is a very slight buckle in the disc. Even with this it is now 100% better. Stuart Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 22, 2014 Member Share Posted July 22, 2014 Well done. Are you going to tell the bike shop? How will they improve otherwise? Jonathan Link to comment Share on other sites More sharing options...
stuart147 Posted July 22, 2014 Author Share Posted July 22, 2014 Hi Jonathan. I take your point about the bike shop. If I had thought about asking on this wonderous forum the first time it happened, I could have done it myself then. He never got the bike from the shop in Lichfield, he just went there as it is closer to where we live. The bike was originally purchased from an Evans Cycles outlet in the Chill Factor in Manchester. A bit far to take it back for repairs. Having said that, he has just had a fork seal replaced under the warranty. Stuart Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted July 22, 2014 Share Posted July 22, 2014 Good work Stuart. You can gently force the disc back straight but the best solution is a new one really. Try Superstar Components or Chain Reaction Cycles. Bikes are super fun to work on and quite easy to do to a decent standard. Given how well trained shop techs are the bike should always come back tip top. Wouldn't go back Link to comment Share on other sites More sharing options...
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