juleslid Posted March 1, 2015 Share Posted March 1, 2015 Question in brief; has anybody had experience of fitting a new rear caliper and finding it remains applied each time the brake pedal is pressed? Have tried removing it, winding back the piston again then refitting, but after the first press of the pedal the brake drags again.The background was that I had a leak from the original caliper and decided to replace it with a brand new unit from Rally Design. This was fine for a while but on its first track day started locking on and destroyed its pads and disc. Replaced it with one of CCs (rebuilt) units which was fine but was a bit of a rattler. So have just fitted another new one that Rally Design gave me as a replacement, and that is now dragging each time I try to turn the wheel while the car is up on axle stands.Car is 2010 Roadsport 175, low mileage in good condition.Maybe it would sort itself out on the road, but would be grateful for any thoughts you have...Jules Link to comment Share on other sites More sharing options...
SM25T Posted March 2, 2015 Share Posted March 2, 2015 Sounds like the piston is sticking ? Did you press the brake pedal hard a few times before touching the handbrake ? This adjusts the auto adjuster to take up slack travel inside the piston. Then you adjust the handbrake cable. Link to comment Share on other sites More sharing options...
juleslid Posted March 2, 2015 Author Share Posted March 2, 2015 Think I did that, but will wind the piston back again, then try your technique to make sure.While doing that will also try Jonathan Kay's suggestion of checking disc runout, slider movement, and freedom allowed by brake pipe...Jules Link to comment Share on other sites More sharing options...
Paul Deslandes Posted March 2, 2015 Share Posted March 2, 2015 Are both pads binding or just one side of the disk? If it's the piston side only, check that the caliper is sliding ok, as per JK's suggestion. Slide a sheet of paper between the pad and disk and apply brakes. When the pedal is released, both sheets should be free to come out, even though there may still be slight contact, and there should be no resitance to turning. If the non-piston side only is sticking it would suggest the slider isn't freeing off. Also make sure that the pads are aligned correctly with the nib on the pad locating in the slot on the piston (or is it the other way around, I can never remember!). Rotate the piston to suit.Although it doesn't sound like it, presumably the cylinder the other side of the car isn't doing the same. If it is it would suggest that the master cylinder isn't releasing pressure and the rod needs adjusting. Link to comment Share on other sites More sharing options...
Ivaan Posted March 2, 2015 Share Posted March 2, 2015 I had this happen to the brand new calipers used on my disc conversion a few months ago. Brakes dragging and getting very hot.The guy who did the work, took them apart and could find nothing wrong. He then dismantled an old caliper and compared the two. On the hand brake mechanism, there's a pair of spring washers, which take up the normal footbrake movement of the piston, returning the piston and giving the clearance for the pads on pressure release.On the new caliper, this spring washer is much weaker, and failing to give the footbrake tolerance, meaning that all the movement is taken up by the handbrake screw thingy.He swapped over the new piston assemble for the old ones, and I've had no troubles since.Clive. Link to comment Share on other sites More sharing options...
juleslid Posted March 5, 2015 Author Share Posted March 5, 2015 Thanks for more ideas.Paul, the other side is behaving properly. The pads are carefully positioned with the nib engaging the recess at the bottom of the piston.Ivaan, you don't mean the large coil spring that the handbrake cable is pretty much attached to, I suppose?Will be a week or two before I get time to have another play, so any more suggestions will be read with interest... Link to comment Share on other sites More sharing options...
Ivaan Posted March 5, 2015 Share Posted March 5, 2015 Hi Jules,No the spring washers are inside of the calipers behind the pistons.If you have the caliper off of the car, the piston will screw / pull out. You'll need a special tool and you have to be careful of the seal.Behind the piston, there's a threaded rod, which rotates to take up the piston movement as the footbrake is pressed. It also activates the pistion for the handbrake. On this rod there's a threaded sleeve and the spring washers. These prevent the thing from overtightening, meaning that when you take pressure of of the brake peddle, the caliper moves back a tiny amount to free the pads from the disc.These spring washers are of a lighter construction than the original calipers, and I believe this causes the binding up, as they aren't strong enough.Who supplied the new caliper...try going back to them.If you're still having problems, I could put you in touch with Dave Willet, who's based in Tilston, not too far from you.Clive Link to comment Share on other sites More sharing options...
juleslid Posted March 26, 2015 Author Share Posted March 26, 2015 Update for all those kind enough to come up with a suggestion:I've got a track day at Oulton on 8th April so decided to play safe and put my old CC supplied caliper back on (the rattler). The slider seemed to have a lot of movement in it so put a newer one on in the hope that this will quieten it down. Interestingly this one didn't even think about permanently clamping onto the disc after being applied!As an aside, I mentioned this to Rally Design who supplied the unit new quite a while ago. They said that they'd had a couple do this and if I returned it they would send me one from a new batch. And they did! Nice guys.If the roads ever lose their generous coating of salt applied up here, then I'll go and try thing out.Cheers, Jules Link to comment Share on other sites More sharing options...
martyn Posted March 26, 2015 Share Posted March 26, 2015 Jules, sorry to hijack a bit...I acknowledge that the single piston rear brakes are pretty limited, and certain allowances need to be given. But, what level of "stickiness" or pad rubbing is acceptable? My rear wheels are very difficult to turn by hand. When I push my car in/out of the garage there is a loud scraping / rubbing sound of the discs running through the pads. Also audible when driving at low speed. Is this normal? p.s. I have already had the brakes apart to clean everything and grease the sliders. Link to comment Share on other sites More sharing options...
AntonyH Posted March 26, 2015 Share Posted March 26, 2015 Mine sometimes scrape a bit on all four wheels when pushing out of the garage, even to the point of sticking on if the car's not moved for a month or two over the winter (the garage does suffer some damp ingress ), even though the car is restrained by wheel chocks rather than handbrake. I'd never call it "loud" though. Noticable, definitely, but not loud.It clears fairly quickly once underway, especially after a couple of applications / releases to skim the surface corrosion off the rotors. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted March 26, 2015 Member Share Posted March 26, 2015 No rubbing here. Have you had a good look at the discs?Jonathan Link to comment Share on other sites More sharing options...
Gregs79 Posted March 26, 2015 Share Posted March 26, 2015 I have the same issue with one of my callipers having managed to finaly wind my callipers in, so the wheels will be coming off again this weekend! Will have a look at the ideas listed above. :-) Link to comment Share on other sites More sharing options...
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