leeson660 Posted November 22, 2014 Report Share Posted November 22, 2014 (edited) Hi guys I think I've buggered up my rear brake. Having busted my hand in a big DH crash a few weeks back I've occupied my evenings working on the gasser however a little knowledge is a dangerous thing and all that. Completely new to all this so bear with me. My rear brake hasn't been very powerful since I bought the bike few months ago. I tried the getting it hot then putting water on it which worked a treat for a very short period giving a nice sharp confidence inspiring bite but then shortly after it went back to the way it was before. Ordered some Galfer pads which I hoped would do the trick. I took the rear wheel off, had a look at the caliper and it all looked pretty manky in there. So went about trying to give the pistons / caliper a quick clean using brake cleaner. To do this with the old pads out I pumped the rear brake lever to work the pistons out as far as I'd dare. Clean them then push them back in again - repeating this process about 5 times. All looking nice and clean, new pads in, wheel back on job done. Only problem is now the rear brake pedal goes down in two stages with a nice crunching noise. No power in the rear brake at all until right at the bottom where it just about locks the rear wheel. For what its worth the pads do feel like they will bite much better if everything was working properly! Three questions really: What did I do wrong? What has happened? Cost considerations aside what is the best rear brake I can get for my bike without major modification? Coming from mountain bike trials I do really want a really good powerful rear brake and Formula don't seem to be regarded as being very good from what I have read. Like I said go easy on me I'm new to working on brakes in general, mtb disc brakes are very much fit and forget. Any help much appreciated. Edited November 22, 2014 by leeson660 Quote Link to comment Share on other sites More sharing options...
lineaway Posted November 22, 2014 Report Share Posted November 22, 2014 Well at this point I would strip and clean the whole system. Tear the caliper apart and the master cylinder. Quote Link to comment Share on other sites More sharing options...
higgy Posted November 22, 2014 Report Share Posted November 22, 2014 Same here I strip my formula brakes every few rides when I asked at dirt bike show they said they need doing a lot. Clean brake fluid out and bleed you will find them work a lot better. I up graded my front bake to the new formula sherco it works a lot better but not cheep. Quote Link to comment Share on other sites More sharing options...
huski Posted November 22, 2014 Report Share Posted November 22, 2014 Some people change them for the earlier ajp brakes which were far more reliable Gas Gas only used the Formula kit for a year.If you're going to keep the bike it's worth replacing them but it's not cheap Quote Link to comment Share on other sites More sharing options...
leeson660 Posted November 22, 2014 Author Report Share Posted November 22, 2014 Cheers guys thanks for the replies. I really cant be dealing with bleeding the brake every few rides or having regular issues much rather upgrade. The bike already has the front 2013 Sherco forumla brakes and its awesome just want the back to perform the same! Other than going back to AJP are there any other brake upgrades? Can you fit rear brake from a newer model? Thanks James Quote Link to comment Share on other sites More sharing options...
dadof2 Posted November 23, 2014 Report Share Posted November 23, 2014 The formula brakes can be made to work well and reliability. From new they had 2 initial problems. Machining swarf was left in the fine passages Some of the edges and ports that the seals moved over had sharp edges / burrs One or both of the above then wreck the seals or jams the pistons. Thorough clean out, polish and deburr and they should be OK Quote Link to comment Share on other sites More sharing options...
leeson660 Posted November 23, 2014 Author Report Share Posted November 23, 2014 The formula brakes can be made to work well and reliability. From new they had 2 initial problems. Machining swarf was left in the fine passages Some of the edges and ports that the seals moved over had sharp edges / burrs One or both of the above then wreck the seals or jams the pistons. Thorough clean out, polish and deburr and they should be OK Ok thanks I'll give it a try and see if it does the trick. I do find it strange that there don't seem to be any aftermarket options for brakes for any trials bikes. Surely if someone designed a decent four pot setup for the rear with a bigger disc that really worked and was reliable people would pay the extra, I know I would. Anyway thanks for the info, any further advice much appreciated. Cheers Quote Link to comment Share on other sites More sharing options...
lineaway Posted November 23, 2014 Report Share Posted November 23, 2014 Four pots have been done before. Most brakes work fine from the factory. You bought a bike which the brakes worked poorly. On the other hand trials bikes are a very small market, and most riders are by nature cheap! Good luck on the rebuild. Just for your info when the Formula brakes came out, most riders swapped the brakes off the old bike. Some did that several years in a row! Quote Link to comment Share on other sites More sharing options...
steve_earle Posted November 23, 2014 Report Share Posted November 23, 2014 Been browsing an auction site earlier and noticed there's a rear formula caliper on there cheap from a 2012. Quote Link to comment Share on other sites More sharing options...
leeson660 Posted November 29, 2014 Author Report Share Posted November 29, 2014 Been browsing an auction site earlier and noticed there's a rear formula caliper on there cheap from a 2012. Thanks for the heads up Steve. Four pots have been done before. Most brakes work fine from the factory. You bought a bike which the brakes worked poorly. On the other hand trials bikes are a very small market, and most riders are by nature cheap! Good luck on the rebuild. Just for your info when the Formula brakes came out, most riders swapped the brakes off the old bike. Some did that several years in a row! Point taken.It was my mistake for assuming the 'uprated' brakes on the pro version would be better than standard - lesson learnt do proper research Just a quick update: Rather than doing a full rebuild straight away I thought I'd try to bleed the brakes first. Post bleed rear brake is absolutely spot on. Really nice lever feel with loads of power. Time will tell how long it will last but for now I'm really pleased with the result. All the back wheel stuff is making a lot more sense now Thanks again for everyone's help and apologies for my simple questions - I'll post back if it all goes belly up! 1 Quote Link to comment Share on other sites More sharing options...
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