caddabs Posted October 1, 2011 Report Share Posted October 1, 2011 Can anyone help me to improve my front brake? i have a 2000 290 with a single pot AJP. The brake is really useless with no feel at all and not enough bite to hold it on a downhill. the pads are relatively new (although i have just ordered some more), there is no air in the system. the disk is old, and a little scored but ok. when i put the brake on you can still push it forward. no amount of handlebar adjustment helps.the disk has been cleaned and i have cleaned all the crud off of the pads. i was wondering about taking the pistons out (not sure how) and cleaning them. would that be sensible or are they best left alone? getting a bit fed up as on small downhill sections i cant stop it on the front brake and often over run markers. (thats my excuse) any help gratefully received. all the best Caddabs Quote Link to comment Share on other sites More sharing options...
bambam_n_chunx Posted October 1, 2011 Report Share Posted October 1, 2011 If its not broke I would leave it alone. You say its no good even if you adjust the lever. Its a hydraulic system so if you are screwing the plunger in you are making it worse. the screw needs to come out as far as it can with just a little play. That way the piston in the master cylinder gets the full travel and pushes as much fluid through as possible. Also a little water on the pads will help, dont ask me why as I dont know it just works. Best way to make sur there is no air in is to take the cap of the master cylinder, push the hose down so its below the bars and just gently pull the lever in and out a lot keepiing it pressed in for a while every now and then. Good luck!! Quote Link to comment Share on other sites More sharing options...
baldilocks Posted October 1, 2011 Report Share Posted October 1, 2011 (edited) people were doing stoppies long before 4 pot calipers so you should have better performance than you describe. first of all I'm assuming if you hold the lever tight to the bar the pressure is maintained ? if not check seal in master cyl or hose for damage. once thats done I'd take the pads out and remove caliper from bike, put a bolt in the caliper where it normally attaches to fork leg to stop caliper splitting then pump the lever whilst holding one piston with pliers and see if the other moves. Do the same with the other piston. The exercise above will let you know if the piston is seized as both should move when the other is clamped. If they are not moving you need to get the pistons out and check for pitting / corrosion. if the piston is damaged either get a rebuild kit or buy a complete four pot caliper. what brand of pads are you using ? Edited October 1, 2011 by Baldilocks Quote Link to comment Share on other sites More sharing options...
godzilla Posted October 1, 2011 Report Share Posted October 1, 2011 Have you mover the lever inboard yet? Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted October 1, 2011 Report Share Posted October 1, 2011 You need to ride the bike around for a minute or so dragging the front brake, then squirt the rotor and caliper with a hose. Make sure you get the rotor hot enough that it hisses when the water hits it. If all your parts are in order, this will get you your brakes back. I don't know why it works, but it totally does. I had an '01 that I updated to the 4-pot caliper. It's a bolt-on and it's a nice update, but not totally necessary. Quote Link to comment Share on other sites More sharing options...
lineaway Posted October 2, 2011 Report Share Posted October 2, 2011 You stated you removed all the crud off the pads. If the pads have had oil contamination they are basically ruined. They can be burned out with a torch, but new pads are the best cure. Quote Link to comment Share on other sites More sharing options...
jse Posted October 2, 2011 Report Share Posted October 2, 2011 You need to ride the bike around for a minute or so dragging the front brake, then squirt the rotor and caliper with a hose. I don't know why it works, but it totally does. Charlie, As I understand, the process changes the temper of the disk and/or possibly the pads depending on their composition. When I had a bike with the single AJPs, I had pretty good luck with the EBC Kevlar pads. Jon Quote Link to comment Share on other sites More sharing options...
nzralphy Posted October 2, 2011 Report Share Posted October 2, 2011 Perhaps your disk is warn out and/or dished. Put a ruller across the disk face and check if there are any gaps by shining a torch from the other side. I had this once an a new disk fixed everything. Quote Link to comment Share on other sites More sharing options...
caddabs Posted October 2, 2011 Author Report Share Posted October 2, 2011 Thanks all. The pads are Kyoto, which i suspect may be at the cheaper end of the market - as above, i have just ordered some new more expensive pads so i'm hoping that will do the trick. i have previously tried the dragging until hot and then pouring water over them which seems to work for a while, but they soon fade. ive also tried taking the pads out, cleaning them with emery and scoring grooves in them with a file (well new ones are on order) - no better. the disk is 100% straight. just checked it. its 11 years old so its a little worn, but basically sound. not sure what is meant by moving the lever in board - its in the normal place. it is a short lever, but i dont think that should make any difference. The adjustment is fine, plenty of piston movement - but i take the point. i prefer the lever to be further out than in anyway. i'm going to see how the more expensive pads work out, but if not i'll have a look at the pistons as described. stoppies are totally out of the question at the moment !! If that doesnt work then maybe junk the caliper for a new one. many thanks all - very helpful. cheers Caddabs Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted October 2, 2011 Report Share Posted October 2, 2011 When I was more involved in road bikes, I always used the cheapest pads. I found that anything added to the material (usually bits of metal) added longevity but reduced friction (braking). I worked on Harleys, which have the worst brakes on earth, so every little bit helped. I don't know about Kevlar. It may well be strong, long-wearing and have a high friction coefficient. And Jon... That's exactly my take on the heating/quenching: the process changes the temper of the disk and/or possibly the pads depending on their composition. Especially the "and/or possibly" part! Well...it's a rough, vague, general, ballpark estimate of what I guessed. Quote Link to comment Share on other sites More sharing options...
rev3 Posted October 2, 2011 Report Share Posted October 2, 2011 Try this, dead simple and always works for me. at lever end screw out the adjuster as far as it will go. This will make sure the piston has moved back past the very small inlet hole for the fluid ( this is a must as it causes 99% of front brake trouble). undo caliper bleed nut and let the fluid run out, make sure you keep an eye on the reservoir level. Keep going until the fluid runs clear in colour. tighten up, replace reservoir lid and gently apply the front brake. Normally 3 or 4 pumps and jobs a good un. repeat again if needed. The trick is not to worry about pumping the fluid through. Quote Link to comment Share on other sites More sharing options...
copemech Posted October 3, 2011 Report Share Posted October 3, 2011 Thanks all. The pads are Kyoto, which i suspect may be at the cheaper end of the market - as above, i have just ordered some new more expensive pads so i'm hoping that will do the trick. i have previously tried the dragging until hot and then pouring water over them which seems to work for a while, but they soon fade. ive also tried taking the pads out, cleaning them with emery and scoring grooves in them with a file (well new ones are on order) - no better. the disk is 100% straight. just checked it. its 11 years old so its a little worn, but basically sound. not sure what is meant by moving the lever in board - its in the normal place. it is a short lever, but i dont think that should make any difference. The adjustment is fine, plenty of piston movement - but i take the point. i prefer the lever to be further out than in anyway. i'm going to see how the more expensive pads work out, but if not i'll have a look at the pistons as described. stoppies are totally out of the question at the moment !! If that doesnt work then maybe junk the caliper for a new one. many thanks all - very helpful. cheers Caddabs Caddabs, I had two bikes with that caliper that worked fine. I converted one, could'nt tell much difference but possibly a bit better progression and feel. The stock Galfer pads are the hot s--t in the dry conditions. I have gone to the ones from "Braking" for their overall (wet) performance, but they are not quite as good dry. Quote Link to comment Share on other sites More sharing options...
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