I have Avid Juicy 5s Disc breaks on my Mountain Bike, and the front brake just isnt fulfilling its potential, I've compared them to Juicy 7s on another bike which seem worlds ahead, more so than any two pairs of hydraulic breaks should ever be in my opinion. and I'm getting to the point that I'm not sure if the calliper is working properly.
The difference in performance which i have noted is that the front break on my bike doesn't lock at all, no matter how hard you pull the leaver (which doesn't even nearly bottom out on the bars) comparatively the other bikes brakes will lock instantly and the bike easily pulls and endo, so much so that you can throw your self off it if you so wished, with just the front brake.
I've spent hours bleeding them several times, I bled them twice, and no change so then I emptied the system and took the lever apart and cleaned the seal on the reservoir, and refilled the system, and then bled it afterwards to be completely sure, the lever is so tight now that its clearly got less air in it than the back break which works fine. And made me think that i have wasted my time all together bleeding the brakes because they work ever so slightly better now, and afterwards I cleaned the disc and pads with methylated spirits, and rode round for 10 minutes trying to pull an endo, to no avail.
Instead of locking on the disc as I expect it to the disc slides through the pads at a very slow rate, quickly stopping the bike, but as i am only travelling slowly on flat, obviously this is a useless comparison to when I'm landing on downhill stretches at 30mph, thinking crap that's a tight berm. In which case i will need the brakes to work properly for safety if nothing else.
One thing i have noticed when i looked at the back brake pads is that the caliper on the back brake has left a large clean shiny copper ring around the pad back, however this isn't present on the front pads which is making me wonder if the piston is working properly for it to let the rust show on the pad. Obviously this could be a matter of coincidence as I am learning on the job with this, so i'm relay asking does anyone have experience with disc brakes that don't grip the disc properly.
Another gem of information ive forgottern, the bike was bought about 4 months ago, but it was new but 2 years old if that makes sence, its a 2008 model but was never sold on the original sales line, and then i got it half price earlier this year because they couldn't shift them. There are no obvious flaws with the bike other than alot of the fluid-mechanical systems do seem to be failing i assume this is because the seals have decayed. The forks went back last month because they lost about 80% of their travel. I can well believe the bike needs a new brake caliper, but i dont want to take it back to the shop again because they take ages to fix things.
Any ideas on what's wrong with my brakes.
My bikes front disc break doesn't work as well as it should?
I would put on brand new pads first to see if some oil got on the original pads cleaning them probably isn't adequate for proper bite (or just switch front and rear pads so you don't have to spend any money). If still no change then I would squeeze the lever without a wheel/rotor in it and see if the piston moves, if not then I would say time to upgrade...
My bikes front disc break doesn't work as well as it should?
I would guess that your problem stems from contamination on the front pads. Most hydraulic disc systems recommend using only alcohol to clean the pad surfaces, never any petroleum based product because they will leave residue in the pad material and render the pads useless.
You could try switching the front and rear pads if you know the rear are okay. If they fix your problem on the front you'll know the old ones were the problem and can install new. Be sure to clean the disc itself with alcohol before you make the switch because if those front pads are contaminated some of it will be on the disc and you don't want to transfer it to the rear pads too..
Be careful if you apply those brakes without either the pads or a spacer in place as you can force the caliper piston completely out of its bore creating even more problems. Your bike should have come with a couple of the spacers which are nothing more than a small piece of plastic about the same thickness as the pads themselves.
One other point as far the bleeding of hydraulics go... as on a vehicle, if there's a need to bleed the brakes regularly then there's a leak somewhere in the hydraulic system. Under normal conditions the pad wear is compensated for by adjusting the lever throw and bleeding should not be necessary unless the system is opened for repair. If you're having to bleed them at all something is wrong.
