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Evening all,
I've got some XT BR-8000 brakes and historically their performance has been great and in typical XT fashion they were either on or off and pretty damn powerful too.
The bike that they are on didn't get used for 6 months or so over the winter.
Since then, they seem to take a while to get their bite back on each ride. The braking performance is really bad for the first few descents and I struggle to even lock the wheels up. It's pretty scary! After a few descents though they get much better and stay that way for the rest of the ride. Almost as good as they used to be. I don't think it's about them warming up / getting heat into them as they'd cool down during the ride anyway but it's not until the next ride / next day that the performance drops off again.
Could it be a bleed issue? The levers feel really positive and not spongy.
Same discs and pads.
Cheers
Contaminated pads. Get some new ones.
That sucks. I've got some new pads. Would you recommend changing rotors too?
The braking performance is really bad for the first few descents and I struggle to even lock the wheels up. It’s pretty scary!
Personally when the wheels lock it's the start of something bad!!
Anyway clean the lot with some brake cleaner, then if that doesn't work new pads, a bleed wouldn't go a miss generally but sounds more like pads
Yep, I had the exact same thing the other day. Pads were a month old and were contaminated.
Sorted with new pads and a quick clean of the disc with an alcohol wipe.
sounds to me like the leaking calliper seals that some shimanos suffer from. Otherwise where is the contamination coming from?
If they were contaminated with brake fluid then they wouldn't work at all - a mate of mine who's useless with all things mechanical asked me to look at his bike when he complained that his front brake was a bit crap. I rode it and it just didn't work. It had a long and soft lever feel - though all Shimano's have a long and soft level feel to me, but in this case longer and softer than usual, and it simply didn't work - no retardation at all no matter how hard you pulled on the lever. Closer investigation confirmed the leaky calliper seal....easily spotted because the disk was wet and covered in fluid and the pads were darker in colour as they were saturated with fluid, so very easy to spot.
But like tjagain says, if not the seals what are they contaminated with? I think some closer investigation is required if they are not obviously wetted with brake fluid - as assume if the were you would have already spotted it as it's so obvious.
sometimes the leak is so slight its difficult to see. the symptoms described sound like leaking callipers to me. Put some tissue between pad and piston and then hold the brake on with a cable tie fo9r a couple of hours - the leak will leave a few spots of brake fluid on the tissue
Have Shimano really not fixed that problem yet?
Could be leaking calipers but the OP doesn’t mention change of lever feel.
Could be contaminated with numerous things such as chain lube or over spray from Muc Off bike protector. This is what caused mine! Originally thought it was the leaking caliper but all good since new pads and no evidence of oil for me.
you won't get a change in lever feel until the oil drops below a critical level
+ 1 for lever feel not changing for a bloody longtime.
Doesn't take much oil to cause the pads to be banjoed. Takes alot for lever feel to change
I'm also in the leaky seals camp . The main reason I no longer have Shimano brakes on any bike as put the bike away fine and pick it up next time.banjoed is not a good look.
Have Shimano really not fixed that problem yet?
Is is there a fix for the leaking calipers issue with Shimano brakes?
Is is there a fix for the leaking calipers issue with Shimano brakes?
Allegedly a slightly large O-ring cures it. There's a thread on it somewhere. But, whatever, the previous generation were completely fine, so it's clearly possible to fix it if you're the manufacturer.
To be fair, I have a set of XTs which have seem not to have this.
the slightly larger o ring between two caliper halves cures it if that is the source of the leak. If it is piston seals the cure is a new calliper as shimano do not sell seals