Doing the uplift at Inners today,on my fifth run down my brake started to fad until I had no power in it at all. Checked for leaks on the calliper and handle but couldn't see anything. Not opened up the reservoir yet but before I do has anybody any idea
Hope M4 rear brake problem
Sounds like you boiled it up, is it working now?
Now home but still not working. Leaver right back to the bars
Were you dragging the brake? If so, it's likely that you've boiled the fluid. A good bleed and a tweak of braking technique would sort that.
If you weren't dragging it, then there's a very fine leak in the system. Clean and dry the bike. Bleed the brake, then tie the lever back over night. In the morning, go hunting for fluid leaks (a fine talc might help). Or it could be a failed seal in the master cylinder so it's now not pushing fluid.
Thanks,will get onto it tomorrow
Boiling M4s on UK descents would take some doing.
I've had issues where the banjo bolt has come a little loose and fluid has slowly leaked out, almost unnoticeable.
A good bleed should sort them out
How old is the fluid, what size rotors?
Full bleed is worth doing anyway.
The brakes are a year old with a 203 rotor. Just back from a week in the Alps
thegman67 said » The brakes are a year old with a 203 rotor. Just back from a week in the Alps
could have been knocked around during transit, check all the lever-hose-caliper junctions. And.... was the bike stored upside down at all during storage/transit ? Fluid can leak out of the reservoir if stored upside down or vertically with bars at bottom.
check the fittings, the strap in my bike bag managed to pull the banjo round a little and cause a small leak. However you may just have given the fluid a good going over in the alps so just do a full flush through bleed, takes 20 mins.
Thanks for the advice guys
I had a very similar thing happen to my M4's in the Alps.. turns out that the bleed nipple was weeping (could see when I took the top cap off that it was missing some fluid). Replaced it, bled them though and they were fine.
Fluid cant leak out if upside down.
Fade is when no mater how hard you pull the brakes don't work, until you have had it you wont know what it is.
If the levers pull back to the bars and don't do anything you either have no fluid in the system or air in the fluid, or someones pinched your pads.
Me I'd push the calliper off, the pads out, push the pots right back into the calliper [all 4] and dangle it from the bars.
Get a largish 200 ml syringe and a piece of plastic hose that fits snuggly over the bleed nipple.
Brake lever reservoir level.
Take off top cap.
open bleed nipple and pump all the fluid out. maybe catch it in something using tube mentioned above.
Now fill the syringe and tube with new DOT 5.1 fluid, make sure you purge air out [like the doctors do with a syringe on the tele.
Connect it to the bleed nipple and fill the system from the bottom till the reservoir is full, close the bleed nipple and don't forget to roll your diaphragm in to the reservoir lid on and your brakes will be sorted.
Check for leaks at some stage.
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