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Hi all,
I have some oldish XT brakes. The front brake is fine. The back regularly loses all stopping power. I can replace the pads and it’s awesome, but then if I don’t use it for a week or so it loses all stopping power.
Any ideas how to stop this happening? I can’t keep replacing the pads! Is it maybe an issue with the disc slowly contaminating the pads that then oxidise when I don’t use the bike?
I think they are J04c pads (finned XT)
Cheers
Good chance the caliper has a small leak, known issue with Shimano it seems.
Shimano micro leak, if the brakes are over two years old (out of warranty) then bin the leaky caliper as they are non servicable iirc
Replace with another Shimano caliper and play the waiting game on the next micro leak
Or just do as i did and stop buying Shimano brakes, ive had 5 Shimano calipers micro leak over the years before i decided to never run Shimano hydro brakes again
Now run Hope and Sram brakes on my bikes with zero issues in 3+ years
Shimano micro leak, if the brakes are over two years old (out of warranty) then bin the leaky caliper as they are non servicable iirc
Replace with another Shimano caliper and play the waiting game on the next micro leak
Or just do as i did and stop buying Shimano brakes, ive had 5 Shimano calipers micro leak over the years before i decided to never run Shimano hydro brakes again
Now run Hope and Sram brakes on my bikes with zero issues in 3+ years
This ☝️
Has anyone swapped their shimano callipers for Maura?
I like the simple bleeding of shimano levers.
Now run Hope and Sram brakes on my bikes with zero issues in 3+ years
Just for balance, my Hope RX4 caliper has developed a leak.
Clean the disc with paper towel and see if its oily.
You'll see oil on the pads if it's leaking - obvious spots on the back and you can often see a dispersion on the front.
Unfortunately common with shimano - just had to rush order two cheap calipers due to this problem for an imminent trip. When I get back I'll be switching to another brand - 3 or 4 times now for me.
Just for balance, my Hope RX4 caliper has developed a leak.
Just for balance, Shimano leaky caliper out of warranty= no chance of it being replaced for free
Hope leaky caliper(rare)= no problem, Hope will just repair/replace even if its 10 years old! and give you a new set of pads for free most times too!
Let us know what Hope do about your leaky caliper
I have all the symptoms of a micro leak without any actual evidence of that leak.
I would expect any leak to attract an accumulation of dust.
bin the leaky caliper as they are non servicable iirc
There was a thread on here a few weeks ago with a link to repair instructions. Split them in half and replace and replace the o-ring with one a little harder was the jist of it.
Yes apparently it's the transfer port o-ring between the caliper halves that leaks alot rather than the piston seal.
I have all the symptoms of a micro leak without any actual evidence of that leak.
I would expect any leak to attract an accumulation of dust.
Me too, but I replaced the 'o' ring between the caliper halves & added some sealing compound, and it has cured it.
Now a believer 🙂
Which sealing compound and where did you put it?
Which sealing compound and where did you put it?
Loctite 542 (because I had some) - I put the new 'O' ring into the caliper and added a drop of sealer around the outside of it.
I think that the problem with my brakes was that the drilling for the fluid passageway was quite a way off centre to the 'O' ring recess.
New O ring fitted. Happy brakes.
Now to do all the others!
Where did you get the O ring, and what size/make etc was it*
*For the benefit of others.
It makes more sense that it's the transfer port, I assume it can leak slowly onto the rotor. I've never had any evidence of a leak on my m785 XT brakes but they would always be rubbish if I left them for a few weeks unused
Other thread here https://singletrackmag.com/forum/topic/o-ring-for-fixing-leaky-shimano-calipers-2/
Including link to https://simplybearings.co.uk/shop/p20584406/1.5mm-Section-3mm-Bore-NITRILE-90-Rubber-O-Rings/product_info.html
I bought a pack of 50. I haven’t tried fitting them yet (so no warranty) but if any of you DM me your address I’ll post 4 for a dose of karma. I’m away for a few days from Wednesday though so get in quick.
The 90 shore / buna hardness bit is the important characteristic.