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OK, I've got a front and rear set of 2010 Deore brakes. The bike was left in a shed for a couple of months when something newer and shinier came along, and when I returned to the bike both brakes were squidgy.
I bled the brakes per the instructions (down from lever to caliper until the bubbles stopped at both ends), and performance returned albeit temporarily. However, leaving the brakes for any more than around ten minutes returns them to softness. Given that this happens on both front and rear brakes, is it likely a technique thing leaving air in the system or are my brakes goosed?
The Avid Juicys that were in the shed at the same time are fine, and similarly I've never had any problems with another, far older, set of Shimano brakes - 7 years old and never bled.
sounds like seals failed. Unusual to be both at once tho
I thought as much TJ - strange that both would require a bleed at the same time in the first place.
all a bit odd tho
er, check that the hose connections are tight?
and bleed from the bottom up (with a syringe attached to the calliper) - with the calliper unbolted from the frame/fork so you can hold it / let it dangle in such a way that the air can escape more easily.
I take it you used mineral oil?
Hose connections were and are tight.
It is mineral oil I'm using 😀
sounds like seals failed
disagree.
If there are signs of leaks around the pistons, then perhaps.
More likely there is air still in the line. Much more reliable bleeding from caliper to lever. Load a syringe with new oil, set lever reservoir level and take the lid off, progressively inject fresh oil at the caliper while sucking old oil out of the top with another syringe and dispose. I sometimes flick the line/tap the caliper a few times as I bleed to make sure there's no bubbles clinging on. Fill until you think youve purged old oil and bubbles, leave reservoir full. Tighten nipple back up. Bingo.
stoner - if there is still air in it would it do this "performance returned albeit temporarily. However, leaving the brakes for any more than around ten minutes returns them to softness."
Just asking like cos I would have thought they would either be spongy or not?
when I first got shimanos and bled from the top (three times before switching to the [i]vox populi[/i] preferred method of bottom up) I had similar symptoms which I put down to a bubble at the calliper that couldnt be bled out from the top, but could from the bottom with agitation. I suspect a bubble could be in a number of different locations between the calliper and the reservoir and effect performance differently at each.
it certainly would appear odd for them both to develop a fault at the same time
calliper unbolted from the frame/fork so you can hold it / let it dangle in such a way that the air can escape more easily
just read this by ahwiles. Similar idea to agitation. I also rotate the bike in the workstand to similar effect. I think there's an inflection in the oil route in/at the caliper which can cause problems.
A bottom up bleed works for me. When I first bled my M595s I did a top down (as I used to with my M585s), it worked for the front but not the rear. A bottom up bleed didn't seem to cause any problems at all.
Regarding the OP's situation though I can't see why air in the system would only begin to cause a problem after 10 minutes. It could be a leak but if the seals have gone I'm sure someone would have spotted the oil by now, it's a fair amount to leak out.
Just bled my new saints yesterday using the syringe at caliper method.
Definitely the simplest bleed ever, almost a pleasure.
stoner - if there is still air in it would it do this "performance returned albeit temporarily. However, leaving the brakes for any more than around ten minutes returns them to softness."
There has been air in my saints since I bought them, I pump the lever 5 times and the brakes are fine for a day.
...if there is still air in it would it do this:"performance returned albeit temporarily. However, leaving the brakes for any more than around ten minutes returns them to softness."
?
Just asking like cos I would have thought they would either be spongy or not?
it's weird, but it happens.
i shortened a hose and didn't bother bleeding the brake after - sometimes you can get away with this.
obviously i let some air into the system, because the brake was very spongy, but if i squeezed the lever a few times it started working nicely, only to return to sponge after a few minutes.
i bled the brake (with a syringe), out came a load of bubbles.
odd.