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I've just swapped out my ancient LX and Deore disc brakes for a new SLX set. I'm fairly ham fisted so cutting the hoses (with the intention on not needing to bleed afterwards) was a little more protracted than it might have been. One issue I had was that although the olive for the front brake came perfectly dry I didn't spot that the olive for the rear brake was full of grease which I then had to wipe off the hose/insert; it's possible that the cloth could have drawn out some mineral oil.
Everything is set up and both brakes pump up nice and firm but there is always the possibility of a bit of air in the system. It used to be suggested that zip tying the levers to the bars overnight would pull any air into the reservoir.
If I did this could I top up the system using the cup tool? I've got a bottle of Shimano mineral oil (that I've had for years) so the fluid is like-for-like but would mixing it with the fluid in the new SLX brakes be a problem?
Should be fine
You'll need to open the bleed nipple to get things moving.
Tim
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You'll need to open the bleed nipple to get things moving.
Not actually the case. For a quick lever bleed (which would hopefully be all you need after trimming the hoses) you just need the cup on top of the resevoir.
Anything more protracted and you will need to start getting the bleed nipple involved too
How's that work then? It's a sealed unit isn't it?
Maybe squeeze the lever gently to force the air out insuring a bleed block in the calliper?
Yeah, just put the funnel on, fill halfway with mineral oil, and flick the lever until bubbles stop coming out. If you read through the official bleed instructions you're just doing the last step. Either put a bleed block in the caliper, or for a really quick top up you can leave the wheel in.
Not a permanent fix, but it should solve your problem. I'm guessing holding the brake leavers on overnight should put most of the air in the lever and make it easier, but I've never tried that.
timbur - MemberHow's that work then? It's a sealed unit isn't it?
Nope, the screw in the top is access straight into the resevoir.
If you've got Shimanos that work well (see other threads) sometimes you can actually bleed them really well just by attaching the funnel (with fluid in it) and repeatedly pumping the lever until you stop seeing bubbles. As raisinhat mentions, it's the finally step in all the bleed techniques anyway. If you've got air in the caliper you'll be there a llloooonnngggg time of course!
Interesting. Today was a school day. Normally I just re-bleed them as it's so easy.