I'm bleeding my new GRX820 rear brakes and I don't have this spacer. Yes, I should probably buy it, but I did my front brakes without it (using two old brake pads from another bike and the thin spacer that came with the brakes) and they're working perfectly with a good amount of lever travel and no spongeyness. I can't get the back brakes right, though.
Is the idea that, when adding the oil/bleeding the system, the pistons do not move out from their depressed position at all? So your spacer needs to be the full width of the space between the depressed pistons?
by the68thdimension
9 Comments
Two small wood wedges, one from either side, so they expand and provide even pressure on the pistons.
Literally anything that fits. Small bit of wood, shim if required.
Keep it simple.
Once or twice I used a larger allen key (8 or 10mm) stuck in the caliper and it worked perfectly. That being said, bleeding hydraulic brakes is a normal maintenance thing and you end up doing it often enough to totally justify buying the correct tools for the job.
>Is the idea that, when adding the oil/bleeding the system, the pistons do not move out from their depressed position at all? So your spacer needs to be the full width of the space between the depressed pistons?
Yeah, that’s exactly right.
>I can’t get the back brakes right, though.
It’s often the rear brake that’s trickier as it’s less likely to be a straight up/down hose run, and a longer hose too. Look to angle things so there’s as much vertical run as you can manage, and/or it can be worth preparing ahead and leaving your bike front-wheel up overnight before doing a bleed too.
I usually just string 2 or 3 plastic tire levers together and stick them between the pistons. Works great for me.
A lot of new bikes come with bleed blocks, and the shop throws them in a bin. Stop by your bike shop and ask if they have any spares. They might charge you a $1 or so.
There’s a bunch of wedges you can 3d print. You can also buy a disc brake piston tool on Aliexpress that works for $10-$20. SRAM makes a universal bleed block that’s really handy.
You don’t need a spacer. It’s to stop accidental lever pulling.
Just make sure the pistons are pushed in all the way.
Almost anything will do you there, last I did this I put a flat blade screwdriver in the gap, it’s only real purpose is to stop the pistons coming out too far