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I have an old Magura Julie disk brake. It seams that new pads are too thick for the brake. I already tried 2 different types. But when I insert the new pads the gap between the pads is completely closed. There's no gap left for the disk.
Re-inserting the old pads is no problem.
Are there brake pads with different thicknesses?
Did you push the pistons back into the callipers?
Hydraulic brakes automatically adjust for pad wear and the home position of the pistons moves slightly out. When you change pads you need to gently push the pistons back in gently with something like a plastic tire lever to return the fluid to the reservoir, then pump the lever to set the correct level of adjustment for the new pads.
I solved this by inserting the new brake pads even though they were pressed together tightly, then twisting a flathead screwdriver between the metal outer edges of the pads, forcing them apart a bit. Then I used the small gap between the pads to wedge a big flathead screwdriver between them (carefully), which completely pushed them apart and reset the calipers. This was the only way I could get enough leverage to reset the calipers with limited tools, even though the screwdriver does slightly damage the resin on the pad. Wasn't an issue for me.
Are there brake pads with different thicknesses?
No. You need to reset your pistons before installing the new pads.
Use one of the old worn pads as a spacer between the new ones. Push them in between the caliper and pull the brake lever a few times they will adjust and you can drop the assembly back on.
When you replace the pads, the pistons are self adjusted to the thin worn pads. The new thicker pads will not fit before you push the pistons back.
I use flat scewdriver to push the pads back before removing them (slightly rotating). This damages the pads but who cares about the worn already pads we will trash immediately after removal?
There is also a special "piston pusher" tool for this.
One possibility where this can happen is if someone has bled the brakes without inserting a bleeding block between the pistons. With new pads and disk between the pistons, in theory you could bleed the system without the bleeding block. However, if you bleed the system with old pads and disk between the pistons, the system becomes overfilled with brake fluid, and you are never able to install a new set of pads anymore, unless you untighten the bleed port screw on the levers, and push the pistons in with the bleed port screw removed.
Warning: pushing the pistons in with the bleed port screw removed will be messy, brake fluid will leak out from the levers.
