Koyote

I’m installing a new set of disc brake pads in these Ultegra brakes: exactly the same as the old pads. L03A. I’ve done this before with no problem. But this time, when I slide the pads in, they are pretty much up against each other - with no room for the rotor in between them. And no, I did not grab the brake handle while the wheel was off… And I have checked to ensure that the backing plates are completely separated, pushed as far outward as possible. Any ideas?

Barry2 

Push the piston back into the caliper.
IIRC, my pistons go almost flush with the caliper face.

Barry

Koyote

Did that already. Still too little room between the pads to even get the wheel back on — rotor will not slide between them. Rode the bike 40 miles this morning with the old pads, working perfectly. Now with new pads, can’t even get the wheel on.

Barry2 

OK then, I measured a new pair of L03A pads and they measure 4.03mm thick.
That's the pad and the backing plate together.

What cha got on yours?

Barry

Crankycrank

You might have to bleed a little fluid out to allow the pistons to retract all the way.

Barry2 

Or with the bike upright and the reservoir cap open, push the pistons back until the oil stops dripping on the carpet!

Barry

Polaris OBark

If you or someone bled the brakes with worn down pads and/or rotors in place, or decided to slightly pressurize them at the end of the bleed to get them nice and firm (NTTAWWT), this can happen with new pads or new rotors, and in my case nearly always does when replacing both simultaneously.

Polaris OBark

There is also a newer, less expensive version of this, that looks like a piece of rotor.

Barry2 

I'll see your fancy park tool, and raise you a multipurpose tool.

Koyote

Barry, I spoke too soon – – I pulled the pads back out, got in there with a plastic tire lever, and pushed like hell. Did manage to move the pistons back a bit more. They’re all good now. So, you were right! Thanks for the assist.

That’s a little embarrassing. I have done this, many times, and never had that experience.

Barry2 

We expect this kinda behavior from noobs!

Welcome to Bike Forums!

Barry

cxwrench , WHERE ARE YOU????
Come kick him while he's down!

cxwrench

You should always clean/lube the pistons before pushing them back into the bores. Mineral oil for Shimano.

Koyote

Noted. Thanks.

Barry2 

Koyote ,
Glad you got your pads squared away. (and your leg pulled a little)
I had to fight mine last time. Hence the new brake tool. Can't wait to actually use in in anger.

All the best

Barry

Koyote

Even though a plastic tire lever works just fine for me, I'm always looking for am excuse to buy a new tool. You guys are not helping.

Polaris OBark

You will be happy to know I just reproduced your problem.

Koyote

Polaris, found this on the product page for that tool:

NOTE: Wedge-style piston tools, such as the PP-1.2, are not intended for use with brake systems that utilize ceramic pistons, such as Shimano road disc brake calipers."

Guess it's not a good idea for my Ultegra calipers...?

Polaris OBark

Huh.

I never saw that before. I have ultegra and XT pistons, which I think are ceramic. (Not sure about that, either.)

The way I use them is to leave the pads in and I jam it in between the pads.

I used to do it with a broad screwdriver, but that was more likely to scratch the pad surface.

I wouldn't apply the tool directly to the pistons. Even with a plastic tire lever, you have to be really careful. I keep old pads so I can indirectly press on the pistons through them.

Polaris OBark

Maybe the new one is safer? https://www.parktool.com/en-us/produ...-spreader-ps-1

Barry2 

Edit: below is my procedure, a mechanic here in BF claims you should not press directly on the ceramic.
That’s not a bad rule, a sharp edge on the retraction tool would cause an excessive pressure point on the ceramic.
——————-
It's not pressing on the ceramic directly that's the issue.
It's trying to retract the pistons from one side/edge.

You can force the piston to become crooked in the bore and chip the ceramic.

Barry

cxwrench

I replace pads in Shimano calipers w/ ceramic pistons daily. If putting the 'pad spreader' between the old pads doesn't work I remove the pads, clean/lube the exposed pistons and then push them back carefully w/ an 8 or 9mm combination wrench. At this point I have not ever broken a piston. Of course the important words here are 'clean, lube, and carefully'.

Polaris OBark

For the record, CXWrench is the one who got me to quit using a large flat-blade screwdriver between the pads while I was ahead. The pad spreader definitely works better. (I've never had the joy of a pad that was stuck.)

Koyote

I guess I've been lucky: I typically remove the pads, then use a flat-blade screwdriver to push back each piston, or sometimes a plastic tire lever directly on the pistons -- I kind of use one piston as a fulcrum to press against the other. I haven't broken anything, but will definitely do it differently next time.

Polaris OBark

My kid cracked one of his pistons using a screwdriver. I think it was a ploy to loot all of my tools before he went back to college.

NoWhammies

I thought the pad spreader was not to be used on road bikes with ceramic pistons. Am I incorrect in this?