Anyone know anything about disc brakes?

This was the problem I had when using the spacer, rotor came too close to forks. Stupid plastic/stupid everything.

Hey, I'm having a bit of an issue with my shimano road ultegra hydraulics.
I'm changing my heavily worn pads and gone to fit new ones.

The Pistons won't go back in though. They sit out so that the worn pads and rotor fit, but with the new pads, there's no room for the rotor and it's a very tight squeeze to get even the pads in.

How can I get the Pistons back in? This was meant to be a 5 minute job. Ive tried pushing them in with a screwdriver and even bled the system now thinking, no fluid, no pressure to hold the Pistons.

Have you lubricated the pistons? Sometimes they get stuck, so you need to give them a drop of lube.

It's definitely stuck. I read not to use lubricant though as it'll stay in and then go on the pad. What should I use to lubricate it? Without liquid in the system, should the Pistons just go all the way in with no force?

A bit of hydraulic fluid usually does the trick.

with the old pads, it;s best to open it up with a screwdriver before fitting new pads.

As andy quite rightly said, the piston is merely sticky because it been pushed out for quite some time.

Get a q-tip, dose it in mineral oil, clean the piston, pour in the oil if you have to, put old pads back in, and try and pry it back in (old piston mean less risk of contaminating the pads, and easier to push piston in).

if you bled the system with the piston sticking out, you may need to open the port to let some oil out when prying it back into the calipers with a screwdrivers.

IMPORTANT: once it start working, get some isopropyl alcohol and clean it thoroughly before putting new pads back in.

Thanks guys. I'll have lunch, and get going. Great feedback. Much appreciated

Today's post

Ok, so I put the old pads in with the plastic bit in between, added the mineral water and it felt really tight on the brake, then pulled the plastic bit out, squeezed the brake with the old pads still in but nothing in between them and all the mineral water came out the left piston.

Is my brake broken?

shimano brakes use mineral oil

the suggestion was to clean the pistsons that are protruding with mineral oil (this will also help lubricate the pistons)

then push the pistons back (ideally with the pads in so you don't damage the pistons themselves).

finally rinse everything off with isopropyl alcohol so you don't contaminate your new pads with disc brake fluid (mineral oil)

mineral water should not be involved in this process

Is my brake broken?

Give it to a bicycle shop it make it less broken by you.

Sorry I mean mineral oil

Just need to stop pad rattling in calliper and we are done. Oh, want a replacement pad set too.

The latter may bring the former...

I know, which is why I've not bothered to look at it yet. I'll try and buy some spare pads today and learn how to install them when I'm no longer scared to look at my bike.

Easy to replace pads
Even you could do it

Just try not to crack the Pistons ya?

I know, but I've literally not even looked at the calipers yet so I just want to get some spare pads and do it in a lit room before I have to try it with numb hands at the top of a mountain at night in the pissing rain, blah blah.. you get the idea.

L02A or J02A?

https://www.rosebikes.co.uk/article/shimano-l02a-brake-pads/aid:864325?channable=e8467.ODY0MzI1&gclid=CIaA8b_e7c0CFUEaGwodQ8UC7A

I think my calipers are the flat mount RS805 so the L02A appear to be the correct choice.

Any disc nerds care to confirm before I buy another wrong part?

L02A. Check the shimano docs for pad types here.

Definitely the L's but resin or metal?

12 Y8N398010 Resin Pad (K02S) & Spring A
13 Y8N398020 Metal Pad (K04S) & Spring A
14 Y8N398030 Resin Pad (L02A) w/Fin & Spring A
15 Y8N398040 Metal Pad (L04C) w/Fin & Spring

Resin push heat back into the discs so I e always wondered what the point of fins is for them... I'd go sintered if you're riding all weathers and might have some gear on board. Prepares to be told I'm wrong

I like how they work now so I'll just check what they are and use them. I can get fussy later.

Definitely the best solution.

Pulled out the front pads last night. They are definitely resin pads.
14 Y8N398030 Resin Pad (L02A) w/Fin & Spring A

I reckon they could do with another squeeze without the disc in place to take up the slack. I'm just worried they might move too far out. The rattling was the inner pad. It doesn't seem to be held too tightly in place and shakes around.