I need a new master piston for my BL-M9020 brakes. The only place I can find them is ebay from China, but I want the bike back on the road for Friday!

I’ve tried some of the usual suspects (swinnertons, bikeparts.co.uk, I’m sure there is a webshop marketed towards female riders that stock small parts too but if anyone can jog my memory?!)

I don’t know what I’m searching for as I can’t find a parts diagram, does anyone know the part number or where I can find a parts diagram? (couldn’t see one on Shimano’s website) My brakes are M9020 but I bet pistons from various other M9000 series brakes would fit…

Good luck finding any Shimano brake spares even with lots of notice never mind needing them urgently.

If you need it back on the road for Friday then a new brake lever is going to be your best option I think

I want the bike back on the road for Friday!

I would just buy whatever cheap Shimano lever I could find to use in the interim. The levers are compatible, you just need to make sure the hose fittings are.

Thanks, probably good advice! Someone must have sold them aftermarket at some point as I found a diy guide where the replacement piston used was ‘drilled out for weight saving’! but the ones from china don’t appear to be drilled!

The piston was so stuck I used a syringe on the line to pop it out of the calliper, took a lot of effort and then it escaped the rag, bounced off the door alot with a load of black gunk, and is now somewhere at the back of the garage! Would be nice to check the dimensions against the ones on ebay!

I’ve always found sjscycles.co.uk to be really well stocked when it comes to Shimano spares.

Yeah. SJS is your best shot, but Shimano are not good with supplying brake spares generally

I had a look for this very part last night so I can confidently say you need to go look harder in the garage and clean it up. There are indeed some titanium replacements available but you won’t be getting them this week.

Mine got a decent dose of looking at and an extensive flush through with fresh fluid to try and stop it sticking. Something’s still not quite right but it should do fine.

I’ve now found it! I don’t really get it, I’ve wiped out the bore and lubed the seals with mineral oil, the spring is clean and just trying to cycle it back and forth with hex key it constantly sticks, after a few minutes of fiddling I managed to get it to extend properly.

Had a feeling there was an issue as it didn’t seem to be adjusting the pistons out properly last time I bled it, and both levers go a bit floppy if I leave the bike in the sun. Yesterday I pushed the pistons back just before riding due to a bit of minor rubbing, the lever just went completely floppy.

Stab in the dark…I used LHM+ fluid when I serviced them. Any correlation with others who have had issues? And is there anything else I could try to free it up without further damaging the seals, silicone spray?

I used LHM+ fluid when I serviced them. Any correlation with others who have had issues? And is there anything else I could try to free it up without further damaging the seals, silicone spray?

I would wash it in hot water and dish detergent, then rinse it in very hot water and blow dry it, then use Shimano fluid to lube it before reassembly.

The only time I’ve had issues with Shimano seals is when they’ve had Halfords LHM fluid in

the m9020 trail brake ? doesnt look to have an exploded diagram,
difficult to find unless you go via all m9000 components.
https://bike.shimano.com/en-EU/product/component/xtr-m9000.html

theirs been a few of these levers popping up on evans cycles for £22 / full brake £66
in recent weeks.

The only time I’ve had issues with Shimano seals is when they’ve had Halfords LHM fluid in

Genuine question, why do people do this?

Because it’s cheaper than Shimano mineral oil.

https://www.paul-lange.de/de/service/downloads/explosionszeichnungen.html?file=files/01_Paul-Lange/07_Service/04_Downloads/Shimano/explosionszeichnungen/BL/BL-M9020-3781A.pdf

Here’s the spare parts diagram for that lever. No internal parts supplied by Shimano.

Because it’s cheaper than Shimano mineral oil.

Thanks.

And also Shimano fluid was out of stock for a large part of the last 2 years.

I’ve always found that Shimano brakes are pretty much disposable. I’ve never been able to find individual replacement parts over the years and had to buy a new brake each time and then mix/match parts from there. It’s one of the reasons I stopped using them as I felt it was a waste when other brands will sell you the individual brake components.

That and the wandering bite point eventually annoyed the hell out of me.

Mister-P

Because it’s cheaper than Shimano mineral oil.

Not in the long run.

thisisnotaspoon

And also Shimano fluid was out of stock for a large part of the last 2 years.

Think I paid over £30 for a litre off eBay during the drought. Definitely was scarce and not cheap.

Have you checked the exploded diagram for the M6100, does it have the same part?

Slight waste of £30 if you only need one part, but might be the quickest and cheapest way to get you riding by the end of the week.

Or just swap the whole lever over until parts arrive from China, functionally all shimano brakes seem to work the same so you won’t notice unless you look at them.

grrrr…still hard to get hold of!

Ebay is full of sellers decanting 1 litre bottles into unbranded bottles (or selling for £70) and I’m not paying £90/litre for a little 100ml tub!

This is the problem I had last time, might just have to order a bottle from Europe! Last time I only had one set of mineral brakes (and I think they were already sticking hence the first bleed, so I’m not sure it was the LHM) but now we’ve 4 sets of Shimano.

@thisisnotaspoon

Thanks for the heads up, a bit of research required I think as apparently the way to disassemble the XTR lever is completely different to the other models (not sure if true or not).

@spooky-b329 – I have some Shimano fluid, if you need it.

P.S. remind me to stay behind you, on Friday (and have the camera running, for YBF potential) 😉

spooky_b329

Thanks for the heads up, a bit of research required I think as apparently the way to disassemble the XTR lever is completely different to the other models (not sure if true or not).

It’s certainly tricky. The worst bit is getting the tiny pin out that holds the piston stop. I’m aware it’s quite a neat design and probably fine to assemble in controlled dry conditions but as a greasy, 1/2 disassembled caliper, it’s a nightmare. I didn’t bother in the end as I could tell it was only going to end one way and simply flushed mine through with fresh oil a few times and will hope for the best.

Best of luck @spooky_b329

Spooky, if the old piston is sticking i.e. the outer diameter is effectively too large and it definitely sticks and you’re at the point of hunting for a new one then you have nothing to lose so try cleaning up the master piston, any seals off, pop it on some time foil on an oven tray and shove it in the oven at 50 degrees for about an hour.

I can’t remember if I did 50 or 100 degrees but 50 is probably a better starting temperature, it was back in early 2020 I had to do it, and I’d found a post or video else where about it. Got my slx working perfectly and stayed good for at least the next 18 months. Still have the spare slx lever I bought but was delayed hence the oven trick, but don’t have the bike anymore…

The idea being the plastic has absorbed mineral oil and swelled, heating allows it to evaporate and shrink slightly as a result. It’s only a tiny amount of swelling that causes the sticking as tolerances are so tight normally.

Basically if it’s borked, you have nothing to lose, so why not give it a go

Edit: this assumes the master piston is plastic on the xtr similar to slx and not metal or some such

That’s interesting wibble, I was about to point out its plastic (unlike the Chinese replacements which are apparently ti alloy.

I just put it in the bore backwards slightly to check the head wasn’t too large/mushroomed, I’m going to clean it with some AC-90 which I’ve just checked is mineral based, if it’s still sticking I’ll try and get the two rubber seals off and bake the piston!

The worst bit is getting the tiny pin out that holds the piston stop.

I’m finding a bradawl makes short work of the pin… Unlike the massive decking screw and assorted nails the guide recommends! (this being the second time I’ve stripped it)

Bob, no panic, I can swap bikes for Friday, but it’s a bit annoying that the singlespeed is out of action with SSUK coming up, I should be ramping up the rides to the coffe… training right now 😉

PS managed to get a litre of Shimano magic red fluid from bikester for £25 posted, 10 day delivery window though! I’ve got about 50ml of some fake Shimano oil though.

Well, it’s now moving a bit more freely but with a notchy resistance. I think one of the seals is folding back on itself as the piston is pushed in, and then when it returns it flips back. That’s what it feels like anyway.

Just went and got some spray silicone after seeing it on a maintenance video (wanted grease but can’t find it in a local shop) and the piston is feeling better, still suspect the lip of the seal is flipping over but I’m wondering if that’s by design to give the lever a positive feel.

Progress, hopefully!

wanted grease but can’t find it in a local shop

Try screwfix/toolstation/DIY sheds for plumbers grease or dielectric grease.

still suspect the lip of the seal is flipping over but I’m wondering if that’s by design to give the lever a positive feel.

Lip seals only seal one way, so sounds more like it’s binding where it should be sliding .

I’ve used spray silicone to test it, proper grease coming tomorrow courtesy of Amazon. Just tried those alternative terms on Screwfix, no luck.

There are two lip seals (I presume they are lip). Resisting the urge to put it back together until I have proper grease 🙂

Well silicone grease seems to have fixed the returning lever issue and the piston is moving smoothly 🙂

Clearly mineral brake fluid isn’t sufficient to keep the piston moving! I’ve managed to bleed it with the 50ml of remaining fake shimano brake fluid (came with an Epic bleed kit) and got a firm lever, I’m sure I can get a better bleed when a new bottle turns up as I didn’t really have enough to cycle the fluid back and forth at each end.

Thanks for the suggestions!

Update…after my extra brake fluid turned up I rebled the brake and it’s never felt so good. Did a few rides and decided it wasn’t going to suddenly fail so I decided to do the other brake this evening (same symptoms but not as bad, but I know when I need to change the brake pads it will give up)

Well, I took the brake apart about 4 times during several bleed attempts, finally I managed to get the master piston to return reliably but not before sanding the bore with 3000 grit, soaking the piston in brake fluid, some silicone grease, and then cycling it back and forth whilst spraying with aerosol silicone lube from both sides of the piston.

Massive pain in the backside so I’ve now ordered replacement XT pistons from eBay (apparently they are compatible with XTR) for £20…