Brake piston spreaders

@cord thanks, I’ll try those for £5. Cheers

SRAM specifically say not to lube the pistons as it actually prevents them retracting properly rather than helping.

It also enables dirt to get past the seal and causes damage to the seal

I’ve never heard that before. Drop of brake fluid worked in and wiped off has always kept mine working lovely. Totally standard practice ime. Never had a seal fail or piston stick.

I’ve never heard that before

Says it in the manual innit..

I’ve ordered a Sumart from The Cornish Bike Mechanic. Quite possible that is what I’d seen an ad for as mentioned in my first post.

As b33k34 posted I can’t help but think the Sram type could put uneven pressure on at least one piston side.

SRAM specifically say not to lube the pistons as it actually prevents them retracting properly rather than helping.

It also enables dirt to get past the seal and causes damage to the seal

So, it doesn’t “really” say that. They probably don’t want numpties getting oil or grease on the rotor or pad. Or leaving a sticky mess that dirt will stick to.  Or using the wrong lube and knackering the seals, etc, etc.     Same debate regarding forks: if you know what you are doing, then go for it. If not, then leave alone 🙂

So, it doesn’t “really” say that.

Eh? It quite literally says in a highlighted section “Do not apply DOT brake fluid or grease to caliper pistons”.  Clarified further by saying it may cause rotor rub. It repeats this elsewhere in the manual and a SRAM video I’ve seen explains that the piston isn’t supposed to move in and out past the seal during braking but rather the seal itself flexes in order to draw the caliper away from the rotor.

This is a technical manual not ham fisted amateur guidance so I very much doubt they say that just to prevent overspill.

Anyway, you do what you think is best obv. I’ll follow the manual.

@oceanskipper you are 100% right

The Sumart one is in this week’s Fresh Goods Friday which links to a UK seller, which looks like it’s a website of the Cornish Bike Mechanic.

 

I went right through to checkout with one of those Sumart tools (clicking the link for STW goodness) but then pulled out as it’s a lot of money (for me), if I was still working as a bike mechanic I would buy one, however, now I’ve got time to work more slowly and only on my own bikes I’ll stick with the Shimano tool I have. I’m not saying that I will never buy one, it’s a desirable tool in my “cheer myself up” wish list!

The Sumart one is in this week’s Fresh Goods Friday which links to a UK seller, which looks like it’s a website of the Cornish Bike Mechanic

It says its designed specifically for 2 piston calipers so will be of limited use for most brakes these days

Wouldn’t you just push back two at a time?

Wouldn’t you just push back two at a time?

It’s a bleed block as well so if it only works on 2 pistons its no use for any of my brakes, definitely not worth £40 when a tyre lever will push the pistons back perfectly well and I already have some

Okay, I wasn’t intending to use it as a bleed block, just wanted something to push pistons back evenly without damaging anything. Tyre levers ain’t up to the job sometimes.

Ok. Thanks. I stand corrected. I’ll still continue to pump out the pistons and clean with dot fluid before pushing them back in. I’d rather have the pistons clean and smooth rather than dragging dirt into the seals. But I hadn’t considered that the seals flex to return the piston during use. In reality, the way I do them probably leaves very little lubrication on the piston as I push them (easily) all the way in this the clean and flexible seal wipes the fluid away. Then I wipe again.

Again, thanks for explaining. Excellent stuff ?

That question mark is supposed to be a thumbs up

Another thumbs up emoji…. ?

The trick is to clean with isopropyl alcohol rather than DOT fluid/mineral oil/ silicon etc I think, as DOT etc will actually do what you are trying to prevent ie dragging dirt past the seals…