Caliper rebuild seals

[Matt]

Hi,
I have a caliper with sticky pistons (right side front). The left side still moves nicely but the right will stick when the brakes are pumped up and won't retract properly. It's an '01. I doubt the calipers have ever been rebuilt. I'm 2nd owner. My question is, I've received my seal kits for both of the front calipers (this is a non-ABS bike). I'm not noticing any marks on the seals indicating which side or if there's a bevel on the piston side of the seal as I've seen on other calipers I've rebuilt. I'm only seeing that there is a thick seal and a thinner, grooved, seal. Is there a bevel on either of these seals? How do you tell which way they go in?

 

[Bigmak96]

I don't recall there being a certain way the seals went in when I rebuilt my '94, but it's been a few years!

There is no right or wrong way.
They retract the piston because of their square cross section, they flex forward when the brake is applied, and return to their original, non flexed shape when the brake is released, thus pulling the piston back.
That is my take on them anyway, if I am wrong, I need to know!

 

[Matt]

John, Smash, Mark, thanks for the comments. I was about 90% confident this would be the answer when looking at the replacement seals. I've done plenty of auto calipers in the past and there is a noticeable drop in the number using beveled seals. It's actually getting hard to buy rebuild kits for auto calipers. I imagine that's due to the danger and manufacturer liability associated with customers putting beveled seals in backward (suddenly having your brake fluid go gushing out of your calipers at 60 mph is a little inconvenient). I thought I'd post the question here for a couple reasons. First, these are the first motorcycle calipers I've rebuilt and I wanted to be quite sure I was seeing what I ought to be seeing. Second, since this doesn't appear to be documented anywhere in the service manual for my ST1100 and no directions at all come with the new seals from K&L, I thought it'd be a good idea to get it in searchable form here on this excellent forum and resource.

 

[ST1100Y]

Make sure you get all of the crud out of the seal grooves with something that won't scratch the metal.

+1...
I'd soaked the callipers of the (neglected by PO) '94 ST1100 with automotive wheel cleaner (one rated for aluminium) as advised, rinsed carefully and used a home made 'pick' to get all the sludge out there...
All parts turned out nice and shiny like new out the box (replaced the pistons due some pitting corrosion visible), brakes work again like on a brand new bike.

And I've to agree with Matt's statement that nowadays workshop mechanics don't see much guidance (not that they'd care anyway...) on those basic skills... in today's time pressured world of business their simply reduced to parts exchangers...

 

[Jim Van]

No bevel on the seals that I replaced a few years ago. BTW (FYI) , I remember reading a past post that heating up the "junk" in the seal groove with a propane torch will basically cause the crud/corrosion to flake away without a need to scrap the groove, even with a piece of wood or plastic.

 

[Dinosaurbuilder]

I did my rear caliper seals a few weeks ago, pumped the pistons out and managed to get the seals out ok just cleaned the crud build up from behind them and re-used them with no problem, perfect brakes again.

 

[zx-boom]

No bevel on the seals that I replaced a few years ago. BTW (FYI) , I remember reading a past post that heating up the "junk" in the seal groove with a propane torch will basically cause the crud/corrosion to flake away without a need to scrap the groove, even with a piece of wood or plastic.

This is really interesting, because I just hate that crud, takes an age to get out. Isn't there a risk of melting the alloy? Has anybody tried this?

 

[John OoSTerhuis]

This is really interesting, because I just hate that crud, takes an age to get out. Isn't there a risk of melting the alloy? Has anybody tried this?

My friend George Catt gave us this tip years ago and I have used a small propane torch successfully on my calipers' corrosion. Just use a light touch. Next time I'll buy one of those pocket size butane torches for a smaller flame and better control. FWIW YMMV

John

via iPhone 4S

 

[zx-boom]

My friend George Catt gave us this tip years ago and I have used a small propane torch successfully on my calipers' corrosion. Just use a light touch. Next time I'll buy one of those pocket size butane torches for a smaller flame and better control. FWIW YMMV

John

via iPhone 4S

Thanks for the info, I'll give it a go with a chef's blowtorch next time I'm doing them.
Cheers
Marc