Vapour blasted calipers

[crogthomas]

Considering the age of the bikes on this forum, there must have been a significant number of people who have rebuilt brake calipers. I recently got a pair of averagely crusty F2 YPVS calipers vapour blasted and am trying to decide if they are good to reassemble.

They were blasted by someone I trust to do a delicate job, but the surfaces of the areas where the half seals fit appear to be much rougher than I would expect to seal properly. The main joining faces were similar, but I have flattened them with abrasive paper on a flat surface.

My gut feel is that I need to spot-face them back to a smooth surface, so that they don't piddle brake fluid all over the floor the first time I use them. Has anyone encountered similar?

20230419_131643 by crogthomas, on Flickr

[lcmarky]

I would for sure & I'd machine the face too assuming you can get a datum from the outer surface. If you take the same off from both operations the original square section O Rings should be fine too.

[midlifecrisisrd]

In an ideal world yes clamp them flat then just remove enough to clean up the face then as said skim the whole face to keep the recess depth the same

In reality I think if you stuck a fresh seal in there it would be fine as the rubber will deform into the defects

Steve

[crogthomas]

Thanks gents (or ladies, who's to tell?). I think in the back of my mind I was hopeing that someone was going to say, they're all like that, just stick some new seals in. But I think the only sensible thing to do is to machine them properly. Not quite the quick rebuild I was hoping for.

[JonW]

To be honest just sealing them with new seals would probably be fine, but I understand wanting to do things as well as you can before you accidentally ruin something else cos of a leak later.

[midlifecrisisrd]

I'd have just rubbed the pitting down with wet and dry and slapped it back together 🤣

Steve

[crigar]

This is a vital safety feature ! Is it possible to find used calipers in excellent condition at an affordable price in the UK ? Personally, I would not dare to refurbish them, but that's just me.

[midlifecrisisrd]

Age certainly changes opinions on these

Remember ack in the day I fitted new lines to my gpz750 turbo

After bleeding I tightened the nipple on the anti dive unit and the alloy split right down the side

Needed the bike, never had ebay back then so tightened a hose clip around the bleed nipple housing and nipped it up 😬

Rode it for weeks like that before I found a replacement 🙊

Brakes were poor enough without bodges

Steve

[alankelly]

I think to refurb will be fine

Pitting looks light so as other have said I just stick them on a mill and touch up the seal face with a correct size slot drill (to create a clean flat seal face) and then skim top

Don’t think you would be removing move than about 8 thou in old money (0.2mm) and the only change would be a slight closing up of the disc “clearance gap” by 0.2mm when the caliper was assembled

Just my thoughts

Best wishes Al

[jon]

As we know, upper and lower crankcases are machined as a matched pair.

Do people think caliper halves are in some way? If not I bet there’s loads of those going spare. Might even have one myself.

Jon

[crogthomas]

I'm certain they are not matched in any way. There would be no need for precision alignment between the halves.

I did note that each casting has letters to indicate which position it goes in, (F)ront, (L)eft and (R)ight, plus (F)ront, (C) presumably for centre? What I can't understand is how the centre halves are any different to the rear caliper, so why are they marked (F)ront? I don't have a rear one to hand.

The pictured caliper wasn't what I would even call in particularly poor condition, just old. The one below was from the same set:
20230121_100901 by crogthomas, on Flickr

I stupidly didn't look too closely at the surfaces before sending them for blasting, but there must have been too much corrosion. Perhaps this is a good excuse for a set of blue spots?

[midlifecrisisrd]

Is the bleed nipple not in the opposite end on a rear

Steve

[crogthomas]

It is, but the inner half, next to the wheel is identical as far as I can tell.

[crogthomas]

Apr 20, 2023 18:21:43 GMT 1 jon said:

As we know, upper and lower crankcases are machined as a matched pair.

Do people think caliper halves are in some way? If not I bet there’s loads of those going spare. Might even have one myself.

Jon

If you do have any, I'd certainly be interested. It would get the bike up and running quicker than me faffing about for ages getting the machining done.

[jon]

Apr 22, 2023 8:59:52 GMT 1 crogthomas said:

Apr 20, 2023 18:21:43 GMT 1 jon said:

As we know, upper and lower crankcases are machined as a matched pair.

Do people think caliper halves are in some way? If not I bet there’s loads of those going spare. Might even have one myself.

Jon

If you do have any, I'd certainly be interested. It would get the bike up and running quicker than me faffing about for ages getting the machining done.

Is it just the one you’re after?

Jon

[crogthomas]

Apr 22, 2023 9:36:59 GMT 1 jon said:

Is it just the one you’re after?
Jon

I'd need both Left and Right outer halves, i.e. the parts with the fork mounting lugs on. I can salvage the inner parts easily enough, because they are completely flat with no recess for the seal.

[jon]

Apr 22, 2023 10:08:27 GMT 1 crogthomas said:

Apr 22, 2023 9:36:59 GMT 1 jon said:

Is it just the one you’re after?
Jon

I'd need both Left and Right outer halves, i.e. the parts with the fork mounting lugs on. I can salvage the inner parts easily enough, because they are completely flat with no recess for the seal.

I’m confused? You show a picture of an outside half. Above you mention you want both outer halves, with the fork mounting lugs on. The lugs are on the inner halves.

Jon

[crogthomas]

No, the mounting lugs, bleed nipple, banjo bolt and the seal between the halves all go on the 'outer' half. My picture in post #1 is not very clear, but you can just see the mounting lug at the bottom of the photo.

[crogthomas]

I decided not to use these calipers. However, since I already had the rebuild kit handy, I decided to build them up and test them. Sure enough, with a firm squeeze of the lever, brake fluid started seeping out of the join between the halves. Not a gush, but enough that I wouldn't get more than a few miles before running out of fluid.

I'll put them in a box to possibly fix them properly at a future date. Got some 45mm piston V-Max calipers instead, which bolt straight on, but are equally crusty. Lesson learnt though, I'll not be blasting these ones.

[JonW]

Good update, glad you didnt use em.