Bought a bike for parts but Hope caliper threads stripped

To add to what's already been said, if I'm remembering my engineering things from ages ago correctly 6 threads is all you need to get full strength of the connection there. So that hole that has 6 threads in it already, I wouldn't even touch it.

The helicoil thing is different. Yes you're only drilling out a bit past the 6mm thread, but the tap that you run in next (for the helicoil itself) is gonna eat more of the material around the opening this making the walls thinner exactly as you're concerned about. Not ideal situation I think. That said, the wall of the holes in the fork's brake mount is only 3mm thick at most (I have a Jr T of that vintage so I literally just measured it) and that's a casting so it should have less material strength than the billet chunk that Hope used to mill the caliper, yet it's still sufficient for the job it does.

Personally I'd look into how much space I got between the brake's mounting ears and the rotor. If 2-3mm or more I'd be leaving the holes untouched and I'd be running some class 12.9 bolts in from be back of the caliper with sleeve retainer compound (or high-strength thread locker) in the threads of the caliper, then shaving the hex heads down to 1-2mm thickness. This leaves the caliper mounts wall thickness untouched, and provides you with the peace of mind that no matter how hard you tighten the nuts on the outside of the fork you physically can't pull the bolts thru the caliper's semi-strippped holes (can't rip the heads cause 12.9 is high-strength steel, as opposed to the 8.8 regular mild stuff). Yes you'll need to pull the wheel to remove the brake assembly off the fork, but that's hardly a huge deal plus ain't that Super T already QR20 type with the eccentric levers on the bottom?
 
If there is enough clearance use pan head bolts fed through from the rotor side, then put a nylock nut on the other end.
 
My solution has been to buy another caliper.

This one was cheap on eBay as spares or repair due to chipped pistons. It looks to be in very good condition and the threads are good, next step is to strip it down

20220523_164945.JPG

The good thing is the inner pistons are sitting proud so I can get them out relatively easily. You can just about see some the chips on the pistons.

20220523_164958.JPG

Bore caps off and greeted with all this gunk.

20220523_170226.JPG

Get all the pistons out and find more gunk in the bottom. I have no idea what it is.

20220523_171653.JPG

With the seals removed and the caliper dry I can see that some of the gunk is really hard, and in the threads of the large bore it looks like there's the remains of some sealant. That might explain the gunk, so this caliper must've been stripped before. Behind the seals is also some of the dried gunk which I've managed to clean out. So it's all stripped down and pretty clean.

20220523_172541.JPG

I'll wait for some new seals to turn up before I strip down the other caliper and decide whether the other pistons are OK to reuse.
 
Just that bit of cleaning and it all looks so much better.
Might I suggest(if not already owned) you buy a small tube of Hunter brake lube. This is the one hope recommends. On the O rings and smothered onto the piston sides prior to sliding them in.

Also. If you get a new toothbrush, trim down the bristles, it works wonders for cleaning in the Oring seats. Grime that gets in has a habit of sitting tightly in those recesses and a toothbrush, solvent does well to make sure you get it all out. It I feel is an important job because you cant really easily see into them.

Said Lube
https://www.ebay.co.uk/itm/23454086...MIg9bokLr29wIVc41oCR1DIQN1EAQYASABEgLQ4vD_BwE s-l1600.png
 
When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Just that bit of cleaning and it all looks so much better.
Might I suggest(if not already owned) you buy a small tube of Hunter brake lube. This is the one hope recommends. On the O rings and smothered onto the piston sides prior to sliding them in.

Also. If you get a new toothbrush, trim down the bristles, it works wonders for cleaning in the Oring seats. Grime that gets in has a habit of sitting tightly in those recesses and a toothbrush, solvent does well to make sure you get it all out. It I feel is an important job because you cant really easily see into them.

Said Lube
View attachment 629948
Cheers for the tip.

I have got some of that lube left over from the last caliper rebuild and I need to go out and buy so cheap toothbrushes just for cleaning bike bits.

Even with that gunk behind the seals it looks like it wasn't leaking from the pistons which was a surprise.
 
Rebuild complete, a few years ago I'd be scared to do this job but it's actually very simple. I like that hope still support some of their old products. The pistons of the damaged caliper were in very good condition so I reused them. Had some ti bolts off an old cross country bike so they'll help tart it up a bit. Now all I need is a downhill frame to put them on.

20220619_132710.JPG
20220619_132741.JPG
20220619_132826.JPG
 
Rebuild complete, a few years ago I'd be scared to do this job but it's actually very simple. I like that hope still support some of their old products. The pistons of the damaged caliper were in very good condition so I reused them. Had some ti bolts off an old cross country bike so they'll help tart it up a bit. Now all I need is a downhill frame to put them on.
Came out looking real good!

As for a DH frame, couple nice ones for sale on here, I was actually planning on grabbing both of them but damn unexpected expenses ruined my fun there ugh!
 
Back
Top