Bought a bike for parts but Hope caliper threads stripped

[Roasted]

I've been looking for a set of Hope M4 brakes for a DH build and saw a bike for sale at the local bike park that had a set, and it only cost £100, what a bargain!

The bike is a 2001(ish) Saracen Havoc, a budget bike back in the day, but had front and rear M4s, Marzocchi Super Ts, Hope Front Hub, Truvativ Hussefelt cranks, Blackspire chain device, Kore Stem, Truvativ Seat post and Truvativ Bars. So not a collection of cheap parts and not really worth putting on that frame.

The only 2 problems that I've noticed is the wrong axle for the fork and the threads stripped in the front caliper. It's really annoying about the caliper as the brakes look like they're in excellent condition with barely a mark on them.

Anyway, has anyone tried to fit helicoils to a caliper? I've seen people mention it but not seen any pictures of it being done. There's not much meat on them so I'm a bit worried about seriously weakening the mount.

 

[mdvineng]

Hope Mini - Stripped Caliper Thread

I've managed to be a colossal helmet and strip one of the caliper threads on my Hope Mini. It was 100% my fault, as I was using a regular length bolt and quite a few washers, so the bolt ended up being slightly too short to thread all the way into the caliper and the rest, as they say, is...

www.retrobike.co.uk

It's difficult to advise as the consequences are potentially dire!

 

[Roasted]

I did see that thread but it didn't have a satisfactory conclusion!

One of the luggs has about 3 threads and the other has about 6, so not completely stripped. Looks like it was caused by using the wrong length bolts (I'd better check my other bikes brakes now).

My options are:
1) leave as it is and use correct length bolts and hope it holds
2) pack with chemical metal and re-tap
3) fit helicoils and hope it's not seriously weakened
4) buy another brake/caliper

 

[Zer0]

I have had good success with re-tapping threads

 

[TreaderSteve]

I'd go with Zer0 - tap them first. Failing that helicoils are used everywhere in high-stress situations. I had to fit them to the brakes of a Skoda and it was easy and satisfying to do.
You'd only lose a tiny bit of the 'meat' of the caliper and once the steel helicoil is in it should consolidate things. But as mentioned no-one likes losing front teeth - find a local old-school engineering shop and ask their opinion/ get them to fit them although helicoil kits are cheap on ebay.

 

[mdvineng]

3 or 4 would be my preference. Try 3 as the load is in shear and if your not comfortable with it, 4.

 

[hamster]

The helicoil replaces the thread only. I wouldn't be especially concerned. When you drill out all you are doing is removing the thread. All that said, I think you are absolutely right to sense the danger. I would use a pillar drill and go up in small drill size increments (0.1 or 0.2mm) to be sure the wider bore is centred and dead in line with the old.

One other thought is to grind down a nut and see if there is space to fit it on the other side of the calliper to provide a bit of 'belt and braces' if you don't fancy helicoiling.

 

[ishaw]

You could try a threaded sleeve like a frame saver mech hanger affair, if such a thing exists. Not sure but would be like having a nut on the back. Might not be enough meat to drill out the calliper though, just a random thought.

 

[mattr]

A properly fitted helicoil will be stronger than the original thread in a chunky piece like that.

The trick is fitting it properly...

 

[novocaine]

My formula b4 caliper has a helicoil in it. Has done for 15 years.