Brake caliper stripped thread - OK to helicoil?

[Dr Strangeglove]

In the course of refurbing my swivels and hubs, I have stripped a thread when refitting the brake caliper. It seems odd that this one has stripped as it was the other side that needed action to get the bolts out - typical! BTW I was using a torque wrench when putting the bolts in.

So, can I fit a helicoil into the swivel pin housing to repair the thread?

My existing caliper bolts were a course thread but I am looking to refit with the later metric m12x1.25 bolts. I have measured the diameter of the different bolts and they are the same.

 

[MattYorke]

My general view is that as long as the repaired thread can take the correct spec torque, your’re good. Esp since most of the caliper load is in sheer, not tension.

With regards to changing the thread though, I’d do the sums. What I mean is that with a different thread, you need to make sure the helicoil drill size for the new thread is entirely bigger than the male thread dia of the old thread.

As this is “internet”, I’d say helicoil fine as long as it torques up properly, but I don’t know the level of your enginneering skills, so I'd recommend only repair with like for like.

 

[kermit_rr]

I don't know enough about threads or helicoil to answer, but i would be thinking whether the different thread is suitable for the intended purpose

 

[MattYorke]

It's a finer thread, so will have a different (lower) torque setting to achieve the same clamping force. I'd be repairing like for like though and make sure it's a good job.

 

[Disco1BFG]

My general view is that as long as the repaired thread can take the correct spec torque, your’re good. Esp since most of the caliper load is in sheer, not tension.

With regards to changing the thread though, I’d do the sums. What I mean is that with a different thread, you need to make sure the helicoil drill size for the new thread is entirely bigger than the male thread dia of the old thread.

As this is “internet”, I’d say helicoil fine as long as it torques up properly, but I don’t know the level of your enginneering skills, so I'd recommend only repair with like for like.

Some excellent advice there IMO. OP, if you have the tackle to make sure the helicoil is fitted square, and the thread pitch is the same, then it's possible - there appears to be enough material in the housing to allow this...AFAIK, LR use helicoils as they are stronger in given situations ....

If you can't, then as new housings (IIRC FTC5297 / FTC5296) are available, I'd replace it. they are on eblag for £150 ish

 

[lynall]

I tend to do things up by feel, as things age you have to be a little careful with the original torque figures.
Have to say on that old bolt the threads look well shagged.

Helicoil kits cheap as chip on ebay
Also point worth considering is, I assume the threaded hole is open ie not blind? if so that new style bolt with built in loctite will catch the helicoil thread and keep on winding it out the open end of the threaded hole.
So I would suggest use the correct threaded helicoil for the old style bolt and use a little lube on the bolt with a slightly lower torque to allow for the lower friction.

 

[MattYorke]

Generally I agree - but on a critical part such as brakes, with a new helicoil, I would stick to the spec.

If it can't take the torque, it's not been repaired properly. A good helicoil job with a new bolt should be as strong as, and sometimes stronger, than the original. But more general purpose nuts and bolts - I'm with you.

I tend to do things up by feel, as things age you have to be a little careful with the original torque figures.

 

[Dr Strangeglove]

Well it seems I may have been a bit of a pr1ck. When I took the first caliper off it was a bit of a challenge and it took quite a bit of effort and keeping the fingers crossed. The heads were rounded before I went anywhere near them and it ended up with me cutting the caliper in half to get to the rear of the bolts so I could put copious amounts of plusgas on the thread. Even then I had to drill them to release some tension on the thread, lots of release agent and two sets of nut extractors and heat via mapp gas. I got them out and noted the coarse thread so I had to go and get a set to replace the fine thread I had got to replace them.

So, when the other side came off with only the use of a good socket and braker bar, I was just happy to put that caliper to one side and carry on with the refurb.

However with the discussion about thread types and diameter I decided to go and check the parts that came off. The right hand caliper (the one that was an ar*e to get off) was fitted with coarse bolts. The left caliper was fitted with fine M12x1.25, and I had refitted with M12x1.75

So perhaps its no wonder the thread stripped, though I think originally it would have been a coarse thread!

So after considering the above, do I go for fine or coarse thread.

One point - the fine threaded bolt comes with threadlock applied whilst the coarse thread is slightly longer but uses a spring washer which roughly equates to the additional length of the bolt.

Lesson learned - don't assume!!

 

[lynall]

I would double check that both swivels are the same thread, as may have had a replacement swivel at some time in its life.

 

[kevstar]

Ive got a couple of spare complete hubs if you need one as I done a vented disc conversion.
If you have solid discs I can strip & post it pal.

 

[Dr Strangeglove]

Ive got a couple of spare complete hubs if you need one as I done a vented disc conversion.
If you have solid discs I can strip & post it pal.

That's a kind offer. How much are you looking for?

Also, can I ask why you have had to change them when you fit vented discs?

 

[kevstar]

That's a kind offer. How much are you looking for?

Also, can I ask why you have had to change them when you fit vented discs?

Dont want anything pal. I bought 2 fully recon axles with ashcroft diffs, new swivels ect
so just swapped the lot over except the axle casings as my rear axle is 4 linked.

 

[MattYorke]

I didn’t change hubs when I upgraded to vented? Although I did put a new axle on when I upgraded rear from drums to discs.

 

[Dr Strangeglove]

Dont want anything pal. I bought 2 fully recon axles with ashcroft diffs, new swivels ect
so just swapped the lot over except the axle casings as my rear axle is 4 linked.

 

[Dr Strangeglove]

Wow, that is both very kind and extremely helpful. I would certainly be happy to take you up on the offer. If you pm me some details of how much to cover it then I will get it sorted.

 

[kevstar]

Wow, that is both very kind and extremely helpful. I would certainly be happy to take you up on the offer. If you pm me some details of how much to cover it then I will get it sorted.

No probs pal I will try & get it stripped tomorrow which side do you need.

 

[Dr Strangeglove]

It's the left hand side.
Thanks again for this, you are very kind

Mick

 

[kevstar]

It's the left hand side.
Thanks again for this, you are very kind

Mick

No worries pm sent.