Helicoiling thread on front fork brake bracket?

Technical Small Block V Twins (not new V7s)
1

I have a problem with a weak thread (M8 x 1.25) on the lower of the two brackets holding the brake caliper to the fork leg.

It’s a small block - specifically a V65 Lario.

Has anyone tried helicoiling these threads. I’ve not tried it before but I’m wondering if it could be a suitable repair or not?

Thanks,
Nigel

2

As long as the helicoil insert is fitted correctly, it should not be a problem.

Notice I said “as long as”…

:grinning:

3

Ok, understood - thanks for your reply.

4

If you’re married to this bike, I would also consider re-doing it to M10x1.25. You could also do a bespoke stud, with imperial 3/8BSW(no, you need 20tpi, is it UN? I am not imperial…) or above M10 part screwed and glued into the leg, and then, without reboring a hole in your caliper, a dome M8 nut will neatly do the job over M8 sticking out part of the stud. Then, forces don’t work along the bolt anyway - why not use longer bolt and a nut behind factory thread?
I imagine some of you are shocked now:> Yes, helicoil is so neat. And so PITA:)

5

Thanks for your thoughts. A longer bolt with a nut would have been ideal but the clearance between the fork leg bracket and the disc is very very small - so it wouldn’t be possible to get a nut of any useful size to fit.
So it may have to be Helicoil…the other thought was Timesert.

6

Helicoil is strongest but both will be stronger than original thread.

If fitted correctly…

7

Thanks, looks like it’s going to be Helicoil then!

Any tips greatly appreciated…

8

I would prefer Timesert, having had it done on a final drive box. Ideal where the metal is thin and or soft, e.g. alloy. I had helicoils on my BMW R80 heads and was not impressed at all, in fact they both failed, weren’t able to take too much torque and pulled out. (Not by me.) :slightly_smiling_face:

Yes fitted properly, take it to a works place that have the expertise and tooling.

2 Likes
9

Timesert is always my preference helicoil unless there’s not a lot of clearance for the top of the timesert. I use these at our workshop.

Do you have the kits?

Where are you as I’m 8n Bolton.

2 Likes
10

Thanks, no I’ve not bought anything yet.

I’m in the Midlands, near Lichfield.

11

If you fancy a drive to God’s county feel free. We can sort it out quite quickly. We have some M8 timeserts ready with your name on. Well they will have if you want.

12

Thanks, that’s very kind of you. Ideally I’d like to find somewhere closer to home but if not not I’ll get back in contact with you.

13

And afterwards - over the years i have found that with MotoGuzzi short threads in alloy (and Aprilia and KTM) a torque wrench is generally cheaper than the part with the thread in it :slight_smile:

14

Agreed. This was done before my ownership…I used copious amounts of ptfe tape on the bolt when I first discovered it about 4 years ago when I bought it and did my usual strip down checks, and it’s been ok and undisturbed since.

But I have just replaced the sealed damper units in the forks and put in new seals too, and clearly just the act of removing the bolt together with some bits of the thread, has upset it a bit more…

So, yes - use a torque wrench and always slacken it off when not in use to take the pressure off to help keep it correctly adjusted!

2 Likes
15

I would also recommend going down the Timesert route. I did a caliper thread on my Harris Bonneville a few years ago on a Paioli fork leg and it has worked fine.

16

That’s good to know, thank you.

17

This is very interesting (if you like that sort of thing)…

The guy presenting it is a bit Marmite, but undoubtedly some good info here.

Hope it’s useful.

18

Yup Mr Marmite spent a lot of time and effort. So I’ll keep using timesert or helicoils.
:slight_smile:

1 Like
19

Thanks very much for posting - I’ve watched it twice now. Really interesting. A couple of the metal insert products don’t appear to be available in the U.K., and the Helicoil and Timesert products appear to perform similarly in the tests.
They use the brand ‘Heli Coil’ in the tests but I can’t track that down as a brand here - lots of different makes available for the Helicoil type insert, most of which I’ve never heard of so I guess the performance may vary.

Any experience of a good brand? Sealey?

20

Plenty of Helicoil “branded” stuff on the web:

https://www.zoro.co.uk/shop/materials-and-maintenance/thread-repair/eco-thread-repair-kit-8-32-unc/p/ZT1243937P?utm_source=google&utm_campaign=pla%2B|%2BMaterials%20%26%20Maintenance&utm_term=ZT1243937P&utm_medium=pla_css_3&targetid=pla-953381781984&loc_physical_ms=1007071&dev=m&gclid=CjwKCAiAlp2fBhBPEiwA2Q10D1ihDLwHoiAI0q-ugGVUrmW_cBY1ahLC0RASKGz6cbyRhuVnVIoJbBoCh0AQAvD_BwE

PS I AM NOT ENDORSING “ZORO”.

This was just an illustration…of what Mr. Google can serve up if asked politely…