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Stripped thread on front hub


TomB

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I’ve done a School boy error and stripped a thread on my front hub while fitting a new brake disc, despite using a torque wrench! I’m so cross - probably serves me right for rushing while toddler was sleeping!

 

Aside from replacing it, is there anything I can do? I’m thinking tapping and fitting a bigger bolt isn’t the answer as it’s rotating and will be out of balance, plays I’d have to drill the disc too.

 

Has anyone upgraded and got one or a pair knocking around? The ones I have are alloy, the felt seal and fairly light weight, but not the later uprated one with thicker stub axle.

 

See wanted advert, thanks

 

https://www.lotus7.club/forum/wanted/front-hub-0

 

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The pillar drill makes it much easier to get the drilled out hole vertical and similarly the tap for the helicoil.  Without it it's very easy for the thread to deviate from the vwertical.  Once it's drilled put the tap in the pillar drill and turn it by hand with lots of cutting lube.  Don't switch it on for goodness sake!

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Yes Paul, it’s the hub that has the thread. Got to the conclusion I think it will be ok to coil.

I could upgrade, but I haven’t a spare £300 for something that for a road car is probably over kill. The bearings are new in the last couple of year since I fitted wide track, so they’ve probably only done 5-6000 miles. 

Ive been offered a used one, but I don’t know it’s history so I think I’ll coil and may look to replace with new ones when/if I manage to get round to a rebuild. 

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Further to this, I haven't placed an order yet for a coil kit, but I was wondering whether to use thread lock after the coil has been inserted. 

Threadlock is recommended and a torque of 20-28lb/ft for the standard bolt into the ali hub.  Would you threadlock the helicoil in place then put the bolt in, or put threadlock on the bolt? Or not at all?  Could I risk gluing the hub/coil/bolt together and having problems if I wanted to change the discs in the future? 

 

 

 

 

 

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Tom

You shouldn't need to thread lock the helicoil in place but you can treat the bolt thread as you would any other.  In fact the hardened steel thread insert will be hugely stronger than the original.  Generally it's not recommended to use fine threads in castings as they are inclined to strip out, as you have discovered, so the helicoil will make the disk fixing better not worse.  In light of the above you could increase the tightening torque but I'd stick with the original spec and use thread lock.

The thread lock won't be strong enough to glue them together but make sure you don't get any between the two mating surfaces as this can prevent them from being flush as the liquid can act like a thin spacer. You only need a drop of thread lock on the bolt thread, not lashings of it everywhere.

As said before, drilling and tapping vertically can be quite tricky unless you use a pillar drill so I hope you can find one to use as it's all too easy or them to drift off the perpendicular when doing it by hand.

Best of luck

Paul

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Helicoils don't need threadlock to hold themselves in place but it won't hurt if you put some on. If threadlock is recommended for the bolt into the hub then use it when you fit the bolt into the helicoiled thread. Use a "normal" (not high strength) threadlock and disassembly won't be a problem in the future.



I sense your trepidation in working this way on your brakes, but rest assured it's a well proven method.


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Thanks for your help, and you're right Im a bit nervous!  Would it be prudent to do all four at the same time? But it would be simpler to just change the hub I suppose, but I know the history of mine and a used one could easily have tired threads.  

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