Stripped thread on front hub

[TomB]

Ordered a kit from Rally Design at lunchtime for the crazy price of £14.  Hope its not too cheap and nasty and does the job! A HSS drill and tap should work OK in soft ali, even if they're not the highest quality known to man.  Fingers crossed.   

[Paul Deslandes]

That'll work fine.  Jolly good value too.  Just take it easy when tapping after drilling out.  Lots of lube, and back off to clear the tap every quarter turn  If it gets tight, back right out and clear the tap of swarf.  In fact, do that every couple of turns.  Make sure the thread is clear before inserting the coil and, once in, that the coil end is below the surface or you won't be able to clamp the disk tight to the hub.  Before snapping off the tang, screwing in the bolt after inserting the coil will ensure that the coil is seated properly.  Once the tang's been snapped off it's very hard to get the coil out if you need to.

It's a lot easier than it sounds when you read it.  Just like lots of other mechanical assembly jobs, lots of lube and thoroughly clean before assembly.

Let us know how you get on.

Paul

[elie boone]

In alloy i don't use the drill, tread lock isn't needed on a recoil as it will be near impossible to remove to recoil. I also never used tread lock on the disc, torque them up correctly and you never have a problem, in fact it's the tread lock that killed the tread in your hub. 

[TomB]

Well, some progress tonight. With help from Peter (Domus here) we fitted the helicoil and cleaned out the other threads. All looking good, until we tried to put the bolt in and attach the disc.

I’ve been sent, and we’ve fitted a 3/8 UNC, yet my eBay purchase history shows a UNF helicoil! I’ve been set the wrong thread! FFS. I need to find one 3/8 UNC bolt now and have an odd one out on the hub. 

 

[garybee]

That must be very frustrating, you do still have options however.  You could use a thread insert with a significantly larger external thread that still has the correct internal thread (something similar to a Timesert).  If you choose to stick with what you have already fitted you should in theory increase the torque of that bolt to allow for the reduced mechanical advantage of the UNC bolt over the UNF bolts.  It's a simple enough equation to ensure you get the same clamping force.

[Paul Deslandes]

Oh dear, how very upsetting. I would fit a 3/8" UNC, with the same plain shank as the original UNF, plus Loctite. Increase torque to no more than 30lbft.  It won't come loose.  It's an allow hub so I wouldn't muck around with it too much more.

Best of luck

Paul

[TomB]

UNC fitted! All sorted. But.....

...now another thread has gone. Torque wrench was set to the minimum 20ft lbs to get them going, but it wouldn’t nip up. Others, inc the new helicoil nipped up to this level fine. Think my hub might be tired! 

[SLR No.77]

Buy a new one!!!

[Sim]

hub or Torque wrench?

Is it really 20ft lbs?

[SM25T]

Redline has the upgrade kit in stock. They sell them singly too ... you don't have to buy a pair. Old style hubs are due to them this week too ... but upgrade that side has to be the way to go ... price not that different to buying an old hub.

[TomB]

Well, I set my torque wrench at its lowest setting on 20ftlbs.  Recommended for these bolts is 22-28ftlbs apparently.  I wanted to get them going, and was going to increase the torque up to 25 and stop. But one was slipping and wouldn't nip up.  Ill helicoil the second, and if I have another that goes, Ill have to think about replacing it.   

However there seems to be a range of opinions from 'don't helicoil you'll die in flames'  to 'do them all, you'll be fine'.  

Im not convinced by the value of the upgrade kit for road and an occasional track day.  It seems overkill to me.  Ive  got a couple fo offers of secondhand old hubs, but they may have similar dodgy threads.  

[Paul Deslandes]

It looks as though these bolts have been seriously over tightened in the past and are on the verge of being stripped.

Undoubtedly a new hub would be ideal but, given that you have bought the kit, I can see no good reason not to helicoil the remaining holes with UNC. To make sure that everything lines up and is vertical, fit the disk to the hub as a template when you rework the remaining threads.

[Wrightpayne]

Perhaps the hubs were cast from an old K series head = cheese.

I'd be inclined to replace them both - the upgrade hub kit is reasonably priced in my opinion, considering whats included and the fact its beefier and better engineered.

The other thing I would check out is the wheel studs - the original ones on my '98 dedion car only allowed the nut to engage by 5 threads (approx 7 or 8mm) and there were debates (all in the archives) as to whether this was sufficient both from an engineering perspective and peace of mind.

I replaced all 16 studs with the longer ones and now use Elise mk1 60 degree taper open wheel bolts - I picked these as they are black and match the yellow / black look of the car. The stud is flush with the top of the bolt when torqued up, so fully engaged.

I expect the upgraded hubs come with the longer studs, which I believe are now standard fit across the range.

 

Regards

Ian

 

 

[elie boone]

I would replace all 4 with recoils.