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MG MGF Technical - MGF Front Stubshaft Weight Reduction.

Whilst changing a front wheel bearing I took the stub shaft out and pondered the large useless lump of metal on the back of it. Seems it's another parts bin job using the shaft from the rear which included the cup half of the CV drive joint. I think the cup may carry the reluctor ring on cars with ABS.

So after a few rough hand stress calcs I decided there was scope for the removal of a reasonable amount of unsprung weight on each front hub by machining the CV cup off, leaving a flange at the rear of the stubshaft 15mm thick x 50mm dia.

The modified shaft weighs 490 grammes. Unfortunately I omitted to weigh it before the operation but reckon I've removed at least 0.6 kg unsprung weight per side.

Its now all in, torqued up and runnning. Hasn't broken yet; MGoT Castle Combe 6th Sept will be the test.

Pictures :-

Before - http://www.timguydesign.f2s.com/pics/front-stubshaft2.jpg

After - http://www.timguydesign.f2s.com/pics/front-stubshaft7.jpg , http://www.timguydesign.f2s.com/pics/front-stubshaft8.jpg , http://www.timguydesign.f2s.com/pics/front-stubshaft10.jpg

Tim Guy
T Guy

Good idea - can't do any harm!
Mike Cunningham

Something I have been contemplating for far to long! Where did you get them machined and how much did it cost? Dave Kar-Solutions
David Karle

I have an old Colchester Student in my garage.

I machined the first one from the end down but it was heavy going 10 thou at a time because the CV bearing cup is hardened internally as you can see in the photo. It did cost me a couple of carbide tips.

It does finally just go soft for the last few mm which is fortunate.

For the second one I did most of the removal with a slitting grinder, being careful not to put too much heat into the shaft, and leaving just a finishing facing and final OD reduction. I cut down through the small waisted area.

If you cut the cups off yourself, leaving a couple of mm facing to be done, any local machine shop would be able to do the pair in well less than an hour. The dimensions are not precise (+/- 1mm is fine) and doesn't need to be especially concentric; good enough if it runs within .2mm - well within 3 jaw chuck territory.

Tim Guy

This thread was discussed between 23/08/2010 and 26/08/2010

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