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MG MGB Technical - Banjo axle bearing nut
|Been a little stressed out since weekend before last when my MGB racecar broke an axle half-shaft in Las Vegas. It was apparently caused by the use of the stock bearing nut retainer which can loosen in hard usage and allow the nut to turn, which lets the bearing and axle move. The threads for the bearing nut were a little banged up, making it difficult to remove the old nut, so I probably made the threads even worse taking it off. Now I know I should have sliced into it with a cutting wheel and carefully split it with a chisel.|
I could not find the thread size anywhere in the archives so I called University Motors. Happily, Brooks was in the shop and answered the phone. I explained the problem and that time was critical, because the last race of the season is next weekend. He contacted his Dad, who knew the thread size. It is 1 and 9/16" diameter, 18 TPI. I was able to clean up the threads with a thread file, and get the new nut started.
To prevent another occurence, and after consultation with Dave Headley of Fab-Tek http://www.fast-mg.com and Dick Luening of MG Ltd http://www.mgbracing.com I am going to discard the retainer and torque the nut to about 200 ft-lbs using Loctite 271. I looked at Barney Gaylord's web site http://www.mgaguru.com also and checked the tech articles. Theoretically you can't overtighten the nut using ordinary hand tools.
Just wanted to get this information into the archives, so someone else isn't panic-stricken looking for it. Thank you John, Dick, Dave, and Barney! You have (hopefully) saved my season, unless something else breaks (fingers crossed).
|A number of midget racers, including myself - with similar bearing/axle arrangement - discard the lockwasher and use Loctite to secure the nut.|
The Midget workshop manual doesn't give a torque figure for the nut, but the general consensus is FT!
Having said that, one Midget owner has apparently stripped the thread at 80ft/lbs, which seems a little the light side, to say the least.
|Dave O'Neill 2|
|He must have been using a Chinese nut. I tried using one from the largest parts supplier of British cars and it almost immediately cross-threaded and ruined itself. Took an original one from my 63 future resto and no issues. Ended up at 250 ft-lbs with no problem, stripping at 80 means something was drastically wrong with the parts.|
This thread was discussed between 01/11/2008 and 03/11/2008
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