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MG Midget and Sprite Technical - rear hub nut torque for 1 7/8 ' nut

Are there any guidelines for a reasonable torque value for the rear axle nut? Bob C
chamberlain Bob

the big tab washer provides positive nut retention so the nut only has to be tight enough to remove free play in the components behind it; IMO 60 lb ft should be about right.
David Smith

I've heard as low as 40.
I used 45 on mine.

Have also heard of folks stripping their axle housing when they went too far, so I would definitely not go above 60. 45 "felt" like plenty.

As David pointed out, the lock tab holds things, so "fully snug" is enough (funny that the factory never bothered to define it though).

Norm
Norm Kerr

Interesting theme. This was discussed in Safety Fast, I believe in june or july. Someone from Brown and Gammons says very clearly that the rear hub bearings on the midget axle should have 140 lb ft, and give several reasons why.

Also have a look at this on Barney Gaylord
Tore

Another interesting discussion from the MGA Archive.

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=6&subjectar=6&thread=200801131611089904

Tore

Sorry, that last link did not work. Donīt know why, but you will find it if you look in the MGA Archive for Banjo Axle Hub Bearing Nut Torque.

Tore
Tore

Red locktite. I do not trust that little tab on the lock washer (though I've not ever seen or heard of a failure). Does that make me paranoid?

I torqued mine to approx 100 lbs, and I felt I was pushing my luck given how few threads there are in that slim nut.
Trevor Jessie

WOW, thanks, Tore, for sharing that.

Based on the calculation that he included I am now convinced and am going to re-torque mine as he recommended.

Without that thread strength math, discussion about this before was pretty much just "opinion". But with the math, it is now, for me, a matter of fact.


Norm
Norm Kerr

The sliding T bar handle on the correct factory wrench is about 2 feet long, and in the days when we were taking apart virgin cars, it was not uncommon to need two guys, one pusher and one puller. Same Churchill tool is double ended for A * B series axles. Ambitious souls may want to know that this tool has a pilot that fits down the axle hole, which prevents it slipping off the nut.

FRM
FR Millmore

I have not seen the "correct" factory tool but it will have a hexagon at one end and an octagon at the other (for B Series)
Robert (Bob) Midget Turbo

I haven't read the MGA thread, but...

Although the nut may be quite thin, it has a heck of a lot of thread surface, due to its large diameter.

On the racer, I used a 2-foot bar with a lot of weight on it!

Also, a lot of racers omit the tab washer and use Loctite on the threads, instead. The theory being that the tab washer is quite soft and can compress under severe loading...extreme cornering!

I have had hub nuts work loose when using a tab washer but not with Loctite.

For normal road use, the tab washer should be fine.

All IMHO
Dave O'Neill 2

This is such a tricky one. While I know my torque wrench is not of the finest quality it at least came with a calibratiion certificate. My axle threads stripped before i got to 140 which was the figure i was given by the owners club. They also said as tight as you can.

I read the mga thread and it does not tally with my personal experience. Interestingly when i bought my replacement axle (thank you andy jennings) he told me it was not an uncommon problem. In fact someone else had been to see him the previous weekend having done exactly the same as me and stripped the threads. He said there is a fine line between doing the hub nut up tight enough and overdoing it.

Not sure whaat the right answer is... just saying... be careful...
TonyJH

Bob's right. Picture of tool is in all factory WSM under "special tools". The number for the one mentioned is 18G152; in the pic in the mgb book it shows the hex end for A series! And, I just found an earlier version in my Z Magnette manual, which is just a double ended tubular socket 18G267 without the T handle or pilot, stated to fit both A & B series.
I actually have the 18G152, went out to take a pic, but it is temporarily lost in the chaos of my shop.

Couldn't say for sure, but I expect that cases of stripping are due to the thing having been run loose for a long time. This will result in thread (and axle spigot) wear on both parts that will weaken it a lot. The wear is exactly like the wear on WW splines, only circumferential rather than radial; threads get all pointy and thin. I've seen quite a few that are a very sloppy fit, in which case I examine it all closely, replace the nut, and "adjust" torque as seems appropriate. Per Barney's piece, I would say that if the bearing is sloppy on the housing, use of a mild Loctite on the bearing is appropriate, then there would be no movement, but it sure will make it hard to get off without heat - takes 400F to weaken Loctite.

FRM
FR Millmore

A friend of mine lost the left hand rear hub on his early MGB with banjo axle last summer. The half shaft was half way out of the axle casing before he managed to stop. He has been driving the car for 15 years. The threads on the axle casing were damaged, so we could not understand why it had not happened before. FRMīs theory on thread wear probably explains that.

Tore
Tore

Finally bought myself a new Norbar torque wrench (is there anything Amazon doesn't sell?) Brilliant torque wrench for the price. I just torqued up the left handed hub nut to 140... nothing broke and it all looks good. There is a good chance I guess that maybe my old axle had worn or damaged threads on it so that probably explains the thread stripping. Just the offside hub nut to do. I'll stick with the 140 figure from now on...

'torqued up' Tony
TonyJH

I forget what I torqued mine up to , possibly 80. It certainly wasn't 140 as my torque wrench doesn't go that high.
Daniel Thirteen-Twelve

This thread was discussed between 14/11/2010 and 27/11/2010

MG Midget and Sprite Technical index

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