This page shows various WRENCHES for the large OCTAGONAL NUT holding the wheel bearing onto the rear axle housing. These tools work for all MGA and also early MGB with banjo axle. The nut is an odd size, but not as odd as many people think. Large tube sockets sold by many Brit parts suppliers are commonly 1-61/64" octagonal sockets, but the octagonal nuts are actually 1-15/16" across flats (1-60/64"). The extra 1/32" clearance in the big socket causes some undue difficulties getting a good grip on the nut.

In a prior life many of these cars may have been abused with improper tools, having chisel or punch marks on the corners of the octagonal bearing retaining nuts, and often leaving the nuts loose. These nuts should be VERY tight, like 140 to 150 lb-ft torque, to prevent the bearing from moving around on the axle housing, wearing the surface of the housing, and causing leakage of the hub seal. The nut can take several hundred lb-ft of torque without damage, so don't worry about over tightening it. But the nut is also fairly thin, so it's difficult to get a good working grip on it without the proper tool.

Here is a picture of the typical application of an octagonal tube socket for removal and tightening of the hub bearing nut. Below are some commonly available tools for this job. The first one below is the same one in the picture above. It was purchased through British Tool Company in the early 1990's. It bears the logo 'Melco' TBS.55, Sheffield England, 1-61/64" AF Octagon. It is made from tubing 2-3/8" OD with 1/8" wall thickness. The working end is reduced slightly to form the octagon opening, while the back end has a welded plate with 3/4" square drive hole, and 11/16" diameter cross drive holes for a 5/8" tommy bar.

The second tool below is similar to the first, and was purchased more recently through Victoria British, bearing V.B. stock number 17-872. It also bears exactly the same manufacturer's label as the first tube socket, 'Melco' TBS.55 part number. This one is made from tubing 2" OD with 1/8" wall thickness. The working end is expanded to form the octagon opening, while the back end has a welded plate with 3/4" square drive hole, and 11/16" diameter cross drive holes. Current suppliers catalogs do not indicate which of these tools you might get if you order one, but it wouldn't matter much either way, as they are about equal (equally bad) in form and function.


Compare the clearance around the nut inside of the socket in the pictures above right. Both are a loose fit on the nut with excess clearance. Part of the problem stems from the nut being about .020" smaller than the socket (2 samples of old parts from different cars). Both tube sockets are also .020" to .040" oversize (not perfectly formed), and measure in the range of 1.975" to 1.995" inside dimension. The combination of undersize nut and oversize socket makes these tools fit up to 1/16" loose. With the thin nut having rounded top edges, that makes it difficult for the socket to get a good bite on the nut, so it tends to slip off easily if not held straight and firmly in place during tightening. I find it practical to apply no more than 150 lb-ft torque to the nut before the socket slips off. When that happens it chews up the inside of the socket (made of mild steel), which further aggravates the situation of poor grip. Occasionally I take the socket to a bench grinder to grind the working end back a bit, then dress it flat against the side of the grinding wheel to restore a sharp corner inside. I am not very happy with these tools, as they are somewhat difficult to use with these problems.

The tube socket shown here is a fairly new issue in Spring 2003, available from British Tool Company. This one has a 1/2 inch square socket drive hole in the back end, is case hardened for durability and cadmium plated. Current listed price (in 2003) is $40.00. I had one in hand recently, and it looks like a quality tool with a better fit on the nut, having close fitting flanks and relieved corners. I haven't tried to use one yet, but it certainly looked good to me. It has been seen recently on eBay, but getting a good deal depends on the final bid and shipping charges. Otherwise buy it directly from British Tool.

Addendum:   At 11:23 PM 5/19/06, Neal Weinmann wrote:
"The tool arrived in 2 or 3 days, and using it proved anti-climatic. It simply worked as advertised, allowing me to loosen the nuts and then tighten them again after the hub seal changes with absolutely no fuss or concern. Full, positive engagement of the nut allowed for confident application of recommended torque. Nicely made product that works correctly."

Eric Taylor in CLT, NC, USA had this one custom made by Custom Machine Components. It was $55 delivered in 2011. They might make it cheaper the second time around or in larger quantity.

"New nut from Moss inserted - no movement at all". I would measure a new nut to be sure before ordering one of these sockets custom made. Modern replacement nuts may not be exactly same size as original parts, and it would be a shame if the new socket came out a couple thou too small.

Addendum September 8, 2015:
This one is recent issue. The working end looks very much like the blue ones above, rather sloppy forming of the flats and corner radiuses. The 3/4-inch square drive hole was too small and had to be filed considerably before the drive adapter could be inserted. It has not been used in earnest yet, so the jury is still out on functionality.

Addendum May 13, 2017:
Kenny Snyder in La Center, Washington, USA wrote: "This works.

Sunex 10213 -- 1-59/64" Ball Joint Impact Socket 3/4" Drive
http://www.jegs.com/i/Sunex/344/10213/10002/-1
https://www.amazon.com/Sunex-10213-64-Inch-Joint-Socket/dp/B003IOEQ1O

Addendum December 26, 2017:
On 12/25/2017, Peter Shattock wrote:
"I have a 1967 MGB in Australia and need to replace the rear axle oil seal. ... The latest addendum from Kenny Snyder stated that the Sunex 10213 1-59/64” Ball Joint Impact Socket worked for him. I purchased one of these but it is too small for my nut and there is no sign of damage to my nut. You may want to mention that it may not fit all nuts. At half the price of the tube wrench, it was worth a try".

When I first saw the report that a 1-59/64" socket might fit I was somewhat skeptical. While I knew the 1-61/64" sockets were a loose fit, I thought I had once measured one of the nuts to be 1-15/16" across flats. It could be that some replacement parts may be a bit undersize.