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, supposedly 1-61/64 inches across the flats (1.953" nominal). 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.

Above 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" undersize (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 corners, 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 immediately above 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."

The black tool shown immediately above here is a 1/2" drive forged steel socket intended to be used on the front drive hubs of some small trucks and sport utility vehicles. It has four square drive keys inside which will catch 4 sides of the 8 sided nut (shown on the right). This appears to be a little loose and not an ideal fit, but because it is a strong forged steel part it seems to work quite well. It works like a flank drive socket, bearing on the flat sides of the nut a little away from the sharp corners. A club friend has recently used this socket with an air impact wrench to R & R a couple of these hub nuts. Perhaps one of the best features is a price as low as $12-USD at a local auto parts store. Markings on the socket are "PT" W1269 CR-V Taiwan (by Performance Tool) for Ford F150, F250, F350, Bronco, Ranger, Explorer with manual hubs 1995 and later. Here's a link to a similar tool (maybe the same one) sold by Advance Auto Parts - Ampro Wheel Bearing Locknut Tool T72044. Another number OTC socket part #7157.

This flat wrench recently appeared on eBay with opening bid of only $4.99. I'm just a little skeptical about this one, because the octagonal nut is recessed slightly inside of the hub for the steel wheel car. For this tool to work I'm sure that at the very least you would have to push the hub inward toward the brake backing plate to allow the large nut to be exposed for a clear grip. Since the wheel bearing is supposed to be a very snug fit inside the rotating hub (at least a light press fit), the difficulty of having to push the hub back on the bearing leaves me wondering about the setback distance and possible seal damage. Apparently the wire wheel hub is different with less setback for the octagonal nut, so it may work okay for the wire wheel cars. I had a short correspondence with the seller who insists that it works well (some satisfied customers as well as his own use), but perhaps he wasn't aware of the setback problem on the disk wheel hubs. If anyone should happen to try one of these tools, please send me a short review.