Re: Rear Hub Nuts
Posted: Wed Sep 27, 2017 4:26 pm
hi Guys - I have only just caught up with the emails about the Rear Hub Bearing Nuts c/w Integral Lip-Seals, so to clear up a few misconceptions, here are the facts:
In the TA parts list, the hub nuts are shown as Hexagonal, and they were 1 1/4" BSW size, of 2.050" AF (=52.07mm). They are now very rare (although I have a few) because they were replaced later by the slotted ones which most cars have on now. A special tubular spanner was needed which engaged with the slots, but as only MG workshops had them, owners had to resort to using a drift, or worse, a cold-chisel. This resulted in major distortion of the nuts, and probably shards of metal going into the bearings, especially when it was not realised that N/S (L/H side) nut had a Left Hand thread. How many owners actually [b]tightened[/b] them before realising?
The oil-return scroll bushes in the ends of the axle casing are only partly effective, even when new, and for that reason the hubs were required to be filled with Castrol "Heavy Grease", by using the grease nipples behind the spinners. However, this grease has been unavailable for many years, and indeed hubs made in England likewise have had no grease nipples for years. Even those with them (as still supplied by Moss) have probably been filled with the much lighter Chassis Grease, which does not form much of a barrier to leaking EP140 diff. oil. Indeed, combined with over-filling with the grease-gun, it usually led to a hub full of black oil, streaks along the spokes, and of course saturated brake linings...
For these reasons, many years ago I designed Hexagonal Hub Nuts which are 1/4" wider than original to incorporate a double-lipped nitrile-rubber seals. Now the half-shaft splines protrude from the inside of the hubs, often by 1/2" or more, so I made sleeves from stainless steel tubing which are glued (Araldite or JB weld) over the splines for the seals to run on. The scrolls should be removed because the seals need oil to stop them running hot.
Now, although the bearing journal is 40mm diameter, the thread for the nuts is [b]NOT[/b] 40mm - it is 1 9/16" (39.69mm) x 16tpi and is a size commonly used on British cars (fully in the spirit of "Mad Metrics" of mixing metric and Imperial threads and spanner sizes!). Incidently, the MGA was still using the same thread, but the nuts were [b]octagonal[/b] - go figure!
When I started making them, the 1 9/16" bar stock was available, and so were 1 1/4" BSW sockets: however, in the rest of the world, only 50mm or 2"AF were found (52mm was never an ISO metric size), so I went down to 50mm AF. This is what Moss are referring to.
I have supplied many hundreds of these nuts over the years, to NTG and Octagon Club in the UK, and also to FromTheFrameUp. Most recently I have supplied them to Moss. The only problem reported has been that they won't screw on, always as a result of damage to the axle threads: I have over-size nuts which usually solve the problem (for really bad threads, either use a thread-restoring file or fit new axle ends, which I now stock). Many people have had the same seals for several years without leaks (the record is 15!) although I recommend changing them every 5000 miles).
The numbers on the seals, 175-112-25 are the inch dimensions (not metric!) 1 3/4" OD, 1 1/8" ID and 1/4" wide: the ones I supply are nitrile rubber, made in Taiwan, and are marked "TC" (probably means double-lip in Taiwanese!). Chicago Rawhide probably have an equivalent (although do they still use hide?).
Hopefully this will make things clear (it not, I'm sure you will say so!)
oc[b]T[/b]agonally
Roger
Devon Olde England