Front hubs, bearing swap and refit

MGB Reconditioning the hubs- changing wheel bearings

Sorting out the hubs was pretty straightforward. The oil seal is easily levered out with a screwdriver and the inner races then just fall out. My hub was a second hand part and it came with the rear (stub axle radius) spacer oils seal collar but not the internal semi-conical spacer so I needed to get a new one of those.

The outer races do remain fixed in the hub but are easily removed using a drift and supporting the hub on wooden blocks while the race is tapped free. New inner races were installed using the old ones as drifts to start them. I usually grind down the edges of the old races when I use them this way just to make sure that they don't bind in the hub themselves. In this case it probably isn't really necessary as the recess is so deep that the old race soon became flush with the hub and could no longer be tapped directly anyway. At this point I switched to a soft flat-faced punch to finish them and kept tapping until they were flush up against the internal shoulder. The tone that the punch makes when struck changes when the races are properly seated. I could have used my press for this but this way is quite rewarding and makes it easy to tell when the races are properly seated.

Old inner race ground down on the edge to prevent binding

Old race on top of new as a drift.

Finishing with a soft punch

New outer race installed

... and new inner.

Since this is a new bearing and a new axle/hub combination getting the shimming right will be a bit of a challenge. I know from bitter experience that its sheer madness to try and do these adjustments when there is grease on the bearings as this makes them a magnet for all the crud and grid that you really don't want in your bearings- and the fitting, measure, refitting process gives ample opportunity for it to find its way in! Secondly the oil seal will foul on the inner race which can remain fixed to the stub axle and it will be damaged if there is a lot of removal/refitting. I decided therefore to get the adjustment right on the bench and then properly assemble and grease it after its been sorted. I can then re-check end float when on the car, but both grease and oil seal should move out of the way as the hub is tightened anyway.

There are two ways of sorting the shimming- and both try to deal with the problem that as you tighten the axle nut in order to align the split pin holes you must also move the nut inwards along its thread- compressing the shims etc but altering (reducing) the end float on the hub. The two methods therefore suggest:
1. Shim the hub for the max end float (4 thou) at 40 lbft, tighten the nut to align the holes at the next possibility but not exceeding 70 lbft. Since the thread on the stub axle is 11/16 16tpi, one complete turn of the nut moves it inwards or outwards by 62.5 thou. The castle nut has 6 slots then turning the the nut a complete distance from one slot to the next moves the nut 10.4 thou. Check distance to next pin alignment hole match (clockwise)- if its within 1/5 of the distance between adjacent alignment holes (ie no more than 12 degrees of turn required) then you are lucky! Tighten the nut to the next hole and check end float. Of course tightening the nut will move it inwards and your endfloat might vanish. There seems no alternative but to try it. If it works then fine, but if the end float vanishes then try plan "B"!

However, the MGB end float cannot be less than 2 thou and if you've set it at 4 but have only just missed on the pin alignment hole, you would need to go forward to the next  moving both nut and hub 10 thou but this would completely eliminate any end float! So if this is the case, remove the hub, measure the shim stack and then add a few more. Note - As you are adding shims the nut will reach 40 lbft further out from the hub than it did before- you are therefore now aiming to align to the next hole backwards (anticlockwise) not forwards. 10 thou of shims will move one complete hole, 5 thou half the distance etc.  You need to get the holes to align at 40lb ft, although obviously adding shims will will lead to excess end float at that setting. Make a note of the extra shims you add. Remove the hub again and check the thickness of the shim stack necessary to align the pin holes. Remove shims equivalent to the excess shimming you have just added and refit the front bearing with the original thickness of shims in place ( ie the thickness that gave 4 thou of end float). Add the excess shims you have just removed in front of the bearing and behind the tab washer where they will not affect end float but will still affect the nut's position when tight. Tighten the nut and check torque is at least 40 lbft when the holes are aligned- preferably a little higher. Recheck end float, disassemble, grease and reassemble with oil seal. Refit, torque and recheck.

In order to get a good measure of end float, even when on the car I made this simple jig using a 12.5cm length of 10mm x 35mm steel. I drilled two clearance holes for the wheel studs (1/2" at 3.18" centres) and drilled a 7mm hole in between (above the brake disc mounting bolt hole) and tapped this to M8 to accept the shaft from a cheap dial gauge holder I bought on Ebay. Ideally this would be fitted to the hub using hub nuts- but it turns out that I don't have any! ... and as the car is at the shop for bodywork at present I can't take a couple off the car. I secured it using a G clamp- a little cumbersome but very effective and I was really pleased with the function.

Jig for dial gauge attaches to hub use wheel nuts if you have them.

 In use... G clamp to hold it on this occassion.

I bought a new pack of hub shims and got 2 each of 3, 6, 8 and a single 12 thou in the pack. I fitted them all and measured end float at 14.5 thou. I removed the shim stack and reduced its thickness by 9 thou before refitting and torquing to 40 lbft. This gave end float of 7 thou. I removed another 3 thou shim and refitted. This gave me an end float of 4.5 at 40 lbft. Checking the alignment showed that this was very close to the next split pin hole in a clockwise direction. This meant I was able to tighten towards 70 lbft to achieve pin hole alignment. Rechecking the end float showed I now have 3.5 thou on this hub with pin hole aligned. However, since this is a spare hub its not actually complete and I need to swap the brake disc from the old car to this hub before it can be fitted properly.  I will then be in a position to dismantle, grease and refit the hubs with the oil seal before torquing to 70 lbft again. 

The other hub needed even more shimming and I was able to remove only  a single 3 thou shim from the MGBHive wheel shim set but I could at least align holes between 40-70 lbft. As above I will need to fit the brake disc before I can finally grease and fit the bearings.