Spitfire Spitfire MkIV - Rear Hub Questions

[dklawson]

I am working on the rear hubs of my '72 Spit. I found a few contradictory things on the left and right sides and also did NOT find torque values in my manuals (2 of 3... I have one left to check).

1) On the rear wheel cylinders, there are two u-shaped clips securing them to the backplates. Which u-clip goes on the top and which goes on the bottom? (One is thinner, bowed, and made of spring steel, the other is thicker and flat).

2) It appears a previous owner removed the drive flange on the right rear and probably did not put it back right. I've addressed a few related issues and am ready to re-assemble. What torque is applied to the nut holding the drive flange onto the shaft?

3) The key that was in the RR hub was broken, partially sheared. It appears that the previous owner did NOT torque this up properly as the flange was loose on the shaft. The key appears to be hardened. Why? This goes against standard machine design practices.

Thanks for your replies.

 

[Andrew Mace]

1. The "thinner, bowed...." clip is underneath; the other is on top. And the thinner one's open end (judging by the picture in my manual) points away from the side with the piston and handbrake lever.

2. Rear hub to axle shaft torque setting is 110-110 ft./lb.

3. Can't help on that one, at least not philosophically. Does there appear to be any damge to hub or shaft caused by the looseness? If not, hopefully a new key and proper torque (perhaps on a new nut) will be all you need!

 

[guzzul]

To add to Andy's comment about the horseshoe clips - as he said, the 'bowed' one faces the rear of the car, and note that the 'dimples' on it should face the differential. Then the flat horseshoe clip goes on top, facing the front of the car, and the holes in it engage previous-said dimples.

WRT to the hardened key, could this be from heating? Or maybe the PO did not use an original part? How does the end of the axle shaft look? Can you see if it has been heated up (i.e. bearings) or if the threads on the inside portion are maybe stripped and did not allow for torquing properly?

 

[dklawson]

Thank you both for the replies.

Andy: that's a pretty tight tolerance on the torque setting (110-110 ft-lb) !

Both: Something was "not right" on the hub. I don't know what the previous owners did but something did NOT go together right. There was some minor galling on the bore of the hub and a raised area of material around the shaft's keyway from "wobbling". Frankly I was surprised there was not more damage based on how loose the hub was.

The Mini uses a tapered crankshaft tail and a taper-lock flywheel mount very similar to this so I used that repair/treatment method on the Spit hub/shaft. You carefully file down the raised areas adjacent to the keyways and likewise gently file away material transferred by galling. Once this is done you apply valve lapping compound to the shaft and offer up the hub (without key). You gently work the parts together, flooding with a bit of oil periodically, and check until you get a reasonable amount of the surfaces "matte grey" indicating that they are bedded together. Anyway, This method appears to have restored the hub I have to a usable condition. Now that I know the correct torque I'm sure it will be OK. I also machined a new key from standard (not hard) key stock.

Prior to my work today I had read about what was involved to remove the hub from a Spitfire. Imagine my surprise when I saw I could turn the hub about a degree or two forward and back without the shaft moving... and then find I could wobble the hub forward and back about the same amount.

 

[Andrew Mace]

Andy: that's a pretty tight tolerance on the torque setting (110-110 ft-lb)!

Chalk it up to fat fingers rushing to reply before my son got here with a needy Toyota Paseo! It should read 100-110, so there IS a bit of a range there. :wink: