www.jec.org.uk

Second question of the day.

I bought new stub axles and bearings. The car is on stands and the new brake discs fitted.

As I tighten the hub nut, it gets to a point where there is no more play - the disc will not rock at all. How much should I then back off the nut to get the right amount of play? What might the right amount of play feel like with the wheels removed? Barely detectable or more?

Thanks in advance

Simon

You definitely need some play - unlike more modern cars that use pre-loaded bearings, the old XJ series hubs need some slack to allow for thermal expansion. The book says to use a dial gauge to get 0.001-0.003" (0.03-0.08mm) float on facelift cars; AFAIR, in theory it's a bit more for older cars.

This is actually often quite difficult, as the roller bearings tend to wear a groove in the stub axle, which allows for a wobble top to bottom but not left to right. ... AFAIR it's about 1/2 a flat, but I don't have the necessary docs to hand to let me work it out. One flat is 1/6th of the pitch of the stub axle thread, so work from there.

I just know I'm going to hate myself for saying this. I think I'm correct that (without access to a dial gauge) the absolute maximum torque is 5 lbs. That said, when on something a little old, where there is wear I tend to tighten until I feel the hub beginning to bind and then wind it off a flat or two. There will, and needs to be, some play on these tapper roller bearings. Either way, too tight or too loose will damage them quite quickly.

I tend to inspect and grease on an annual basis when I'm looking at the discs and pads.

Nick