[CobraV8]

Heat treating the parts will make them grow a very small amount in volume, because the crystals with the metalurgical structure of hardened steel (martensite) take up more volume than that of non- hardened steel.

Maybe the hubs were out of specs?

On the other hand, 900 degree fahrenheit is more in the range of heat treating aluminium, than hardening steel. I can offer this as a second option.

The last thing that comes to my mind is that rust free chrome- moly steel will begin to rust when exposed to high temperatures, such as brake system parts are. That is because of the chrome will begin forming carbids with the carbon, and so a layer of chrome oxide will not protect the surface of the parts from oxygen any longer (that's what actually makes them rust free).

In order to re-solve the carbides and get the chrome back into the steel, solution annealing of the material is necessary.

That's all I can think of. No further ideas so far...


Simon