One Wheel Heating up!

[Hoopy Frood]

No, I don't think you are being pedantic at all. This kinda stuff is interesting, and I enjoy learning the details.

But isn't "preload if the castle nut was not backed off" the same as tightening down the nut to 50 ft. lbs.? You tighten down the the nut to certain specs, and don't release it, isn't that pre-load?

Yes, if you didn't release the pressure from the tightened castle nut, that would be preload on the bearings. And would lead to short-term failure of the wheel bearings. Which is why you remove the preload by loosening the castle nut, I believe an eighth of a turn, then line up and insert the cotter pin. Newer models use a different type of nut, but the theory is the same.

[Butcher]

Yup, I agree.

You want the adjustment to be correct at operating temperature. Which is why you want freeplay when you are adjusting at shop temperature.

[huntindog]

Tapered bearing like to be set at zero at operating temperature. Since that rarely happens when you are servicing bearings, there is usually a preload or freeplay depending on how the bearings are used.

The hub will expand when heated. If you have zero load or preload cold, when the hub expands, the clearances get tighter. This causes more heat and guess what, the hub expands even more. At some point the bearing overheats and gets ruined. Braking on long passes will make this situation worst.

As pointed out, differential housings tend to expand when they get hot, guess what? That causes the clearance to loosen. That is why they have a preload on them when setting up the differential.

It's not that difficult to understand how a bearing works. It's not difficult to understand heat has a lot to do with this. Do as you wish, but I always have freeplay in my wheel bearings.

I've never understood why there is so much controversy over this.

This isn't important to the discussion, but Differentials are a special situation. The power is input thru the pinion gear which transmits it to the ring gear while changing it's direction 90 degrees, Those two gears will try to come apart from the torque generated, and that is the major force that stretches the housing, and why they have preload.