Torque Settings

[fransser]

Hello, I did a quick search thru the forums and didn't see an answer to my questions so here goes.

For a BX 2380, the owners manual says front wheels torque between 110 and 132 pounds.

The rears are torqued between 80 - 96 pounds.

1. Why such a large range between min/max specs?
2. Why are the fronts torqued more than the rears?
3. I saw a video where the guy said the nuts on the rear are torqued differently than the bolts, but I don't see anything in the manual that differentiates.

thanks for any and all input and feedback.

 

[skeets]

Well those numbers are a lot closer than my grunt and a half when I tighten them

 

[shootem604]

Or count ugga duggas

 

[ccoon520]

It has to do with the size and number of bolts. Basically the wheels need a certain clamping force applied to the rims so that the rim does not wobble and either loosen or shear the bolt head off. Since the front wheels only have 4 they need the higher torque to reach their required clamping force, while the rear uses 5 (probably for Factor of Safety). If you really want you can calculate the force that is being applied by these formulas:

Normal force:
F=T/Kd

(T is torque in in-lbs, K is a constant .2, and d is the bolt diameter 9/16 for the front and 1/2 for the rear)

Multiply the F by the number of nuts/bolts applied to the wheel to get the total normal force: F Normal (N)

Clamping Force:
Fclamp=u(s)*N

(u(s) is the coefficient of static friction (.15 for steel on painted steel), N is the total normal force you calculated previously)


This is probably a little more detail than you wanted but what you'll find is that the force comes out to be within ~2% of each other.

I got the bolt and nut sizes from a different forum because I do not own a bx2350. if they are the same size thread then they are within 10% of each other.

This is all fairly theoretical and there are other factors that weigh into the real world number like bolt expansion due to temperature differences when torqued, if the surface or threads were accidentally lubricated, etc...

 

[fransser]

Makes perfect sense. Thank you!