<VV> LM Rear Wheel Bearing press fit

[UltraMonzaWest@aol.com]

In a message dated 1/6/2005 10:11:45 AM Pacific Standard Time, jld@wk.net 
writes:

> Typically Ultra Van carry 1,400 on each hub as opposed to 800 lbs on a car 
> hub so rear hub failures are quite common.   Any deficiency in the hubs 
> design or setup is greatly magnified by Ultra Van usage.
> 
>   It was thought that when the hub assembly with the press fit removed, 
> the clamping force of the yoke nut would hold the assembly and prevent the 
> inner races turning on the shaft.  That has proved to be incorrect. I 
> assume it is because of thermal expansion.  Most Ultra owners carry a 
> optical pyrometer to measure hub temps. Typical temps. for me after a 
> couple hours of interstate cruise are 200 on the left and 250 on the 
> right.  The right runs hotter because the torque convertor exhaust into the 
> right wheel well. If I check the temps after coming down a mountain pass 
> the temps usually run 60 degrees higher due to the brake drum heat.  Due to 
> the loads, I would assume the bearing temperatures to be somewhat higher. 
> This temperature differential leaves the bearing assembly without 
> preload.  100 ftlbs; 20 pitch nut on a 5.8 inch shaft is about 0.0001 inch 
> shaft stretch.  Steel expands at  0.000062 units/degree, so 100 degree 
> differential would remove the nut preload.  That my theory why the inner 
> races turn on the shaft.  The heat produced by the friction of the race on 
> the shaft soon melts the grease allowing for the bearing to fail.
> 
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All true for Ultravans..........but for cars.....apples to apples please!


Matt Nall / Patiomatt / WCUH / Chairman V V
69 Monza Cpe., 66 Monza vert, 65 Crown v8 Cpe.
Somewhere between Reno, NV and Coos Bay, Or.