[Fot] Differential Pre-load

[Bob Kramer]

Only a post mortem on the parts could tell for sure, but it is fun to speculate. If we take the inspector at his word and the wheel bearing was “loose”, the question of why that condition existed should have been answered before tightening down the hub. Either bearing could have already sustained damage from misalignment and bringing damaged and scarred rollers back to spec could quickly result in overheating and terminal failure. 

That would not be fun.

Sent from my iPhone

> On Jan 30, 2020, at 4:08 AM, van.mulders.marcel--- via Fot <fot at autox.team.net> wrote:
> 
> 
> 
> TeriAnn,
> Some years ago, a friend of mine took his freshly restored TR4 to the MOT. There he was told he had to adjust the front wheel bearings. He tightened these there and then to pass the MOT and on the way home a stub axle broke off because the bearing had seized, luckily without too much damage : besides the  stub axle and brake caliper bracket,  a wing had to be repaired.
> Marcel
> Van: "fot" <fot at autox.team.net>
> Aan: "fot" <fot at autox.team.net>
> Verzonden: Donderdag 30 januari 2020 10:16:08
> Onderwerp: Re: [Fot] Differential Pre-load
> 
> On 1/30/20 2:11 AM, van.mulders.marcel--- via Fot wrote:
> Barry, if that is true about the rollers/races, how do you explain the prescripion about the front wheel bearings : you need to back off the stub axle nut to get some play for the bearings?
> Marcel
> Likewise with Series Land Rover wheel bearings. Leave them tight and they quickly die.
> TeriAnn
> 
> Van: "fot" <fot at autox.team.net>
> Aan: "fubog1" <fubog1 at aol.com>, "Bob Kramer" <rkramer56 at gmail.com>
> Cc: "fot" <fot at autox.team.net>
> Verzonden: Woensdag 29 januari 2020 19:02:55
> Onderwerp: Re: [Fot] Differential Pre-load
> 
> Preload is more for the life of the bearings than the gears. You preload a bearing to take up manufacturing tolerances and account for the anticipated (by the manufacturer of the bearings) wear during their life time. There does need to be some 'squeeze" between the bearing races and the rollers or the rollers will not roll in lubrication. If any of you have ever rebuilt the rear outer suspension on old XKEs, the tapers roller bearing in the outer wishbone pivots wear out because the wishbone only moves up and down a few degrees. The tapered roller bearings never fully rotate and cause the rollers and race to pit. Roller bearing must roll 360 degrees around to survive. Preload makes them do that.
> 
> Barry
> 
> On Wednesday, January 29, 2020, 09:41:34 AM EST, Bob Kramer via Fot <fot at autox.team.net> wrote:
> 
> 
> I think the main reason a specified amount of  preload is required is that it sets it up so that the bearings roll under mild tension. To tight and the components slide over each other.  Too loose and they cock in place. Without rolling, bearings will soon fail the same way a lifter that doesn't spin fails.
> 
> Bob Kramer
> 
> 
> 
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