Spare Tire Size??

[4x4junkie]

No, stopping to change a 2nd tire around would serve no purpose, holding people up for no reason would be inconsiderate.

I don't disagree that wear is increased if running different tires on an open diff, I disagree with your assertion that it will happen in the radically short time frame you're implying.

The owners manual for my Ford pickup that came equipped with a 3" smaller temporary service spare tire actually has the following statement in the section about spare tire usage:

Extended use of other than matching size spare tires on a Traction-Lok axle could result in a permanent reduction in effectiveness. This loss of effectiveness does not affect normal driving and should not be noticeable to the driver

(Traction-Lok = Ford's brand name for their limited slip)

This is the only paragraph in the manual that suggests anything about the axle regarding spare tires, and makes no mention of anything relating to safety or reliability of the axle other than you will kill off any effectiveness your limited slip differential might've had. So clearly Ford doesn't seem to be too overly worried about it either (no mention at all is made about use of temporary tires on a conventional axle).

 

[Ducky's Dad]

FWIW, I run 35s on the ground for my Power Wagon, and I have the original 33" spare under the bed. But I also have onboard air and a patch kit and a few cans of sealer/inflator. If I can't keep the truck moving with that stuff, I will put the 33 on the front and keep going until I can get to civilization. I won't use the 33 on the limited slip rear unless it's a real emergency, and I won't lock the front diff with a 33 unless I need that to get out of a fix. In sand, mud, snow, loose gravel there will be enough traction loss that the tire difference will not be a problem over moderate distances. Once on pavement, the 33 goes onto the front until I can replace the blown 35. If I have already lost one of my five tires, I'm not going deeper into the boonies unless I have a sixth tire with me.