flat tire

[myranger26105]

i got a flat on the way to work today and i was noticed when i was changing the tire that the spare that i had wasnt the same size as the others ones on the truck its a 235/65/16 and the rest of 245/65/16 will this hurt the frontend in my truck i knoww if i put it in 4x4 it will but i am talking about just running it until i get my new tires since the front hubs dont unlock????

 

[srteach]

A differential is designed to allow the tires to turn at different rates during cornering.
If you have a locked differential, you will put stress on the drive parts (carrier, driveshaft, tires, or other parts) and will scrub tires. If you're locked, you probably are already scrubbing rubber anyway.
If you have a limited slip diff, you could possibly (not likely) damage those parts or the clutches / mechanism.
There is a very low likelihood of damage in an open diff, because it is designed to allow different tire speeds in a corner. Now it will allow differences while going straight.
It may cause some problems in terms of control of the vehicle. That is why it is not recommended to run different size tires on a vehicle.

 

[JohnnyO]

Ford would put matching size spares only in trucks with limited-slip axles. As srteach said, with open diffs it doesn't matter much so they put in something smaller and cheaper for a spare.