I am thinking of going to a 285 tire and get rid of these R4S's. I am getting increasingly disappointed in their winter traction, even with weight in the rear. I've been looking at some Bridgestone AT's and can get them for about $130 each and they are willing to give me $65 each for my trade ins. Not bad I think. Any way I would like to save the extra cash and not replace the spare with a 285. How much do you think this would affect my system in case of a flat and I had to run a 265 for a short distance say 10-20 miles?

Another question I have is how much do you think my mileage would suffer by going up in size? I figured that my speedo would be off about 2.5 mph but that doesn't bother me since I think it is 2 MPH slow anyway. Thanks for the replies.

PS I've also added a Flowmaster Force II system to my sig. and I like it!!

 

I'd replace the spare at the same time
Your getting a good trade in price
I'm sure on one tire latter it wouldn't be that good
you can get the 285 up in the spare carrier
and it can be used in a 5 tire rotation
it's cheap insur. if you need to run the spare for a long time.
The 285's do look great on the truck also
but they do bulge a little on the stock rims
I put 285's on my truck and didn't really notice the gas mileage
go down.

 

Ive got the same tires manx does and no mileage decrease. I also suggest replacing the spare. I did it at the same time I replaced my tires.

 

I would recomend getting the speedo recalabrated.

 

If you have a limited-slip differential, you will definitely want to have a spare the same size as the rest of the tires. Putting a different sized tire on the rear can wear out the LS pretty quick. And, a 285 will fit into the spare carrier.

Also, you might want to check your speedo to see how far it's off before having it "corrected". My F350's speedo is 1mph off (according to GPS) with 285/75R16 tires and is 3mph off with the OEM tires.

 

Since your truck is a 4x4, it'd just make sense to have all of your tires the same size. The different tire sizes/diameters can be hard on the 4x4 system. nomo makes a good point about the LS and the speedo too.

 

I convinced myself while I was originally posting that it would be in my, or anyone’s best interest to change all. The only problem I have is purchasing a new tire and probably never using it. Especially since I don’t rotate all. At least if anyone does a search, if and when they can, they can stumble on to this.

Thanks.