Updating your spare when you go to bigger tires

[AlanL]

I was talking to a friend of mine last night about tires and we had an interesting discussion (OK, we had a few beers so maybe we just *thought* it was interesteing).

He had a 2500HD gasser that he's put 285s on. I have 265 on my 2500HD DMax.

He asked if I'd updated my spare and I said no (he hasn't either yet). In thinking about it, I'm not so sure that I'm going to. Not only to save money, but for the following reason...

The argument that people have given in terms of switching spares is that the two tires, especially on the back of the vehicle, won't be the same size and it will mess up your axles, ABS, etc...


The 245 and 265 tires are one inch different in diameter when both are new. With every mile of driving the 265 is getting smaller and the 245 spare tire is staying the same size. When half of the 13/16 of the tread is worn off the 265, the spare and the 265 are going to be almost the exact same size. The same would be true if you're starting out with 5 new 245 tires on the vehicle. With every mile driven the in-use tires are going to wear away and when half of the 13/16 of tread is worn off an in-use 245, that tire and the spare are going to be off by almost an inch... the same amount of difference as a new 245 and 265.

So, it seems to me that for a 245 to 265 swap, changing the spare is unnecessary. If you're going to 235/85 or 285/75 tires, it probably makes more difference.


Am I wrong here?

-Al

[MAV]

Your logic seems good but......what if you get a flat with a new 265 (under 10K) and have a 245 spare?

Yesterday I put 285's on my 2500HD. I found a used tire dealer and got a 50% used 285 for the spare. Gave me a credit for the new Firestone and mounted and balanced the new used 285 for $30. Bets the price of that 5th new tire. I did jump from 245's to 285's though so it was a must reguardless.

I had new Michlen 225/70-19.5's on my dually. These were 14 ply "G" rated tires. Running heavily loaded on a gravel road I drove over a very sharp rock (3' long and 2" dia) and shoved it right through the tread on the drivers inside dual. New $245 tire...shot. If not for the dually.....well you get the picture.

Bottom line is you never know when you will need that spare. You never know.

[HD-Nate]

OUCH

Thanks Alan, my brain hurts now :(

Its too early to think that hard, since beer does tend to kill off the weaker brain cells,I will give this some thought tonight :D

Fortunately, any flats that I have ever had, I have been able to repair on the truck with a plug kit and a portable air compressor. I have this in every one of my vehicles.

If I absolutely had to put the 245 on my 285 equipped truck, I would put it on the front until I could get to the closest Firestone store.

[sdaver]

I have a spare thats the same.......lockers do not like different size tires on the same axle :D dave

[AlanL]

Don't get me wrong, I don't mind spending the few bucks for a cheap 265 to use as a spare and even another new steel rim on which to mount it (I don't think I need a brand new Revo sitting under the truck for "just in case") I spent $1400 for the rims and Revos, what's another $75 or $100 to have a correct size spare?

Does a 265 fit under the truck ok?

Next time I'll focus on drinking beers rather than the finer points of the tire sizes.

-Al

[MAV]

265 should fit fine. My USED 285 fits good.

[MAD-MAX]

i bought the 285 spare , next time i get tires ill just have to buy 3 and use the new spare put one of my used ones for the spair than!!!

[MAD-MAX]

i bought the 285 spare , next time i get tires ill just have to buy 3 and use the new spare put one of my used ones for the spare than!!!

[JimWilson]

I upgraded my spare when I did the 285's.