Is .51 inch difference overall diameter a problem for a spare tire?

[c good]

A friend getting rid of 2 almost new Falken tires, size 235/65/17. My current tires are 245/65/17. One year old. My spare is 245/65/17 and is 15 years old or older. It might even be the original spare. I looked up the difference and it's about .51 inch difference in overall diameter. Will the diameter difference be a problem if I am just using it as a spare? I know it's not a good idea, but was just curious.
Envoy is 4x4.
Thanks for any input.

 

[azswiss]

Ideally speaking (no difference in wear, inflation, etc.), at 60 MPH the 245/65/17's will be rotating at 683 RPM whereas the 235/65/75's will be rotating at 695 RPM. Might not sound like much but I don't know . . . Not sure how to calculate the difference in contact area but I would have to think that there would be some reduction in grip. Big enough to make a difference? No idea. This seems to me to be one of those situations where if you have to ask the question then a part of you already believes the answer is no.

 

[TequilaWarrior]

FWIW, I haven't carried a spare on my daily in many years....

In 30 years of driving, I can count the number of times I "needed" a spare on 2 fingers.... it would be 3, but I would've needed 4 spares at the same time so the last one doesn't count.

IMHO, a better investment is AAA.... I've needed gas more times than I've needed tires.

I also now carry a tire patch kit in my daily instead of a spare - and have used it more for others than for myself to the point that I've had to buy plug refills twice.

Quick story .... had a buddy of mine put a wrong size spare on his 77 Trans Am with a locking rear diff.... car was awful to drive the 15 or so miles home. It ruined the other tire and the front diff seal started to leak.

Your 15 year old spare is likely not safe to use anymore. I ditched my spare when I dropped it out of the Bravada to inspect the carrier and found that not only was the rubber completely dry rotted - but the rim was so rusty it wouldn't seal no matter what I did. That rim is now a fire ring in my backyard.

Inspect your current spare, if it's shot... and the price is right for the spare, it may be worth the peace of mind... but replace/repair the damaged tire ASAP.

 

[Mooseman]

My spare is also original, so 17-18 years old. Never used. I should just chuck it, like @TequilaWarrior did. I drive it mostly in the city and have CAA so might as well save some weight.

 

[c good]

I inspected the rim and tire last month. The rim is good. It's a California car so no rust.

I do desert camping during the winter and go to some pretty remote spots. I wish I could eliminate the spare but will have to keep something available.

I won't use these, don't want to risk damaging a differential or transfer case. Was just curious what everyone thought.

 

[TJBaker57]

ruined the other tire and the front diff seal started to leak.

Read this and thought " a front differential on a Trans Am?!?"



Before I sidelined my TrailBlazer I needed the spare at least 3 times in as many years. None on paved roads and at least one time where no tow truck or AAA was going to go !!

 

[TequilaWarrior]

Read this and thought " a front differential on a Trans Am?!?"



Before I sidelined my TrailBlazer I needed the spare at least 3 times in as many years. None on paved roads and at least one time where no tow truck or AAA was going to go !!

Yes... poor wording on my part. Pinion seal is what I should've said.

Uncle Murphy drives a GMT30... I'm certain of it.

Running spareless isn't for everyone... it's not the greatest idea... I fully admit that.

 

[Beacon]

Sometimes you can find a good spare, for not much money at a junk yard. The best deals, seem to be a U-pull it yards. If not, the next time you buy new tires, just have them mount one of your old tires on the spare rim.

 

[jerflash]

A small differance in diameter is fine for SHORT distances on axles that do not have a posi or a G80.

Case and point, A 31" tire is the absolute tallest that will fit under out trucks. 235/75r17 is what i got under there.

I am running 32" tires, 255/75r17s and i have a g80 locker. if i get a rear flat off road i can swap it on and probably get off the trail fine. If it is on the road I would put a front tire on the rear then put the spare on the front.

If a front gets damaged, no reason to worry, it has an open diff.

Really though i usually plug my tires on the side of the road, never really use a spare.