Tire size mixing?

[robfg67]

I have 4 Jeep Wrangler Moab rims (16x8) with LT265/75R16 tires without a spare.

 

I found a C/L wheel from a 2017 Jeep Wrangler Sport with the Moab rim, but with a P255/70R17 tire.

 

https://boston.craigslist.org/bmw/wto/d/foxboro-2017-jeep-wrangler-spare-wheel/7639219913.html

 

Could I use this wheel as a spare?

 

On an aside, yes, I would love to get a set of Turbines, but they're not easy to find in decent shape (or inexpensive).

[pizzaman09]

In general, if a vehicle has a mixed size spare, it is recommended to put it on a non driven wheel.  So put that spare in the front an stay in 2wd, it will prevent excessive wear of the differential and minimize odd handling until the bad tire can be fixed.

[robfg67]

Good advise, thanks.

 

I think I'll buy the C/L wheel and replace the tire with the correct size down the road. The rim itself is worth it.

[Pete M]

that's a different moab than yours.  the 17" version is a different bolt pattern.

 

I can still find entire sets of the 17" moabs with tires for under 300.  150 for a single isn't worth it. 

[robfg67]

Thanks Pete.

 

Back to the drawing board.

[gogmorgo]

But as for mixing a different sized spare with the others, it will get you out of where you are and to where you’ll end up. OE manufacturers do it all the time with compact “donut” spares. Jeep even did it on the MJ if a full-size spare wasn’t spec’ed. 

But as stated you do want to avoid different sized wheels on a drive axle in the long-term. It’s especially noticeable if you’ve got a limited slip diff, as it’ll tend to steer your vehicle towards the smaller tire under acceleration. Even with an open diff you might damage something inside by excessively spinning the spider gears, which aren’t really designed for constant motion. But on the flip side, uneven braking across the front axle is going to be a more significant problem in an emergency stop. 
So this is why it’s just a short-term solution. 
I’m also of a mind that your spare tire should be your best tire. Nothing quite like pulling out your spare only to discover that it didn’t hold air over the winter, or hitting a piece of tire chain someone lost in a snow storm and ending up runnning a racing slick on one corner.

Also look into your tire changing equipment before you head out. I just got a flat in the middle of nowhere with a buddy’s truck and discovered his factory jack didn’t actually lift the truck high enough to get the spare on in the factory location. So that was annoying.

[robfg67]

All good info, thanks.

 

I saw a the exact tire size that I need recently on C/L, but the date code on the tire was 11 years old, so I passed. 

 

Not sure if it's a DOT law or regulation, but tire shops won't mount a tire older than 10 years.

[gogmorgo]

More a liability thing on the part of the shop. There are definite consequences to prolonged UV exposure, and ten years is a nice cutoff to write a policy about. And initial inflation or seating the bead is when a catastrophic tire failure is most likely to happen, and no one wants anyone to get hurt. 
But if it’s got reasonable tread and no age cracking I wouldn’t be super concerned. Tire age isn’t mentionned in any safety inspection guidebook I’ve encountered. They generally only look at pressure and tread depth, and any damage to the tire. In my current jurisdiction they actually go so far as to list how long or deep the age cracks can be before the inspector is allowed to reject.

And while I’m all for workplace safety, I do find it pretty convenient for places in the business of selling tires to have come up with a way to arbitrarily deny mounting random tires from somewhere else that aren’t legally unsafe.

And as anecdote to further to my point, I’ve got a barn-find car sitting outside on winter tires from ‘97. Good tread depth and no cracking, and they run true. I’ve put over 3000 miles on them at highway speeds, taken them down fire roads that have eaten truck tires, driven them hard up and down steep twisty mountain roads, and I’ve only ever had to put air in them once in the three years since I first got the thing. Obviously I can’t advise going out and putting 25-year-old rubber on a car because it definitely won’t perform as well as a newer tire, and with used tires you never really know what you’re getting. In my case I just haven’t gotten around to replacing them, despite continually intending to.

My point is just that I can’t find anyone else saying you shouldn’t do it who isn’t either in the business of selling new tires or relying on data provided to them by people in the business of selling new tires. My personal expertise and training only extends to pointing at vehicle safety legislation that doesn’t account for tire age, so I can’t really argue with anyone about it. But it’s definitely something that makes a guy wonder.