Smaller diameter spare OK for short term emergency? (1 Viewer)

[John E Davies]

The manual says nothing about this.

If I am running 33 inch tires, can I install a 31.3 inch tire in an emergency? If so, which end of the truck, and I guess I should I turn off all the nannies (traction/ stability control)? I’m guessing the rear axle would not be good due to the limited slip diff.

I am selling my little P metric tires and buying 33 inch LT snow tires for this season, next Spring I will buy five 33 inch all terrains. I am wondering if my OEM spare would be OK short term until then....?

Thanks,

John Davies
Spokane WA

 

[NLScooby]

The question is..."How lucky do you feel?"

I am paranoid about running different size tires on an all wheel drive vehicle - so I always have a matching sized spare. But then I've never had a flat on my AWD vehicles either! In an emergency - I would do it if I had no other choice....but I'd recommend not running a tire that was off by nearly 2 inches in diameter. I notice you gave a specific measurement for the spare. Did you actually measure both?....(sometimes a "33" tire actually measures out closer to 32.)

 

[John E Davies]

I notice you gave a specific measurement for the spare. Did you actually measure both?....(sometimes a "33" tire actually measures out closer to 32.)

Nope, I am using factory published data for the size, from the manufacturers. The spare is a brand new Bridgestone something or other. The Nokian LT2 tires are 33.2, as are the Nitto Ridge Grapplers on my shopping list. I have no idea how accurate those numbers are.

But I suppose that is a moot point.

John Davies
Spokane WA

 

[luke27617]

Tires never rotate equally unless going straight or when differential is locked. I don't see an issue, but of course would go slower as the balance is off which will effect braking, cornering, etc.

 

[linuxgod]

I debated this, but I ended up buying 5 since:

• I went from factory 31.5" to almost 34" and
• I wanted the confidence when wheeling 1000 miles from home that if I did puncture a tire I could drive (and tow) on the spare reliably.

I figure I'll do a 5 tire rotation so I get an extra ~25% of life out of 5 tires, and can then decide when I replace them if I just want to buy 4 and live with a worn down spare or replace all 5.

A smaller tire will cause excessive wear on the differentials. In fact it's really advisable to do a 5 tire rotation anyway since a new spare will be taller than a worn tire you removed. Depending on the tires tread depth and the wear it could be as much as an inch different circumference.

To answer your question, officially it's a bad idea, but in practice if you got a flat and used a smaller spare to drive to the nearest repair shop it's probably ok. However if you drive on a smaller donut spare for hundreds or thousands of miles don't be shocked if you have excessive differential wear and end up with an expensive bill.

 

[TonyP]

Depends on your definition of "emergency". I'll drive on three wheels dragging my brake rotor if it's an actual emergency.

In a serious pickle? Sure, you'll probably be ok in a very short distance at very slow speeds.

Long term, no.

It's a far better idea to have all 5 matching for the numerous reasons stated above.

 

[Taco2Cruiser]

The manual says nothing about this.

If I am running 33 inch tires, can I install a 31.3 inch tire in an emergency? If so, which end of the truck, and I guess I should I turn off all the nannies (traction/ stability control)? I’m guessing the rear axle would not be good due to the limited slip diff.

I am selling my little P metric tires and buying 33 inch LT snow tires for this season, next Spring I will buy five 33 inch all terrains. I am wondering if my OEM spare would be OK short term until then....?

Thanks,

John Davies
Spokane WA

No.

Also we don’t have a LSD in the rear.

I won’t bore everyone with the massive strain on the spicer gear inside the diff. But I offer that you do it and see how long you can handle it.

I put one new 33 on the front right with stock tires just to test flex. I couldn’t hold the truck strait past 10 mph for 10 house lengths.

 

[TeCKis300]

No one will be able to say it's okay with any certainty. So this is a do at your own risk type of thing if you get in a bind.

Besides the potential premature wear issues with the differentials.

There's also the stability control system. Part of the input into the system is wheel rotation speed from the ABS sensor. Whether you can drive down the road without it freaking out, past some threshold of difference, is unknown.

Then there's the pull as taco2cruiser points out. Combine that with poor weather and traction conditions, and incorrect electronic vehicle stability compensations because it's confused. Makes for a bad recipe in my mind just to save a little bit of money. You'd be better off getting a cheap non-matching tire in at least the same diameter if money is a concern.

 

[linuxgod]

There's also the stability control system. Part of the input into the system is wheel rotation speed from the ABS sensor. Whether you can drive down the road without it freaking out, past some threshold of difference, is unknown.

I've triggered a VSC light when towing before. I had the friction anti-sway cranked down and accelerated out of a turn. The light came on since I guess the VSA system thought I was trying to drive straight but the wheel was turned fighting the trailer resistance. The only way to reset it was with Techstream (my OBD2 reader couldn't see the code). Annoying. When I got into it in Techstream it showed "steering wheel not centered" and "yaw sensor threshold exceeded" with a value of ~35 degrees, or something like that.

So yes, if you do this, expect to set off some lights. Again if I blew a tire on the highway and needed to limp the truck to a tire repair shop a few miles down the road I'd run the smaller spare, but outside that just buy a proper 5th tire do a 5 tire rotation instead of the standard 4 tire rotation. In the end the cost is actually the same, since you get additional mileage between tire replacements.

 

[SWUtah]

My spare is 31.2" my new tire's are 32.3", if I have a flat and have to use a spare it will only be for a few miles to the closest garage. With open diff's the consensus is not a big deal. Getting my wife to spend another $400 for a new spare is a big deal. Yes I would drive very slow and only a few miles. But since my LX570 will never leave the road. I think I'm good. Now if I was going off road I would have 2 spares
PS. I also carry a portable air compressor and a patch kit with me at all times which if my TPMS went off, it would be what I would do first. Plus I would call Lexus roadside assistance and have it flatbed to the closest Lexus dealer before I would use the smaller spare. In the past I have had the Tpms go off indicating a tire leak. Located the nail in the tire got out the air compressor pumped it up 10 psi over normal and drove slowly to the closest garage and had the tire patched.

 

[TonyP]

What tire do you have that's $400 each? Not saying you're wrong, just curious since my 35in Toyo M/Ts aren't even that much.

 

[Taco2Cruiser]

My spare is 31.2" my new tire's are 32.3", if I have a flat and have to use a spare it will only be for a few miles to the closest garage. With open diff's the consensus is not a big deal. Getting my wife to spend another $400 for a new spare is a big deal. Yes I would drive very slow and only a few miles. But since my LX570 will never leave the road. I think I'm good. Now if I was going off road I would have 2 spares
PS. I also carry a portable air compressor and a patch kit with me at all times which if my TPMS went off, it would be what I would do first. Plus I would call Lexus roadside assistance and have it flatbed to the closest Lexus dealer before I would use the smaller spare. In the past I have had the Tpms go off indicating a tire leak. Located the nail in the tire got out the air compressor pumped it up 10 psi over normal and drove slowly to the closest garage and had the tire patched.

Yeah know, I've never punctured a tire off-road. That includes my gun trucks in Afghan. But I've lost 3 tires on roads, go figure.

Just as I mentioned to the OP, put your stock tire on a steer axle, and have your wife drive it. Maybe when she feels how hard it is on the expensive 200 you own, she may think it's a good idea to get an new spare.

I'm not being condescending at all, I think that when things are more tangible, it is much easier to help make financial decisions, plus you know what you're getting into before you actually need to use the spare... and your 45 miles from town on the interstate. It might not bother you or your wife to drive on a small spare, but at least you will actually know.

 

[Markuson]

When you get a flat, you don’t always get to decide how far you need to drive on the spare. The situation often determines that.

Spend $300-$400 on the right tire and rest say knowing you can safely drive wherever you need to go...and also protect one of your truck’s most expensive systems.

Plus... When you add the 5th tire to your regular rotations, it's basically the same $, since your tires will last just that much longer with 5 vs. 4.

It's basically insurance on several levels. Safety, system protection, flexibility to travel as needed. Money well spent in my thinking.

 

[SWUtah]

What tire do you have that's $400 each? Not saying you're wrong, just curious since my 35in Toyo M/Ts aren't even that much.

Tire $347 the other is tax, mount balance, etc. $1600 for 4 tire's at discount tire. Tire rack is the same price. The price goes up $100 per tire on BFG AT/KO's when you go from 275 to 285. It costs $100 more per tire for that additional 1" of thread width. From a safety standpoint I was willing to spend that additional $100 for the larger tire patch.

 

[TonyP]

Wild. My Toyos are only $320/tire, shipped.

Check out SimpleTire - New Tires. Every Vehicle. Best Prices. | Free Shipping of Popular Tires!
I got my tires from them (with a 5% discount code).

 

[Markuson]

Tire $347 the other is tax, mount balance, etc. $1600 for 4 tire's at discount tire. Tire rack is the same price. The price goes up $100 per tire on BFG AT/KO's when you go from 275 to 285. It costs $100 more per tire for that additional 1" of thread width. From a safety standpoint I was willing to spend that additional $100 for the larger tire patch.

Really? 4 BFG AT/KO2 tires at 285/70/17 for my 200 were less than $1200 out the door. That's with mounting, balancing, and repacking the TPMS at Discount tire. I then added a spare for $300 or so.

 

[Markuson]

Tire $347 the other is tax, mount balance, etc. $1600 for 4 tire's at discount tire. Tire rack is the same price. The price goes up $100 per tire on BFG AT/KO's when you go from 275 to 285. It costs $100 more per tire for that additional 1" of thread width. From a safety standpoint I was willing to spend that additional $100 for the larger tire patch.

$347 before tax and install seems way too high. Here's the larger of the two 285's at Discount tire:

Have a look here:
BFGoodrich All-Terrain T/A KO2 285/65R18

 

[gaijin]

If you are only ever going to use your spare as a spare and only in emergencies, why noy just buy a cheap tire that is the same diameter as your other tires?

 

[Markuson]

Man, I wish I always knew ahead of time where, how many miles, and under what conditions I'll need a spare!

 

[TonyP]

One of the benefits of having a matching 5th is a full rotation, which adds overall milage to the set.