…maybe after all these years someone knows:

What happens if one tire is 2” (OD) smaller than the other three?

…say you get a flat, and that’s all you have; so you mount a stock sized tire while the rest are 275/65R18? We all know that it’s expected that DSC will go crazy and all that…but has anyone tried it?

 

Haven’t tried it. BUT. Many vehicles have been delivered with a space saver rather than a full size spare and they do work. Not sure on the exact dimensions but the space saver is smaller than the 255R55/19 for example.

 

Checked, the space saver is just thinner affecting the width but equal in diameter. Compared 255/55R19 and 175/80R19.

So, ignore my answer because it doesn’t help you out.

 

i have done this. Drove about 40 miles. The computers did not give me any alarms at all. No faults appeared from it. This was a rear tire

My concern would be that the differential on which ever axle would get damaged in the long run

 

Thank you....so it's a "get back to civilization" only option.

I have a 32" spare that I throw in the boot when I'm running the larger tires (my winters are stock sized) and keep the 30" spare under the rig. I'm about to embark on a longer (and more remote) off-roading trip. I'll have the 32" spare in the boot, and the 30" spare underneath, and hopefully I will not need either one!

 

2" over you'd expect the ABS/DSC to be creating havoc and the system having a tantrum.

 

Yes, loanrangie.....that's why I started the thread!!!!

We "expect" that to happen, but we have never collected any actual data or feedback from those that have done this.

 

I ran one tire barely under size, I think it was 1"??? On straight runs, no issue. But high speed curves in roads would trip the DSC/ABS. It really comes down to math. The vehicle expects all tire RPMs to match, when they dont it assumes there is skidding/sliding, etc. But as an emergency measure, should not really be a huge deal. I think my only concern would be the rear diff - if it is a locking version. The center diff/transfer case - no worries there because the outputs from the front and rear driveshafts will not be far off with just one tire being smaller - its sorta "halved"? Kinda like having two tires one inch smaller instead of one at two inch. But I dont think I would run two tires up front with both being two inches smaller than both rears.

Really it comes to to this, if you find you have to run that smaller tire keep the milage/speed low. And really if you are on the trail with one smaller, it probably wont do anything since you are crawling along and pretty low speeds. Its the highway speeds that would worry me more.