Short Term 35" Spare W/37s

[kmc0929]

Would the factory 285/75R18 spare work very short term on a truck with 37x12.50s? Possible damage to the rear diff? How about if it had to be mounted up front?

 

[Apples]

It'd be better than so spare at all, but... your PCM may throw a fit.

I don't know what would trip, but there are anti-lock braking sensors to consider, of which traction control uses a portion of that system, Roll Stability Control (also uses much of the ABS hardware).

As for diffs, the front is a clutch-type limited slip (on all Super Duty Tremors), so you'd want at least one front hub in freewheel) and the rear diff is open until it is E-locked by the driver.

Other than that you'd have a bit of a traction problem w/ the smaller tire since the other three, larger-diameter tires would be taking the truck's weight away from the smaller tire's contact patch.

There may be more but that's all I can muster at the moment.


IMHO one should always buy five matching tires on five matching wheels because of the above factoids (then you have the option to run five-tire tire rotations! and have a 20 or 25% longer tire lifespan). I am compelled to have my exhaust system tailpipe section modified in order to carry my 37" spare tire and wheel in it's factory nest under the rear of the truck but right now it's taking up valuable space in my Tremor's bed.

 

[MVI]

Would the factory 285/75R18 spare work very short term on a truck with 37x12.50s? Possible damage to the rear diff? How about if it had to be mounted up front?

In two wheel drive and the hubs unlocked, you can run a front no problem. You loose all 4wd capability
In the rear, it is an open diff, so it can be run, BUT you cannot use the e-locker period.

if I were ever in that situation of 4x 37's and only a 35" spare, I'd run it on the spare on the front with hubs unlocked.

Most here carry tire plugs and a gluetread kit to fix a flat, and a compressor, enough to keep you on the road until you can patch or replace the 37" tire.

plus this method saves you from dealing with a tire swap

 

[ramv]

Most vehicles, including several pickups I have had, come with less than a full size spare. It won’t be perfect but it will get you to the tire shop. No LSD on the rear so no worries there. Generally they recommend less than 55 mph with the temporary spares.

 

[shermanator2]

You will be fine in 2H. make sure front hubs are not manually locked if on the front. Might throw some codes but you said this was short term.

 

[TX Crawler]

I found a decent used 37 on Marketplace and had it mounted on the stock steelie. I also bought a cheap "titanium" header shield and put it on the exhaust where it gets close to the spare.