Recently put 285/75R/16 Goodyear MT/Rs on, but I didn't do anything with the spare. Is it necessary to get a 285 spare tire or can I use the stock 265 spare if I get a flat? Thanks.

 

If you are in 2WD and run the spare on one side of the rear, you can ruin your diff.

If you are in 4WD, and put a spare on, you can ruin the transfer case and/or front diff.

I know of a pathfinder that ran chains on the rear tires in 4WD, that increase in diameter alone ruined the transfer case.

Get a spare of the same size. Not only is it mechanically a good idea, its also much safer.

 

I agree, you need a 5th new tire!

 

If you had 265/75R16s & your spare was 265/70R16 it's not too bad as long as you put the smaller one to the front and put it in 2WD.

For 285s though, I definitely say get a 5th.

 

That's what I'm currently running... 265/75s all around and 265/70 under the bed. So I should be okay? Or should I really get the 265/75 spare?

 

You should be fine because you are a 2wd and the difference between a 70 and a 75 is not that great. However, safety always becomes a concern when tire sizes are varied (should you have to run the spare).

I say get a new spare when you get around to it.

 

definitely get the 5th wheel replaced w/ the 285's!!!

As for you tacomadude: since you're 2wd, if u ever experience a flat, just make sure u put the spare in the front and put the 265/70 in the rear... this way u won't mess up the diff

in any situation, make sure you have the same size tire to the one where the power is being distributed.... if you have full time then you're stuck w/ gettin all the same size tires.

 

I figured it wouldn't make a difference as long as you are in 2WD. Those dinky donut spares are of smaller diameter and you can run those on a 2WD vehicle. Isn't that the point of a differential? I think as long as 4WD isn't involved it's ok in an emergency.
But then again, I'm not positive about what is and isn't turning in the transfer case when you are in 2WD on a shift -on -the -fly system.

Actually, this is a good question.

 

Ah... another new thing I've learned.
Of course... I have a LOT to learn


This is another one of those obvious-after-someone-points-it-out-to-you things.

 

I disagree, I think they are of smaller width. At least on all the cars I have owned they were.

 

I'll have to check on that. If that is the case then those donut spares certainly look decieving. I once got a flat with my Accord and I immediately put on the donut spare. The spare went flat as soon as I let the car down on it. That's because I didn't check the pressure for 5 years. Anyways I had to call a tow truck and when the driver tried sliding the hydraulic wheel chock device under the front end, it hit the body of the car. That is how low the car was sitting on this spare rim. Now I'm just curious. I'll have to check it out tonight.
It's not that I don't believe you 96 Runner! I just want to look at that spare again and curse at it some more

 

I've got a 225 radial for my spare and I am running 31X10.50's. I think them donut tires are definitly smaller than the regular tires. So who's going to settle the dispute. I can't a get a 31" tire here very easily. I have run my spare once before for about 5 miles on the front with no probs. Wouldn't want to go very far with it though.

 

No problem Tstango. I am mainly talking about cars, which is funny because we have an Accord too, but luckily the spare was filled with air when we got a flat.

I agree, the donut spares are definetly smaller, but I swear the diameter is the same. Hmmm, now you have me thinking.

I have seen some trucks where the donut spare (I am talking about a Heep Cherokee) was way smaller. And it was 4WD! Talk about cheap.

 

Thanks for the help.

 

Umm won' t the diff take up the slack on the smaller tire. I mean what happens when you spin just one tire when out wheeling?? I am keeping my 225 spare.

 

yeah, this is news to me too.

okay, so if i get a flat in the rear, i need to put the stock spare tire (265/70/16 i think) in the front, and put that front MTR tire (265/75/16) in the rear??
and if i get a flat in the front, just put the spare in front like normal?
that would be okay in 2wd right?

what about when i upgrade to 33s, same procedure even though they're bigger?

 

Correct.

 

I measured the donut spare rim on my 91 Accord and it is rougly an inch smaller than the alloy rim. Overall diameter with that ridiculous tire is 20.5" vs 23.25" on the regular tire. Those are rough figures because it was dark and I couldn't see the measuring tape too well.
To the differential, driving a smaller diameter wheel on the driver side is like driving with equal size tires down a road that continuously veers right. In both cases, the driver side tire is rotating faster than the passenger side tire.
I think in a part time 4WD system this will not be a problem. Just stay in 2WD when using the spare. I really don't want to buy a fifth M/TR anyways.
This whole topic reminds me that I do need to buy a tire repair kit to keep in the truck.

 

I heard about a guy in a F-150 that blew out his front diff because Ford gave him a 16" spare when his stock rim size was 17".

I always wondered about this though. Since a diff allows one wheel to spin faster than the other around turns, what difference does it make if you have different size rims/tires? Wouldn't different size rims/tires cause the same effect as turning a corner? That has always confused me.

Those doughnuts are definitely smaller than stock wheels. I just put one on a friend's car (Honda Civic hatchback--no it's not riced ) about 5 hours ago. The rim size looked a tad smaller, but the real difference was in the tire. That thing was puny! I never want a doughnut as a spare.

Well, that's my thoughts and questionts on that.
Have fun all.
DH6twinotter

 

I run Pirelli ATs 31.10.5 R15s and I had a flat on the NSR, so I changed it for my spare: a Dunlop Grandtrek 265.70 R15. It's been sitting on the rear for a while now with no problems but this thread has started me thinking: should I now move the spare to the front and then even out the drive balance at the back?