Acceptable size differential for full size spare

[avacado11]

I have a Chrysler Pacifica Hybrid that did not come with a temp spare. My summer set is on the original wheels wrapped with 235/65/17
I came across a good deal on 18” Jeep wheels and put 235/60/18 snow tires on them as my winter set.

The diameter difference between the two is 0.07”(1.9mm)

I figured no problem I’ll just buy an HF scissor jack to keep in the trunk for when I need it. Well I needed it and turns out the van(PHEV) is too heavy for the scissor jack to lift. So I’m SOL ended up calling for a tow back home so I could use my floor jack.

I have a long road trip planned for this summer and I was thinking about putting together a 235/65/17 full size spare. My worry is If I get a flat on the drive axle roadside may not want to mess around with swapping wheels between front and rear. But then again it’s an *if* situation.
Is it going to be worth $170($90 used oem wheel plus $50 used tire plus $20 M&B and tax) to have a matching size spare that I very likely will never use? Or can I get away with 0.07” in tread difference for emergency use?

I’d rather not spend the money if I dont need to…but it would also be nice to just bolt the wheel on and forget about it. Could I realistically do the same with what I have now?

 

[berniedd]

I don't see a problem if you run the 18" spare for only short distances till you get the flat fixed, the difference in diameters is only 2mm. But do bring your floor jack in case you need it.

 

[shortyb]

Take your floorjack on the roadtrip, or find a place to always carry it with you. How about a HD hydraulic bottlejack? More compact and easier to store than a full size floorjack.

And you can probably use the different sized spare on the drive axle as long as you keep speeds down. Those doughnuts work fine for people that keep speeds down to avoid overheating the diff fluid. Thats why yo seen them plastered with max. speed ratings and for limited miles of use. The folks that you see doing 90MPH on a doughnut? They don't care about themselves or their cars and well, Darwin .

 

[nwjones18]

I see no issue with that diameter difference. You could have that much difference between a new/worn tire of the same size..

 

[slacktide_bitog]

It's better to use the correct size, but the 18 you have should be ok if you only use it on the back (the non-drive axle).

 

[SC Maintenance]

From https://tiresize.com/comparison/

2 revs difference per mile. Should be fine. Go for it.

Worst case if you couldn't get your original fixed, you could put the snow on the back.

 

[Number_35]

That's a very disappointing scissors jack. One corner of the van would be, what, 1200 lbs at most?

 

[shortyb]

Are you talking about making up a separate 17"wheel/tire as a spare and having to replace a flat with an 18"? Again, should be no issue. But for summer, won't you be on the summer set which is the exact same size? Or are you asking if during winter, you could use an existing 17" as a spare for the 18" winters and vice versa for summer?

 

[avacado11]

Are you talking about making up a separate 17"wheel/tire as a spare and having to replace a flat with an 18"? Again, should be no issue. But for summer, won't you be on the summer set which is the exact same size? Or are you asking if during winter, you could use an existing 17" as a spare for the 18" winters and vice versa for summer?

Basically during the summer I’m on 235/65/17 and my spare would be one of my winter wheels 235/60/18. I was thinking about having a 235/65/17 spare instead due to the very small diameter difference.

I don’t leave the local area during the winter so not too worried about having a 235/60 spare.

 

[avacado11]

That's a very disappointing scissors jack. One corner of the van would be, what, 1200 lbs at most?

It’s a 3000lb rated jack. The battery pack is located between the axles. once the jack made contact with the pinch weld it became impossible to turn the handle. Curb weight is 5000lb on the van. Maybe I could’ve made it work if I had more leverage with the jack handle but I don’t want to get it half way up just for it(the handle) to snap.

 

[avacado11]

From https://tiresize.com/comparison/

2 revs difference per mile. Should be fine. Go for it.

Worst case if you couldn't get your original fixed, you could put the snow on the back.

Yup my plan was to run the spare on the rear but last time I had a drive axle go flat. I couldn’t do the swap myself and idk if AAA techs are willing to swap front & rear.

Just thought about getting one of the small HF aluminum jacks to keep with the spare. I need another floor jack for the garage anyways.

 

[SC Maintenance]

Yup my plan was to run the spare on the rear but last time I had a drive axle go flat. I couldn’t do the swap myself and idk if AAA techs are willing to swap front & rear.

Just thought about getting one of the small HF aluminum jacks to keep with the spare. I need another floor jack for the garage anyways.

So there is not going to be a proper answer for this, but on an open diff 2/700 turns different would not bother me, but having very different treads on opposite sides of the steering axle for an extended period would - its apt to pull is my guess. If I had to go hundreds of miles and I wasn't able to swap myself, I would go to a tire shop and ask them to swap them for me. Still better than a donut by a long shot.

 

[shortyb]

Basically during the summer I’m on 235/65/17 and my spare would be one of my winter wheels 235/60/18. I was thinking about having a 235/65/17 spare instead due to the very small diameter difference.

I don’t leave the local area during the winter so not too worried about having a 235/60 spare.

You will be fine either way then, it's a very negligible difference between the two.

 

[Ang]

Donut tires are often an inch difference from the full size tires, so it's fine.