A note on spares

InCommando · **Posted:** Tue Dec 16, 2008 2:32 pm

I have seen numerous pictures on here showing people with lifts and tires that are 2"-3" taller than the spare they still have hanging on the back.

You guys know never to use that smaller spare, especially in 4wd, right? Just making sure before you end up picking up pieces of your aluminum transfercases up off of the ground.

tommudd · **Posted:** Tue Dec 16, 2008 4:47 pm

Now you went and ruined all the fun :cry:

One of the "toy" KJs I have has at least 44s on it with a what looks to be a 6.00 X15 spare will that work? :wink:

Seriously I have seen it a lot as well and cringe when I think what may happen, of course right now I am running 265-70s with a 245-75 spare but they are within .01 of each other

Robbrez · **Posted:** Tue Dec 16, 2008 5:29 pm

tommudd wrote:

Now you went and ruined all the fun :cry:

One of the "toy" KJs I have has at least 44s on it with a what looks to be a 6.00 X15 spare will that work? :wink:

Seriously I have seen it a lot as well and cringe when I think what may happen, of course right now I am running 265-70s with a 245-75 spare but they are within .01 of each other

id assume that would be fine

tommudd · **Posted:** Tue Dec 16, 2008 5:51 pm

Robbrez wrote:

tommudd wrote:

Now you went and ruined all the fun :cry:

One of the "toy" KJs I have has at least 44s on it with a what looks to be a 6.00 X15 spare will that work? :wink:

Seriously I have seen it a lot as well and cringe when I think what may happen, of course right now I am running 265-70s with a 245-75 spare but they are within .01 of each other

id assume that would be fine

Yep know it will be fine just playing with everyone, worked in the tire business too long to do anything "real" stupid :lol:

Robbrez · **Posted:** Tue Dec 16, 2008 6:04 pm

Albert · **Posted:** Tue Dec 16, 2008 8:06 pm

oh man.......ya mean I gotta take my lawn mower tire off the back cause it won't work......geeeeezzzzzz

jeepskate · **Posted:** Wed Dec 17, 2008 12:39 am

Well, I haven't seen anyone whose spare is two FEET three inches smaller

InCommando · **Posted:** Thu Dec 18, 2008 3:48 am

try 2"-3".

Proofreading not is my strong point

As Tom knows, many tires of the same size & brand can be over .1" off of each other, but when you go from a 235/70/16 to a 245/75/16 or bigger, they are probably getting into the danger zone. Width matters not, only diameter.

Maybe I should have kept quiet as sometimes the carnage pics postings are interesting??? :shock:

chrispitude · **Posted:** Wed Dec 24, 2008 3:03 pm

Can someone explain why this is a problem if the transfer case is unlocked? I understand it'll bind itself into little bits in 4PT, and is not a good idea in 4FT, but how mechanically is the damage caused in 2WD or 4FT?

- Chris

Diggerfreek · **Posted:** Wed Dec 24, 2008 3:13 pm

It is a problem for the differentials. instead of the carrier rotating as if you are going straight, the spider gears will be turning all of the time like you are going around in circles. in turn, the diff will create more heat due to friction and will blow

tommudd · **Posted:** Wed Dec 24, 2008 4:08 pm

Diggerfreek wrote:

It is a problem for the differentials. instead of the carrier rotating as if you are going straight, the spider gears will be turning all of the time like you are going around in circles. in turn, the diff will create more heat due to friction and will blow

good simple explanation Digger, and exactly what happens, then if you have lockers :shock:

sleeve84028 · **Posted:** Wed Dec 24, 2008 4:10 pm

For a temporary solution (say less than 30 miles) a smaller tire would be OK for an open differential.

Assuming:
1) The diff has been taken care of
2) The driver will keep speeds below 55MPH

Remember those compact spares that almost all cars have these days?

chrispitude · **Posted:** Wed Dec 24, 2008 4:38 pm

Diggerfreek wrote:

It is a problem for the differentials. instead of the carrier rotating as if you are going straight, the spider gears will be turning all of the time like you are going around in circles. in turn, the diff will create more heat due to friction and will blow

Thanks Digger! This is what I expected (constant spider rotation) but I wasn't positive if they were designed to handle that through proper lubrication. You figure that with any small tire circumference difference (wear, pressure, idiotic mismatches) or city driving with lots of weaving and turns, the spider would be moving fairly constantly as well, although less in overall magnitude.

- Chris

Diggerfreek · **Posted:** Wed Dec 24, 2008 4:55 pm

I wouldn't even drive 10 miles. as for the cars that come with compact spares, it is stated that if the flat tire is on a power driven wheel, that the spare must be put on a no power driven wheel and that the good tire should be put in place of the flat one

Diggerfreek · **Posted:** Wed Dec 24, 2008 4:58 pm

chrispitude wrote:

Diggerfreek wrote:

It is a problem for the differentials. instead of the carrier rotating as if you are going straight, the spider gears will be turning all of the time like you are going around in circles. in turn, the diff will create more heat due to friction and will blow

Thanks Digger! This is what I expected (constant spider rotation) but I wasn't positive if they were designed to handle that through proper lubrication. You figure that with any small tire circumference difference (wear, pressure, idiotic mismatches) or city driving with lots of weaving and turns, the spider would be moving fairly constantly as well, although less in overall magnitude.

- Chris

like you said, they do move a little but with the rotation of the carrier, it is splash lubricating the spiders, but with the match ups listed above, things are going to blow up

A note on spares

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