# Tire sizes



## BubbaBlue (May 11, 2004)

My turn for the dumb question of the day. 

A while back I upgraded the tires on my XJ to 30x9.50xR15 BFG AT/KO's from 225/75R15 GY RT/S's. All is well and good but I never sized up my spare. Finally getting around to it. I know the size difference there ain't cool.

Not wanted to drop the coin for another AT/KO for the spare, I stopped at a used tire joint on the way home yesterday. He had a number of appropriate tires, but nothing in my size. Said oh well and left.

Question. He had 235's and 29's. I know these are too small, but is either one close enough to get by with as a spare? Price is right. $20 mounted. 

My concern is that, worse case, one of my front tires would go flat, get replaced with the smaller spare, and create the conditions for the death wobble. No, I haven't had the problem in the past, but it is a concern.

Any thoughts?
.


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## narfpoit (Jun 16, 2004)

It would be similar to riding on a donought but I would suggest you make sure that the smaller tire ends up on the back axle. So if you get a flat in the front first put your spare in the back and move the good one from the back to the front. This will prevent you from having a lot of steering problems while on the spare. Also if your spare is the 225/75 R15 I wouldn't bother getting one of the other sizes mentioned because they would not be that much bigger than what you have. It would be better to save your money and wait and get the right size when it is available. The difference in size will be compensated for by your differential but this will put a lot of extra strain on it to be working all the time so make sure it stays lubed well and of course only use it for a temp fix.


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## Shooter (Nov 14, 2004)

Yup running the smaller spare on the back would be your best bet, the only time you would have any problem with a smaller tire is if you had to engage 4 wheel drive. 
We know how wild and crazy you drive so stop mud jumpn and hopen curbs and ya might not have as much trouble.


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## BubbaBlue (May 11, 2004)

narfpoit said:


> It would be similar to riding on a donought but I would suggest you make sure that the smaller tire ends up on the back axle. So if you get a flat in the front first put your spare in the back and move the good one from the back to the front. This will prevent you from having a lot of steering problems while on the spare. *Also if your spare is the 225/75 R15 I wouldn't bother getting one of the other sizes mentioned because they would not be that much bigger than what you have.* It would be better to save your money and wait and get the right size when it is available. The difference in size will be compensated for by your differential but this will put a lot of extra strain on it to be working all the time so make sure it stays lubed well and of course only use it for a temp fix.


Thanks. I figured getting a "closer" size would be better... guess not. Think I'll just keep looking until I find one the right size.



Shooter said:


> Yup running the smaller spare on the back would be your best bet, the only time you would have any problem with a smaller tire is if you had to engage 4 wheel drive.
> *We know how wild and crazy you drive so stop mud jumpn and hopen curbs and ya might not have as much trouble.*


I'm just trying to keep up with my *elders *out there on the sand. 

Oh by the way, you got some *wide ruts *there bud. 
.


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## Railroader (Apr 13, 2005)

BubbaBlue said:


> My turn for the dumb question of the day.
> 
> A while back I upgraded the tires on my XJ to 30x9.50xR15 BFG AT/KO's from 225/75R15 GY RT/S's. All is well and good but I never sized up my spare. Finally getting around to it. I know the size difference there ain't cool.
> 
> ...


Just run the doughnut on the rear......And save space in the back for other crap...


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## BubbaBlue (May 11, 2004)

Railroader said:


> Just run the doughnut on the rear......And save space in the back for other crap...




The spare right now is a brand new 225/75R15 CrapYear RT/S. Still has the blue soap on the letters.  Previous owner bought it, not me. 

Gonna just leave it until I find another 30x9.50 somewhere.
.


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## Railroader (Apr 13, 2005)

BubbaBlue said:


> The spare right now is a brand new 225/75R15 CrapYear RT/S. Still has the blue soap on the letters.  Previous owner bought it, not me.
> 
> Gonna just leave it until I find another 30x9.50 somewhere.
> .



I wouldn't buy another tire, that tire is close enough you'd never know the difference, front or back..


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## narfpoit (Jun 16, 2004)

yeah the size spare you have now has a diameter of 28.29 inches the BFG you have is 29.3. So your respective Circumferences would be 88.87 inches and 92.0 inches. This is only a 3.3 inch difference and probably would not be felt espescially if you place it in the back. But remember this will still be working you differential overtime and is ment only to be used as a temp fix.


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## BubbaBlue (May 11, 2004)

Cool. Thanks for the info guys. 

Glad I checked with the experts. Saved me some money again. 

Hmmm... guess it all evens out considering this site is the reason I now own an XJ, a fishing yak, conventionals, etc, etc, etc... 
.


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## Shooter (Nov 14, 2004)

Hey now I aint that fat,,, oh, oh ,oh opps sorry you said RUTS and not Guts :redface:

Wait till ya see how big and deep I make the ruts now with my new toy added on


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