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Old 08-26-2013, 11:02 AM   #1
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A spare spare

Anyone carrying two spares? I'm wondering if for the second spare I could get away with a wheel/tire combo that is smaller in width (height/diameter is almost the same, although that's ummounted so I assume it would squish perhaps a bit smaller). The advantage is it's a bit smaller and lighter than my full size, and I'd only be using it in emergencies. Sorta like a semi-donut for SMBs, if you will. Basically it's similar except narrower by 1.25" and with a bigger wheel (18" instead of 16") and less aggressive tread.

285 75/15 vs 255 75/18. Not sure about the rim size, and the offset may be a bit different, but again it's for a spare spare.

BTW, for future use here's my current fav tire calculator: http://tire-size-conversion.com/tire-size-calculator/

Rob
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Old 08-26-2013, 11:24 AM   #2
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Re: A spare spare

Too many graphics
http://www.miata.net/garage/tirecalc.html

It's unfortunate the above is in Java because that's a PITA now

Anyway, I carry double trailer spares, and doubling for Alaska is pretty standard. Doing the same rolling diameter is fine, I've always wanted a 9" wide 35" tire so I could do a spare on the hood of the Jeep and still see over it.
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Old 08-26-2013, 12:22 PM   #3
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Re: A spare spare

You guys seem to read my mind. (Assuming that you don't mind that my mind is generally slightly OT.) I want only a single spare and I want to move it from underneath to the back driver's side door area, but I have been on a quest to reduce weight and to move weight from the back to between the axles and to the center if possible and to move weight from up to lower on the vehicle.

So any ideas on a narrower tire on a narrower wheel which is the same height would be appreciated.

Obviously road contact patch would be less, and tread would likely be different, would load rating be less as well?

I know I have not posted my specific 17" rim size or my tire size, but I would like to know if anyone has successfully implemented a narrower/lighter spare configuration. (BTW, I bought a fifth aluminum rim many years ago to reduce weight, but there is a lot of weight in the tire itself which I would like to reduce especially if mounted on the rear door area.)
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Old 08-26-2013, 02:55 PM   #4
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Re: A spare spare

Another option is an all around smaller wheel/tire for emergency use. You wouldn't want to use on a limited slip axle or a full time locker, but it could get you out of trouble when used on an open axle.

Worst case, you pull a front tire off and put the small spare on the front and swap the good front tire to the limited slip rear.

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Old 08-28-2013, 04:56 PM   #5
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Re: A spare spare

Quote:
Originally Posted by E350
Obviously road contact patch would be less, and tread would likely be different, would load rating be less as well?
Perhaps, but probably not enough to matter. I like the calculator I cited over the Miata one for uses like this cuz you can use it to find a skinnier tire on the same rim diameter and tire circumference, just vary the profile & it will give you dimensions.

Rob
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Old 08-29-2013, 06:53 AM   #6
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Re: A spare spare

Quote:
Originally Posted by E350
Obviously road contact patch would be less, and tread would likely be different, would load rating be less as well?
Except you're not running it for 50,000 miles, you're getting to a tire store.

To reduce weight I'll look at a larger rim, smaller sidewall. We're talking specifically a spare-only, not something that you rotate into the mix.
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Old 08-29-2013, 09:40 AM   #7
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Re: A spare spare

Quote:
Originally Posted by E350
I know I have not posted my specific 17" rim size or my tire size, but I would like to know if anyone has successfully implemented a narrower/lighter spare configuration.
I have 265/70R17 tires up front. They are the same height as the 235s I run in the rear and also the spare. A 235 tire should be enough to make a few hundred miles at slower speeds, even on the rear axle.

But I have noticed that bigger than 265s, it becomes hard to find a narrower tire with the same height.
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Old 08-29-2013, 11:22 AM   #8
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Re: A spare spare

I know you are trying to drop weight but if you wanted a second full size spare two-lost on the expedition portal has a nice solution

http://www.expeditionportal.com/forum/t ... s-has-been
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Old 08-29-2013, 01:12 PM   #9
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Re: A spare spare

Quote:
Originally Posted by catmandu
I know you are trying to drop weight but if you wanted a second full size spare two-lost on the expedition portal has a nice solution

http://www.expeditionportal.com/forum/t ... s-has-been
Sorry...couldn't find anything about a spare. Hint?
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Old 08-29-2013, 01:38 PM   #10
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Re: A spare spare

Maybe he's talking about the second full size spare he carries off the hitch if IIRC.

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