different sized spare tire
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Senior User
Joined: Oct 2004
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different sized spare tire
I'm running LT285 75R16's all the way around on my '99 SCab 4x4 5.4L. My spare is a LT265 75R16. Would it be a problem if I had to use my spare since it is a different size? I've always kinda thought in the back of my head that if I got a flat, I'd just put the smaller spare on the front, regardless of which tire went flat, and make sure I had the same size on the rears, as long as I didn't need four wheel drive. Is this true? Or should I break down and buy a 285 spare? And if I did, would it even fit under the rear where the spare goes?
Logistics Pro
Joined: Jul 2002
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From: South Dakota
You'll be okay as long as you keep the speeds at a resonable rate, like say 50 mph or lower.
Running the wrong size on a LS diff is a pretty bad thing. I currently have the same problem with my F150, only I have the stock 17" size spare and a LS.
Personally, I'd just invest in a good used matching size for your spare. This way you don't have to worry and won't have to worry about driving too fast.
I'm trying to find a good used 285/70R17 to fit my rim and match my existing tire height (285/75R16).
Running the wrong size on a LS diff is a pretty bad thing. I currently have the same problem with my F150, only I have the stock 17" size spare and a LS.
Personally, I'd just invest in a good used matching size for your spare. This way you don't have to worry and won't have to worry about driving too fast.
I'm trying to find a good used 285/70R17 to fit my rim and match my existing tire height (285/75R16).
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yeah I have an open diff on the front, but the rear is an LS. That's why I had always thought I'd just make sure the smaller spare was in the front if I had a flat - even though that might result in changing two tires instead of just one. I think I'll go the same route as Super and try to find a good used one that won't cost me much but is the same size. Oh yeah, anybody know if a 285 will fit on the spare carrier underneath?
Senior User
Joined: Mar 2004
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From: Carthage, IL
nope it wont i have 285 on my f 250 ld and the stock spare is 245 i dont worry about flats as long as im driving right to get it fixed but i know that when i tried to put a 285 spare under it was way off
Logistics Pro
Joined: Jul 2002
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From: South Dakota
I dunno, a 285 is not that much bigger than a 265.
I think that it will fit as there is some of room for a bit bigger tire on my rig, even with my dual exhaust.
The only problem I see is that the spare rim is usually much narrower than the stock rims.
I think that it will fit as there is some of room for a bit bigger tire on my rig, even with my dual exhaust.
The only problem I see is that the spare rim is usually much narrower than the stock rims.
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Joined: Aug 2002
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It won't be any problem at all. If you look at what the size means on a tire:
LT = Light Truck
265 = 265mm width of the tread
75R = 75 is the sidewall or height of the tire. R means Radial
16 = wheel size
Since the only difference is the width of the tire, you will not have any issue with the LS. You are not changing height or wheel size. Go forth and prosper, grasshopper...
LT = Light Truck
265 = 265mm width of the tread
75R = 75 is the sidewall or height of the tire. R means Radial
16 = wheel size
Since the only difference is the width of the tire, you will not have any issue with the LS. You are not changing height or wheel size. Go forth and prosper, grasshopper...
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Logistics Pro
Joined: Jul 2002
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From: South Dakota
Originally Posted by lm1d
It won't be any problem at all. If you look at what the size means on a tire:
LT = Light Truck
265 = 265mm width of the tread
75R = 75 is the sidewall or height of the tire. R means Radial
16 = wheel size
Since the only difference is the width of the tire, you will not have any issue with the LS. You are not changing height or wheel size. Go forth and prosper, grasshopper...
LT = Light Truck
265 = 265mm width of the tread
75R = 75 is the sidewall or height of the tire. R means Radial
16 = wheel size
Since the only difference is the width of the tire, you will not have any issue with the LS. You are not changing height or wheel size. Go forth and prosper, grasshopper...
Generally speaking...
The 265 is the cross sectional width (not tread width) in milimeters, and is measured sidewall to sidewall through the tire.
The 75 is called the aspect ratio, it is the ratio of height vs width using the 265 number. The higher the number the taller and narrower the tire.
16 is the rim size.
A 285/75R17 is taller and wider than a 265/75R16 because the cross sectional width is greater. Almost a full inch to taller to be exact.
heights and widths of my favorite tire
A 1'' tire height difference is more than enough to chew up a LS or a 4x4 system.
Last edited by superrangerman2002; Feb 7, 2005 at 11:36 AM.
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Thread Starter
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Senior User
Joined: Oct 2004
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yeah Super, you're right about the tire size being more than just a width difference. I worked at Discount Tire for 2 years and you got it just right. I think I'm gonna go try to find a used spare thats the same size. I actually have 5 identical factory rims (from the Discount days) so my spare rim is not a concern. Thanks for all the input guys.