305's and fuel
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From: Shelbyville
305's and fuel
I am changing to a sey of 305/70's and am wondering about my milage. Does anyone know how much it should drop? I know if I let my 265/75's down to 50 psi my milage drops from 19-20 to around 14-16. Also do I need a larger spare now? Thanks.
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From: OK
Running larger/wider tires generally costs a couple MPG in economy. You only need a similar sized spare if you have a limited slip differential. Since the tire size will be noticeably different, I'd get one regardless of the differential.
Also, you may want to size things up before making the change. Stuffing a 305/70 into the spare carrier may cause some grief. Specifically, the tire can rub against the frame or exhaust.
Also, you may want to size things up before making the change. Stuffing a 305/70 into the spare carrier may cause some grief. Specifically, the tire can rub against the frame or exhaust.
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From: Shelbyville
So I can use my 265/75 spare? I do have a limited slip rear end. Thanks I have always been told all tires have to be the same size. I would not plan on using the four wheel drive with the spare. 
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From: OK
IMO, you should buy a 305/70 spare.
If you have a flat on the rear, using two dissimilar sized tires will cause the LS to wear more quickly- even in 2WD. Driving in 4WD with different sized tires can also cause the drivetrain to "bind up".
If you are 100% sure that you will neither have a flat on the rear nor need 4WD while driving with the spare, you can get away with using the factory spare.
If you have a flat on the rear, using two dissimilar sized tires will cause the LS to wear more quickly- even in 2WD. Driving in 4WD with different sized tires can also cause the drivetrain to "bind up".
If you are 100% sure that you will neither have a flat on the rear nor need 4WD while driving with the spare, you can get away with using the factory spare.
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From: I'm lost somewhere in NJ -- can someone please find me?!?!?!?
I went from stock 265's to 285's. I left the factory spare alone, being too cheap (oops... meant to say "thrifty") to replace it.
If I get a flat, I carry a repair kit & cordless compressor in the truck. It's actually quicker to repair a tire than to put on your spare (oddly enough, never had to repair one of my own tires yet, but I have done it for others -- dad twice, mom once, and a stranded motorist).
In the event that I have an unrepairable flat on the rear, I will definately wind up changing two tires. The smaller spare tire would go up front, and the tire removed from the front would go on the back of the truck. You don't want to run dissimilar sized tires on the drive wheels, for reasons aleady mentioned.
Even though my "thrifty" choice to not replace the spare is less than an ideal situation, I figure I'm still better off than cars that run "donut" spare tires.
If I had it to do all over again, I would have bought an extra rim from eBay to replace the steel spare and run a 5-tire rotation on the stock 265's (including the spare tire in the rotation mix). Then replace all 5 of them when I went to 285's, continuing the 5-tire rotation with the new ones.
If I get a flat, I carry a repair kit & cordless compressor in the truck. It's actually quicker to repair a tire than to put on your spare (oddly enough, never had to repair one of my own tires yet, but I have done it for others -- dad twice, mom once, and a stranded motorist).
In the event that I have an unrepairable flat on the rear, I will definately wind up changing two tires. The smaller spare tire would go up front, and the tire removed from the front would go on the back of the truck. You don't want to run dissimilar sized tires on the drive wheels, for reasons aleady mentioned.
Even though my "thrifty" choice to not replace the spare is less than an ideal situation, I figure I'm still better off than cars that run "donut" spare tires.
If I had it to do all over again, I would have bought an extra rim from eBay to replace the steel spare and run a 5-tire rotation on the stock 265's (including the spare tire in the rotation mix). Then replace all 5 of them when I went to 285's, continuing the 5-tire rotation with the new ones.
Last edited by haroutd; Feb 17, 2004 at 04:21 PM.
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