mileage comparison between 235/85 and 265/75 tires - Diesel Forum - TheDieselStop.com
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1999-2007 General Questions General questions related to 1999-2007 Super Duty trucks. If it doesn't fit the other categories, post it here. Gas engine discussion that pertains to all models is allowed. Specific gas engine questions should use the Gas Engines forum.

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Old 08-04-2006, 06:02 PM   #1 (permalink)
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mileage comparison between 235/85 and 265/75 tires

Has anyone tried a set of the 235/85 16 tires to see if you would gain significant fuel mileage over the 265's?
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Old 08-04-2006, 09:03 PM   #2 (permalink)
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Re: mileage comparison between 235/85 and 265/75 tires

I swaped from 215's to 238's and the speedo didnt change, but then you wouldnt see any differance untill you have the speedo programed for the tires. Im sure Im going much further per tank but cant tell.
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Old 08-04-2006, 09:42 PM   #3 (permalink)
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Re: mileage comparison between 235/85 and 265/75 tires

I got the 235/85 16 in michelin, Right from the get go. Bought vehicle used & never drove on highway before. I turn about 2000 rpm at 70ish mph. So far the best milage is only about 13.5 (hand calculated) . I just ordered jody's chip, & hope I'll make a difference. Disapointed so far.
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Old 08-05-2006, 09:57 AM   #4 (permalink)
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Re: mileage comparison between 235/85 and 265/75 tires

235/85s and 265/75s are exactly the same diameter, with exactly the same tire revs/mile. So theoretically, the only cause for a difference in fuel mileage would be the very small increase in drag of the slightly bigger tire patch and the small incease in aero drag of the wider profile of the 265s.

There should definitely be a slight difference in fuel mileage, but with the same tread pattern it is probably not measureable in less than several thousand miles with each tire.

I'm now running Michelin XPS 235/85R16 Ribs (summer highway tread) - replaced LT285/75R16 AT. With calibrated speedo, there is no measureable difference in towing MPG, but there is about one MPG improvement in unloaded MPG.
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Old 08-05-2006, 11:48 AM   #5 (permalink)
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Re: mileage comparison between 235/85 and 265/75 tires

[ QUOTE ]
Has anyone tried a set of the 235/85 16 tires to see if you would gain significant fuel mileage over the 265's?

[/ QUOTE ]

I've done exactly that. From 265/75 16 Steeltex to 235/85 16 Michilin LTX. Fuel economy average was actually better on the last 20k miles of the 265 than the first 20k miles have been on the 235. Probably had a few more highway miles on the 265s. Really there is no difference.
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Old 08-05-2006, 11:51 AM   #6 (permalink)
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Re: mileage comparison between 235/85 and 265/75 tires

[ QUOTE ]
235/85s and 265/75s are exactly the same diameter, with exactly the same tire revs/mile. So theoretically, the only cause for a difference in fuel mileage would be the very small increase in drag of the slightly bigger tire patch and the small incease in aero drag of the wider profile of the 265s.



[/ QUOTE ]

What about rotational mass in stop and go driving?
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