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Old 01-04-2009, 07:28 PM   #1
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tow vehicle tire size

I am zeroing in on a Toyota Tundra crew cab 5.7L V8 for my tow vehicle. I was going to opt for the 20" wheels but read somewhere that can generally lower the tow rating or ability? Does anyone know if that is right? Dang those 20's look sharp. But i'd rather know now if i have to start warming up to the 18's or heaven forbid, anything smaller
thanks everyone
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Old 01-04-2009, 08:43 PM   #2
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Yes, that is what Trailer Life's annual towing guide says. Someone will correct me if I'm wrong, but I believe this has to do with the bigger wheels resulting in greater unsprung weight on the axles.

It should not have a significant impact on towing a Bambi, but may factor in if you decide to move to a larger trailer.

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Old 01-04-2009, 08:54 PM   #3
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Whizzo is partially correct, but the more significant reason is the tire diameter has an effect on the overall drive ratio. A larger size tire defeats the value of the lower rear end ratio of the Tundra which is 4.30 and one of the reasons it has a relatively high maximum tow rating for a 1/2 ton. Go with the 18".
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Old 01-04-2009, 08:58 PM   #4
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I can't help you on the towing capacity, but I've found a very limited selection of snow tires available in the 18" size. Given your location, this may be a factor if the towing reduction isn't a lot.

The 255/70r18 has a calculated diameter of 32.05. The 275/55r20 has a calculated diameter of 31.09. This might give a slight advantage to the 20 in terms of moving a load.
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Old 01-05-2009, 09:04 AM   #5
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18" inch tires on our 08 f150 dropped the tow rating 500lbs. For what it is worth the beast takes the beating every day and no issues. By far the toughest tow yet was yesterday, hwy 1 from lompoc to mossy bay ca. The old 150 got a real work out and never missed a beat. I would suggest NOT do this with any thing larger than a 28. I loved the challenge, my wife however thought i lost my mind.
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Old 01-05-2009, 09:15 AM   #6
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I have 20" wheels on my Yukon. The overall diameter of the 18" tire/wheel combo (on the GMC anyway) was the same as for my 20" tire/wheel combo.

my 20" wheel is very close to the same weight as the 18" wheel. The tire on the 18" wheel is therefore heavier than the 20" tire due to the taller sidewall.

A taller side wall can result in a less controllable ride while towing.

I would go with the 20" wheel tire combo.

just my 0.02.
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Old 01-05-2009, 09:42 AM   #7
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I've got 20" tires on my 05 Dodge Ram. No problems towing anything. The problem is with replacements. THEY COST A FORTUNE. Also not a lot of places are equiped to work on the 20" here.
I would go with the 18" next time.
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