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Old 01-15-2010
Green-80's Avatar
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Tire size

I have read that a 31X10.5 tire is the largest that can be run on an unlifted Scout II. If I use this size tire is it going to be tall enough to kill the gear ratio on my basically stock Scout? My line ticket says that I have a 2:74 ratio (If I recall correctly). Is a taller tire going to hurt me with a 392 engine? I don't want to have to swap gears for an occasional trip off to the woods.
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Old 01-16-2010
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Re: Tire size

Doesn't anybody know?
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Old 01-16-2010
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Re: Tire size

If your sure it is 2.74's what trans are you running, also they never put a 392 in a Scout from the factory. If it is a auto you may want to add an extra tranny cooler.
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Old 01-16-2010
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Re: Tire size

Quote:
Originally Posted by ragtopkid View Post
If your sure it is 2.74's what trans are you running, also they never put a 392 in a Scout from the factory. If it is a auto you may want to add an extra tranny cooler.
The PO had the 392 built and installed it. It has a torqueflite trans. I have wondered about the extra cooler. It was so cold when I got the Scout that I haven't even crawled all over it yet. Monday is my day off and I hope to check it out closer.
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Old 01-16-2010
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Re: Tire size

Quote:
Originally Posted by Green-80 View Post
I have read that a 31X10.5 tire is the largest that can be run on an unlifted Scout II. If I use this size tire is it going to be tall enough to kill the gear ratio on my basically stock Scout? My line ticket says that I have a 2:74 ratio (If I recall correctly). Is a taller tire going to hurt me with a 392 engine? I don't want to have to swap gears for an occasional trip off to the woods.
Short answer no.
Long answer, switching to 31's from stock will not grossly affect your drivability. There is an approximate 10 percent change in road speed at any given RPM. (Speedometer will read 60 when you're going 65, 30 @ 33 etc.)Your 392 will have the power to push through although your 727 will feel a small amount of additional work.
As Ray stated an additional transmission cooler is a good easy addition.

Click here for a good gear ratio calculator to see how different tires and gears will affect your rig. (Stock SII tires are about 28.5" tall)
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Last edited by Halfbox P; 01-16-2010 at 11:10 AM.
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Old 01-16-2010
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Re: Tire size

I have a 304 with 3.31 gears and 31x10.50's, while in high range I am a bit underpowered for any real "off roading". I find that while on logging roads etc, high range is fine. I find low range to be low enough I can get out and walk faster than it will go, which I truly enjoy for the snow and aired down.

I would think for power a 392 would be great, your Scout would be fine with your gears, assuming you can use low range and are not looking for a "crawl" speed. Rocks and snow may not be your friend with those gears.

In others words, think about what you are doing, figure out what your scout is comfortable with, and make adjustments.
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Old 01-16-2010
Eric Eric is offline
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Re: Tire size

Since you have the 2.73 gear ratio I would stay away from the 31" tall tires. Yes going from the stock 29" tire to a 31" tire will have a noticable affect on useable power. The 2.73 gear ratio was only offered in later years to improve hwy fuel economy.

Both of my SII are indentically equipped except for the tires, 345 3.73 gears. The one with the stockish sized 235/75 can pull the hill coming from my work at 50mph in 4th gear w/o even laboring, the one with the 31 x10.50s can't maintain 50mph w/o either flooring it or down shifting to 3rd. It is not because of the engine either the one with stock sized tires has over 200k while the one wearing 31 x 10.50 has only about 120K. Both have fresh carbs and have the timing set at the same 7 BTDC.
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Old 01-16-2010
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Re: Tire size

Thanks. Went I saw what the stock ratio was I had trouble believing it. My old Scout had lower gears and would only do about 60MPH if you were lucky. This one is not really geared for off-road, but for my limited use I guess with a 235/75 will be okay.
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Old 01-16-2010
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Re: Tire size

Quote:
Originally Posted by Eric View Post
Since you have the 2.73 gear ratio I would stay away from the 31" tall tires. Yes going from the stock 29" tire to a 31" tire will have a noticable affect on useable power. The 2.73 gear ratio was only offered in later years to improve hwy fuel economy.

Both of my SII are indentically equipped except for the tires, 345 3.73 gears. The one with the stockish sized 235/75 can pull the hill coming from my work at 50mph in 4th gear w/o even laboring, the one with the 31 x10.50s can't maintain 50mph w/o either flooring it or down shifting to 3rd. It is not because of the engine either the one with stock sized tires has over 200k while the one wearing 31 x 10.50 has only about 120K. Both have fresh carbs and have the timing set at the same 7 BTDC.
If you can't hold 50 or for that matter accelerate on any paved city/county/state road in Washington without down shifting with 31's/3.73/345 in a stock SII you need to find out why. It my not be your engine but you have problems.
I'm running 35's/3.73/360 and can accelerate on any paved hill.
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Old 01-16-2010
Eric Eric is offline
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Re: Tire size

Quote:
Originally Posted by Halfbox P View Post
If you can't hold 50 or for that matter accelerate on any paved city/county/state road in Washington without down shifting with 31's/3.73/345 in a stock SII you need to find out why. It my not be your engine but you have problems.
I'm running 35's/3.73/360 and can accelerate on any paved hill.
It is a 12% grade. No there aren't any issues with the vehicle it is purely the tire size. When I ran the exact same tires on the other rig the result was the same. With 235's either one will accelerate up that hill w/o trying very hard. The only significant difference between the 2 rigs is the one currently running 235's is a TravelTop with the back seat and the one currently on 31's is a CabTop.
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  #11  
Old 01-23-2010
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Re: Tire size

How much of an advantage flotation-wise does a 31 enjoy over a 235? In sand, say aired down to 15-20, each mounted on a stock 6x15 wheel?

Thanks! My Scout II: 304, 727, 3.54 gears. Full top, benches.
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