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Old 07-18-2010, 11:08 AM
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Trying to figure max tire dia

Run into a lot of formulas but they all seem to give different answers and none seem to adress how the car will perform out of the hole
The 3700 pound car,has the 383 stroker,650 AVS edelbrock on an airgap intake. Edelbrock 70cc heads. Hedman headers out to 2 1/2".. 9 3/4:1 compression. 270 HR cam. I have a 3:73 gear now and 25.5" dia BF's.2400 stall on a th350.Its very nicely responsive out of the hole now. I wonder how much I can grow the tire diameter and still keep a goodly portion of that response?Cause when I pay canukian prices for my new Mickeys I'd like to be pleased first go. Thoughts

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Old 07-18-2010, 11:46 AM
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Bottom line is

The taller the tire ...
the less the effective gear ratio


The taller tire does not take as many revolutions to cover the same ground ( like a higher gear ratio )

If you go to a ... say ... 27 inch tall tire ... the car will react like a car with a 3.42 gear and a 25.5 tall tire

I did not run the ACTUAL numbers ... the above is just a estimate to show what I mean
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Old 07-18-2010, 12:28 PM
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Quote:
Originally Posted by Deuce
Bottom line is

The taller the tire ...
the less the effective gear ratio


The taller tire does not take as many revolutions to cover the same ground ( like a higher gear ratio )

If you go to a ... say ... 27 inch tall tire ... the car will react like a car with a 3.42 gear and a 25.5 tall tire

I did not run the ACTUAL numbers ... the above is just a estimate to show what I mean
ya, I guess what
I'm trying to get a feel for is although I'll suffer some at what tire dia will that combo just lay down like a dog on launch?
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Old 07-18-2010, 01:34 PM
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Quote:
Originally Posted by sooper
I'm trying to get a feel for is although I'll suffer some at what tire dia will that combo just lay down like a dog on launch?
It really depends on how much torque and low end Horsepower you have. A big inch engine ( like a 454 LS6 450 horsepower Chevelle ) can stand the effective gear reduction much better than say a 69 Z28 302 car.

Your cam is fairly mid range RPM ( for a 383 ) and the rest of your combo seems suited to the mid range. It should not suffer too much. It will not LAY DOWN like a DOG

Why do you want a taller tire ?

To reduce RPM at highway speed or a larger footprint on the pavement ??
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Old 07-18-2010, 01:49 PM
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Quote:
Originally Posted by Deuce
Why do you want a taller tire ?

To reduce RPM at highway speed or a larger footprint on the pavement ??
A bit of both but more the latter, and ecspecially the looks to be honest. I'm sick of all the rims out there now that look like a section of 45 gallon drum with a rubber band around em. I like the look of some sidewall up inside the fender. However I dont want to pick up looks at the cost of off line get up and go. Given that the cams power curve in a 350 starts at 1800 and I'm running a 383 which should knock that closer to 1500 and I have a bit of forgiveness in that 2400 stall I'm kinda hoping to migrate from 25.5 dia up to say something in the 27's. Sound reasonable?
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Old 07-18-2010, 04:05 PM
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Depending on the vehicle,
you may be able to go wider ... to achieve the " LOOK " you are after and stay at the same tire height.

If you go to a lower series tire ... ( like a 60 series if you have 70 series ) you can go up from size 215 ( 70 series ) to maybe a larger 235 ( 60 series ) and still be the same height. Depending on your vehicle ... you may be able to just get a wider tire under the fender. I have changed the wheel offset ( new rims ) to move the rim closer to the inner fender and went wider on the rim ... for a wider tire.

Most tire dealer have a chart to tell you the installed tire height and width of performance based tires.

Deuce
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