Will 28" tires to 26" hurt my ET ?

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Moparnutt340

Moparnutt340

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I ran my car last weekend for the first time at the track. Currently running a 28x12.5 drag radial, car was spinning but ran 11.40's.
My buddy gave me a set of 26x10 slicks with lots of life left in them. If I drop 2" shorter tire, will this improve my ET or hurt it ?

Some info on the car....
peek TQ is 4250rpm
peek HP is 5800rpm
gear is 3.55
was crossing finish line at about 6200rpm with 28" tire
 
2 inch drop in diameter is like changing the rear to 3.91... going to increase trap rpms...
 
Moparnutt340 said:
I ran my car last weekend for the first time at the track. Currently running a 28x12.5 drag radial, car was spinning but ran 11.40's.
My buddy gave me a set of 26x10 slicks with lots of life left in them. If I drop 2" shorter tire, will this improve my ET or hurt it ?

Some info on the car....
peek TQ is 4250rpm
peek HP is 5800rpm
gear is 3.55
was crossing finish line at about 6200rpm with 28" tire
Click to expand...


The results.......
Put on the 26x10 slicks and the car hooks hard now.
The results where no surprise other than the trap rpm
Car ran 11.50's and trapped at 6000RPM
So the slicks helped me get off the line quick but the 2" shorter tire ate up the difference over the rest of the track.

Next year I will be running a 28x10 slick and a 3.91 gear:burnout:
 
70aarcuda said:
2 inch drop in diameter is like changing the rear to 3.91... going to increase trap rpms...
Click to expand...

exactly, and if your peak HP is at 5800, and you're already crossing at 6200, i can't see it helping you. MPH will probably drop a few as your final drive ratio is changed, and you will probably be nosing over across the line if not before. Sounds to me like you're about tapped out now at the fine line a few hundred rpm's past peak HP, where your ET doesn't suffer despite the engine is actually losing HP by increasing RPM. However i think you'll be finding that spot rather quickly with a 2 inch tire height decrease, because you'll be far enough past peak HP in your RPM range, your ET's will suffer.

For comparison sake:
My dart makes peak power at 6900, so that's about where i shift. I can tell you with 3.91's a 26 inch tall tire, and an engine that can hit 7000 RPM...my shift-light is on at the 1000 ft mark, and i'm crossing probably at 72-7300. 26 inch tire does not allow much of a buffer with short gears. 3.91 doesn't sound like much for a drag car...but then again, not too many ten second cars run a 26 inch tall tire.
 
Moparnutt340 said:
The results.......
Put on the 26x10 slicks and the car hooks hard now.
The results where no surprise other than the trap rpm
Car ran 11.50's and trapped at 6000RPM
So the slicks helped me get off the line quick but the 2" shorter tire ate up the difference over the rest of the track.

Next year I will be running a 28x10 slick and a 3.91 gear:burnout:
Click to expand...

So the shorter tire trapped at a lower RPM??? What was the 1/4mi MPH difference from the two?
 
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