How much does tire size affect trap speed?
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From: Harford Co. Maryland
Depending on when you hit the limiter ....maybe not at all ?
25.5" Vs. 28" is about a 200-300rpm +/- difference....but the rolling resistance and inertia to get rolling.....could be equal mph, but better ET since you're not on the limiter.
Can you borrow a pair for a test ?
25.5" Vs. 28" is about a 200-300rpm +/- difference....but the rolling resistance and inertia to get rolling.....could be equal mph, but better ET since you're not on the limiter.
Can you borrow a pair for a test ?
Thread Starter
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I'm hoping to trap higher and I bet you I will. It's going to change my gear ratio enough to go thru traps in 3rd. Last night went 11.0@130 going thru in 4th gear . They weren't too happy about it lol . ( no cage)
MPH x Rear Gear x Trans Gear x 336 ÷ Tire Diameter = RPM
Example:
148 x 3.73 x 1 x 336 ÷ 28 = 6624.48 RPM
If it is an unlocked automatic, then multiply your final answer by estimated torque converter slip and add that to the RPM
Example: 6624.48 x .06(6%)= 397.4688.
6624.48+397.4688=7021.9488 or 7022 RPM.
Example:
148 x 3.73 x 1 x 336 ÷ 28 = 6624.48 RPM
If it is an unlocked automatic, then multiply your final answer by estimated torque converter slip and add that to the RPM
Example: 6624.48 x .06(6%)= 397.4688.
6624.48+397.4688=7021.9488 or 7022 RPM.
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No. Unfortunately, you will not automatically pick up 10 mph. You need a great deal more power and/or weight reduction to do that. Depending on the atmospheric conditions, your 130 mph trap speed in fourth will most likely be indicative to what you will trap with the 28s.
Last edited by GARY2004Z06; May 14, 2017 at 08:48 AM.
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From: South Florida
Thread Starter
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No. Unfortunately, you will not automatically pick up 10 mph. You need a great deal more power and/or weight reduction to do that. Depending on the atmospheric conditions, your 130 mph trap speed in fourth will most likely be indicative to what you will trap with the 28s.
Last edited by jimmyg; May 14, 2017 at 08:52 PM.
Thread Starter
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Well I put 28s on. Used to rev 3200@80mph now it's down to 2700. The nittos looked better, but the m&h racemasters hook way better and I should be able to go thru traps in 3rd @peak torque
Look weird?
Just food for thought: I was running 26 inch radials and trapping 122. I switched to 28 in bias tires (among several other small changes) and can now only trap 117. the general consensus is that my loss in speed is from the tire change. I wasn't hitting the limiter before but I was right at it. When I get my speed back, I'll let you know what it took.
Thread Starter
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Just food for thought: I was running 26 inch radials and trapping 122. I switched to 28 in bias tires (among several other small changes) and can now only trap 117. the general consensus is that my loss in speed is from the tire change. I wasn't hitting the limiter before but I was right at it. When I get my speed back, I'll let you know what it took.
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Trap speed indicates HP. All things being equal, to increase trap speed, you have to increase HP.
If someone sees a significant gain in trap speed from just a tire diameter change, then the prior gearing/tire combo was inadequate.
Al
If someone sees a significant gain in trap speed from just a tire diameter change, then the prior gearing/tire combo was inadequate.
Al
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Exactly.this is what's up with my combo. It hits redline in 3rd about 3/4 track.