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Engine RPM @60MPH


63 Avanti R2
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This is all stock: 1964 Avanti R1, AT. Tires are slightly bigger, don't know if that makes any difference. Same motor, rear-end etc.

My tach is reading around 2600,2700RPM's @ 60MPH

Bruce, I hope everything works out well for you and that you will have it ready for the meet.

Steve

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Steve...thanks for the kind words. The body shop will be picking the car up in a day and the insurance estimator will go over the car with them once they have it. That way, if the estimator comes up with a different figure than the body shop boss, they can argue it out on the spot.

As far as your tach goes, I wouldn't worry about it. The tachs and speedometers were well known for being inaccurate even when new...usually to the optimistic side and the error increased with speed and rpm's. Even if your tach is accurate the taller tires won't change it's readings as it's strictly a measure of engine rpm's and that's independent of tire size. The speedometer is what's affected by the rear axle ratio/tire size.

Actually...at an indicated 60 mph you may notice slightly less rpm's as the car will roll a bit further on one revolution of the driveshaft and tires. But...the rpm's are merely an indication of engine revolutions as I said. Your engine just won't work as hard to maintain a specific speed with the taller tires. You might notice a slight loss of acceleration from a standing start as you're effectively lowering the axle ratio, but that's probably minimal and not even noticeable unless you radically change the tire size.

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This is all stock: 1964 Avanti R1, AT. Tires are slightly bigger, don't know if that makes any difference. Same motor, rear-end etc.

My tach is reading around 2600,2700RPM's @ 60MPH

Bruce, I hope everything works out well for you and that you will have it ready for the meet.

Steve

Bruce, I have an Excel spreadsheet that will calculate the RPM with the following input:

Tire Size (example: 215/70/15); transmission type; rear axle ratio

If you would like me to tell you the actual RPM for 60 MPH to verify your tachometer reading just send me the input data above.

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Bruce, I have an Excel spreadsheet that will calculate the RPM with the following input:

Tire Size (example: 215/70/15); transmission type; rear axle ratio

If you would like me to tell you the actual RPM for 60 MPH to verify your tachometer reading just send me the input data above.

Tire Size: P205/70R15 AT Twin Traction Std 3.34

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Tire Size: P205/70R15 AT Twin Traction Std 3.34

For the above Tire size the diameter is approximately 26.3", The final drive ratio in 3rd gear for the Powershift (Drive) is 1.0 and for the 3.34 ratio rear end I calculate the following RPM's

2561 RPM at 60 MPH

2988 RPM at 70 MPH

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For the above Tire size the diameter is approximately 26.3", The final drive ratio in 3rd gear for the Powershift (Drive) is 1.0 and for the 3.34 ratio rear end I calculate the following RPM's

2561 RPM at 60 MPH

2988 RPM at 70 MPH

Thanks for your input, Bruce and okc63avanti :)

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