Gear ratio Vs. 55 MPH w/3.50 gears.

[kjspeed]

Took a ride this morning and remembered to check this out. Richmond 5-speed (5th is 1:1), 3.50 rear, 235-60R15 tires. Tach showed about 2600 RPM at 55 MPH. That's about 150 more RPM than the calculator says it should be. The speedometer checks to be fairly accurate with my phone's GPS app. The hardest part was slowing down to 55. 

[Greg]

Took a ride this morning and remembered to check this out. Richmond 5-speed (5th is 1:1), 3.50 rear, 235-60R15 tires. Tach showed about 2600 RPM at 55 MPH. That's about 150 more RPM than the calculator says it should be. The speedometer checks to be fairly accurate with my phone's GPS app. The hardest part was slowing down to 55. 

So if he is running a 4 speed, 3000RPM at 55 is probably an accurate reading.

[1967 eight barrel]

You're about an inch taller than I am according to the tire chart.

                                                                                   -Keith

[kjspeed]

Took a ride this morning and remembered to check this out. Richmond 5-speed (5th is 1:1), 3.50 rear, 235-60R15 tires. Tach showed about 2600 RPM at 55 MPH. That's about 150 more RPM than the calculator says it should be. The speedometer checks to be fairly accurate with my phone's GPS app. The hardest part was slowing down to 55. 

So if he is running a 4 speed, 3000RPM at 55 is probably an accurate reading.

He should be closer to 2700-2800 all things being equal even though the calculations indicate it would be 2586 or so. My combination calculates to 2478 @55MPH but actually reads 2600 on the tach. I've got a stagger gauge somewhere so I'll have to check actual tire dimensions or check the circumference with a tape. BTW my 5th gear is 1:1 the same as 4th gear in a 4-speed. 1st through 4th is like running a 4-speed with a 5.00 rear gear.