Mazda never offered an RX-7 with a 6-speed transmission. Learn why a 6-speed transmission would be a benefit here:
http://auto.howstuffworks.com/transmission.htm

Unfortunately, the costs outweigh the benefits for most people. The transmission is probably one of the last things on my list of "stuff to upgrade if I had too much money and wanted to spend it on my car."

-s-

I was riding in a stock FD one time and the driver had green shoes. The car only went 160 MPH. I got another ride in an FD and this time the driver had an Jamaican accent. The car went 171 MPH. Therefore, it is clear that Jamaican accents make your car faster.

-Max
(fearing that I will read about how Jamaican accents make cars faster in another RX7Club.com thread three months from now)

i want a semi with a 7 spd cuz that is 2 better than 5! :bigthumb:

I don't think we've seen enough data to support your theory. What color were the shoes of the driver with the Jamaican accent?

:weed:

That's some good ass shit you're smoking there Mr. Cooper! :D

They were lace-up sneakers. Duh!

-Max :)

I guess I'll give you that one.

What the hell do you expect from a guy who owns an RX-7 GT.1?

Dude.. I'm swapping the rotary out for a Jamaican tomorrow.

That's only a +1. The overall diamater should be the same as a 50-16 shouldn't it?

Hey, my buddy Frank is Jamaican. He's kinda short; I wonder if I can close the hood with him pedaling in there...

Damn kind of you, Sir. Damn kind.

The stock P225/50-16 tires are a nominal 24.86" tall. A P275/40-17 is a nominal 25.7", so about 1" taller. Consider the difference that makes in circumference (2πr or πd)...

P225/50-16 - 78.09" or 6.51 feet
P275/40-17 - 80.62" or 6.72 feet

It makes a noticeable difference when they're turning at ~2,710 rpm (redline in 5th).

P225/50-16 - 200.49 mph
P275/40-17 - 206.95 mph



To calculate nominal tire height...
Tire Width (mm) * (Profile / 100) * 2 / 25.4 + Wheel Diameter (in.)
225 mm * (.5) * 2 / 25.4 + 16 in.
8.56 in. + 16 in. = 24.86 in.

To calculate nominal tire circumference...
24.86 in. * 3.14159 = 78.09"
78.09" / 12 = 6.51 feet

To calculate wheel speed at X rpm in a given gear...
Engine RPM / Transmission Ratio / Differential Ratio
8,000 rpm / 0.72 (5th gear) / 4.1 = 2,710 rpm

To calculate nominal vehicle speed...
Wheel RPM * Tire Circumference * 60 min./hr. * 5280 feet/mile
2,710 * 6.51 feet * 60 min./hr. * 5280 feet/mile = ~200.49 mph


Keep in mind that this is just the gear limited top speed, not actual top speed. You still need enough power at the wheels after drivetrain losses to overcome wind and rolling resistance, and tires are not perfectly circular, obviously. Measuring the actual circumference of your tire will improve accuracy, but tires grow slightly at high speed, and traction is never 100%, so there will be some tire slip as well. Add in the inaccuracy of your analog tachometer and speedometer, and you'll see why you'll never reach the calculated top speed in a given gear. :)