# Gear Ratios : Speeds In Gears : When To Shift a Skyline GT-R

Gear Ratios : Speeds In Gears : When To Shift a Skyline GT-R

This post is all math. If you don’t have some math, to fill into the blanks, you can’t figure any of this out.  What you need to know:

• Tire Height – can be calculated from
• Width
• Aspect ratio
• Wheel size
• https://spicerparts.com/calculators/tire-height-calculator
• Transmission in the car
• Is it stock?
• Is it modified?
• 5 speed
• 6 speed
• Overall Gear ratio
• 4.111 is stock R32/R33 GT-R
• 3.545 is stock R34 GT-R
• It can be something else
• Shift Point
• If you shift with the stock tach you are shifting at 7600 rpm
• If you shift at the limiter then that is most likely 8000 rpm
• If you shift at a different point, the links are below to figure that out

 Gear 1 2 3 4 5 6 R32/R33 3.214 1.925 1.302 1.000 0.752 R34 3.827 2.360 1.685 1.312 1.000 0.793

One example, my bluecar.  It has a 275/35/18 tire on it, which is 25.58 inches tall. It has a stock 5 speed transmission. Overall/Final gear ratios are 4.111. It is shifted at 8500 rpm.

https://www.blocklayer.com/rpm-gear.aspx
 4.111, stock transmission, shifting at 8500 rpm.
 4.111. stock transmission, shifting at 8000 rpm on the stock tach, aka 7600 rpm.
So you can see that by shifting at a higher RPM, you fall into a bit better point on the dyno chart for this car, and this turbo combination.  https://www.gtrusablog.com/2019/10/finally-running-bluecar-on-dyno-results.html
So about if we swapped to a Getrag? Well actually the bluecar used to have a Getrag in it, but we sold it to a friend, that needed one.  So add a 6th gear, keep the 4.111 gear vs the 3.545 gear of the R34. Then we get:
 5242, nearly that magic number.
Now onto a sequential.  My Nismo has(had, till I stole it out for Big Bird 2) OS88 sequential transmission, and 4.3 gears. The OS ratios are:
 4.3 gears, OS88 transmission.  58 mph in 1st gear

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Index and Start Page

Published at Sat, 16 May 2020 01:37:00 +0000