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MG MGA - rpm to mph- 5speed

You folks who have installed a 5 speed with a MK11 4.1 rear end please respond.
I haven't installed the speedo cable and have been driving my MkII with the Sierra five speed. Could you tell me what speed would be 2500rpm's in 4th gear and the same rpm's in 5th? I have been guessing about 55mph in 4th gear at 2500rpm's and 60-62mph in 5th.

Ray Ammeter

Start here:
4th gear is direct drive, same as the original 4-speed. As such, engine speed to ground speed would be the same, 44.6 mph at 2500 rpm (4.1 final ratio and 165-80-15 tires).

Standard Sierra gearbox has 5th gear ratio of 0.82. That would give 54.4 mph at 2500 rpm.
Barney Gaylord

I have recently installed the Siera 5 Speed in my MK 2 Coupe 4.1 rear end
At 2500 in 4th I am doing around 44 MPH in 5th around 55 MPH.
Cruising at 70 mph my rev counter indicates just under 3500 revs.
I recently had the speedo recalibrated by Speedy Cables
Trust this helps

P D Camp

Thanks for your responses. Since I hadn't driven the car in almost three years it felt like I was going faster than I was. You know how it is, wind in the hair, sitting a foot off the ground makes it feel like I was ripping up the pavement when I wasn't. Thanks again.

Ray Ammeter

This thread was discussed on 16/11/2008

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