Hi guys, I have a 70 GS 455 4-speed and am wondering how far off my speedo is. I am running 275-60r15 28"tall tires, 3:08 gears, and am wondering what rpm's you guys out there are getting around 70 mph. I did some calculations and came up with 2700 or so, but my speedo must be considerably off, since I am around 3,000 at 70. I have tried switching speedo gears, but I have the smallest one in, brown I think. Kevin
Here is an excellent speedo calculator page: http://www.1bad69.com/calc.htm According to it, you should be spinning at around 2600 rpm's at 70 mph.
My speedo reads 1 1/2 to 2 MPH slower than actual with 325/50-15's (27.9 inches dia) on the back. I checked it with my GPS. :Brow:
I have done the calculations, I guess I had better verify that my tach is on and figure I am about 15% off! Yikes, I guess I was going close to 80mph crusing instead of 70 like the speedo is reading. One good thing though, I guess I should get a little better mileage if I can keep my foot out of it. Kevin
