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Explaination (archive)
[ Follow Ups ] [ 3-series (E21) Message Board ] [ Msg. Board FAQ ]
Posted by Paul on March 19, 2001 at 14:39:00:

In Reply to: I dont get it.... posted by mongoose on March 19, 2001 at 14:12:26:

My 140mph speedo was buried so I just calculated using the following formula

"speed" = RPM x circ x 60
---------------
trans x rear x 63371.4

205/50-15 tires = 72.5" circ
trans = .8
rear = 3.64
6500rpm works out to 153mph

You probably have the 3.90:1 rear end which would work out to ~115mph in 4th with stock wheels/tires
5spd would allow 145mph at 6800rpm with 3.90:1 rear end.

Paul
PS the car was rock solid at that speed.


my 78 320i, stock except a header at the time, in fourth gear at 6800rpm on the highway maxed out at 110-115mph, I couldnt tell because it bounced too much, so putting in a 5 speed is that much faster?! (in topend of course)




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