View Single Post
Old 05-03-2010, 10:09 PM
wildemere wildemere is offline
Motorized Bicycle Elite Member
Join Date: Feb 2008
Location: Newcastle
Posts: 269
Default Re: digital tachometer

Far out man, you have typed a novel, and all of your steps and numbers are wrong, I have attached some spreadsheets (not my own) to show you the correct maths,

For a HT

Initial engine ratio is 4.1:1 20t drive, 82t driven

Secondary is usually 4.4:1 10t drive 44t driven

It equals around an 18:1 reduction ratio. I like an 16:1 ratio on my single speed bikes.

Normal 26" bike wheels are usually between 26 oto 27" high, the bare rims are around 23"

Measure it all up and a speedo is a tacho.

A stock 26" HT setup turns around 5800rpm at 25mph. Not 6959 or any other random number.
Attached Files
File Type: zip (20.1 KB, 32 views)

Last edited by wildemere; 05-03-2010 at 11:30 PM.
Reply With Quote