Motor gearing

[Roaringbadger]

Hi people
I am trying to get my head round gear ratio's and have found the charts giving final drive etc. BUT how do i know what it the appropiate final drive for a specific motor wind? I am running a B4 with a 17 turn motor so i have fitted an 84 tooth spur with a 24 tooth pinion giving me a final drive of 9.1 is this ok for the motor? and how do i know the range i.e should i fit an 81 tooth spur giving me 8.775 of a 21 tooth pinion with the 84 spur giving me 10.4? ...just looking to clue myself up so that i can gear my car appropriately.....any help appreciated

[sosidge]

BUT how do i know what it the appropiate final drive for a specific motor wind?

Unfortunately there is no definitive guide apart from experience and asking other people for advice!

I am running a B4 with a 17 turn motor so i have fitted an 84 tooth spur with a 24 tooth pinion giving me a final drive of 9.1 is this ok for the motor?

I don't think this is far wrong. You won't find many people running 17T motors but I Imagine it could be geared similar to a 19T spec motor, I have run 19T in a 4wd buggy in the past at around 9.5:1 overall so 9:1 for the 17 in a 2wd is probably in the ballpark.

and how do i know the range i.e should i fit an 81 tooth spur giving me 8.775 of a 21 tooth pinion with the 84 spur giving me 10.4? ...just looking to clue myself up so that i can gear my car appropriately.....any help appreciated

I don't really understand what you mean here. Choose a spur based on the usable range of ratios it gives you, in the B4 with a slow motor you will probably need a small spur to give you a range of big pinions that will mesh with it.

[bigchris]

Anyone got a good starting point for a bonded 7.5?in both 4 and 2wd?