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FAB Racing Tweets
Quite a few threads have popped up recently with people asking about gearing and what works best at certain tracks.
I thought it may be a good idea to have a definitive gearing thread so everyone can see what's what
PLEASE NOTE - the Polini Reverse engines I will cover towards the end as they are different calculation.
Firstly its important that you know how the sprockets work, the front sprocket (Pinion) is a lot smaller, normally around a 6 or 7 teeth, larger sizes are available but rarely used.
The rear sprockets have a larger range from around 50 to 80 teeth, these let you adjust in small increments whilst changing the front pinion has a bigger effect.
Final Drive Ratio
You can calculate the final drive ratio simply by dividing the rear sprocket teeth amount by the front i.e.
72 divided 6 = 12
The higher the final drive ratio the faster the acceleration of the bike, obviously the lower the ratio the less acceleration but the bike will have a higher top speed.
A very useful calculator can be found here http://www.minimotogarage.com/ecm_speed_calc.html
This will show you final drive ratio, top speed etc etc, be sure to input the correct tyre sizes and max revs for your bike.
The trick is to balance top speed Vs acceleration to fit the track that you are racing at.
Polini Reverse Engines
These work in a different way to the normal engines.
I have zero experience with them but here is a calculation that I stole from another thread on the forum:
Rear sprocket teeth No. divided by front teeth No. x 2.157 i.e
56 divided by 10 x 2.157 = 12.079 Near as dammit 12
Normal engine track gearing guide
- - - - - - - - Aircooled--Proddy--Super--Proddy Drive Ration
o Stretton ---7 x 66 -- 7 x 64 -- 7 x 62------9.14
o Whilton ---7 x 66 -- 7 x 64 -- 7 x 62-------9.14
o Swaffam --7 x 72 -- 7 x 70 -- 7 x 68-------9.71
o Red Lodge 7 x 66 -- 7 x 64 -- 7 x 62-------9.14
o Wroughton 6 x 68 -- 6 x 66 -- 6 x 64------11
o Ipswich --- 6 x 73 -- N/A - - - N/A-
o Witham --- 6 x 73 -- 6 x 72 -- 6 x 70-------12
o Hully - -- - 6 x 73 -- 6 x 72 - - 6 x 70------12
o Llandow - - 7 x 67 --7 x 65 -- 7 x 63-------9.28
o Angmering -6 x 66 -- 6 x 64 -- 6 x 62-------9.14
o Yarmouth - 6 x 72 -- 6 x 72 -- 6 x 72-------12
o Kinsham ---7 x 70 -- 7 x 68 -- 7 x 66-------9.71
o Cheddar -- 6 x 70 -- 6 x 68 -- 6 x 66-------11.33
o Rowrah ---- 7 x 68 --7 x 66 -- 7 x 64-------9.42
Obviously the above is a guide only and some people will fare on the smaller or larger side either way, but I thought it would be a good starting point for someone who hasn’t been to one of the tracks yet and is looking to go and not be a million miles off the pace.
If im being honest I've guessed most of the super gearing so chip in if need be, ive also added the Proddy ratio so you can make the reverse engine calculation should you need to.
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