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Thread: Gearing "The definitive guide"

  1. #1

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    Gearing "The definitive guide"

    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.

  2. #2

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    Wikid mate what i needed ****, the other table is just like WTF?

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    Angmering is a 6 tooth on the front.

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    jibberwobble's Avatar
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    Quote Originally Posted by sa 71 View Post
    Angmering is a 6 tooth on the front.
    Done ........

    and stickied

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    Any chance of a kids gearing chart. I ask cos at Stretton we're running 3 -4 less on the rear and 6 -7 less at kinsham.

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    On supers at Wilton and Llandow we have run as low as 7/56.

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    I can't help with a kiddies chart as I'm a 12 stone heffer, maybe if we could work out the difference for them it could be a rule, say above is good for around 12 stone, 6 stone is a reduction of 6 teeth, making a stone a tooth if you catch my drift?

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    jibberwobble's Avatar
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    If people with experience of any particular track can just post what works for them on what sort of HP and rider weight that would be a good start, maybe an rough estimation of your rider ability. Doesn't matter if you run different to someone else, if we can get enough views we can eventually come to some sort of average ruling for each track and adjust the guide to suit.

    For me, 11 - 11 1/2 stone with gear on. Reasonably quick.

    Whilton/Llandow/Rowrah (base setting) - 4.2 - 7/67 ------ open 40 (11hp) - 7/64 ------- super - 7/61 or 2

    Woughton - 6/68-------6/67--------6/66

    Cheddar -- 6/68--------6/66--------6/65 (poor clutch!)

  9. #9

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    Can anyone chip in with their Hully experiences ready for Sundays open day? Ive run with the 73 air cooled as last time i was hitting around 12,000 on a 72, and just bunged the 72 on the proddy as i thought why the hell not

  10. #10
    HugheskiRacing's Avatar
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    I run 6/68 @ Hully on an aircooled just like the hire bikes do

  11. #11

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    Blimey quite a few teeth down then, maybe im slacking on the fast corners

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    jibberwobble's Avatar
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    I think people are wanting to keep their gearing a secret! pussies!

  13. #13

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    I think your right mate, is it worked out by just trying to get the revs to the top point at the end if the fastest part of the track?

  14. #14
    Chute's Avatar
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    at hully I used to go with 6/74 on the proddy and 6/70 on the super. I weigh **** all.

  15. #15
    jibberwobble's Avatar
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    Quote Originally Posted by alboyevovi View Post
    I think your right mate, is it worked out by just trying to get the revs to the top point at the end if the fastest part of the track?
    Yeah pretty much but generally you need to sit at high revs beyond the engines max power output for a portion of the straight in order to get out of the bends well, thats where the balancing act comes in.

    Quote Originally Posted by Chute View Post
    at hully I used to go with 6/74 on the proddy and 6/70 on the super. I weigh **** all.
    I've run all sorts at hully, 68 - 73 and really not fussed what is on there as long as it's at least a 68. On one of the old layouts I used to get higher max revs from a 68 over the 72, I could never figure this out at all. The only thing that springs to mind is that you can pin it earlier with the stability of the higher gearing and the extra time on the throttle compensates.

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