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#Post#: 14082--------------------------------------------------
Torque convertor and gear ratio thoughts: A starting point.
DIR By: Jimr1999
Date: November 28, 2025, 3:40 am
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I have put together a document with my thoughts on the TAV2 30
CVT and gearing choice to try and explain to anyone interested
why we go with the usual recommendation of a 7:1 gear ratio as a
starting point when the question is inevitably asked by new
builders. It expands upon the recommendation so that the builder
can then make several more choices from that starting point
while in build. It is my opinion, and therefore, possibly wrong
in some respects. I am sure someone will point out my wrong
headedness here, but if you are reading this, you can take that
into account in your own thinking ;D
See document attached. (Log in needed to view)
JimR
#Post#: 14083--------------------------------------------------
Re: TAV2 30 CVT Torque convertor thoughts: A starting point.
DIR By: RhysN
Date: November 28, 2025, 9:42 am
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Well written Jim. It's great to see things written with clarity.
#Post#: 14085--------------------------------------------------
Re: TAV2 30 CVT Torque convertor thoughts: A starting point.
DIR By: Ian F
Date: November 28, 2025, 11:04 am
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Nice one Jim ;D
As has been mentioned many times, we are a "design and
construction" club, not an "assembly" club. At the end of the
day it is all a compromise and each builder has their own
reasoning and thoughts when building their cyclekart. This
guide gives lots of good information to enable members to reach
their own conclusions and to have a lot of fun working out what
is best for them :D
#Post#: 14098--------------------------------------------------
Re: Torque convertor and gear ratio thoughts: A starting point.
DIR By: Ade Colmar
Date: December 3, 2025, 11:14 am
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A very helpful overview, Jim.
At the last event, I ran with both the standard Vevor TAV clutch
and then swopped for the Juggernaut clutch. Based on what
others had said, I was expecting (and got) faster acceleration.
However, what I did not expect was the change in the effective
final drive ratio. From rough calculations using GPS speed and
a digital rev counter, I seemed to get at least 10% overdrive
from the standard Vevor clutch but still using the same belt I
was getting 1:1 drive on the juggernaut at max speed.
I mention it here because if builders are struggling to get
their final drive gearing up to or beyond 7:1, fitting a
juggernaut has the additional benefit of giving you a good 10%
on your final drive ratio. (That is 10% more revs for the same
speed, so better employing the headroom gained by removing the
governor and adding various tuning mods.)
#Post#: 14103--------------------------------------------------
Re: Torque convertor and gear ratio thoughts: A starting point.
DIR By: Glynn
Date: December 4, 2025, 3:32 am
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The other thing you can do to influence the final drive ratio
with the Comet TAV is to fit a collar on the driven pulley,
between the sheaves. By restricting the movement of the outer
sheave you can vary the drive ratio between 3:1 and 1:1, I have
mine set at 2:1 which allows the engine to rev a bit higher.
#Post#: 14105--------------------------------------------------
Re: Torque convertor and gear ratio thoughts: A starting point.
DIR By: Jimr1999
Date: December 4, 2025, 4:16 am
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An update to #35 chain availability of sprockets from the
states.
One supplier that states it will ship to the world is BMI Karts,
Ohio USA they have #35 x 10t cogs for the TAV2...
HTML https://www.bmikarts.com/35-Sprocket-10T--12T_p_45741.html
And a range of split sprockets up to 85t in one tooth
intervals...
HTML https://www.bmikarts.com/35-Split-Sprocket-53T--85T_p_1413.html
Giving a total available gearing of 8.5.
This info has been added to the original document
Don't know what shipping would be but the prices seem
reasonable.
JimR
#Post#: 14108--------------------------------------------------
Re: Torque convertor and gear ratio thoughts: A starting point.
DIR By: Andy Dunn
Date: December 4, 2025, 5:41 am
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Hi all,an update on the pit bike wheels and tyres from Red
Circle ,out of the latest batch of 70,Alex has about 14 wheels
left in stock,nearly all the rest have gone to cyclekarts
#Post#: 14130--------------------------------------------------
Re: Torque convertor and gear ratio thoughts: A starting point.
DIR By: Jimr1999
Date: December 7, 2025, 3:26 am
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I have updated the document above (see first post) to include
the theoretical top speed calculator I use as a link after a
question. I have also added a couple of other useful links to
keep things handy for the design stage.
JimR
#Post#: 14695--------------------------------------------------
Re: Torque convertor and gear ratio thoughts: A starting point.
DIR By: tim.wheater
Date: March 11, 2026, 5:15 pm
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If you want to blow engines up 15:1 is a good starting point
😜
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