Gearing ratio for my race bike question

2192 Views 3 Replies 2 Participants Last post by Todd, Mar 20, 2015

SFoyil

Discussion Starter · Mar 20, 2015

Hi All,

Here's the quick of it... I'm running a 16/48 on my race bike, this is the gearing selected by the previous owner (no idea why he didn't just do 15/45...much more common and is the same ratio).

The track where I race I am always only in 3rd and 4th gear but sometimes I come out of a turn in 3rd and am in the mid-range of the RPMs and want to be higher up when I get on the throttle. What would be the best gearing to do this? I'm thinking 15/46...Thoughts?

Also, someone at the track said to do 15/45 even though this is the same as 16/48 they said the large rear (48) can cause issues but I don't see how that is valid.. :O

Thanks!

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Todd

· #2 · Mar 20, 2015

The easiest way to figure gearing for a race bike is too look and see what the max top speed of the most competitive 600's is at your track. Gear the bike so you are reaching that top speed in 6th gear at peak power rpm.

15/46 is not going to much of noticeable difference.

I'm running 14/45. The tracks I run at the top speeds are under 140, so the lower the gearing the better for me. Too little of a front sprocket can cause issues with the chain having to wrap tighter around smaller diameter. I don't think there are any issues with too big a rear sprocket as long as you have the chain length. I actually bought a 47 rear sprocket last year to try but I didn't have the chain length to fit with the 14 front sprocket so I never used it.

This a great tool for playing with gearing options;
Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator

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SFoyil

Discussion Starter · #3 · Mar 20, 2015

Todd said:
The easiest way to figure gearing for a race bike is too look and see what the max top speed of the most competitive 600's is at your track. Gear the bike so you are reaching that top speed in 6th gear at peak power rpm.

15/46 is not going to much of noticeable difference.

I'm running 14/45. The tracks I run at the top speeds are under 140, so the lower the gearing the better for me. Too little of a front sprocket can cause issues with the chain having to wrap tighter around smaller diameter. I don't think there are any issues with too big a rear sprocket as long as you have the chain length. I actually bought a 47 rear sprocket last year to try but I didn't have the chain length to fit with the 14 front sprocket so I never used it.

This a great tool for playing with gearing options;
Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator

So maybe I'll try dropping the front to 15 and keep my 48 in the rear and see what that does (that puts me close to your 14/45). I already ordered a 15 for the front, just debating what to do with the rear.

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Todd

· #4 · Mar 20, 2015

Theoretical speed with that gearing in 6th gear at 14500 rpm would be 153mph. As long as competitive 600's are going faster than 153 you would be fine to start with that gearing.

Gearing for top speed isn't always the best though...sometimes you make changes because you want to change where on the track you are having to shift. Of course as you improve and get faster it changes everything so the gearing that works best at the begining of the season might not be the best gearing at the end of the season if you are on the fairly steep part of your learning curve.

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