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Discussion Starter #61 (Edited)
I'm not a motorcycle gearing expert, but I do have experience with gearing on a road bicycle, and gearing does have an affect on acceleration across the board. I can't see how that would be any different on a motorcycle. Is the increase in acceleration going to be drastic? I doubt it but there almost certainly has to be some change. Anyway, I'm doing this more out of curiosity and fun, then anything serious. If I notice a difference, great. If not, no biggie. I will let you all know in a few weeks when I have everything installed.
 

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I'm not a motorcycle gearing expert, but I do have experience with gearing on a road bicycle, and gearing does have an affect on acceleration across the board. I can't see how that would be any different on a motorcycle. Is the increase in acceleration going to be drastic? I doubt it but there almost certainly has to be some change. Anyway, I'm doing this more out of curiosity and fun, then anything serious. If I notice a difference, great. If not, no biggie. I will let you all know in a few weeks when I have everything installed.
Let’s pick a target speed of 50 kph for your push bike.

With standard gearing you can reach that speed in 20 seconds.

If you lower your gearing by 20% will you reach 50 kph in less time?
 

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Let’s pick a target speed of 50 kph for your push bike.



With standard gearing you can reach that speed in 20 seconds.



If you lower your gearing by 20% will you reach 50 kph in less time?
Why not increase the gearing by a factor of five and see if you can reach 50kph at all
If you reduce gearing by 10% will you reach 50kph faster? Bear in mind that first gear is restricted by the front wheel leaving the ground, so any gearing below that point is unuseable.
It's all fundamental physics. Petrol engines have zero torque at zero rpm, which is why we need a clutch as a torque converter to pull away. Push bikes aren't comparable as they don't have a clutch, because human legs have maximum torque at zero rpm, like a steam engine.

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I'm always trying to improve the acceleration for Thruxton R. The drag strip gives me a good objective measurement tool with time and speeds at five intervals up to quarter mile. I use Gopros to help me evaluate what I did at the track and then I always correct the density altitude.

As many of you know and some may not the density of the altitude effects naturally aspirated engines. For instances I run at a track at 2695 feet above sea level but in July the density of altitude could translate to 5500 feet above sea level. If you correct for density altitude then it can help compare runs between the hot summer to cool fall.

Track temperature, wind speed and direction has a big effect on traction and elaspe time/speed.

I said all the above to say the rider's ability to launch and shift the bike is the biggest factor in acceleration . The best acceleration is usually determined in the first 60 feet. You might add one to front sprocket or take two away from the bike for your style (higher gearing) but the stock gearing has the best potential.

If you want better acceleration out of your Thruxton R my suggestion is practice your launches with stock gearing before you make any changes.

Here is my last time (1006B) slip that shows the actual times and I believe the corrected time and speed penciled in. Find a track and let me know how you did.
 

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Discussion Starter #65
Finally had everything installed today by A&J Cycles. Bike feels great. Tiny bit of acceleration in 1 and 2, and I have to shift them a tiny bit earlier. Still have a enough of 1. Overall, it’s just a slight shift, nothing drastic. Exactly what I wanted. The bike is still very comfortable to ride, definitely wasn’t thrown out of whack. You folks overreacted big time.

It was a fun little test, and the Renthal sprocket and chain look damn sexy.

 

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Did you end up with a 17/50 combination? Glad your happy with that combination...have admit I'm a bit surprised.

When you get a chance I'd like to 60, 330, etc times. If you can't do the timing maybe a Gopro run up through the first three gears.

Thanks
 

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Discussion Starter #67
Did you end up with a 17/50 combination? Glad your happy with that combination...have admit I'm a bit surprised.



When you get a chance I'd like to 60, 330, etc times. If you can't do the timing maybe a Gopro run up through the first three gears.



Thanks


Thanks. Yeah, went with 17/50. Don’t have a GoPro. Any other way to get accurate times?
 

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Well the drag strip but it is a little late in the year for that. I know some hand held GPS functions on phones can give a distance and speed.

We used one recently for a couple top speed runs. My curiosity sometimes gets the best of me.

As long as you are satisfied is the main thing, but if you ever run a quarter mile please let me know.

Thanks
 

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Discussion Starter #69
Well the drag strip but it is a little late in the year for that. I know some hand held GPS functions on phones can give a distance and speed.



We used one recently for a couple top speed runs. My curiosity sometimes gets the best of me.



As long as you are satisfied is the main thing, but if you ever run a quarter mile please let me know.



Thanks


There’s gotta be an iPhone app that can do this. I’ll look into it.
 

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I'm thinking about changing the gearing to something more aggressive, want to get more low end acceleration. I know I need to go bigger on the rear sprocket, or smaller on the front. Was looking at Renthal, and they make 47, 48 and 50t sprockets that seem to fit.

What do you folks suggest that will give me more acceleration and won't throw things out of whack?
Your first post asked for suggestions.

All I see on Gear Commander is that you have lowered your speed in each gear.

The Thruxton R has its power very well matched to its standard gearing for road use.

I just drop down a few notches if I want more acceleration.

Just one more overreaction for you mate.:wink2::grin2:

Nice looking sprocket and anyway who needs the top speed.

Enjoy your new performance.
 
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