Sprocket Ratios

[Max99]

I've been playing with a few numbers that a few of you might find interesting or helpful.
Count your front and rear sprocket teeth and check it on the quick reference table. Then find that ratio on the sliding scale and you'll get and idea if your bike is geared for top or bottom end. It is then a guide for which sprockets to chuck in your tool kit if you want different gearing for different tracks or conditions. Keep in mind a front sprocket is quicker to change so a range of front ones might be the go for a range of gearings on hand.

 

[tysons_201]

i've been waiting for something like this! Be good to have a full chart like on in the pocket bike section displaying what speed you would achieve with each sprocket at how many rpm.
At the moment i got a 14t front with 37t back and i can only pull 78km/h.
Just bought a 17t front sprocket for maximum top end speed .
I just want an estimate of what it would pull with the 17t front.
And i got a 12" back wheel as that makes a difference also.

 

[crazzy #1]

with that gear ratio the 17t and 37t you should achieve a good speed at 5500 rpm

my old bike was geared poorly and i still got to 60kph with struggle, and although i didnt have a problem with it going over jumps and doing in rear hubs and axles the rims were still pritty crap...

sorry to hijack this thread but has anyone had any problems with there foot pegs and them braking off cleanly?

 

[Mack]

Dodgy link on the pdf dude... anyone else having trouble?

 

[Max99]

Dodgy link on the pdf dude... anyone else having trouble?

Is that better? The PDF was working for me but probably cause it was in my cache. I just picked a range of sprockets but what is the biggest and smallest available in both front and back? Rim size will also affect the final gearing. Tysons...you'd have to use a GPS or something to measure top speeds etc which someone who was keen could do. If you measured top speeds with a few evenly spaced ratios, all with a 12" rear wheel you could get and idea how it would graph. For the maths heads...I wonder if the progression would be arithmetic or geometric?

 

[Mack]

I'd say it'll be an eliptical isotronic parabola....

The link is working now.

 

[Max99]

I'd say it'll be an eliptical isotronic parabola....

Smartarse....I just wondered if the top speed increased exponentially with each sprocket ratio.
Tysons...how are you measuring your speed?

 

[Mack]

just wondered if the top speed increased expotentially with each sprocket ratio.

or exponentially....

 

[tysons_201]

I measured my speed along side a motorbike with a speedo. But would be a little inacurate as it was on a gravel road and also because its hard to keep the same speed on the speedo'd bike. Will get a push bike speedo and try and get it set to the correct speed and then test and should be fairly accurate.