Gearing

Mark65 · World Chat Champion Joined: 16 May 2008 Karma :

Hi
Now the windy days are here i noticed my YBR125 struggling to keep 60mph in 5th, so after looking at bonny ricardos gearing chart it shows that a 1 tooth drop on the front will give me a speed increase of 4.6 mph at 60mph or hopefully allow me to stay at 60mph rather than 50-55 or will this just be in theory. Now looking at sprockets wemoto has them for around £4.60, are these good quality? as i could not find an afam one in 13 tooth. Any advice pls.

Ta
Mark
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07 Yamaha YBR125, 07 Honda CG125 , 15 CBR300R (Chocolate Crank, Deaded), 16 CB500FA, 19 Honda Forza 300, 70 Suzuki SV650

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

1 tooth smaller on the front will make the bike slower for the same revs, not faster.

What it might do is make top gear low enough to provide enough umph to overcome wind resistance.

However in the short term try just using a gear lower.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

Acemastr · World Chat Champion Joined: 01 Oct 2008 Karma :

Also interested, what impact would this have on acceleration?
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2017 KTM 350 XC-F - 2014 Yamaha R6 - 2005 Yamaha YZ125
2016 Toyota Tacoma Limited

Mark65 · World Chat Champion Joined: 16 May 2008 Karma :

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

smaller front sprocket/bigger rear = higher revs, lower top speed, increased acceleration.

bigger front/smaller rear sprocket = lower revs, higher top speed, decreased acceleration.

But this does not take into account engine power. e.g. whack a huge front sprocket on, and theoretical top speed maybe 100mph but you would only get to say 5k revs and the engine couldn't push itself any further so you want a balance.

Standard spec is usually pretty good but many people "downgear" stunt bikes e.g. smaller front sprocket by 1-3 teeth meaning acceleration is brilliant but top speed is significantly reduced but they have no need for top speed do they.

Buy a few sprockets if you can and have a play around with each. I would try -1 tooth and -2 teeth see what they are like.

You won't notice a difference on 125 between wemoto sprockets and posh expensive gold ones. Laughing

johnsmith222 · World Chat Champion Joined: 26 Dec 2008 Karma :

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

tbh, the chain on most bikes would wear out at the same time and £4 on top of £20-£80 for a new chain is not much.