sprocket change- effect on speedo

[birdy]

Looking at either front or rear sproket change to make it quicker. Will a change at either end affect the speedo and if so by how much per teeth change?
Thanks

[Zakalwe]

Looking at either front or rear sproket change to make it quicker. Will a change at either end affect the speedo and if so by how much per teeth change?
Thanks

How do you meant "to make it quicker"? A smaller rear sprok will raise the top speed (assuming the engine can rev out) but will reduce acceleration. A larger rear sprok (or smaller front one) will give faster acceleration, but a lower top speed.

The Gearing Commander websiteis a great site for investigating the effects of gearing changes. FWIW, dropping 1 on the front and +1 on the rear make a massive change to the overall feel of a bike.

Gearing changes will affect the speedo accuracy. Having said that, most speedos are out by about 8% (fit a Speedohealer to correct the difference)

[birdy]

It's the faster acceleration I was after- that's what I menat by quicker (rather than faster).
So, if I go for the smaller front what % will the speedo under/under read?

[Zakalwe]

It's the faster acceleration I was after- that's what I menat by quicker (rather than faster).
So, if I go for the smaller front what % will the speedo under/under read?

Dunno. But the Gearing Commander website will give you a good indication.

Dont drop the front by too much for a few reasons:
1) You will be forcing the chain to turn a much smaller radius, which will increase wear on it,
2) Go too small and you might end up with the chain wearing into the swingarm as the suspension moves up and down,
3) A change of 1 tooth on the front is roughly the same as a 3-tooth change on the rear
4) You *might* end up with the same chain links hitting the same gear teeth every 3rd or 4th revolution of the chain, which will wear the chain more in that spot (nerd note: thats why gearbox ratios are always fractional i.e 1.941, to prevent this from happening)

Also, check your chain length. I went -1 (front) +2 (rear) on my trackbike and found that the standard length chain was too short :mad2 I had to insert two rivet links to get it to fit.
Finally, new sprockets on an old chain will accelerate wear. Are you changing the chain as well (though I did go -1 (F) +1(R) on my CBR Though when the chain had about 3000 miles on it).