Gear Ratios

One thing which always puzzles me is the effect with raising the overall gearing has on internal gearbox ratios. I was using a four speed close ratio gearbox, and was used to the drop in revs on the up-changes. As I raised the overall gearing, the distance between the gears did not seem to change. But I would have expected the gaps to be wider. I think mathematically they are wider.

If you were geared low like 19 tooth and then went to 24 teeth (on the box sprocket)
you will find you are in each gear longer because you have less advantage, no?

I’ve always thought the ratios feel closer when you lower the overall gearing.

But it is because you run through each gear more quickly. If you run 19 teeth and you go down a cog to pass
you feel like you are shot from a gun. If you run 22 or more you spend more time in that gear and accelerate
more slowly. Or so it feels. Acotrel will probably disagree!

Onder said:

If you were geared low like 19 tooth and then went to 24 teeth (on the box sprocket)
you will find you are in each gear longer because you have less advantage, no?

Click to expand...

My 500cc Triton behaved like that, but the Commando 850 is different. At one stage, I tried to raise the gearing high enough to knock the 850's backside in. It just got to the corners quicker. I find it very deceptive. You would think that lowering the overall gearing would make the bike accelerate faster. The Commando engine always seems to gain revs at the same rate regardless of the gearing. The only way I get mine going fast enough is to keep the revs very high and race-change up through the close gears - that way, I use the crank inertia to get it to go. But I find it is a much better way to go than with a top end motor with a light crank.

I have replaced my 4 speed close box with a 6 speed TTI box. When I ordered it, I asked Bruce to put first gear halfway between a Commando and a Manx. He said ' I know what you mean'. When I first received the box, it had the wrong change drum in it. So far I have not raced with that box, but I have raised the overall gearing one tooth at the engine and one at the countershaft. If the gears spread out because I have raised the overall gearing, the bike might become more sluggish as I come up though the gears.
With the virus our local raceway is closed, so I cannot get a practice day. If I get the chance to race next year, I will not need to hang about. Every time we relax our lockdowns we will go back into lockdown very quickly.