| As a quick response;
If you make the front sprocket smaller this has the same effect as increasing the number of teeth on the rear sprocket. (if you reduce the front sprocket by 1 tooth, this has the same effect as adding approx 3 to the rear).
This move will make the rear wheel rotate faster for a given amount of revs, and the bike will accelerate faster, but then when the bike reaches maximum revs in top gear the rear wheel is actually spinning slower than if you had the standard gearing on. (if that makes sense). In reality this effect on top speed may be worth 10mph or so at the top end, but as you're unlikely to hit top speed too often (if at all) has no significant impact.
For a 996/748 changing the gearing is a popular move as you can improve the rideability of the bike. The easiest way to do this is to reduce the size of the front sprocket. This will have a potential detrimental effect on the chain (as its not designed to rotate around a smaller cog than standard. So this may effect the wear rate of the chain.
The best way to achieve this gearing change is to add 2 or 3 teeth to the rear, but here you run into the potential problem of requiring a longer chain. Do most people do what's easiest and swap the front sprocket for a smaller one.
For the DD racing, I am trying to gear trhe Monnie so that she will reach peak revs in top at the fastest part of the track, (which may only be 110mph) this may mean gearing the bike by going down one on the front and up 2 on the rear (as I did at Cadwell).
HTH
Tim  |