standard rear sprocket size?

[mike26]

anyone know the standard rear sprocket size and if so anyone used more or less teeth on the rear if so hows performance effected.
btw i do alot of motorway miles and high speed riding/filtering
thanks
mike

[Captain Haddock]

48 & 15 are standard sprocket sizes.

[mike26]

so what do you think getting a 38t renthal sprocket will do ?

[Captain Haddock]

10 teeth is a big jump, it will make acceleration very sluggish and probably won't be able to pull 6th gear, I'd try 1 tooth extra on the front as the sprocket will be cheaper and you won't need to shorten the chain, 1 tooth on the front is about equal to 3 teeth off the rear.
If the engine can't reach the rpm it can't produce the bhp.

[limax2]

Totally agree with all the Captain's comments. 10 tooth drop on back sprocket is way too much. You would probably have problems with chain rubbing on the swinging arm as well.
It would make 4th gear not much different to existing 6th gear with standard sprockets. Put another way, in top gear you would have approx 15 mph per 1000 revs instead of 12 mph per 1000 revs.

[mike26]

ahh okay might go for a small change thought 44 on the back or something (i really need a new babe one however im gonna spin it round first)