[mrurban]

Going to swap out the stock 39 tooth rear sprocket for a 41 tooth on my 749S, does anyone have experience doing this? (I'm assuming yes) and did you have to change the chain to a longer one? I'm assuming 2 teeth up isn't that big of a deal. Stock front sprocket is a 14 tooth and the current chain and sprockets are healthy.

thanks for any input

 

[Shazaam]

It depends upon where your chain adjuster is currently positioned in the slot. Consider that each tooth added to the rear sprocket will shorten the wheelbase (move the axle forward) 4mm.

 

[mrurban]

Well the adjuster is almost dead smack in the middle of the adjustment, so I guess I'll lose 8mm of wheelbase.
Will that drastically effect the stability?

 

[Shazaam]

As a general rule, the effect of a shorter wheelbase is toward faster steering and reduced straight-line stability.

That said, notice that Ducati uses a swingarm for all it's superbike models that has the same eccentric-to-swingarm pivot distance even though they have different front/rear standard sprocket sizes. They all use a standard 94-link chain. For example:

15/36 (916,996) (0mm)
14/36 (916SP) (+4mm)
14/37 (748SP,748SPS) (0mm)
14/38 (748) (-4mm)

So it's not a sensitive parameter.

Factory racebikes use a revised suspension linkage and a swingarm that's 15 - 30mm longer than production bikes for enhanced high-speed stability (at the sacrifice of cornering.) The shorter swingarm/wheelbase is considered better suited for street riding.

 

[mrurban]

Thanks Shazaam.
It seems like it'll be fine, but if it isn't I'll know why!