Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Wheel spindle to swingarm pivot distance !

[Shazaam!]

Unfortunately, you can control only one variable here - the chain length. And since a chain always has an even number of links you can't use chain length as a very fine adjustment because you can only add or subtract two links at a time. This also means that you can't set up at a exact eccentric position and wheel spindle-to-swingarm pivot distance. They're the variables.

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)
14/36 (916SP)
14/37 (748SP,748SPS)
14/38 (748)

So when you change from a 15-tooth to a 14-tooth front sprocket you'll move the eccentric rearward and end up with a longer spindle-to-swingarm pivot distance (a longer wheelbase) and a reduction in ride height. You can move your ride height adjuster to return to the proper ride height but the wheelbase ends-up longer. In fact, anytime you tighten a chain - on any bike - you get a slightly longer wheelbase.

The effect of a longer wheelbase is toward slower steering and enhanced straight-line stability. For the range of the eccentric's offset between the specified 4-5 o'clock position (that accommodates the above gearing variations), it's a real, but minor effect.



Factory racebikes use a revised suspension linkage and a mag swingarm that's about an inch longer than production bikes for enhanced high-speed stability (at the sacrifice of cornering) but they also combine this with mag triples that have a different offset. Both of these changes make the bike harder to steer and put higher loads on the front wheel that has a tendency to allow the front to slide out easier. Consequently, the standard swingarm suits street riding better then the race setup.