Wheel spindle to swingarm pivot distance !
 

Right so i need the spindle to swingarm pivot as near 500mm as poss & the rear excentrc between 6/9 oclock ( wheel side) 4/5chain side !
Correct me if a im wrong Please !

What if the swingarm to pivot it longer than 500 ( remove links)

I am thniking that i should remove the chain put the swing/pivot to 500 ish & get the excentric near the correct place , then measure up a chain ???
Running std rear sprocket with 14 tooth front !
Unless some one has already done this & could tell me the correct chain lenght !

Any thoughts !:)

Just Adjust the Chain ...
 

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.

Closest i got was 490mm,with a 15/42.

Sorry, Shazaam, but I am not sure I follow your conclusion about the front wheel experiencing higher loads. Certainly, the speeds are higher, but you can carry much more speed on the front with the race setup. Of course, there are many other changes that affect this as well on the race bike, but how does longer wheel base and adjustable trail correlate to higher front wheel loads?

[Edited on 21-9-2003 by Felix]

Felix,

The increased wheelbase and steering offset result in larger trail dimensions and consequently higher front wheel loadings for a given steering input.

Here's a good article on this:


Trail Article

What's the trail on a street bike?

It depends on the steering head angle setting. The superbike steeper steering angle (23°30' vs. 24°30' ) shortens the trail dimension to 91mm from 97mm. The steeper angle will not affect the wheelbase.

[Edited on 9-21-2003 by Shazaam!]

I found that by adding links(4 i think) to the chain,ie pulling the rear wheel back,allowed me to run the steep head angle,with a bit more ride height AND keep stabilty as well as quick steering.Not sure if that statement agrees with what you've said Shazaam or not!!