JA-Moo's post on the "What is a cafe-racer thread", brought up a question I've wondered about for a while.
What causes tank slappers/speed wobbles/the hinge in the middle?
As long as bikes have been designed and built, why hasn't this been eliminated?
Is it a matter of designing on a fine edge, too much one way and you have a hard steering pig, too much the other and you have a twitchy beast? ???
"I would have to disgree on this point, at least on most of the late 60's and mid 70's Japanese bikes. They figured out the HP thing but handling was still almost a decade away. The steering was "lazy", or the suspension was so bad they wobbled all over the place when pushed hard. I had spent a few years in the mid 90's testing and re-testing all sorts of set ups on my Kawi triples. (my specialty) And found some "numbers" that other guys also ended up with other makes. If the rake doesn't get too "steep" right around 100mm of trail, a wheelbase close to 54" and getting the weight bias close to 50/50 as possible will give a very nice handling bike. I ended up shorten my swinger 2", dropping the front 1/2" inch (from 19 to 18" rim, and less steering effort) and lacking up the back almost 4"s with longer shocks and extenders. Vast improment with the handling."
What causes tank slappers/speed wobbles/the hinge in the middle?
As long as bikes have been designed and built, why hasn't this been eliminated?
Is it a matter of designing on a fine edge, too much one way and you have a hard steering pig, too much the other and you have a twitchy beast? ???
"I would have to disgree on this point, at least on most of the late 60's and mid 70's Japanese bikes. They figured out the HP thing but handling was still almost a decade away. The steering was "lazy", or the suspension was so bad they wobbled all over the place when pushed hard. I had spent a few years in the mid 90's testing and re-testing all sorts of set ups on my Kawi triples. (my specialty) And found some "numbers" that other guys also ended up with other makes. If the rake doesn't get too "steep" right around 100mm of trail, a wheelbase close to 54" and getting the weight bias close to 50/50 as possible will give a very nice handling bike. I ended up shorten my swinger 2", dropping the front 1/2" inch (from 19 to 18" rim, and less steering effort) and lacking up the back almost 4"s with longer shocks and extenders. Vast improment with the handling."
