Why not just move the swingarm instead of stretching it?

[Audiomaker]

Ok... probably a silly question but...

Since a lot of guys get extended swing arms for drag racing, what would be the difference performance-wise in moving the fulcrum point and shock mounts using a stock swing arm to lengthen a wheelbase.

Myself, I've thought I'd like a 2" stretch (yes 2"), and this seems like it might be a way to go?

Thoughts?

Sean

 

[GIXERHP]

Ok look at your frame where the swing arm mount's, how are you going to move the pivot hole that the swing arm is mounted in?

It is much cheaper to make a swing arm, than to re manufacture the main frame!

Stop thinking,, go ride your bike!

Miles and smiles!

 

[raydog]

Kind of like, "going around the block to go next door". BUT, open ended thinking is a strength! Don't ever stop inventing alternatives in your mind. Raydog

 

[dragonbusa]

2 inches aint worth effert

 

[Busa1166]

Ok... probably a silly question but...

Since a lot of guys get extended swing arms for drag racing, what would be the difference performance-wise in moving the fulcrum point and shock mounts using a stock swing arm to lengthen a wheelbase.

Myself, I've thought I'd like a 2" stretch (yes 2"), and this seems like it might be a way to go?

Thoughts?

Sean

Guess anything is possible, I saw a guy turn a VW beetle into and airboat, sealed it with foam and put a fan and motor assmbly to pop out of the trunk and slide into position. Guess they went with arm to be easier and accomplish the same thing. But you can build and adapter for anything.

 

[Audiomaker]

Ok look at your frame where the swing arm mount's, how are you going to move the pivot hole that the swing arm is mounted in?

It is much cheaper to make a swing arm, than to re manufacture the main frame!

Stop thinking,, go ride your bike!

Miles and smiles!

Dunno, I'll have a look, but...

It just seems to me like for those who have these 9" extended swing arms, that it must make a huge geometrical difference in addition to simply making the wheelbase longer?

I see all kinds of crazy mod's... single sided swingarms and such... I'm just wondering *if* relocating the swing arm would reduce any detrimental effects over lengthening it.

I'll likely stick with the SWB myself, but there are drag racers and part-time drag racers.... so one has to wonder if having a stock length swing arm moved further back on the bike would work better for that application.

As for manufacturing parts to make that happen... based on things I've seen it should be doable.


Going to ride now...thanks

Sean

 

[bigjohn141]

I think you are over engineering things here. You are basically talking in terms of sprung and unsprung weight by changing the way the bike is lengthened. A longer arm will have more unsprung weight while a longer frame will have more sprung weight, this comes into play for handling which is not so important when going in a straight line. If you did extend the frame you would have to build some pretty sizable braces to handle the flex the extra length would impart on the bike, so that would in turn add to the overall mass and slow the bike from the extra weight. A longer arm can be built easier, cheaper, and lighter so I really couldnt see a reason to change but I have no claims to be a engineer or anything close so I could be totally wrong here.

 

[Busa1166]

Dunno, I'll have a look, but...

It just seems to me like for those who have these 9" extended swing arms, that it must make a huge geometrical difference in addition to simply making the wheelbase longer?

I see all kinds of crazy mod's... single sided swingarms and such... I'm just wondering *if* relocating the swing arm would reduce any detrimental effects over lengthening it.

I'll likely stick with the SWB myself, but there are drag racers and part-time drag racers.... so one has to wonder if having a stock length swing arm moved further back on the bike would work better for that application.

As for manufacturing parts to make that happen... based on things I've seen it should be doable.


Going to ride now...thanks

Sean

I think the results will be the same, the wheel will be farther back so you will have less traction from less weight on the rear wheel but a harder for the front end to come up. By moving the swing arm you will have to deal shock placement. whether getting a longer shock or making some kind of adapter to move the position of the shock at the swing arm or at the frame. imo

 

[beachz]

2 inches aint worth effert

Wish I had a $ for every time I heard that...

 

[dk55belair]

2 inches aint worth effert

Thats what she said.

 

[Postal]

Because then it would look like an ugly ZX14.....

 

[thasnake]

The pivot for the swingarm needs to be close to the front spocket. Otherwise the chain would swing to much and clearance would be an issue.

 

[fallenarch]

From what I know about motorcycle geometry (which sort of relates to the 2 inches thing ) the original point of stretching the bike was to increase traction. This is a function of both moving the center of gravity further forward of the driving wheel (less tendacy to wheelie,) and the longer swing arm creating a longer lever arm (swingarm) to get power down. There is also the chain issue already stated above, although there would almost have to be some sort of dual drive setup to do this. There is the issue of sprung and unsprung weight but this would be either a trailer queen or a drag bike, so that's less important as they don't use the suspension that much anyway.

I think wheelbase is wheelbase so they would be equally poor handlers. But remember the "geometry" of a bike is dynamic not static. As the suspension compresses for example, a bike turns better. So I can imagine this setup playing all kinds of games with handling and stability.

The final issue is weight and stiffness. Your frame is designed to take forces at certain points. Adding an out-rigger plate or something to the frame to move the piviot back could induce forces that either increase flex in the frame or even cause it to fail.

All in all a bad idea I think. But don't stop thinking out of the box. For every revolutionary idea there are hundreds of losers

 

[Tufbusa]

2 inches aint worth effert

Geeeeeze! Depends on what you are adding the two inches to, eh?

 

[GNBRETT]

2 inches aint worth effert

3 inches makes quite a bit of difference so yea maybe id agree with 2 inches being not enough but id hardly say its not worth the effort if ur primary concern is traction without giving up too much handling. especially if ur riding a bike with lots of power.

 

[SKnight]

Lengthening the point from pivot to wheel centerline has a lot to do with aiding traction and more importantly, controlling that traction. There's a lot of geometry in play and just like a drag car the longer links help with traction whereas on a road racer the shorter arms provide the best handling characteristics.

Plus the mentioned trouble it would be to move the pivot point back. And for 2" you can get extensions that bolt in place on the back of a stock swingarm although I'm not sure what the minimum length is on those.

So why 2"? Why not stock or 6" 2" wouldn't change much that you couldn't fix with tuning unless you're going after a very specific problem.

 

[m_ridgeway]

You can get the 2" and similar short arms built from stock arms cheap. They are called cheater arms for a reason.....

 

[busa-saga]

Ok look at your frame where the swing arm mount's, how are you going to move the pivot hole that the swing arm is mounted in?

It is much cheaper to make a swing arm, than to re manufacture the main frame!

Stop thinking,, go ride your bike!

Miles and smiles!

you have no idea what you are talking about

 

[karnage]

Thats why I started with 2-9inch over extensions and was happy with 5 over so I bought a 2-6 over arm.It handles pretty good at around 6 over.The geometry does change so you need a stiffer spring and maybe a revalved shock.It hooks pretty well and it does awesome roll on burnouts.