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Old 08-15-2013, 10:56 AM   #16
xr400r
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Quote:
Originally Posted by zig06 View Post
It shouldn't. A shorter swingarm will put the rear wheel closer to the center of gravity, and that would physically put more weight on the rear wheel giving it more traction. A longer swingarm will transfer that weight to the front wheel giving the front more traction and the rear less.

So unless they picked up some additional rear wheel travel and used that to soften the rear suspension to make it easier to load the rear before it breaks loose, then the longer did nothing for traction. But even then ~ a softer shock would do that reguardless of the arm length.

I think they need to explain their posistion a little bit better. Because a longer arm will give you more stability but not more traction.
Wrong, read a physics book, or change a tire with a short tire iron and a long tire iron.
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Old 08-15-2013, 01:28 PM   #17
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Wow, what a cluster-fuck.
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Old 08-15-2013, 03:17 PM   #18
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Quote:
Originally Posted by boatpuller View Post
Been reading the reviews of the new water cooled GS, and most talk about the 2 inch longer swing arm, and that that provides better traction in the dirt or off road.

Why?
Copied from http://www.mcnews.com.au/2013_Bikes/...00GS/Intro.htm

"The steering head angle has increased slightly to 64.5 degrees. Wheel castor is virtually identical, having previously been 101 millimetres and is now 99.6 millimetres. The wheelbase of 1507 millimetres has remained unchanged. The length of the swingarm has been considerably increased. Previously 535.6 millimetres in length (measured from the swingarm centre of rotation to the middle of the rear axle), the new figure is 588 millimetres."

Distance between tires remains the same, so, weight distribution and tire's traction remains about the same.
Rear suspension should be a little better.
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Old 08-15-2013, 04:15 PM   #19
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Quote:
Originally Posted by das ist gut View Post
we can let it ride (give it some time) for others comment also.

member btao has brought up a lot of other factors, and he gives very well comments for them too.

a lot of items contribute to, and effect the handling and the control of a motorbike.

very small changes, very very small changes as little as say 5mm can have a large effect.
that is why so much testing happens on MotoGP motorbikes. A small 5mm change may effect the handling and control just enough to be the difference between winning, and a 5th position finish.

now back to swingarm increases in length (without other changes)
the reason a longer swingarm put on a very powerful sportbike does at least 2 changes.
the major change is it actually REDUCES tire grip (traction)
and then, as a result of less traction, the motorbike will have a less tendency to wheelie quite as easily.

and therefore, the motorbike may be able to get on the gas harder, thus ultimately it may make a faster run.

sounds backwards right?
going faster by having less tire grip?

it is very complex, all of those items that cause traction and control, thus speed and manueverability to increase or decrease.

that is why so much time AND money are spent on something like MotoGP motorbike development.
The reason for the longer arm is related to torque not weight, if you can prevent the front of anything that steers from leaving the ground you improve control. Another way to think about it is the engine as the end of a lever, the further away from the source of the rotation (rear wheel) the better. We need a mechomical engineer to wade in here.
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Old 08-15-2013, 08:27 PM   #20
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Quote:
Originally Posted by boatpuller View Post
Been reading the reviews of the new water cooled GS, and most talk about the 2 inch longer swing arm, and that that provides better traction in the dirt or off road.

Why?
Weight transfer to the rear can apply more leverage on the longer swingarm. The front also rises less, so the rear is pushed down harder if weight is given the opportunity to transfer. If weight isn't given the opportunity to transfer though, burnouts are easier.
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Old 08-15-2013, 08:46 PM   #21
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Quote:
Originally Posted by foggy50361 View Post
The reason for the longer arm is related to torque not weight, if you can prevent the front of anything that steers from leaving the ground you improve control. Another way to think about it is the engine as the end of a lever, the further away from the source of the rotation (rear wheel) the better. We need a mechomical engineer to wade in here.


Dut da da daaaah!

So, your lever in this case is your rear axle to the CG of the bike+rider. It all makes a difference, including your body position. You can and do move it constantly when off road to maintain that traction, right! Hill climbs, drag racers, trials... all utilize extreme body positions to maintain traction.

The advantage of a longer swing arm for the bumps is you can have a longer suspension travel, since it can only go so far as the tire moves in an arc around the pivot forward where it gets ineffective. The longer up and down movement the better and less forward sweep. Cars have it so easy as they can put the pivot perpendicular with linkage to keep the contact patch perfectly on the surface it touches. On a rear tire, the more compressed the suspension, the faster the contact patch moves off the object your trying to maintain traction with because the rear tire starts to essentially, move forward.
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Old 08-15-2013, 08:55 PM   #22
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This thread is getting as STUPID as the countersteering thread. Where DO they all come from?
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Old 08-16-2013, 03:17 AM   #23
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The reason it provides better control is, because it does!
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Old 08-16-2013, 03:52 AM   #24
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Arc of wheel movement

The reason a longer swing arm will improve traction has nothing to do with weight transfer, remember the GS which sparked the thread has the same wheelbase, weight distribution as the previous model.

A longer swing arm will mean a smoother, longer arc for the wheel to follow when the suspension is compressed. This in turn will mean better shock actuation, which itself meant smoother travel allowing the wheel to follow the surface of the track. The longer arc also means the rear wheel travels in a near-vertical path, again better tracking of the road surface

Smooth travel + vertical wheel travel = better traction.

All about angles

If the swing arm is too short, when the suspension is compressed the wheel will initially rise vertically, but will continue to follow an arc around the pivot point meaning at the top of it's travel the rear wheel is actually travelling forward relative to the centre of the bike.

Suspension designers try to mimic longer swing arm movements using suspension linkages, check out a 4-bar suspension set up to see how this works.
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Old 08-16-2013, 02:52 PM   #25
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Quote:
Originally Posted by LtDan View Post
I Traditionally the rear suspension on GS's would pack up, would not rebound over wash board surfaces. After having ridden the Tenere, with a longer swing arm, it does not do this so I hope on the new GS this problem is eliminated.
decreasing rebound damping solves packing issues..the length of the swingarm should have little to do with this.. the tenere was most likely just set up better..
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Old 08-16-2013, 03:37 PM   #26
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Laugh Told you we needed a mechomical engineer

Quote:
Originally Posted by muddyboots View Post
The reason a longer swing arm will improve traction has nothing to do with weight transfer, remember the GS which sparked the thread has the same wheelbase, weight distribution as the previous model.

A longer swing arm will mean a smoother, longer arc for the wheel to follow when the suspension is compressed. This in turn will mean better shock actuation, which itself meant smoother travel allowing the wheel to follow the surface of the track. The longer arc also means the rear wheel travels in a near-vertical path, again better tracking of the road surface

Smooth travel + vertical wheel travel = better traction.

All about angles

If the swing arm is too short, when the suspension is compressed the wheel will initially rise vertically, but will continue to follow an arc around the pivot point meaning at the top of it's travel the rear wheel is actually travelling forward relative to the centre of the bike.

Suspension designers try to mimic longer swing arm movements using suspension linkages, check out a 4-bar suspension set up to see how this works.
It's all about the angles.
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Old 08-16-2013, 07:35 PM   #27
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in, but only for the stupid shit people will repeat that their buddy (who knows, because he works at a dealer) told them so.

awesome thread of lol
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scrolling through the words to get to the pictures is cool, but i'm really just here for the tracks and waypoints... post some ok ?
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Old 08-16-2013, 08:57 PM   #28
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Quote:
Originally Posted by muddyboots View Post
The reason a longer swing arm will improve traction has nothing to do with weight transfer,
Try abruptly dumping the clutch on a powerful bike, instead of getting into it gradually, or try doing a brake-torque, and you'll actually get LESS traction and easier tirespin with a longer swing-arm. Get into it gradually, allowing weight-transfer to happen, and the rear tire will hook up better with the longer swing-arm than with the short one.

This is very similar to how squeezing a front brake allows better braking traction than grabbing a front brake suddenly, especially with a raked-out front end. Squeeze gradually and the front tire is forced down harder by weight transfer.

Quote:
remember the GS which sparked the thread has the same wheelbase, weight distribution as the previous model.
With a swing-arm the same length as the previous model's, the wheelbase would now be shorter. I'm guessing that they kept the wheelbase identical by making that change to the steering angle...or also moved the swing-arm mount further forward on the frame. With a shorter wheelbase, weight distribution would be more biased to the rear tire, making the bike easier to loop when the front became unweighted. Extending the swing-arm while maintaining the same wheelbase as the previous model probably didn't improve rear traction on straight and flat surfaces, but it could potentially allow longer wheel-travel in the rear if they're using the same shock setup as before.

A longer wheelbase, given the same front-end geometry, will also provide more straight-line stability at high rates of speed and acceleration.

Quote:
A longer swing arm will mean a smoother, longer arc for the wheel to follow when the suspension is compressed. This in turn will mean better shock actuation, which itself meant smoother travel allowing the wheel to follow the surface of the track. The longer arc also means the rear wheel travels in a near-vertical path, again better tracking of the road surface

Smooth travel + vertical wheel travel = better traction.

All about angles

If the swing arm is too short, when the suspension is compressed the wheel will initially rise vertically, but will continue to follow an arc around the pivot point meaning at the top of it's travel the rear wheel is actually travelling forward relative to the centre of the bike.

Suspension designers try to mimic longer swing arm movements using suspension linkages, check out a 4-bar suspension set up to see how this works.
I disagree. Replace the rear shock with a solid bar. You'll still have better traction with the longer swing-arm, given that you allow weight-transfer, even if the suspension isn't allowed to compress at all.

A longer wheelbase allows the rotational force from the axle being acted upon to be better-converted into downward force by the increased leverage from the more-distant front-to-rear COG of the bike, which is now sticking out further. Increased lever length (distance from front-to-rear COG to fulcrum) allows more torque at the fulcrum, given allowing weight transfer to happen, and the same amount of weight at the end (the COG of the bike). More torque converts into more downward force at the fulcrum.

Max acceleration rate typically occurs when the rear tire is just starting to break loose and the front end is just starting to lift off.
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Kommando screwed with this post 08-16-2013 at 09:55 PM
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Old 08-17-2013, 01:28 AM   #29
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Originally Posted by stainlesscycle View Post
decreasing rebound damping solves packing issues..the length of the swingarm should have little to do with this.. the tenere was most likely just set up better..
If you have no idea of the correct answer to the OPs question, then why bother to post up a response which simply isnt accurate?
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Old 08-17-2013, 01:33 AM   #30
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Originally Posted by joexr View Post
This thread is getting as STUPID as the countersteering thread. Where DO they all come from?

Joe if you do not understand many of the interesting and helpful responses posted here, then maybe you should take the opportunity to learn, rather than simply indicating you do not understand?
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