High speed WEAVE

[Peder_y2k]

Check out this old Dunlop tech film on 'wobble and weave'. You'll end up knowing more than you did before!! The info is still relevant today...........

-Pete, in Tacoma WA USA

 

[ame=http://www.youtube.com/watch?v=z3OQTU-kE2s]Dunlop Wobble & Weave.wmv - YouTube[/ame]

[Flyinfool]

WOW!

 

I sure hope I never experience that.

Watching this has officially ended my diet.......

Having more stones seems to help......

 

I found it interesting that they were able to demonstrate that a trunk behind the rear wheel increases weave, and leaning forward over the take will stop weave, then at the very end they say they have no idea why leaning forward stabilizes the bike.

They just proved that a rearward CG (Center of Gravity) is unstable and a more forward CG is more stable. Yet they were unable to make the connection that leaning down over the tank will move the CG forward. This same CG thing is critical to getting an airplane to fly straight also.

Edited August 19, 2013 by Flyinfool

[Trader]

They must have bigger stones to ride with a bike as unstable as those!!!!!

Especially with no hands

[Venturous Randy]

That brought back memories of when I had Avon Venoms on my 83. When solo above 70 mph, the faster I got, the worse the tail waggle got. When I went to an E-3 on the back, it went away. I loved the way the Avons handled at lower speed and even 2-up, but solo was not good. As soon as the E-3 became available for the front, I got one and even though the bike felt very stable, I still feel the best overall handling was with an Avon front and as E-3 rear.

Speaking of stones in this video, some of these guys must have had some big stones to ride these bikes and let go of the handle bars.

RandyA

[Peder_y2k]

I also noticed the reference to the front shocks moving independantly while weaving. That must be why we have fork stabilizers, robust ones at that for our heavy bikes.

-Pete, in Tacoma WA USA

[LilBeaver]

WOW!

 

[..]

I found it interesting that they were able to demonstrate that a trunk behind the rear wheel increases weave, and leaning forward over the take will stop weave, then at the very end they say they have no idea why leaning forward stabilizes the bike.

They just proved that a rearward CG (Center of Gravity) is unstable and a more forward CG is more stable. Yet they were unable to make the connection that leaning down over the tank will move the CG forward. This same CG thing is critical to getting an airplane to fly straight also.

 

Curious about your perspective: How do you figure that 'proves' anything? The position of the center of gravity is one of MANY variables that are not even close to being independent...

 

From a scientific standpoint, from what they showed in the video there is hardly enough data for anything to be considered conclusive other than this stuff happens and that the effects of increased weight and rider position are clear but the actual source and mechanism(s) responsible are far from being explained...

[Patch]

Petder thanks for post the video.

I have done quit a bit of work on my bike and was disappointed when this started to happen, I only remember this experience once before on the 1st mono swing arm 500 back early 80s.

Here is my VR experience over the past two weeks, new Shinko tire 120klm felt like the rear was running on ice, after 300klm on them they settled down, on the Q2 here in Alberta last week- now have 1500 klm on the tires I went to pass a double tanker on the HW when the weave hit hard and fast at 125klm, now had some weight in the compartments a little heavier on the right saddle, I am light weight eased up and backed off. Same ride say 800 klm later, less wind I would only get a mild weave at 130klm nothing else changed but the extra milage and the wind.

I like the tires mind you there sticky wet and dry quiet too, so I will monitor her behavior near future see what if any changes.

Now I have to tell you I checked the brace for loose fit or cracks when I parked that night, having already checked the swing arm!

I've had my old Cade way faster with more load in the bags and trunk never experienced weave, it has the super brace.

S/G

[Flyinfool]

Curious about your perspective: How do you figure that 'proves' anything? The position of the center of gravity is one of MANY variables that are not even close to being independent...

 

From a scientific standpoint, from what they showed in the video there is hardly enough data for anything to be considered conclusive other than this stuff happens and that the effects of increased weight and rider position are clear but the actual source and mechanism(s) responsible are far from being explained...

 

They shifted the CG using two different methods and got the same repeatable result for both cases. They even said that the action that caused the CG to move was the only action taken.

That sounds like proof to me. Proof of a cause and effect is one thing, understanding the reason and/or physics for that cause and effect is something totally different.

[awsmsrv]

Well, what about adding the pillion? That most certainly shifted the CG back, yet no weave then. & with the weighted belt, no weave. I agree, more than one thing going on there. I also think today's models have improved in design. Besides, these bikes are a lot heavier than what they were riding. I'm sure that helps, too.

[LilBeaver]

They shifted the CG using two different methods and got the same repeatable result for both cases. They even said that the action that caused the CG to move was the only action taken.

That sounds like proof to me. Proof of a cause and effect is one thing, understanding the reason and/or physics for that cause and effect is something totally different.

 

Okay -- I understand where you are coming from and your phraseology there.

[Flyinfool]

Well, what about adding the pillion? That most certainly shifted the CG back, yet no weave then. & with the weighted belt, no weave. I agree, more than one thing going on there. I also think today's models have improved in design. Besides, these bikes are a lot heavier than what they were riding. I'm sure that helps, too.

 

As a separate test showed, greater total weight was one of several things that can cause an increase in stability.

Adding a pillion is still adding weight forward of the rear axle, and as the separate

test showed, greater total weight also has a calming effect. It is possible that the total weight gain of a pillion has more of a stabilizing effect than the rearward CG change has a destabilizing effect. It would take more testing to determine that.

 

There are a lot of combinations of variables that were not shown as being tested in that vid.

 

From back in the days when I was driving stock cars, the CG does make a big difference in handling, even just a couple percent change.

 

I'm sticking with my original plan of ending my diet for safety reasons.:essen_018:

[IronMike]

The Jest of it is, if you get into a high speed weave, lay down on the tank. Excellent post.

 

The probability of a flat-er rear tire when matched with a new front may explain some of the scary stuff that happens when some light weights go to the darkside and do not change the front tire to a rear.

[MikeWa]

Thanks Peter. Great post.

 

Mike