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fraid of heights
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Check out the video of this dude at Kona demonstrating brake jack. And how the brake therapy thing fixes it.

http://www.konaworld.com/dope.htm

Amazing, I wouldn't have thought a faux-bar would be so dramaticly effected by brake jack. I wish I had a true 4-bar so I could try out this test to see how much effect brake jack has on it. And I can't wait to try this on my Heckler just to see it happen. :)

It would be cool to see all the major suspension designs subjected to the same test to see how much their suspension designs are effected...
 

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I don't think that is a legit demonstration. In that situation the momentum of the spinning wheel suddenly being stopped is what causes the suspension to jump up.
A real world riding situation is totally different. The kinetic energy of the spinning wheel is much less significant than other forces acting on the suspension.
 

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Where is my mind?
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Anyone notice that the brake was attached to the chainstay vs the seat stay. That's going to jack upon breaking no matter what. Or was this a given.
 

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noMAD man
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I don't know...I think it's a pretty good demonstration. Now, obviously everyone knows the rear wheel isn't going to move that dramatically with the shock operating and a rider on board, but it's intended to show the forces of something that we normally can't really see at all. If you think about it, it's still impressive that it throws the tire, wheel, swingarm, and other components back there that violently.

Picture this...you're coming down a steep, technical decent where traction is at a premium. You have to hit both brakes because conditions just won't let you roll it out just yet. So...how much disruption would you want on your rear wheel's traction at this moment...a tiny bit, a moderate amount, or none at all. I think all this demonstration was intended to do was just to point out that there really is a notable influence on the rear suspension and thereby the rear wheel on many bike designs without a floating brake. There are still lots of people who don't believe it's so, and granted, before this I don't think it was something ever seen in action.
 

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Beermaker said:
I don't think that is a legit demonstration. In that situation the momentum of the spinning wheel suddenly being stopped is what causes the suspension to jump up.
It's not the momentum because when he uses the floating system the suspension doesn't move at all.
 

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Some Assembly Required
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TNC said:
I don't know...I think it's a pretty good demonstration. Now, obviously everyone knows the rear wheel isn't going to move that dramatically with the shock operating and a rider on board, but it's intended to show the forces of something that we normally can't really see at all. If you think about it, it's still impressive that it throws the tire, wheel, swingarm, and other components back there that violently.

Picture this...you're coming down a steep, technical decent where traction is at a premium. You have to hit both brakes because conditions just won't let you roll it out just yet. So...how much disruption would you want on your rear wheel's traction at this moment...a tiny bit, a moderate amount, or none at all. I think all this demonstration was intended to do was just to point out that there really is a notable influence on the rear suspension and thereby the rear wheel on many bike designs without a floating brake. There are still lots of people who don't believe it's so, and granted, before this I don't think it was something ever seen in action.
TNC chiming in w/logic & reason. You have no idea how much that keeps things in perspective for me. Thanks.

Most people will never experience the abrupt, dramatic movement shown in the demo. That said, no matter wheather or not its that dramatic, when the rear suspension becomes, for all intense purposes, locked up, your on a hard tail. I try to minimize any brake jack by trying to say off of the rear brake as much as possible. I try to stay off of the ft too, to get faster.
 

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Oh, So Interesting!
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Yes, it is. The angular momentum of the wheel is stopped by the BRAKES, and the braking force is transmitted to the suspension linkage causing squat without the floating brake (DOPE).

This will not be seen in such a dramatic way while on a bike, but the demo shows how braking forces tend to compress the rear suspension. In the real world this happens not in an instant, but over the entire time you are on the rear brakes.
 

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Lets ride
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Price

That's pretty cool, I have the '05 Coiler and have been looking at floating breaks but haven't pulled the trigger. It would be nice to know what price point Kona will be selling the after market "DOPE" systems for and how it differs from the other ones currently on the market.
Anyone have ETA on roll-out or pricing of "DOPE"?

LB

stiingya said:
Check out the video of this dude at Kona demonstrating brake jack. And how the brake therapy thing fixes it.

http://www.konaworld.com/dope.htm

Amazing, I wouldn't have thought a faux-bar would be so dramaticly effected by brake jack. I wish I had a true 4-bar so I could try out this test to see how much effect brake jack has on it. And I can't wait to try this on my Heckler just to see it happen. :)

It would be cool to see all the major suspension designs subjected to the same test to see how much their suspension designs are effected...
 

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I think it's fairly realistic.
I owned a Foes DHS Mono with a neutral floating brake on it. With the shock off i could hold the bike in the middle of the travel to see if it would pull up or down and it did neither unless you held it very deep into the travel and it would pull up toward bottom out only because the parallelogram would be so out of shape it would no longer be effecive. In some ways it was good and in others it was not. It is largely personal preferance.I'll explain.

Sliding around a slippery corner the bike would arc nicely instead of the rear end breaking loose and sliding/slowing down.

Dragging the rear brake down a steep section of trail was not so hot IMO. The fully neutral braking caused the rear end to rise up as my body weight shifted onto my hands.This caused the fork to compress and made it really hard to make a blown out 90 degree corner at the bottom of the rough straightaway.

The funny thing is that people call the brake induced squatting 'brake jack' which really would be the rear end jacking UP not down...but a floating brake and/or 4 bar WILL cause the rear end to rise up!

I've discovered that higher pivot single pivot bikes have more brake squat since the rear wheel is literally pulling away from the front end until the rear wheel becomes level with the pivot due to rear wheel traction while braking. This is more squat than i like.

A mid/low pivot bike offers a reasonable amount of squat to keep the bike's attitude relaxed and steering geometry good. Yes there is a little rear wheel skipping but less over the bars feeling.

Summary-If you ride less steep terrain and want the bike to remain fully active a true 4 bar/floating brake is good. If you come hot into corners and like steep descents a single pivot is A OK.
 
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