Why cantilever the rear suspension?

[elroyjetsn]

Just throwing out this for discussion...

Can anyone explain the theory behind the cantilevers used on the rear suspension(monoshock) of motorcycles?

Anyone tried doing some computer simulations to sort of improve the design.?

Any of you guys CAD gurus or mechanical engineers? :)

[elroyjetsn]

Red,

Know you've worked on this a lot and was wondering if there's a thread that details how you fabricated the parts to get the full travel- though i recall it was with a longer shock.

[red2003]

The linkage is needed to get a rising rate of spring / shock rate as the swingarm goes through it's travel. Without it, the throw of the shock is linear throughout the swingarm travel. When the suspension experiences a big bump and the wheel moves up fast, you need a higher spring/shock rate to compensate for the increased load. The linkage accomplishes this by moving the bottom of the shock out on the swingarm and increasing the angle of the shock to the swingarms perpendicular. The other option is a linear mount with a multivalved shock like the KTM motocross bikes run; directly mounted on the top of the swingarm. The trouble is the shock needed to accomplish this is worth more then our China bikes are worth new. Here's the link to my old thread about my rear shock mod. It's 4 pages long, but some good reading.

http://www.chinariders.net/modules.php?name=Forums&file=viewtopic&t=1315&highlight=clicker+installed

[liverchip]

"Some" good reading Red? It's awesome!

[red2003]

"Some" good reading Red? It's awesome!

Thanks. It was a lot of work, but the suspension has worked flawlessly for two thousand miles. I wish I had the time / resources to make a bolt on kit for you guys, because I can remember how sucky the rear suspension used to be. Hopefully the new DS's coming out have a better, redesigned setup.

[elroyjetsn]

Excellent work Red!! :D

Just makes you wonder why they did all that engineering to develop the components and never bothered to give the swingarm more than half the available travel... :lol:

[elroyjetsn]

Red,

It appears that u used 2 cradles that are connected at one point and that gives the "scissors" action keeping the pullbar from hyperextension.

Is that correct??

[red2003]

Red,

It appears that u used 2 cradles that are connected at one point and that gives the "scissors" action keeping the pullbar from hyperextension.

Is that correct??

No, what made the difference was changing the mounting points to get a rising rate geometry (swapping the linkage end for end), and extending both the cradle and pullbar to allow for more swingarm travel. As designed, the stock shock and linkage allow for about 3 inches of travel. After that, you are essentially riding a hardtail. I didn't realize this until I pulled the stock shock out and tried to lower the bike. After a few inches it wouldn't budge WITHOUT THE SHOCK EVEN IN THERE. The reason was the linkage binding up. If you get on the floor and have someone bounce the bike up and down, you'll see what the problem is. Watch the linkage separate under load and notice that it can't move any more once it is extended.