NC30 SREAR SUSPENSION GEOMETRY

[roop298]

I am considering increasing the length to the two centres (distance between the arrow) to move the shocker lower mounting point 10mm forwards.
Does anyone know what effect this will have in terms of damping rates and arm swing?
And would shortening the dogbone have a greater or lesser effect?

Just so you don't think I'm pulling random questions out of the air. This is what I've got so far: The standard shock is quite chunky and whether I replace it for a slimmer one or not it's position needs to be centralised inside the swing arm tunnel.
Also, the swinger is from a NC29 and the tunnel is along the centreline of the frame and the tunnel on the single sided swinger is offset to accommodate the rear exhaust downpipes, hence having to reposition the shocker mounts.

So, without having to get my old books out on statics, does anyone know what effect moving the shocker forward will have?

[dx400r]

Shortening the pull arm is said to give you more feel on the rear of the bike, a more linear ratio on the shock and the bonus of additional ride height.

[tigerclaw]

I assume you mean extending the triangle bit so that the bottom of the shock moves forward. The way my head works it out, the extra length on the arm is going to reduce leverage on the shock (ie make the shock feel harder), also the arm is going to move through a longer arc when the suspension goes through its travel so you need to consider the possibility that the shock may not have enough travel anymore and you would need to reduce the rebound because you would want to allow the travel to happen easier (not restrict the movement as much as when the shock had shorter travel)... That I think is the principle? To work out the percentage effect you would need to measure the various angles and distances and start working some trigonometry out (although I think it wil be fairly complicated because the dog bone pivot point would complicate the whole thing.)

[roop298]

Yes Tiger, I follow your first point: longer arm smaller moment. I didn't follow the second part. I might just draw it out and measure the movement.

[Drunkn Munky]

Shortening the pull arm is said to give you more feel on the rear of the bike, a more linear ratio on the shock and the bonus of additional ride height.

Isnt that the other way round? ie shortening the pull arm makes the rising rate less linear.

As for the OP, check out the HRC linkage diamensions, i belive this will give you the results your after.