Topic: How do I figure out where to place my shocks?

[Hannibal Smith]

Your green circle is exactly 50% too small! Distance from pivot to axle is the radius, not the diameter. We can get you some exact figures once you get some angles.

[fastbroshi]

  I'm going to measure the CBR arm's other dimensions tomorrow afternoon.  In the meantime, you suggested I...

sit on the raceweight bike, and take the swingarm angle from zero (roadsurface) then get another at max deflection

.    Well it's in pieces now.  How to get around this?  The swingarm angle from 0;  I don't know how to ask how to get this without rambling.  Max deflection is what I would assume to be the highest the swingarm could be allowed to go. 

[Hannibal Smith]

We can close enough without this.

Just give me am idea of rear shock deflection (length of travel in normal use)-

Distance from swingarm pivot to rear axle-

Distance from swingarm pivot to frame shock mount point.


Let's make the constant your 2 lower fram rails (right below the mill) and make them parallel with a flat surface.

Give me your frame shock allocation in straight line, measure straight back with a tape measure (on the ground) with a tape, give me that number, then measure straight up at 90 degrees and give me that one.

Measure from the flat surface straight up and give me the distance from ground to center of swingarm pivot.

I am going to plug your frame numbers in cartesian coordinates to get my geometry figures, that way you can get some posterboard and draw everything to scale with a ruler, a pencil, and some string.

[Retro Rocket]

Hi guys, i am not going to argue about Hannibals logic here but i have some pictures here of some of the fastest Honda/4 race bikes in the world and most of them have altered shock mounts changing the angle of the shock.  This bike is very quick and has the top mount lowered and the rear mount shifted to the rear.


I am doing something similar on my build.

Mick

[Hannibal Smith]

You can change all sorts of things, but it needs to be tested and evaluated. You don't just move stuff around without a clear picture or experience with that particular bike's handling and application.

If it was my bike, I would mimic stock location unless I planned to do all kinds of testing and swapping.

Your rear works in conjunction with the front, they are not independent, sounds obvious, but how they work together is HUGE.

The above image tells us only half the story, we can see the placement, but what is the rate/damping/rebound etc. for the system. What exactly does it do? What is the action of the shock?

If you just copy some picture, and start moving stuff around, you might get lucky- or, just because we are dealing with a peanut horsepower bike we can get away with it................either way, you still need to know what you are doing. That winning bike obviously has some brains and experience behind it, but I don't have the suspension information.

Rear suspension can get complicated (as far as bikes are concerned) and movement of 1" in the wrong direction can make a handling nightmare.

[Retro Rocket]

The above image tells us only half the story, we can see the placement, but what is the rate/damping/rebound etc. for the system. What exactly does it do? What is the action of the shock?

The points you make there are what i would already do on any bike i own, i have ridden a lot of poor handling bikes mainly due to poor suspension set up. On the GSXR front end i am using, it has around   40 different settings for rebound dampening and spring rate,  that is the main reason i use am using them.  My point was that the suspension technology on these bikes is old hat and there have been massive steps forward, most older bikes i have pictures of {twin shock} have different positions for both top and bottom shock mounts. Looking at these bikes it leads me to believe that if you know how to set up your suspension well then changing the mounts { unless extreme} won't have much if any effect on the handling of the bike, this is totally different with mono shock bikes because of rising rate linkages and such. I have pics of lots of different Honda sohc's that have different mounting points and most of them are race bikes, this is what i based my assumption on.   I do understand what you are saying nut i think on these old bikes, if you know how to set up your shocks and forks, i don't think it will matter much where the mounts are as long as they don't lead to far and start binding.   I am just adding to the discussion, not trying to undermine what you are saying...

Mick

Mick