ET

Member
Feb 14, 2001
7
0
VZ

I don't know anything about the BMW suspension, but in automibles, they can design a complicated linkage system that has the virtual pivot point anywhere they want, not just where the mechanical pivots are. I asume the BMW is like this and they put the virtual pivot point at ground level, this would then have no anti-squat since the tire contact force would pass straight through it. But for our simple swing arm suspensions, the mechanical pivot point is the pivot point, and all forces that do not pass straight through it will try to rotate the swing arm either up or down. If you could compress the suspension enough such that the pivot point was dragging the ground, then the tire contact force would have no effect on the suspension, only the chain force would have an effect and try to bring the rear tire up.
 

CJ 717

Member
Aug 21, 2006
1
0
Theroy

Hey guys I am a suspension guru!

My question to you all is this!

If you take into effect the chain, Wheel, and swing arm does not the forces travel from the chain to the sprocket through the hub to the axle back out through the swing arm up to the pivot point of the swing arm out to the spring and linkage then back in the reverse to the swing arm adversly making it want to push down but squats due to the greater force applied by the engines power coming out of the counter shaft?

I know this that you can not compress fluid in a give volume thus your shock should always be able to move at a constant based on you suspension settings. All other effects of suspension would have to come from outside of the shock (i.e. chain, sprocket, good bearings, proper chain slack etc...)

So why when you hole shot or landing with gas on would you get a squat effect?

Well in my theroy the force of the engine exerted on the final drive and swingarm is greater than that of the spring and suspension. If it was so much to not cause the squat you would loop the bike at every start. (Like taking the shock out and putting a solid bar in place of it). So upon landing the force from landing causes squat and then with gas on you want the bike to squat, or, you would have a bad back by lap 4.

Now to insure less squat you need a higher pivot point of the swing arm. Theres other ways to do this as stated before. Sprocket sizing, the linkage system, or shortening the wheel base by shortening the chain. If you put these all together you might have a better response from the suspension but you will always need a percentage of squat and as I recall that is the sole purpose of race sag correct.

Please correct me on any of this as I am trying to educate myself and understand it more and more indepth.
 
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