Thread: PP shock Dyno?
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Old 09-11-2019, 11:19 AM   #11
Butterman
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Quote:
Originally Posted by Leonardo View Post
So you are saying that the weight of the PP brakes effects the handling more than the difference in weight between the MT and AT transmissions?
TL;DR: bump control is dependent on unsprung mass and body motion (heave, pitch, roll) is dependent on sprung mass

Long story:
It depends, handling is a complex system of suspension response characteristics that isn't just good or bad. Overall grip is just as important to consider as drivability and transient response.

Shocks dampen a couple different types of motions, pitch, roll, heave, bump. Ideally you'd have 10 specific dampers to individually control each motion. On road cars you'll usually only see 4, manufacturers do this because the it takes up more space, it requires more development and it adds cost. MFGers are able to get good enough performance with only 4 shocks to control all types of motions, critical to this is the split between the high and low speed reaction of the dampers.

Pitch, roll and heave are body motions that are relatively low speed motions
and as such are controlled by the low speed damping of the shock. You'll notice this as the first, steep region of velocity-force plot of the shock dyno. Because this motion deals with body motions it is dependent on the sprung mass (mass of the chassis).

Bump is generally a high speed action and is controlled by the high speed damping of the shocks and is dependent on the unsprung mass. More mass = more momentum. Imagine that you're playing a game of catch with somebody and you're using a medicine ball and that you're trying to catch and throw the ball as fast as possible. Imagine, they're super strong and that they take it easy on you and regardless of the weight of the ball they throw it the same speed each time. You're only so strong but if you guys switch to a lighter ball, it'll be easier to catch and throw the ball right, and so you can do the motion faster. Does that make sense?

Consider hitting a bump at 30 mph with a 20lb brick strapped to your control arm, the bump will always push that mass up at the same speed but now you've got more mass (and thus momentum) that your suspension has to push back down to the road. It's only got so much force (provided by your spring and shock) so it'll take longer than without the weight, right? So you'll notice that with the 20lb weight, the bump will feel harsher and your car will feel unsettled for longer after the bump.

Last edited by Butterman; 09-11-2019 at 12:34 PM.
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