[ButtDyno]

I have the Cobb bar in the rear, it's been at both full stiff and full soft. :shrug:

[Siegel Racing]

Originally Posted by idrivearocket

This is similar to what you said too Stretch? Thanks for your comments guys. But I don't understand the fundemental physics going on here... if the bars add the equivalent of so much spring rate, how come the car would ride like crap with springs that are so stiff, but when the bars add so much stiffness the car rides more comfortably?

How can bars resist body roll with so much force and maintain a comfortable ride while springs having 'equal' amounts of preload to combat body roll ride like a kidney crusher? Is it because you are leveraging the force against the other side of the car when you use bars, but you have no such leverage when you adjust spring preload?

I'm not sure if you've gotten the answer you need yet... Bars only "work" when they are twisted, ie when the body rolls. If you hit a bump with both front wheels at the same time, the bar just pivots, rotating up and down and giving effectively zero spring rate. When you lean the car and the outside wheel goes up into the body, and the inside wheel drops away from the body, now you are twisting that big solid bar.

I've always like the big bars soft spring setups...

Siegel

[vmaxlvrs]

Originally Posted by Siegel Racing

I'm not sure if you've gotten the answer you need yet... Bars only "work" when they are twisted, ie when the body rolls. If you hit a bump with both front wheels at the same time, the bar just pivots, rotating up and down and giving effectively zero spring rate. When you lean the car and the outside wheel goes up into the body, and the inside wheel drops away from the body, now you are twisting that big solid bar.

I've always like the big bars soft spring setups...

Siegel

So in other words you lose the independent suspension??

[stretch]

Originally Posted by idrivearocket

This is similar to what you said too Stretch? Thanks for your comments guys. But I don't understand the fundemental physics going on here... if the bars add the equivalent of so much spring rate, how come the car would ride like crap with springs that are so stiff, but when the bars add so much stiffness the car rides more comfortably?

How can bars resist body roll with so much force and maintain a comfortable ride while springs having 'equal' amounts of preload to combat body roll ride like a kidney crusher? Is it because you are leveraging the force against the other side of the car when you use bars, but you have no such leverage when you adjust spring preload?

A sway bar adds nothing to your two wheel bump rate. It just pivots without providing any resistance. So, regardless of what size sway bar you have, your car will feel the same over highway joints and speed bumps.

A sway bar adds to your one wheel bump rate. It acts like a very stiff spring linking your left and right wheels. So, for a 27mm bar, you have a 688lb/in spring in series connecting the two front wheels. Since this spring is just in series with the main springs, what happens is the wheel that hits the bump will compress the opposite wheel a small amount, so the one-wheel bump rate will never exceed twice what your main spring rate is even with the stiffest sway bar. Some one wheel bumps will feel harsher, but the effect is quite small in practice. (The largest effect I personally notice is worse braking on bumpy surfaces because weight rapidly shifts between the front tires on uneven surfaces.)

A sway bar GREATLY adds to your roll resistance rate. The bar's rate for body roll is double what it is for a one wheel bump, since both sides of the car are moving in opposite directions. For a 27mm bar, that is 1377lb/in, and that is not in series with the main springs. Thus, regardless of what springs you run, the sway bar will always add 1377lb/in to that rate to determine your total wheel rate. Luckily, reducing body roll is exactly what we want the sway bars to do, and this is why they are so effective.


Firm springs feel horrible because they effect the roll resistance AND one wheel bumps AND two wheel bumps. Sways only mildly effect one-wheel bumps and don't effect two-wheel bumps at all. On a perfectly smooth track, there would be no bumps, just body roll to deal with. In this case, for firm springs and firm sways (of the same total wheel rates) would feel the same, except for during dive and squat (since sways do not resist these forces).