ok. maybe some of the more educated can help me out here.

why do mac strut cars generally ride better with 300-500lb/in wheelrates then dws cars? is it the low speed sensitivity of the dampers?

with the new koni's and 700/600 for springs, the car does an interesting thing. over small bumps and oscillations i'm in a perpetual pogo. larger bumps don't effect the car nearly as much, nor do sharp small bumps. i am running on the snow tires still, so they may be what is causing my problem as well. the other thing i'm thinking is that i've inadvertently tuned the suspension to have the same natural fequency as the rest of the chassis, resulting in the car rocking back and forth. (that one is pretty far out there, esp. since i don't even know if that is possible)

so, any insights? my brain is effin shot, and if i'm going to run the 700/700 setup this year i need to figure this ***** out now. i never knew a car could feel both good and bad at the same time.

nate-do i ever sound like a n00b now....

 

It is my general impression that a car that's set up decently for the track will feel underdamped on the street.

I really doubt you've got the same natural frequency front and rear - calc it out. And if you it may not be a big deal - sure all the text books say it's forbidden, but several engineer/racers have told me not to get hung up on it.

You are probably just being oversensitive after a big change - I have all kinds of emergent phobias every time I change the car or have been out of it for a while.

Scott, who say's give it a little time and find a way to do some reasonable testing...

 

hadn't thought of that. spending a lot of money tends to amplify that effect too, i think.
speaking of which, i want to do some skidpad testing. i think lime rock has a skidpad. does anyone know if they let you rent the skidpad without having all the safety gear of a typical track car?

what other forms of testing are available?

nate

 

I thought you were mostly an autocrosser - I was picturing a large deserted parking lot and an improvised test course.

Skid pads are ok for a start on the rough balance of the car, but you're going to tweak from there once you start doing what you're doing.

Scott, who can't think of anything else you can do ahead of time...

 

legal implications are scary at best. i think i know somebody who know's somebody who has a friend that know's someone that owns a small airport....
i've never been good at waiting...

nate

 

it would appear that the tires are having a larger negative effect on the ride quality then i had thought. i raised the tire pressures to 50psi and realized a reduction in the "pogo" effect. i'll have to put the falkens on and see what happens.

nate

 

I was actually going to guess the tires.. luckily through the magic of being late to the discussion, I can say that without taking any risk now! ~ Snow tires with lots of soft tread and soft sidewall (relatively) will begin to dominate the system's response once the other stiffnesses starts getting nice and high.

Pretty much, the lowest stiffness dominates the response when that stiffness is seen by the system. The only damping you've got in the tire is it's own constuction.. so it's tougher to get the energy out of it than when the springs are seeing the displacements.

 

I have a quick question here... sorry if it's a bit OT.

If I feel the car is a bit soft in corner, or has a bit over/understeer (for track driving), how should I decide between sway bar stiffness or spring rate to be increased first?

My guess is that it depends on the dive & squad (longitudinal) motion of the car?

 

springs are $55/ea and can be swapped front and rear if you have a gc or other coilover setup. swaybars are $200+ and can't be moved front to back. just that alone makes me lean towards more spring rather then more bar. start a new thread about this after you search all the threads on suspension topics. you'll get more replies that way.

nate

 

problem was _definitely_ tire related. i put the falkens on yesterday (just before the snow) and drove the car around and things are much improved.

i've also learned of why i developed a mid-corner wheelspin problem late last year after increasing my rear spring rate. either these tires are falling off and getting hard, or the tb cleaning un-leashed a healthy amount of power, likely a combination of the two. i drove around for about an hour and even pulling onto the more heavily traveled and cleaned streets, first gear acceleration was met with copious amounts of wheelspin. power-shifting to second was a joke and even doing a pretend slalom in 3rd gear @ 45mph resulted in minor wheelspin from the inside tire.

nate-who's getting a better idea of how determining the effects of one small change is difficult when one fails to look at the big picture.

p.s. turn in with the revalved koni's is phenomenal. tire noise from the flat-spotted, rock hard falkens is also phenomenal.