m030 spring rates

[insite]

jaykay -

much of the information in that post misapplies sound science to draw INCORRECT conclusions. bobbing up and down the road' (known as porpoising) has nothing to do w/ roll bars & everything to do with ride frequencies (long story). his deduction that PSS9 are 'stiffer in pitch' if they 'match the roll control' of M030 just doesn't make any sense. it is the ratio of front to rear wheel rates that determine bounce frequency & the ratio of single axle spring rate to (single axle spring rate + anti-roll bar rate) that determines sway frequency.

gobbledygook aside, EXPERIENCE tells me that PSS9 is a well engineered system that works well with any number of sway bars. for the street, i like M030 S front & M030 base rear. for the track, i like GT3 front w/ H&R rear on half-stiff.

the PSS9 does not 'bob up and down the road' with any of these setups, as roll-bars have little to do w/ porpoising.

FYI: it is the ratio of front wheel rate to rear wheel rate combined w/ wheelbase length that ulitimately determines whether a car will porpoise. imagine going over a speed bump: if the spring rates are the incorrect ratio w/ respect to one another, the rear of the car will pich up as the nose is diving. when the nose of the car comes back up, the rear will squat. basically, the nose & tail of the car would be doing opposite things at the same time. the result is a crappy ride.

a properly designed suspension will attempt to move front & rear suspensions in phase with one another. this results in the entire car moving up & down a bit, but not diving & pitching.

hard to explain; hope it makes some sense.

[stephen wilson]

Originally Posted by insite

properly designed suspension will attempt to move front & rear suspensions in phase with one another. this results in the entire car moving up & down a bit, but not diving & pitching.

Thanks for jumping in insite! IIRC the rule of thumb is that the rear ride frequency should be 10% higher than the front to minimize pitching.

[Topless]

FYI
My PSS9 car is running stock PSS9 springs and does not pitch, nor is it overly uncomfortable on the street. I have been in other PSS9 equipped cars where they ran too much spring rate and were harsh and gave away grip on corner exit (excessive wheel spin). Getting the setup right is important with coilovers.

M030 is Porsche-tuned and you just bolt it on, align and go for 90% of PSS9 effectiveness. A lot of value for the $$.

[jaykay]

Originally Posted by insite

jaykay -

much of the information in that post misapplies sound science to draw INCORRECT conclusions. bobbing up and down the road' (known as porpoising) has nothing to do w/ roll bars & everything to do with ride frequencies (long story). his deduction that PSS9 are 'stiffer in pitch' if they 'match the roll control' of M030 just doesn't make any sense. it is the ratio of front to rear wheel rates that determine bounce frequency & the ratio of single axle spring rate to (single axle spring rate + anti-roll bar rate) that determines sway frequency.

gobbledygook aside, EXPERIENCE tells me that PSS9 is a well engineered system that works well with any number of sway bars. for the street, i like M030 S front & M030 base rear. for the track, i like GT3 front w/ H&R rear on half-stiff.

the PSS9 does not 'bob up and down the road' with any of these setups, as roll-bars have little to do w/ porpoising.

FYI: it is the ratio of front wheel rate to rear wheel rate combined w/ wheelbase length that ulitimately determines whether a car will porpoise. imagine going over a speed bump: if the spring rates are the incorrect ratio w/ respect to one another, the rear of the car will pich up as the nose is diving. when the nose of the car comes back up, the rear will squat. basically, the nose & tail of the car would be doing opposite things at the same time. the result is a crappy ride.

a properly designed suspension will attempt to move front & rear suspensions in phase with one another. this results in the entire car moving up & down a bit, but not diving & pitching.

hard to explain; hope it makes some sense.

You explained it fine and it makes sense. I always like to hear what others have to say; I didn't necessarily agree with it. I think he assumed that a lot of roll control rate must be incorpated in the PSS9 spring rates giving a very stiff ride leading to proposing. The gentleman seems to have reversed his camber change assessment with what actually happens

Yes when it come to suspension, theory is not always supported by testing