Thought everyone here might appreciate this information...

Using the way-back machine, rescued this fabled article from Paragon's now-defunct tech session site. Would post it natively here, but the tables don't lend themselves to posting in the forum.

Rear Spring Rates vs. Effective Rates

Interesting conversion, looks like the 30mm tbars are about eq to 600lb coilovers, don't know what the efective rate conversion for the fronts on a 44 is, but given these numbers it seems that most cars would be undersprung in the fronts with the traditional 350lb coils! With a 50/50 wt distribution you would expect to start at 600+ lbs for the fronts.

Anyone ever try to run that high?

i read the chart as showing 30mm rear bars = 335# so the 350# fronts would seem perfect...

we had a cup car here in rmr running 30mm rear and 500# fronts and it "would not turn" even with slicks on the front.

Maybe I'm raeding this particular chart wrong (nothing new there)....

To be apples to apples usually you'd have to be comparing the effective rates (wheel rates) which account for the lever action of the arm and the angle of the strut against the axis of the lower arm. So given that the 30mm Tbar effective rate = 335 lbs/inch and the coil spring effective rate of 335 effective rate converts to around 600lb spring rate...unlesss this chart is missapplying the term "effective rate". The other issue would be the ratio of the front vs the rear that this is based on but the pivots aren't that far off, I think I'll go measure... This aside from the ability of the konis handling it...

SvoChuck wrote:


Bingo...


Front motion ratio is in the 90% range. So 350lbs-in is something like 300-340 lbs-in wheel rate. I would have to dig up the motion ratio. The rear effective rate means actual wheel rate. So 30mm t-bar creats a spring that will compress 1 inch with 335lbs of weight. Doubt me? Measure actual compression in the rear and it will be just under 2" for our cars given about 650lbs per corner. However due to rear motion ratio it take a 600lbs coil over to get to 335lbs wheel spring rate.

So now you guys know why I run 350lbs front with 30 mm t-bars. Even so 400lbs front could be better, but that comes down to driver feel etc.

The rear motion ratio is something like 46% so it takes nearly a double numeric spring rate. So 400lbs front need like 700 to 800lbs rear to "balance".

Remember stock these cars ran about 125lbs front and 23.5 mm t-bars so 124lbs-in effective rear. The cars are well balanced stock, but just soft.