spring rates and damping question
08-06-2005, 11:55 PM
#1
Burning Brakes
Thread Starter
spring rates and damping question
below is an excerpt from an old post that lists some spring rates and damping rates. i am puzzled why the stock 964 suspension with 160 lb/in front spring rate has much greater rebound damping numbers than the RS Cup or RSR. shouldn't increased spring rates require increased rebound damping numbers?
Stock Spring Rates (lb/in) Front/Rear:
89-91 C2/C4 158/189
92-94 C2/C4 169/189
91-94 Option M030 169/263*
93-94 RS America, ditto
91-92 Turbo 3.3, ditto
1992 Carrera RS (European) 247*/440*
1992 Carrera Cup USA, ditto
Carrera Cup Racing Car 200-600/240-800
Note: * Progressive spring working rate
There are a number of us running 600-650 lb/in in front and 750-850 lbs/in in the rear. FWIW, I run 600/750 lb/in, wanting to retain some ability to drive on the street vs 100% track. Also matched to these spring rates are custom valved Bilstein shocks with digressive valves. Most Bilsteins for Porsche tend to be linear valved, however, Bilstein can revalve with the digressive valves, which, with the right rates, makes a 600 lb/in front and 750 lb/in rear, although stiffer, still driveable on the street as well as good on the track.
Can't help you with Koni adjustable shocks - do they have a web site with technical assistance, perhaps for racers? Again for reference, below are the various standard, not custom, Bilstein valving rates (rebound/compression), front;rear:
964 to 1990 332/104; 274/122
964 1991 on 332/104; 277/124
964 RS 259/84; 415/237
964 Cup 220/67; 379/172
964 RSR 237/96; 402/216
Stock Spring Rates (lb/in) Front/Rear:
89-91 C2/C4 158/189
92-94 C2/C4 169/189
91-94 Option M030 169/263*
93-94 RS America, ditto
91-92 Turbo 3.3, ditto
1992 Carrera RS (European) 247*/440*
1992 Carrera Cup USA, ditto
Carrera Cup Racing Car 200-600/240-800
Note: * Progressive spring working rate
There are a number of us running 600-650 lb/in in front and 750-850 lbs/in in the rear. FWIW, I run 600/750 lb/in, wanting to retain some ability to drive on the street vs 100% track. Also matched to these spring rates are custom valved Bilstein shocks with digressive valves. Most Bilsteins for Porsche tend to be linear valved, however, Bilstein can revalve with the digressive valves, which, with the right rates, makes a 600 lb/in front and 750 lb/in rear, although stiffer, still driveable on the street as well as good on the track.
Can't help you with Koni adjustable shocks - do they have a web site with technical assistance, perhaps for racers? Again for reference, below are the various standard, not custom, Bilstein valving rates (rebound/compression), front;rear:
964 to 1990 332/104; 274/122
964 1991 on 332/104; 277/124
964 RS 259/84; 415/237
964 Cup 220/67; 379/172
964 RSR 237/96; 402/216
08-07-2005, 04:01 PM
#2
Rennlist Member
The 3.8 RSR came stock with 240 N/mm springs front and 260 N/mm springs rear this calculates to 1071 #/in front and 1160 #/in rear and note the shock valving is less agressive than a street RS with softer springs.
08-08-2005, 02:34 PM
#5
Rennlist Member
OK I looked it up again and had the right factor just used it wrong.
The RSR main springs are 240 and 260 newtons per millimeter displacement front and rear respectively.
1 Newton = .225 pounds and 1 inch = 25.4 mm. Soo, 240 N X .225 #/N X 25.4 mm/in = 1372 #/in front.
Doing the same for the rear calculates to 1486 #/in rear spring rate.
Even higher than first calculation.
The RSR main springs are 240 and 260 newtons per millimeter displacement front and rear respectively.
1 Newton = .225 pounds and 1 inch = 25.4 mm. Soo, 240 N X .225 #/N X 25.4 mm/in = 1372 #/in front.
Doing the same for the rear calculates to 1486 #/in rear spring rate.
Even higher than first calculation.
08-08-2005, 05:20 PM
#7
Rennlist Member
One thing. You have the 91-92 turbo as having a rear progressive rate spring. The 94 turbo used the same suspension as the 91-92 and the springs are not progressive.
