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Just looking for a good starting point get going. MK4 chassis, 6 point cage, 2.0 5spd, ~2800lbs wet w/ driver, 28mm rear bar, stock front bar, all new bushings throughout. Running Daytona,Sebring,Moroso, Savanah, Road ATL, and Barber. Strictly Road Racing, no street.
Maybe about 600 ft if you have enough shock, I dont know what the wheel rate ratio is the for rear of the Mk 4. The Mk 2 and 3 is almost 100% and I use about 550 rear. I would guess about 600 for starters in the back.
I would think that these cars will wind up at about 650 ft and 750 rear wheel rates. Better off a littl low than too high for starters tho,IMHO.
That discounts the sway bars, I use the stock rear bar and no front on a welded car, and a small ajustable rear ,on the Quaife cars.
You can figure the wheel rate to spring rate ratio by measuring the leverage of the wheel to the spring. IE; If the wheel moves6 in , and the spring connection moves 3in , you have 50%. To get a wheel rate of 500#, you would need a spring of 1000#,etc.
If the front strut points at the center of the tire contact patch, it is about 100% , IE Mk 3 Golf. The Mk 2 is about 96%, The MK 1 is about 90%(est).
The difference is the strut angle.
So you're thinking 6ish for the rear, any idea on the front? I've been hearing 400 but that seems a little high, but i used to run an rx7.
A good starting point would be to use springs equal to your corner weights. This is not scientific but will give you a good starting point. The car won't oversteer on you and you can get some comfortable seat time. I would expect once you can predict the car's nature, you will be going up on the spring rates in the rear to help induce some oversteer. You can also put tie raps around the shocks as a poor man's weigh of measuring how much your suspension is compressing.
I don't know if Mark's advice transfers well to VWs. I would not run 750 front and 375 rear on my car. I guess worst case is that you end up with an understeering car, but more often closer to even front/back, or even a bit more rear rate tends to be faster.
That said, my original setup was 550 front and 375 rear springs, on a car that is 67% front weight biased. Today is 550/550, though I would like to continue tinkering.
Try a set of 600 front and 500 rear. Design it so that you can use the same lenght springs. That way you can swap them later. I like the 7in. long etc. Seems to work on both ends for my junk. MM
PS, looked at the Mk 4 book today . The rear springs are almost 100% rate. So you can trim it as the rest of us do. Just more weight.
What is the weight of the MK 4?.... I run a MK III Jetta, at a race weight of 2365.....
Mike Ogren is worth listening too.... we are running 650lb x 8 Eibachs on the front, no front bar, and 750 lb x 8 Eibachs on the rear with a very beefy rear bar. We have gotten the car to oversteer on very fast turns, like turn 1 at Sebring (in 5th ) but it does get exciting. Mike's recommendation is also correct that you might want to start a little softer and work your way up.
David Ellis-Brown