samluke

I am planning on revising my suspension set-up over the winter. I am dedicating my car to the track so I can now be more agressive with rates.

I currently run 500lb fronts, and 29mm TB's with 300lb coilovers rear.

I am planning 600-700lb fronts and trying to figure out the best plan for the rear.

I am trying to use the Cup Car setup as a guide, for front to rear ratio.

Cup car Front springs were progressive 375-410. I also understand the effective rear was 335lb. But I can't find what the torsion bars or spring rates were.

I was told that they used the Mo30 T bars, if I back calculate that suggests the springs were 250-300lb.

I have a pair of the Cup rear springs and the wire diameter looks similar to a 300lb spring. PS I have the Bilstein coilovers and Cup springs for sale,

Can anyone confirm the Cup Tbar diameter and spring rate?

special tool

I think the progressive 375-410 were used on the Koni cups, NOT the same as the Bilsteins, which are valved for 600 plus....
I have had both on my car,the Konis with the progressive springs (which I sold, like an idiot) were much softer, but much nicer on a road circuit situation.

I still have the original Koni cup aluminum slide-on perch, if anyone wants them.

Jim will be along soon to set this thread straight.

Skip Wolfe

Porsche lists the 25.5 mm bar as 31 N/mm which is 177 lbs/in and the variable rate coilover helper spring rates at 34-65 N/mm which is 194 lb/in - 371 lb/in.

Are you going to stay with the torsion bars or going to full rear coilovers?

samluke

I was going to go with very light T bars, as the stock class does not allow you to delete them. But I am concerned that the spring force will be very high. I would need 800lb springs or higher at the rear, and I am not sure my shock mounts will take it.

I am considering 650lb fronts and then retaining the 29mm bars and using 400-600lb helpers.

Skip Wolfe

Lower or upper mounts. The RE lower mounts should be up to the task.

pete95zhn

I have quote myself from anothre thread: "While looking through my magazines, I found this Excellence #134's ( Dec '04 ) article about Turbo Cup cars. It says that fronts were 200-370 lb/in progressives and rears 180-460 lb/in progressive PLUS 25.5 mm torsion bar..."

The same article states that Bilsteins were valved 6000/1800 N fr and 5650/2180 rr, measured at piston speed of 0.52m/s.

Skip Wolfe

PM Oddjob (Jim) - he is the Cup car guru around here.

samluke

I PM'd Jim, he is a great resource on the cup,cars. I have also found the matching Turbo Cup, front springs 9514323411 in my parts bin.



Springs and rear shocks for sale if anyone is interested