Spring rate advice Options

[BlueRidge914]

I’d be grateful for some spring rate advice for my vintage race 914.
It’s a narrow body 2L six, 205/50 tires all around. Front torsion bars with adjustable sway bar. Rear is Bilstein Sports with adjustable spring perches, and a fixed sway bar.
My personal preference leans to a relatively softer spring all around.
Any recommendations for both torsion bar size and rear spring rate?
Thanks!
Gavin
VARAC #58

[Thorshammer]

There’s a bit more to consider when choosing spring rates.

What bushings/bearings
Are the rear trailing arms reinforced properly (and that’s not by wrapping them in 10+ lbs of perforated steel)
The anti roll bars: what are they riding in, and how well do they rotate and is their geometry reasonable
Are the shocks standard off the shelf… remember, if the rebound isn’t matched to the spring rate, there can be a some negative heave effect. So, in some cases, if you can’t control the heave, due to an insignificant damper, choosing a spring rate that matches the damper, will yield better performance overall

However:

21/225 or 21/250 works nicely IMO

[BlueRidge914]

There’s a bit more to consider when choosing spring rates.

What bushings/bearings
Are the rear trailing arms reinforced properly (and that’s not by wrapping them in 10+ lbs of perforated steel)
The anti roll bars: what are they riding in, and how well do they rotate and is their geometry reasonable
Are the shocks standard off the shelf… remember, if the rebound isn’t matched to the spring rate, there can be a some negative heave effect. So, in some cases, if you can’t control the heave, due to an insignificant damper, choosing a spring rate that matches the damper, will yield better performance overall

However:

21/225 or 21/250 works nicely IMO

Thanks for this.
So to answer your questions:
Rear trailing arms were reinforced around 30yrs ago the add sheet metal way. Is the other way you refer to the method Tangerine uses ie cut open and reinforced internally?
ARB in front is the Elephant hollow adjustable with teflon bushings. Rear is a stock OEM bar. All set up at least 20years ago.
Shocks front and rear are Bilstein Sports. Fronts were custom valved by Rebel, also many years ago. Spindles raised 19mm with Rebel bump steer kit. Small steering rack lift.
Solid monoballs front and rear. Front is Rebel adjustable.
21mm solid front torsion bar with Rebel solid bushings.
Rear springs are 275lb 2 1/4” adjustable perch, helper springs, thrust bearings.
I’ve raced this car 25 years with basically the same setup. So I don’t know what I may be missing!
I have contemplated the Rebel 935 style kit, but don’t know if that’s worth it (for me - a true vintage, vintage racer)
Any thoughts about what I might change/upgrade?
Much appreciated.
Gavin

[slivel]

So to answer your questions:
Rear trailing arms were reinforced around 30yrs ago the add sheet metal way. Is the other way you refer to the method Tangerine uses ie cut open and reinforced internally?
ARB in front is the Elephant hollow adjustable with teflon bushings. Rear is a stock OEM bar. All set up at least 20years ago.
Shocks front and rear are Bilstein Sports. Fronts were custom valved by Rebel, also many years ago. Spindles raised 19mm with Rebel bump steer kit. Small steering rack lift.
Solid monoballs front and rear. Front is Rebel adjustable.
21mm solid front torsion bar with Rebel solid bushings.
Rear springs are 275lb 2 1/4” adjustable perch, helper springs, thrust bearings.
I’ve raced this car 25 years with basically the same setup. So I don’t know what I may be missing!
I have contemplated the Rebel 935 style kit, but don’t know if that’s worth it (for me - a true vintage, vintage racer)
Any thoughts about what I might change/upgrade?
Much appreciated.
Gavin
[/quote]

If you make a significant change, be prepared to spend some time in development mode. If the car feels balanced and predictable, why change? You say that your vintage racing organization limits your tire so that is a major constraint. If your tire data shows even wear and temps across the tread, I would say you have optimized your setup. If your organization allows for changing suspension pickup points, you probably could achieve better performance but at the cost of being in development mode. For racing I observed a big improvement when I went to the Elephant poly bronze bushings on the rear. Soft bushings deform under side load during cornering and give unwanted changes in toe. It wasn't clear if you had done the rear of your car with high performance bushings. My shocks are also Bilstein's and were custom valved by Bilstein. I worked with one of their shock engineers and they rebuilt all four corners for me. Unfortunately they don't provide this service any longer.