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SZ spring rates
Posted: Thu Mar 31, 2005 2:30 pm
by Bruce
Any one know the poundage and uncompressed spring length for an Alfa SZ? When combining springs with the existing torsion bars (75) what spring poundage and length do I look for?
Posted: Tue Jul 05, 2005 11:47 pm
by Jose_76
The RZ's owner's manual reads the following:
Front springs:
Wire diameter: 11,1mm
Coil outer diameter: 81,9mm
Not-Loaded spring length: 273mm = 10,75 inch
Spring Rate: 0,2mm/dN = 49 Kg/cm = 273,8 lbs/inch
Rear springs:
Wire diameter: 10,5mm
Coil outer diameter: 80,7mm
Not-Loaded spring length: 225mm = 8,6 inch
Spring Rate: 0,23mm/dN = 42,6 Kg/cm = 238,1 lbs/inch
Front antisway bar: 24 mm
Thanks RZ!!!!
Posted: Wed Jul 06, 2005 1:26 am
by Bruce
Coool! Right, time to order some 2.25" springs!
Posted: Wed Jul 06, 2005 1:47 am
by Jose_76
That's ok if you want a not-so-sporty-daily-driver. As I posted in other topics, I tried 285lbs at the front and it was DAAAAAAAAAAAAARN soft and the rear 238 lbs is about the same as standard in the GTV6 and Milano (maybe a 10% or so stiffer in the SZ).
After several tests with different setups in my car I'd go for 120/60 kg/cm for street racing (including visits to your nearest track
) or 100/50 Kg for a sporty and not so uncomfortable one.
Posted: Wed Jul 06, 2005 3:28 am
by Bruce
I have no intention of driving the car on the track; this is my daily driver. What I want is a car that is comfortable, does not roll & handles like an SZ or better!
I am surprised the spring rates do not differ that much because when the car is loaded it really has an adverse effect on handling with the rear bottoming out.
Posted: Wed Jul 06, 2005 4:07 am
by Jarno
I think a 75 has a rear spring constant near 20kg/cm, not much stiffer anyway. The front of a SZ seems to be surprisingly soft. The rear end has more roll resistance than the 75 due to wider distance between coils. Roll center makes the wonder in front...
According to some references, it should have some 6cm wider track than the 75. Where is the difference?
Posted: Wed Jul 06, 2005 4:08 am
by Micke
Remember the SZ has different geometry than the other cars.
The higher front RC of the SZ will make it roll less with same spring rate.
I don't know whether the SZ has the same shock mounting position on the lower control arm as the other cars (or if the control arm is the same length)
In the rear the springs are mounted farther out again reducing roll with same spring rate.
Posted: Wed Jul 06, 2005 4:53 am
by Bruce
erm... what is Kg/cm to Ib/ft conversion? (sorry)
Posted: Wed Jul 06, 2005 5:41 am
by Jose_76
For Kg/cm to lb/inch, Multiply by 55.88, for the inverse conversion divide by the same number.