JasonAndreas

The only progressive springs used on a 964 were on the rear of the RS and RS-America and they are 4" shorter than rear 993 springs. If you try to install rear 993 springs on a 964 without spacers you'll end up with an east LA lowrider look.

993_Pilot

Obviously, the wire diameter affects the rate, but normally progressive rate springs are made by changing the distance between the winds of the coils, rather than the diameter of the wire. When the coils are closer together, the rate is softer and where they are farther apart, the spring rate is stiffer. I think that is how bill is suggesting that you can tell just by looking.

ed devinney

So from Jason's note, by extension we can conclude that 993 US M030 springs are linear.

Jeff - the RoW M030 spring uses a tapered wire as Martin notes.

RallyJon

The progressive springs may not be be very progressive once they get into working range. What's the droop on an M030 suspension? Maybe 2"? Looking at Bill V's photo, the tapered, close coil part of the spring looks like it would be mostly compressed at ride height. Those small, close coils may be effectively a helper/tender spring to keep the main coils from falling off the perch.

Only way to know for sure it to plot force vs compression and observe how the spring compresses.

Bill Verburg

US & RoW 964 C2 use
front 11.4mm wire x 102.7mm coil diameter, rear 12.6mm x 90mm

US & RoW 964 C2 M030 use
the same front but 13.3/9.5mm x 90mm progressive rears

964RS uses
front 8.5/11.3mm x 103.2mm, rear 9/13.2mm x 82.3mm progressive

964RSA uses
front same as normal C2, rear 13.3/9.5mm x90 progressive

964 C4 US & RoW use
front 11.8mm x 102.7mm, rear 12.6mm x 90mm (M030 same front,13.9mm x90 progressive rear)

993 C2 US & Row uses
front 11mm x103.4mm, rear 13mm x 102mm(M030 versions use front 8/11.1mmx103mm, rear 13.5mm x 102mm)

C4versions front 10.9mm x 103mm, rear same as C2(M030 versions front 8/11.1mm x 103mm rear same as others)

993RS
front 11.3/8.5mm x 103.4mm, rear 8.38mm x 12.8mm x 68-77mm

all data from factory shop manuals

Jack of Hearts

We're data-rich and knowledge poor. Is the ROW M030 front progressive or not?

ed devinney

RoW M030 front is definitely progressive (I have them sitting in my shop). In Bill's data you'll see wire size given as x/y mm, indicating the tapered wire.

Martin S.

they are progressive. Had I a set on my desk (sold them), I'd put a caliper to them. BIll V seems to have the data...I am out of this discussion...I have no springs to measure.

Jack of Hearts

Got it, Ed & Martin. Thanks. (I guess that was obvious to everyone else but me.)

autobonrun

I've spent the last 3 hours reading suspension threads. Thought I'd bump this old one rather than starting a new thread. I was trying to gather information on the M030 suspension, spring rates, and progressive versus linear characteristics. I found this thread has just about everything I was looking for.

I've determined from this thread that the M030 springs (I currently have M030US), have the progressive characteristic in the front springs and linear in the rear.

My question is does anyone know whether the H&R spring sets being used on our 993's come with the same combination setup as the M030; are all 4 springs progressive, or are all 4 springs linear? I tried searching the H&R site and could not tell which they offer for the 993.

Come ell or high water, I'm ordering a new suspension setup next week. Just pulling together the final information needed to decide exactly what.

FlatSix911

The H&R springs appear to be progressive - see attached photo.

I have an extra set of new Bilstein shocks and H&R springs - PM if interested.

ed devinney

Check here and above - US M030 are linear up front, RoW progressive.

My 2 cents - the ride quality gain of the progressive spring may be negated by choice of shock. I like my RoW M030 over Bilstein HD setup but it doesn't ride as well as the RoW M030 over nearly new US M030 shocks I had on my former 993.