Bilstein B6 Dilemma: Is it possible to fit late 944 rear shocks on an early car?

[AK944]

Hi everyone,

I'm in the process of putting together a suspension refresh/upgrade for my 944 and have settled on Bilstein B6s.

I did a bunch of research when I was about to buy my front strut cartridges. Bilstein makes two options for the front struts, part no. 34-000403 which is listed as an interchange for regular suspension, and 34-001042 which interchanges with the M474 "sport" shocks and is somewhat stiffer. I ordered the M474 equivalents for the front because I figured sportier was better and early M474 runs stock spring rates.

I then ordered them only to find out that Bilstein only makes M474 equivalent rear shocks for the late 944 (part no. 24-020527). While Bilstein makes a set of rears for early cars (part no. 24-001618), they're meant to interchange with non-sport suspension, not m474.

This is where I reach my dilemma, my options seem to be either to run the non-M474 replacement b6s on the rear and M474 fronts, or adapt the late model B6 M474 stiffness shocks to my early rear suspension.

Any info/input would be appreciated!

[Ish_944]

One correction: early 944s did use different spring rates with M474, the "red dot" fronts and 24.5mm torsion bars (instead of 23.5).

I accidentally bought the late style Konis when I got mine. The workshop made a special screw for them for the lower mounting. I can't remember the specifics, maybe 14 mm hole in the late shock and a 12 mm thread in suspension arm, or something along those lines. 10 years later, still no issues. So not a big deal to use them.

One more thing, I think that early and late style sport dampers have different stiffnesses. Haven't found definitive info regarding this and have no issues with my accidental setup, but you might want to double-check that, maybe with a Bilstein rep or someone.

I hope this helps a bit!

[AK944]

One correction: early 944s did use different spring rates with M474, the "red dot" fronts and 24.5mm torsion bars (instead of 23.5).

I accidentally bought the late style Konis when I got mine. The workshop made a special screw for them for the lower mounting. I can't remember the specifics, maybe 14 mm hole in the late shock and a 12 mm thread in suspension arm, or something along those lines. 10 years later, still no issues. So not a big deal to use them.

One more thing, I think that early and late style sport dampers have different stiffnesses. Haven't found definitive info regarding this and have no issues with my accidental setup, but you might want to double-check that, maybe with a Bilstein rep or someone.

I hope this helps a bit!

Thanks!

If you get a chance, could you get a picture of how your shocks are mounted? It would be really helpful in figuring out my options.

The factory service manual seems to imply that they used the stock springs and early m030 used the red dot springs, but early sports suspension options all seem rather poorly documented (the existence of early m030 in pet being questionable in itself)

I eventually plan to go to the red dot/24.5mm setup on my own car.

[AK944]

Also I should note I’ve done some more research on the difference between the late and early model shock Bilstein sells (reached out to them last week but haven’t heard back).

In general the green b6 shocks are “comfort” versions with the yellows apparently being 10-20% stiffer.

This makes sense when comparing the regular vs m474 front strut options from bilstein. The regular has a 1470/945 (rebound/compression) while the M474 has 1480/1125, a roughly 20% stiffer compression value.

Going off the values we have for the late shock (400/110) and a ballpark estimate of a 20% compression value, we’re probably looking at a rebound value in the 300s and compression of somewhere around 90.

I’ve found a thread from the early 2000s stating that the valving on HD rears was 239/119 but am not 100% sure they’re talking about the same part.