997ajk

Does anyone know what are differences between C2 and C4? From what I can find there is some difference in front upper strut mounts and suspension geometry. But what is it?

Additionally some coilovers list C2 / C4 as the same fit, most likely development took place on C2 but can work on C4.

C2


C4

Brainz

That's pretty much it. The front knuckles on the AWD models are different. On the 2WD models, the strut connects to knuckle more or less in line with the hubs. But on the AWD models, the knuckle relocates the shock behind the CV axle. This changes the angle at which the strut intersects the strut mount as your images clearly highlight (the struts actually angle forward at the top when viewed from the side)

I'm not convinced that this results in different steering geometry at the wheel hub (though it may), but it definitely makes the strut work at a different angle and appears to put more flex on the strut mount bushing as the wheel is steered.

Petza914

When I installed the Cargraphic Airlift kit in my car, the instructions covered the AWD, RWD, and GT models. This graphic shows the different top mounts and the AWD one shows the angle difference. Note the bushing or spring retainer on the top of the coil is different too. The AWD version rides down inside the coil a bit whereas the others are more like caps.

I actually installed the GT version and used Tarret Monoball top mounts, which made them compatible with my C2S Damptronics.

Tj40

C4 have slightly different spring rates and sway bars than C2, front springs are about 10% stiffer (rears are the same), Front sways are slightly softer and rears slightly stiffer than C2

997ajk

Thanks for the response everyone! Very helpful and pictures defiantly help.

Additional question; are front shocks the same design / lengths / stroke / mounting brackets for C2 as C4 ? And then it's simply just the upper mount that makes a difference then .

Tj40

Part numbers are different for C2 C4 applications in the PET catalog - it looks like the lower spring mount is different and angled more than the C2 - logical if you think that the top mount is offset at a greater angle the lower mount will have to be offset by the same angle as well.

Hope this helps....

T4S

Was hoping to find some direction in this thread for my problem. I've installed B6 damptronics in a 997.2
The rear strut has play up and down even though bolted as tight as possible. Is the B6 a direct swap or? The front seems to be proper.. If I'm driving on smooth pavement its relatively unnoticeable and then on bumps it reveals problem. Anything jumping out at anyone? TIA

Brainz

What springs are you running? Is your rear shock mount new? It's possible your rear shock mounts are failed.

BTW, rear suspension on the C4/Turbos is the same setup as on the C2s. As mentioned above, springs (really spring rates) vary by car model.

David Berry

Just replaced my OEM rear shocks, Bilstein B-4, with Bilstein B-6 shocks.
Installer didn’t mention any issues.
The B-6 shocks are listed as proper for my 2010 C2S

Ironman88

How many miles on your car David?

David Berry

Just turned 48,000 miles. My Independent Porsche mechanic noticed passenger rear was leaking, so we replaced both rears. He said other side had small leak. Replaced at 47,700 miles