981 Cayman v Cayman GT4 Suspension

Motorhead · Oct 12, 2015

Ralph,

Struggling with your dropbox files but it seems that individual rear suspension parts aside - hub carriers and hubs, control arms, ARB, driveshafts, etc. unique to the GT4 - the biggest difference appears to be in the additional stiffeners running side-to-side behind the ARB and at the leading edge of the triangular shaped bracket on the underside. These mods appear to be aimed at distributing the transverse suspension loads more effectively across the rear end of the car to the body pick-up locations to minimise local body distortion.

The inverted rear struts are stiffer in bending and are therefore more resistant to buckling loads and with this in mind, I note that additional body stiffening has been incorporated at the top mount location by the use of (glued and riveted?) steel plates.

Presumably Weissach felt the need to incorporated these stiffening mods bearing in mind the intended use of the car for multiple track days.

Just my take on it of course.

Jeff

ralphmusic · Oct 12, 2015

I have been looking at differences between 981C and 981 GT4 suspension as shown by the PET files and the PCA video posted earlier. It looks to me (a non-technical person) that the most obvious differences are the wheel carriers and ARBs but what do I know. I attach some PET diagrams and a further link to the PCA video.

981C https://www.dropbox.com/s/kyfjyzv8a1mthzc/Suspension%20981C.pdf?dl=0
981 GT4 https://www.dropbox.com/s/f2doovb7bn4jaft/Supension%20981%20GT4.pdf?dl=0

PCA GT4 video https://www.youtube.com/watch?v=5SamK54Igm0

Any comments on the differences from the more engineering oriented amongst the team?

Motorhead · Oct 13, 2015

Ralph,

Have now managed to gain access to your PET diagrams.

Not much to be said about the front suspension which has been drafted in from the GT3 - the much beefier LCA, hub/hub carrier/bearings and adjustable ARB are obvious differences compared with the CS as is the alloy inverted damper assembly.

The GT4's chunkier rear hub assembly and LCA and the adjustable ARB are very different from their CS counterparts and the ARB reinforcement strut I mentioned is shown in the GT4 PET (item 27), but despite Mike Levitas noting the additional reinforcement on the leading edge of the cross-member (item 1), it's not obvious in the GT4 PET diagram - although it does have a different part number. Where's the helper spring in the rear damper assembly though?

I'm wondering if the ARB reinforcement strut and the modified cross-member would fit the standard CS Ralph. It might be worth asking if you're looking to beef up the rear end of your car.

Jeff

ralphmusic · Oct 13, 2015

Jeff,

Thanks. The PDK box v manual also creates some CS v GT4 fitting differences on rear ARB, but not something a proper custom mount can't solve but there may well be other fit issues that require a further engineered fix.

I have also been looking at this

(they have a 981 version in a few weeks) which people have been using on 986/7s - whether they have the same effect as the GT4 strut #27 remains to be seen, but I would think that aside from a few extra kgs there are no downsides.