911 GT3 / RS - Thoughts on Passive vs Active suspension

[SonnyM]

Following on from some comments Steve Rance previously made about PASM and the contrast with the 6RS, could those of you in the know kindly explain:

1. Whether GT3 race cars (Cup etc) use PASM or not?
2. Whether a passive setup is better than PASM from a pure driving experience point of view (road or track)? Not talking about ride quality here.
3. Whether there is any GT3 iteration with PASM that matches a good passive setup or gets close?
4. Why the GT3 does not have push rod suspension like the CGT?

Part of this relates to me trying to understand the advantages of the 6RS over other RS models, and also the impact of PASM on the overall performance driving experience (again not interested in ride quality here).

Thanks for your input.

Edited by SonnyM on Wednesday 20th November 10:56

[fergus]

SonnyM said:

Following on from some comments Steve Rance previously made about PASM and the contrast with the 6RS, could those of you in the know kindly explain:

1. Whether GT3 race cars (Cup etc) use PASM or not?
2. Whether a passive setup is better than PASM from a pure driving experience point of view (road or track)? Not talking about ride quality here.
3. Whether there is any GT3 iteration with PASM that matches a good passive setup or gets close?
4. Why the GT3 does not have push rod suspension like the CGT?

Part of this relates to me trying to understand the advantages of the 6RS over other RS models, and also the impact of PASM on the overall performance driving experience (again not interested in ride quality here).

1. No. Std (non active) dampers

2. Generally, yes, as spring rates (and helper springs) can be specifically tuned for a given situation/desired behaviour and then the damper valving and high/low compression/rebound behaviour can then be setup around the chosen spring rate. This is a far more customised solution than PASM can offer, where all it does it alter the damping profile along a specific hysteresis curve.
3. I wouldn't have thought so, given the above.
4. I would imagine it's case of homologation for various race series (perhaps not allowing push rod setups) and also packaging limitations given the platform/chassis.

Ask Slippy for his feedback on the iterative process he followed in setting up his 6.1 GT3

[DiscoColin]

SonnyM said:

1. Whether GT3 race cars (Cup etc) use PASM or not?
2. Whether a passive setup is better than PASM from a pure driving experience point of view (road or track)? Not talking about ride quality here.
3. Whether there is any GT3 iteration with PASM that matches a good passive setup or gets close?
4. Why the GT3 does not have push rod suspension like the CGT?

1. No
2. Yes
3. No
4. Because then it would have a bespoke chassis like a CGT and wouldn't be able to serve its purpose of homologating the 911 for racing.

PASM isn't devoid of benefits and I am not convinced that for most drivers it is anything like as bad as some might have you believe, but high end passive dampers will always be better and even the OE Bilsteins on my old 996 are in some cases on track preferable to the PASM setup on my 997.2 Clubsport (though PASM in soft is certainly better for some of the crappy surfaces on many of my local roads).

[Glenn McMenamin]

Oh god, another 5 pages of purely personal opinion coming up !

G.

[Steve Rance]

Yep, agreed. The PASM issue is entirely subjective. The pushrod suspension on the CGT is there because of the shape of the tub. The narrower the tub, the more difficult to package a virtical strut. On single seaters it also has the advantage of housing the spring and shocker combination out of the air flow reducing drag. Push/pull rod suspension on a GT car probably has no other benefits unless the the Chasis can benefit from bring narrower - mainly at the front - to reduce flex. This is not an issue on a contemporary 911 so there would be no benefit