evoderby

Exactly what gives you the 'impression' that 911's don't like too stiff a front end?

Could it be the H&R supercup spring package at 455 / 685 , the factory RSR package at 600 / 800.....or possibly the Ohlins employee who recently posted his RSR set up on here 685 / 855 ???

Sorry for being sarcastic, but 'impressions' won't help you one bit.

A stiffer rear spring won't necessarily reduce understeer when front and rear spring frequencies are not in tune to begin with!!! Trust me on this: I've done some real world development with an experienced JRZ engineer just to prove how stiffening up a front that, as calculations showed was 45% too soft to begin with, could totally eradicate understeer.

What's more, increased caster at the front won't negatively affect turn in, quite the opposite, since it increases outside wheel negative camber during turning.....this without the negative effects on straight line braking (contact patch) when simply running more neg. camber.

Hope this helps.

Rgds,

Harald

KaiB

Let's ask this: If your car is pushing a bit at turn it, how is it mid-corner and at exit?

NineMeister

Have you allowed for the front/rear motion travel differences (i.e. wheel travel vs spring travel)?

evoderby

Yes I have, as one finds when not doing so creates calculated front spring rates a fair bit lower than the H&R supercup combo of 455 / 685 combo which is already on the low side in front

The analysis is quite easy and gives insight whether performed on standard C2/C4 springs up to H&R supercup, Factory RSR as well as what David (Ohlins engineer) is running on his RSR. They all consitently show the required balance.

Stepping away from this is possible, as their are many ways leading to Rome -roll bars being a spring as well- . As you know it takes great experience more succesfully walking paths other than the ones Porsche has paved in many ways, be it engine performance or race car set up.

If not experienced in such a way as the OP in all fairness probably isn't, I would advocate the old adagium "when in Rome......"

*again all under the assumption that KW spring rates mentioned on the web are in fact correct...I would more expect 'official ratings' in N/mm KW being a German company.

sml

i dont think 685lb springs need too much clearance 'to work correctly'.

i think they are unlikely bottom out.

how much are they going to move at those high spring rates?

Jimjacqmx5

Yes, by 'turns', I meant clicks... Top is Allen key, bottom is built into strut

NineMeister

It's surprising how much the suspension will move under load, believe me.

Jimjacqmx5

Hmmm, well let's not stress re spring rates as I was advised to go with the KW Clubsport kit as its supposedly good out of the box.
As I mentioned, bumping up the rear compression and rebound has helped a great deal. The steering feels heavy and dead on centre and reluctant to turn in so I suspect alignment is a good place to start.

NineMeister

KW do not include top mounts with the 964 or 993 kits, if you want them you use the factory RS versions or other aftermarket equivalents.

evoderby

For reference a discussion on KW V1-3 spring rates / frequency balance:

https://rennlist.com/forums/964-foru...ml#post9296988

Interesting parallels to this thread on KW Clubsport.

onefstm

Colin,

Could you give me rebound and compression guidance for a similar the setup.

The car is a 91 964C2 stipped interior
KW Clubsports, H&R sway bars
Corner balance weight of 2780lbs excluding driver, 2990 with driver.
Corner balanced to 39% front, 61% rear - 50.11% cross weight
Height is based on the KW instructions. Set to minimum or 12.6 inches between wheel center and fender lip
Front camber is -2.4, toe is .03 toe out per side
Rear camber is -2.0 per side, .06 toe in per side
Tires are Hoosier R6 245/35/18 front, 275/35/18 rear
Stock upper shock mounts
Track day - 25 minute session

First time running this new setup will be this weekend, so I need a good baseline setup.

Thanks in advance

Jeremy