jackal2513

just looking for some clarification chaps

the RS rack is a 964 rack as I understand it ?

which is slower ?

but then the RS uprights has shorter steering arms which presumably cancel this out or make the rs rack quicker overall than a standard car ?

Bill Verburg

no
964 uses a boosted rack 2.81 turns lock to lock
base version of the 964RS is unboosted & in the touring version is boosted, turns lock to lock - unknown

993RS uses a boosted rack 2.73 turns lock to lock
993 uses a boosted rack 2.47 turns lock to lock

so in order quickest to slowest 993, 993RS, 964 w/ 964Rs as an unknown if someone does know please post

jackal2513

so the 993rs rack is its own rack

the steering arms on the RS uprights are more stubby so this increases the speed of the steering

jackal2513

hmm the proper part number for the 993rs rack indicates that it is the same as the 964 C2/C4 rack:


964 347 009 04


i.e. what they are selling here:

http://www.zimsautotechnik.org/acata...2_4_92_94.html

http://forums.pelicanparts.com/porsc...ack-964-a.html


where are you getting your info from Bill ?

Bill Verburg

I got my info from the factory shop manuals and the factory tech spec books

there is a tech bulletin wrt to 964 steering Gr.4 7/93 which I don't have

per PET
964 used
964.347.009.02 for left hand drive thru '91
964.347.009.04 for left hand drive from '91
Tech Spec says 2.81 t-ltl

964RS used
964.347.011.02 manual for left hand drive all
Tech Spec says only the base RS used the manual rack, touring used the boosted rack

per PET
993 used
993.347.011.00 for left hand drive
993RS used
993.347.009.04 for left hand drive

Tech spec says
993 is 2.47 t-ltl
993RS is 2.73 t-ltl

so it looks like the 964 started w/ a 2.81 t-ltl rack but then changed to a 2.73 t-ltl rack for '92 up

Premier Motorsp

993 RS is indeed using the 964 rack. The total steering ratio is determined by the rack's gear ratio AND the geometry of the tie rods and hub carriers.

The "Evo" hub carriers (which are not Evo at all, there are on 993 RS and all 993 based race cars, Evo or not) change the distance from the lower ball joint to the outer tie rod end, so the ratio is changed.

My own preference is to use a 993 rack with the RS hub carriers etc. This gives fast steering, which may not be appropriate for autobahn driving. This setup is used all 993 based race cars except the Cup, which has the ridiculous unboosted 964 RS rack.

Bill Verburg

Nice to know this.

so it looks like the RS uprights & tierods & steering stops reduce t-ltl from 2.81 to 2.73

I suspect that it's the steering stops not the geometry, but I've been wrong before

jackal2513

Yes, exactly as I was saying.

The steering arm is shorter.

I fitted RS uprights over the winter and my steering is noticeably quicker. I am runinng the standard 993c2 rack like you.

jackal2513

Its the shorter steering arm on the RS uprights as my first post explains.

jackal2513

yes so same part number, same rack

AOW162435

How about some rack pictures?





Andreas

evoderby

+1

jackal2513

do you mean Bristols ?

Bill Verburg

You are probably correct, I have the stock 993rack w/ RS uprights and tierods, the place where the quickness shines is the 2 kinks at Montecello, other wise it's pretty much a non issue. I don't understand how a non power rack can be used on a track, my shoulders take a beating as it is.

clubsport1

I have driven 993RS CS (assisted) and 964RS CS (unassisted) on the same Uk track on the same day and have to say, the 993 is easier to place, for some of the power turns such as Snetterton, the 64 can be quite a fight...Don't forget 93 cuppies don't have pas,,with the larger 18" wheels these are hard work at slow speeds...unless you are convinced you have to save every gramme of weight, i would stick with pas.
Surely some of the steering feel can be adjusted with set up, assuming you have adjustable RS style suspension.