random notes on 964/993 suspension

[Bill Verburg]

Originally Posted by perelet

......
I think as time went by that design turned to be less liked by enthusiasts. But I think 964 fans are lucky to be spared from 993 rear which has it's own problems that are not easy to deal with.

I agree, full solution will be to redo bushings, there are few models available. Well - leave me topics to cover here in this thread

You are correct that track enthusiasts do everything they can to eliminate rear steer, aka Weissach effect

for 964 a reduction comes from using the RS washers, but ultimately mono-balls are needed to eliminate it

the same happens in a 993, here there are 2 arms that control rear steer, the top rear and the rear of the A-arm, for 993 use the 993RS KT and A-arms which have stiffer rubber bushes these reduce rear steer similar to using the 964RS washers. And again the ultimate solution is t use all mono-balls

here's mine, using RSR A-arms which have mono-balls joints on both legs as opposed to only the leading leg stock and Rennline/Tarret arms for the other 3 arms



The main con is that all this hardware is expensive,

On track the RS setup is great it's only weakness is a tendency to lose alignment settings w/ hard use( the eccentric adjusters will rotate), The RSR w/ turnbuckle adjustment and locks at the eccentrics is the ultimate track solution

[Vandit]

Maybe the ERP spring plate is not made of spring steel like the OE piece? The threaded portion welded to the plate (where the rod-end attaches) would definitely minimize any potential flex points on the spring plate.

[Troky]

Hi all,

I am trying to find out if I can replace wheel carriers on my 964t/3.3L (96534165619) with 993 ones (99334115803).

Can someone help? What modifications are needed?


Thanks,
Troky

[Cobalt]

Originally Posted by Troky

Hi all,

I am trying to find out if I can replace wheel carriers on my 964t/3.3L (96534165619) with 993 ones (99334115803).

Can someone help? What modifications are needed?


Thanks,
Troky

Yes you can however you will need to replace the tie rods complete to the 993 version and use 993TT front rotors. I believe you may need to switch over to the 993 style toothed gear and sensors for the ABS as well but it might be possible to retrofit the 964 ones but I don't know for sure. Interesting the 993 aluminum carriers are around $400 new ea the 964 turbo units are around $1400 new ea. I would save the old parts.

[Bill Verburg]

As Anthony says
You will need to use the 964 45 tooth ABS gear
You will need to use 993 ball joints.
you will nee 2x 14x1.5x90 bolts and
2x 14x1.5mm nuts to replace the 2 lower strut nut/bolts

By far the more usual path is to use the 993RS wheel carriers w/ 993RS tierods which allow the car to be lowered more than the 964 or 993 ones.

[perelet]

In addition to that. 993 balljoint will have 2mm wobble sitting on 964 knurled bolt:



in details described in beginning of this thread:

http://forums.pelicanparts.com/porsche-964-993-technical-forum/693615-random-notes-964-993-suspension.html#post6903464

You may
1. bore out opening in 964 a-arm and press in 993 part
2. Machine 1mm wide washer to go between 964 knurled bolt & 993 ball joint.

[Troky]

Thanks for the information guys!

My mechanic said front right carrier is a bit distorted so I am looking for solution other than buying new for €1600. Not cool price


t.

[Vandit]

Here's a narrowbody 964 RS running the longitudinal mounts in the widebody (Turbo) position.

Porsche 964 Cup Car :: Porsche 911 :: Porsche for Sale :: JZM Porsche

[perelet]

Originally Posted by Vandit

Here's a narrowbody 964 RS running the longitudinal mounts in the widebody (Turbo) position.

Porsche 964 Cup Car :: Porsche 911 :: Porsche for Sale :: JZM Porsche

Thanks,*


Also good view of RS rear spring plates:


Heres reference pic

[Cobalt]

Interesting restoration. The cup cars used the outer mountings for more camber? Why would they not undercoat the wheel wells and undercoat the tub?

[nickd]

Some steering rack measurements to add to this excellent thread. Despite the Porsche TSB, the 993 rack will fit in the 964 C4 with zero problems. I can only guess that Porsche said that it wouldn't fit, because you need to remove the subframe longitudinals first in order to angle the 993 steering rack in to position around the C4 diff.

The two racks that I measured:
993 steering rack tag: 7832.955.169, K054690, 08.07, 2832.501.203, ZF rebuilt
964 steering rack tag: 7840.955.119, 964.347.009.02, 260046, 02.91

lock-to-lock turns, shaft travel, travel per 1 rotation
964 with 6mm steering stops (16" wheels): 2.81, 123.7mm, 44.0mm/turn
964 with 10mm steering stops (17" wheels): 2.64, 116.0mm, 44.0mm/turn
993 with stock stops: 2.47, 120.0mm, 48.6mm/turn

Just as the tech specs say, the 993 rack is faster.

Tie rods measurements:
M14 thread for all inner/outer along steering shaft axis
M14 into steering rack
M12 outer tie rod top nut, 964 and 993
964 inner tie rod -to- adjusting turnbuckle uses a reverse thread

Outer tie rod shaft height (above steering axis)
964 excluding threads=~39.2mm, length of threads=~18mm, to start of cone =~25.8mm
Outer tie rod cone diameters
964 min=14.53mm, max=15.93mm, m12 thread
993 min=15.16mm, max=17.11mm, m12 thread
Outer tie rod length (measured from cone bolt/mount)
964 =114mm, m14 thread end
Inner tie rod length (including steering stop)
993 =150mm steering stop to end
964 = ~100mm steering stop to start of threads, ~50mm length of threaded portion

Anyone know of a spherical inner tie rod replacement for the stock 964 inner? Seems that Porsche is a bit unique having rubber damping/isolation on the inner tie rods.

[perelet]

Due problems with images showing up

I achieved this thread with all images saved here:

perelet.com/cars/porsche/suspension_thread/11111.html


Leaks thread is also achieved here:
perelet.com/cars/porsche/leaks_thread/1.html

[Dlook993]

Can 1996 993 C2 Eibach Springs fit a 1990 964 C2?

[perelet]

Everybody, I still have all original pics. If board admin can help to host pictures and fix links.

Please IM me with ID if admin to talk to.i don’t login here too often.

I restored links on my personal server, but wish somebody can help to restore this thread here on pelican. I IM'ed several moderators from links no replies so far.


Link to backup thread with pics:

random notes on 964/993 suspension

[nickd]

A few more interesting notes:

I measure a 16mm offset between the 964 and 993 longitudinals. The 993 longitudinals push the front wheels outboard 16mm compared to the 964.

I also measure a 3.5mm difference between the ball joint stud hole and the upright wheel bearing front face. This moves the 993 upright 3.5mm inboard. Swapping the 993 uprights into the 964 not only pulls the wheels 3.5mm inboard, but also reduces the available negative camber because of this offset.

This all turns into 25mm increase in the front track of the 993 through these parts. 25mm= 2*(16-3.5).

[Cobalt]

Originally Posted by nickd

A few more interesting notes:

I measure a 16mm offset between the 964 and 993 longitudinals. The 993 longitudinals push the front wheels outboard 16mm compared to the 964.

I also measure a 3.5mm difference between the ball joint stud hole and the upright wheel bearing front face. This moves the 993 upright 3.5mm inboard. Swapping the 993 uprights into the 964 not only pulls the wheels 3.5mm inboard, but also reduces the available negative camber because of this offset.

This all turns into 25mm increase in the front track of the 993 through these parts. 25mm= 2*(16-3.5).

Are you sure of that? I have the 993 longitudinals on my 964 WB IIRC it was only a 12.5mm difference.

[nickd]

This is what I get. Did you change uprights at the same time? How did you measure the 12.5mm? Also, did you use camber plates to push the strut outboard and maintain camber?

[porkkis]

I'm bumping this old thread for some questions. First of all big thank you to all of you. Perelet brilliantly archived the thread and many others have given so much valuable input. This thread cleared up so many puzzling things and pretty much everything is clear now. Almost.

I have a 1992 964 C2 NB ROW car and I'm going to get the factory 993RS uprights / hub carriers now even if they are crazy money these days. I'm going to stick with the original 964 subframe longitudinals because I don't want to add track width. That would cause tire fitment issues.
I did read the uprights actually take few mm out of the track width compared to the 964 units. This can be compensated easily with some spacer plates without messing up the Ackermann I guess.

The actual question is: Can I use RSR/GT2 track rods / tie rods without using 993 longitudinals? I'd rather not modify them in any way. Does the adjustment range cover the needs when using 964 longitudinals? The GT2 versions without any rubber are currently available with part number 993 347 031 82.
Camber adjustability is another potential issue. I'm probably going for the Rennline weather proof top camber plates. Am I going to have a problem here or can anyone guess or state as a fact how much negative camber can I get?
I have not been able to find out if 964 and 993 strut top mounting points in body are equally wide or is 993 wider.

Btw I find it quite interesting that everyone is just talking about bump steer and that the uprights address the obvious problem with the original geometry. No one talks about "bump camber" or camber gain. The RS upright bring the ball joint down considerably and this is very good thing in a MacPherson system.

With my current ride height of about 120mm (clearance of the outermost subframe bolt head to ground) the lower control arms are already facing slightly upwards towards their outer end. This means any suspension travel will decrease negative camber. In a scenario like this a lot of static negative camber would be needed to get the tire somewhat perpendicular with the surface when cornering in race track conditions. After all perpendicular is what we are after. Optimally all the time. Excessive neg camber is also bad for braking and tire wear.
The problem can be of course also be addressed to some extent with adding caster which adds camber to a turned wheel.

Btw I was going for the BBI uprights but there is currently lead time of 2-3 months for them.

[tdiquattro]

Just to add more info, I also measured the longitudinals and found 16mm difference to bolt hole centre lines. (993 pushes the arm pivot out 16mm).

The cast hub lower ball joint hole is 10mm closer to the wheel bearing face on the 993.

So net difference is only 6mm on one side that i can see?

But I suppose the track will be a little more because of the camber?

I will check the disc flange, but I dont see where the 25mm track increase comes from?

Also this must make the steering even quicker on the 993? as the pivot point for the hub is closer to the bearing?

[Cobalt]

Old thread and I have since moved on and would need to pull up my records to verify but we came up with 12.5mm increase per side using 993 longitudinals on a 964 and modifying the 964 control arms to work with the RS uprights.

Everything has been upgraded or custom made. I am using ERP and Tarrett products which are essentially all modified versions of the older factory RS stuff. based on my driving I always had even tire wear on track.





Only pics I can find but after we made the mods this is how the wheel fit and before as you can see a considerable difference visually. The math will need to be revisited.