Torsion bar adjustment

For Pre A discussions and questions
Post Reply
Message
Author
Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Torsion bar adjustment

#1 Post by Paul Jorgensen »

Hi all,

My 54 cabriolet has positive camber which I think contributes to the lack of confidence I have with it when cornering briskly.... I have put a level against both rear wheels and the top is 7mm further out. The stance (wheels) just look wrong when viewing the rear. I would like to set it to 1* negative camber hoping that this will give me better handling..
Most of the comments that I have read have suggested setting the Radius arm without load to 13*, 11-12* have also been mentioned. The little Porsche Spec's book says 356 all engines 6* 30' the 356A is 13*
Can anyone provide advise/experiences that they have had that may help in my quest.

Thank you in advance.

User avatar
Harlan Halsey
356 Fan
Posts: 2339
Joined: Fri Mar 02, 2012 2:05 pm
Location: No Cal SF Peninsula

Re: Torsion bar adjustment

#2 Post by Harlan Halsey »

I think 1 deg is rather a lot of negative camber for a street 356. I prefer closer to 1/2 degree. The workshop manual describes changing the torsion bar setting, but it doesn't emphasize that excellent condition rubber bushings are essential. There is an excellent thread on this site devoted to this subject. Because of the elasticity and settling of the rubber bushings it often takes two attempts to get it exactly right, and you probably will not end up exactly with the factory angle number. It's worth getting the setting you are comfortable with.

User avatar
James Davies
356Talk Moderator
Posts: 2951
Joined: Thu Aug 15, 2013 9:15 am
Location: Heidelberg, DE

Re: Torsion bar adjustment

#3 Post by James Davies »

The 356 and 356A have very different suspension. That was the major chassis upgrade feature with the introduction of the 356A - longer suspension travel for a better ride. So the radius arm angle adjustment on the two chassis are quite different. The 13 degree angle you've seen refers to the 356A suspension and later. Ignore those numbers.

The 356 chassis gets 6 deg 30 min to 7 deg adjustment, half that of the 356A. See below the page from the 1954 Service Manual showing adjustment.

If your car is adjusted as one would for a 356A, then it would be sitting quite high at the back and would show too much positive camber. Perhaps that's the case? That said, unloaded the pre-A can show some positive camber. 7mm difference top to bottom is less than a degree camber.

I've added a few period photos of 1954-55 cars that show what an unloaded Porsche should look like in terms of stance.
Attachments
Screenshot 2023-03-03 at 12.20.15 PM.png
1955 Continental coupe Bruce Baker bw.jpg
1954_1500Super_coupe.png
1954 Terra Cotta cabriolet color.jpg
1954 Speedster red.JPG

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#4 Post by Paul Jorgensen »

Harlan, James

Thank you for your advise and info. I have today ordered new rubber bushes. James the pictures you posted are a great help, mine does not sit like those cars but hopefully will soon.

Thanks again

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#5 Post by Paul Jorgensen »

Tonight when I got home from work I jacked my car up and levelled it in readiness to carry out the torsion bar adjustment tomorrow.
We were going out for a meal with friends but I had time to remove both shock absorbers, I removed the left hand spring plate and swung the drum/axle unit out of the way.
That is all I had time to do but I noted that the radius arm was still sat on the stop, with the sprung weight off it should this have lifted off the stop??

User avatar
Martin Benade
356 Fan
Posts: 12181
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Torsion bar adjustment

#6 Post by Martin Benade »

Actually with the car jacked up the spring plate will be resting harder on the stops. It will go together easier at a lower setting
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#7 Post by Paul Jorgensen »

Ahh I see… thanks Martin

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#8 Post by Paul Jorgensen »

Harlan, thank you for the advising replacing the bushes. I ordered 4 yesterday and they turned up lunchtime to today which was perfect timing as I had stripped it all out and just finished thoroughly cleaning and inspected the parts. I thought I was going to have to wait until next week for the parts.

The old rubber bushes.
0BA6A817-E486-44A0-9387-C27090DCBEE0.jpeg


James, I set the radius arms to around 6* when I put it back on it wheels I bounced the rear up and down and rolled it back and forth a little. I put a a magnetic camber checker on the centre-nuts, RH side (passenger) was 1/2* negative, the LH side just slightly off zero towards negative.
When I get a chance I will take it for a run and recheck it.

Thanks to everyone… will keep you posted.


How the wheel sits in the arch
121B7CA4-4C75-4564-A8CE-EA96ACAB028C.jpeg

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#9 Post by Paul Jorgensen »

Just come back from a spirited drive through the country, the car feels so much better…
I rechecked the camber angle, driver side 1/2* neg passenger side 1*
It is usually only driven with me in it so think I will leave it as it is for now.
It is nice to drive now 😀
Thanks again for all the advise

User avatar
Martin Benade
356 Fan
Posts: 12181
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Torsion bar adjustment

#10 Post by Martin Benade »

Very good. I bet it drives very much better. You may do well to gain 50 pounds so it sits perfectly level while you are in it.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#11 Post by Paul Jorgensen »

Although there is 1/2 degree difference between both sides, I measured from floor to underside of the arch & the passenger side only sits 5mm higher so not really noticeable.
But your right it drives so much better….

Paul Jorgensen
356 Fan
Posts: 193
Joined: Mon Dec 23, 2019 7:20 pm
Location: Southampton UK

Re: Torsion bar adjustment

#12 Post by Paul Jorgensen »

B6F47242-985E-45AD-A140-5AED90AB0CB9.jpeg
James
I found this in my garage yesterday when I was tidying up.
Not sure where I got 7mm out of level from but do remember doing the sketch!!!
Drivers side 24mm
Passenger side 14mm

I also found a bit of paper which said
drivers side 4*
Passenger side 3*
I must have written that down after checking with a camber gauge

Old age must be setting in 😳😀

Maybe you were right it may have been set up for a 356a

User avatar
James Davies
356Talk Moderator
Posts: 2951
Joined: Thu Aug 15, 2013 9:15 am
Location: Heidelberg, DE

Re: Torsion bar adjustment

#13 Post by James Davies »

Glad it's set up correctly now and feeling good Paul.

Yeah, 3 degrees is very much out of adjustment. Whoever set it up was either using 356A numbers or not using any numbers at all. Feel free to readjust in the future after more driving. And those rubber bushes look pretty chewed up for the car not having much mileage on it post-restoration. Good work all around.

User avatar
Mike Smith
356 Fan
Posts: 1275
Joined: Wed Mar 26, 2008 10:55 am
Tag: Its Only for Fun
Location: Ramsden Heath, Essex, CM11 1HS, UK
Contact:

Re: Torsion bar adjustment

#14 Post by Mike Smith »

You will arrive at better handling and ride if you work off the Centreline of the Car and not restored bodywork

Just my 2 pennyworth
Mike Smith (Essex - UK)

Post Reply