Parts Catalog Accessories Catalog Tech Info Tech Forums
 
  Search our site:    
 Cart  | Project List | Order Status | Help    
  We salute a legendary member of the community.
Thank you for selflessly sharing your wisdom with us...
Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > Porsche 911 Technical Forum

Reply
 
LinkBack Thread Tools Rating: Thread Rating: 1 votes, 5.00 average.
Author
Thread Post New Thread    Reply
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Rear toe out of adjustment range - possible fixes?

Problem:
The toe adjustment on both rear trailing arms won't bring the toe back from "way out" (positive toe) to toe-in or even to zero toe.
Background:

The trailing arms are on a '73 that I am just getting on the road after a purchase some 3 years ago. I noticed a roaring noise on having just gotten the car on the road with a rebuilt engine. On closer look back in the garage, I discovered an excessive wear pattern on the inside of the right rear tire, and set up my string alignment equipment to measure front and rear toe. The fronts are pretty close to zero. But the rears are both toed *out* by approximately 40' (that's about 2/3 of a degree *per wheel*)!! Camber on both rears is about a negative one degree, where it ought to be.
With the car on the lift, and checking the position of the toe adjuster on the spring plate, the adjuster was already at the end of the toe-in position. Adjusting the effective length of the spring plate is what affects the toe, with shorter resulting in more toe-in. The adjuster is at the end of it's range in shortening the spring plate.



Anyone have any ideas here? Is there some way I'm not seeing to deal with this? There is some wear in the adjustment slot which might be good for an additional 1/16", but that's not going to be nearly enough. My back of the envelope math says I need a good 1/4" just to get the adjustment back to zero toe and I'd like to get maybe 5' to 10' of negative toe.

FWIW, the PO had installed Delrin? bushings all around on the car, banana arm included. Yeah, I know, that is not the best choice for a place for a solid polyurethane bushing, but I don't see how that would affect this particular problem.

I have a set of SC aluminum banana arms and spring plates nestled away in the attic. I can go that route if I have to, but I'd rather first understand why I have this problem. I like to know what it is I'm fixing, and there's no real assurance that the SC arms are going to fix the problem. And of course, swapping the trailing arms out is not just an afternoon job.

Maybe some one has some thoughts on this........
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)

Last edited by Jim Williams; 11-04-2007 at 03:04 PM.. Reason: add photo
Old 11-04-2007, 06:40 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #1 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Bump......

Surely there are folks out there who have experience with alignment of the 911 suspension who might have some idea that would be of help in sorting out this problem. Maybe the subject of the thread didn't attract the attention of the right people?

I don't want to put more miles on these tires until the problem is addressed and fixed, and short of replacing the trailing arms, or maybe relocating the holes in the spring plate, I'm currently at a loss as to how to proceed.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-06-2007, 06:20 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #2 (permalink)
"farking Porsche hero"
 
Rich Lambert's Avatar
 
Join Date: Mar 2001
Location: Lake Stevens, WA
Posts: 1,822
Garage
Never mind...I just reread your post.

Since it's on both sides, it's got to be something they have in common. I'd look at the bushings first.
__________________
Rich
'66 911 #303872

Last edited by Rich Lambert; 11-06-2007 at 06:55 AM..
Old 11-06-2007, 06:47 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #3 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Keep 'em coming folks!

Rich,

Thanks for the input.

Note in my first post that the PO had installed Delrin bushings. I doubt that even 50 miles were put on the car before I bought it, and from the ride, Delrin must be one of the hardest plastics known to man! However, I am not discounting any possibility here, so before it's over, I may have to pull the spring plate off just to check and see what's inside.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-06-2007, 07:03 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #4 (permalink)
Registered User
 
Chuck Moreland's Avatar
 
Join Date: Apr 2002
Location: Santa Clara, CA
Posts: 5,639
HI Jim

Your description is thorough and it sounds like you know how to measure toe. But just to be sure, how are you setting up your strings?

Assuming you measured properly, and the toe is equally off on both sides, I would take a good look at your torsion tube. It may be bent towards the front of the car.

Some types of impact to the tire will force the control arm forward, bending the torsion tube in the middle. Rust damaged tubes bend more easily.

If it is bent even 1/4 inch over its length, it will have a big impact on toe. Use a straight edge to check for straightness.

Generally inspect the torsion tube and the trailing arm mounts. Any evidence of replacement, repairs or modification?

Report back what you find.

My money is on the bent torsion tube.

----------

I don't think the plastic bushings are the cause of your toe problem. But they are likely the cause of your harsh ride. It's not the hardness of the plastic, it's the friction and binding they are causing.

Plastic bushings should NEVER be used on the trailing arm inner link.
__________________
Chuck Moreland - Elephant Racing
Elephant Racing on Facebook
Old 11-06-2007, 08:14 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #5 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Chuck, thanks for the response. My strings are down while the car is up on the lift, with me checking for something I may have overlooked. So after another good hard look at the arm/spring plates, I am going to put the car back on the floor, re-settle the suspension, and set the strings back up and re-measure. I am going to take photos of the process to post so all can see how I got what I am finding.

Stay tuned.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-06-2007, 08:46 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #6 (permalink)
"farking Porsche hero"
 
Rich Lambert's Avatar
 
Join Date: Mar 2001
Location: Lake Stevens, WA
Posts: 1,822
Garage
Quote:
Originally Posted by Jim Williams View Post
Note in my first post that the PO had installed Delrin bushings. I doubt that even 50 miles were put on the car before I bought it, and from the ride, Delrin must be one of the hardest plastics known to man! However, I am not discounting any possibility here, so before it's over, I may have to pull the spring plate off just to check and see what's inside.
I did read that...the key word there is "PO". Never EVER trust a PO's installation of anything.

I hope it's not the torsion bar tube.
__________________
Rich
'66 911 #303872
Old 11-06-2007, 08:53 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 5,956
Hi Jim:

Just a note to all the kind folks who might read this thread for information,....

Delrin is a type of nylon and as such, should never be used for suspension bushings due to its propensity to absorb moisture. This makes them swell up and bind,... Although cheap and easily machined, its really a poor choice of material.

Trailing arms move in two planes (directions) and plastic bushings of ANY kind should never be used in those applications due to severe binding problems. One should either stick with the OEM rubber bushings or install weather-sealed monoball cartridges.

Hope this helps,
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 11-06-2007, 10:15 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #8 (permalink)
Registered User
 
Join Date: Jun 2005
Location: Birmingham, Alabama
Posts: 204
Quote:
Originally Posted by Steve@Rennsport View Post
Delrin is a type of nylon and as such, should never be used for suspension bushings due to its propensity to absorb moisture. This makes them swell up and bind,... Although cheap and easily machined, its really a poor choice of material.
Steve,

If Delrin is a no-go what do you recommend for track only PCA club racing other than metal bearing and the like? Consider both front and rear busings. I was given the impression that Delrin was the firmest and way to go for minimum suspension movement. Now you rained on that, so to speak.

I learned the hard way about trailing arm plastic bushing and am surprized they are still sold. Luckily, all I received was a great learning lesson in handling and a shorteded weekend.

Thanks for you insight and your contributions to the oil threads.

Jim
Old 11-06-2007, 12:12 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #9 (permalink)
Registered User
 
barney911rs's Avatar
 
Join Date: Mar 2004
Location: Delaware, OH
Posts: 1,256
I had poly graphite bushings on my car. I can tell you that the one for the banana arm mount was a PITA. It will resist the suspension settings you try and put in. That bushing has to not only rotate, but it twists to get the toe and camber settings. I have aluminum arms now with a monoball. A monoball is the best as it does not "give", but still has the freedom of movement to allow suspension changes to be made easily. A rubber bushing for the banana arm is better then the hard stuff. You should be able to use the harder poly bushings for the front and the spring plate.
__________________
John Snodgrass
1973 Porsche 911 "Barney" (race car for sale)
2008 Nissan Maxima - Daily Driver
1999 F350 Diesel Crew Cab - Tow Beast
1990 Airstream 36' Land Yacht - Home Away From Home
Old 11-06-2007, 02:28 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #10 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Quote:
Originally Posted by Steve@Rennsport View Post
Hi Jim:

Just a note to all the kind folks who might read this thread for information,....

Delrin is a type of nylon and as such, should never be used for suspension bushings due to its propensity to absorb moisture. This makes them swell up and bind,... Although cheap and easily machined, its really a poor choice of material.

Trailing arms move in two planes (directions) and plastic bushings of ANY kind should never be used in those applications due to severe binding problems. One should either stick with the OEM rubber bushings or install weather-sealed monoball cartridges.

Hope this helps,
Steve,

Thanks for your input. Quite honestly, "delrin" was dredged up from my memory. I know the bushings in the '73 appear to be made from some white plastic looking material, and that name popped into mind. But all I can really see is the flange portion of the bushings, and there may be another bushing material that resembles the "white plastic" description. I will be replacing the ones in the banana arm regardless of wherever this current toe-out problem leads.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-06-2007, 02:42 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #11 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
John,

The trailing arm is certainly resisting my attempts to adjust out the excessive positive toe. So you may be on to something there.

I set my strings up again tonight and remeasured the toe out. I had the car up on the lift and struggled with a readjustment, getting absolutely all the shortening of the effective length of the spring plate I could get. When I did the remeasure, I had taken maybe an eighth of an inch out, which might equate to 20' or so, leaving another 20' to get it within the limit of zero, but still short of where I want to go, and not seeing how I can improve it with the current setup.

I'll get some photos posted tomorrow of my string setup.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-06-2007, 06:43 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #12 (permalink)
 
Now Available for Ordering:   101 Projects For Your BMW 3 Series 1982-2000  [more info]
Registered User
 
Join Date: Jul 2001
Location: Portland Oregon
Posts: 5,956
Quote:
Originally Posted by jimmcc View Post
Steve,

If Delrin is a no-go what do you recommend for track only PCA club racing other than metal bearing and the like? Consider both front and rear busings. I was given the impression that Delrin was the firmest and way to go for minimum suspension movement. Now you rained on that, so to speak.

I learned the hard way about trailing arm plastic bushing and am surprized they are still sold. Luckily, all I received was a great learning lesson in handling and a shorteded weekend.

Thanks for you insight and your contributions to the oil threads.

Jim
Hi Jim:

LOL,..I'm glad I "rained" on that idea as that saves you a LOT of headaches and stomach lining.

There are a LOT of products on the market that are truly useless in both design & execution. Such items sold by those vendors/manufacturers simply entrap the unsuspecting in the quest to make a buck and have no scruples about it.

The operative words here are "Caveat Emptor" and this situation underscores the need to consult as well as support the folks who truly know this business as thats how their collective knowledge & experience is available to you.


Mr. Williams:

Most common Delrins are white or light tan in color and easy to ID due to their hardness,...

These used to be VERY popular in the 60's & 70's due to the lack of other options and low cost.
__________________
Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com

Last edited by Steve@Rennsport; 11-06-2007 at 10:00 PM..
Old 11-06-2007, 09:56 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Jun 2005
Location: Birmingham, Alabama
Posts: 204
Quote:
Originally Posted by Steve@Rennsport View Post
Hi Jim:

LOL,..I'm glad I "rained" on that idea as that saves you a LOT of headaches and stomach lining.


The operative words here are "Caveat Emptor" and this situation underscores the need to consult as well as support the folks who truly know this business as thats how their collective knowledge & experience is available to you.

These used to be VERY popular in the 60's & 70's due to the lack of other options and low cost.
Steve,

Thanks but a bit late. I installed the delrins this summer after years of hearing from my former mechanic (60&70s era) how great they were. I am unfamiliar with delrin and with it's hardness never contemplated a moisture problem. Due to circumstances they've yet to be tested.

I had removed a set of the old Weltmeister race bushing that had not been properly fitted and obtained the Smart Racing bushing but felt they were too soft for a dedicated track 930.


So, it's back to the learning pit again. Any suggestions? What's another day in the garage?

I will agree on getting the best advice but that in itself can be difficult with the overall noise level.

Thanks

The other Jim
Old 11-07-2007, 04:35 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #14 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Maybe at this point starting a separate Delrin bushing thread would be appropriate. I would like to get back on the topic of finding the problem with the rear toe adjustment.

Just for review, regarding the string alignment, here is the set up I used to determine the toe setting. The diagram was copied from Ray Scrugg's alignment booklet. The string set up is really pretty simple: parallel (to each other) strings, set up parallel to the fore-aft center axis of the car. For those familiar with only the fancy computer alignment machines, this may seem pretty crude, but with a little care, one can get very accurate results.



Here is my string setup. The tubes are electrical conduit with grooves pressed into the ends. The grooves define exactly equal lengths on the tubes which the strings (also equal length) ride in.




The string lengths should be close, but when I checked mine, there was about an inch difference. But doing the math to see if that really made a difference, it affects the parallelism by only 0.010".

Here are photos of the toe measurements on one rear wheel. By the way the suspension was settled out beforehand by the use of slip plates.




That's 1/4" over 17" of rim diameter, and equates to close to 50' of toe out. The larger of the two measurements is to the rear edge of the rim, and the smaller to the front edge, resulting in toe-out and not toe-in.

More coming in the next post........
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-07-2007, 06:25 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #15 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Quote:
Originally Posted by Chuck Moreland View Post
HI Jim

Your description is thorough and it sounds like you know how to measure toe. But just to be sure, how are you setting up your strings?

Assuming you measured properly, and the toe is equally off on both sides, I would take a good look at your torsion tube. It may be bent towards the front of the car.

Some types of impact to the tire will force the control arm forward, bending the torsion tube in the middle. Rust damaged tubes bend more easily.

If it is bent even 1/4 inch over its length, it will have a big impact on toe. Use a straight edge to check for straightness.

Generally inspect the torsion tube and the trailing arm mounts. Any evidence of replacement, repairs or modification?

Report back what you find.

My money is on the bent torsion tube.

----------

I don't think the plastic bushings are the cause of your toe problem. But they are likely the cause of your harsh ride. It's not the hardness of the plastic, it's the friction and binding they are causing.

Plastic bushings should NEVER be used on the trailing arm inner link.
Chuck,

I couldn't figure out how to get a straight edge up to the torsion bar without dropping the engine. So I rigged up a way to get an indirect measurement. I made some photos, but will post them later if there is a need to clarify my explanation. I made up 3 "plumb bobs" with some string and steel nuts on the ends. These were draped over the torsion tube in three places, one on the right, one on the left and one close to the middle of the tube, between the tube and the car body, on the forward side of the tube. I then clamped a 3' metal ruler so that one edge would line up against all three plumb bobs if the tube were indeed straight. However, they did not line up; I found that the tube center is about 3/16" forward of the ends, indicating that it could be bent forward in the middle toward the front of the car.

If this is indeed the case, have you any experience with straightening the tube? It looks like the engine/ trans would have to come out, and some sort of fixture constructed to pull back on the center of the tube to get the 3/16" out.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-07-2007, 07:12 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #16 (permalink)
Registered User
 
Chuck Moreland's Avatar
 
Join Date: Apr 2002
Location: Santa Clara, CA
Posts: 5,639
Jim, I beleive you are measuring toe properly. Just wanted to be sure

I've never tried straightening the tube myself. There might be a creative way to do it with a porta-power or some comealongs.

A good frame straightening shop with the right equipment could certainly do this.

You could also cut it out and weld in a replacement tube.

Check the tube for rust. If structurally rusty, replacement would be the best option.
__________________
Chuck Moreland - Elephant Racing
Elephant Racing on Facebook
Old 11-07-2007, 08:43 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #17 (permalink)
Registered User
 
Jim Williams's Avatar
 
Join Date: Feb 2005
Location: Huntsville, AL
Posts: 1,342
Chuck,

Thanks. I was hoping that someone, like yourself, had some ideas on how to approach straightening the tube. Thinking that I might be faced with this, I had envisioned an "A" frame with the legs of the "A" against the outermost ends of the tube and either hydraulics or a come-along between the peak of the "A" and the center of the tube. If I were lucky, and the tube is not rusty (as it doesn't appear to be), I might be able to give it a short stout pull and measure to see if that had any results, and not have to even pull the suspension. I have a friend with a local body shop who I plan to contact for suggestions.

If anyone else out there reading this has any thoughts on other ways to approach this problem, feel free to keep the comments coming. Otherwise, it's looking like an engine drop and a frame shop.
__________________
Jim
www.jimsbasementworkshop.com
(CIS Primer for the 911)
(73 911T (RS look) coupe)
(Misc. 911 Parts for Sale)
Old 11-08-2007, 04:18 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #18 (permalink)
Registered User
 
barney911rs's Avatar
 
Join Date: Mar 2004
Location: Delaware, OH
Posts: 1,256
Uncharted territory for me, good luck. Keep this thread updated with the details of the fix. It will be good info for someone else down the line with the same or similiar problem.
__________________
John Snodgrass
1973 Porsche 911 "Barney" (race car for sale)
2008 Nissan Maxima - Daily Driver
1999 F350 Diesel Crew Cab - Tow Beast
1990 Airstream 36' Land Yacht - Home Away From Home
Old 11-08-2007, 07:35 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #19 (permalink)
East bound and down
 
Capt. Carrera's Avatar
 
Join Date: Feb 2005
Location: Camden, SC
Posts: 2,130
Garage
Most likely culprit is the delrin/eurathane banana arm bushings. I'd start with that. I doubt the t-bar tubes are bent.
__________________
Rob in Camden, SC - '88 Carrera.
Track junkie.
Carolina Motorsports Park, Turn One Track Events, Carolinas PCA, NASA SE
Old 11-08-2007, 01:26 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #20 (permalink)
Old 11-08-2007, 01:26 PM
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 01:30 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.