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Thread: Upper strut mount bushings

  1. #1
    Senior Member Merv's Avatar
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    Upper strut mount bushings

    While my car is in for stripping and painting, I am ordering a few parts. I need to replace the upper (front) strut mount bushings. The plates, etc., seem fine and I have new Koni inserts ready to go into the strut.

    So, I can see on PP poly bushings and also the Elephant Racing ones. The fright alone is $50 on each. Is there an Australian source for (just) the bushings?
    Merv

    Member # 2633
    Cars:
    Porsche '68 - 911N (Sold)
    Porsche 356B (T-6) S Coupe
    Porsche 2008 C2 997 Cabriolet (Sold)
    Porsche 2010 Gen.2 Boxster S

  2. #2
    Merv,

    The rubber bushes in the 65-69 Camber plates are different to the 1970-89 parts and as far as I know unavailable.

    If the bushes you have are in reasonable shape than I would suggest that you re-use them.

    The Elephant Racing part which is listed as being suitable for 65-89 is, I believe, incorrectly catalogued. This Rubber Bush will not fit your camber plate unless it has previously been changed for one from a later car.

    The Super Pro website (Australian Polybush) lists their part as being 1969-89 but in reality the change occurred in 1970.

    If you have later camber plates or fitted these as complete parts (They are available from Porsche) then you would experience some difficulty in setting sufficient caster when you adjust your suspension.

    The body shell differs slightly in the later cars in terms of the angle of the Macpherson strut mounting and the camber plate has subtly different angles to deal with this change and this affects the degree of camber adjustment when using the later plate in an early shell.

  3. #3
    Senior Member Fishcop's Avatar
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    Hi Merv and Chris

    Merv, I responded on the 901 board that I had used the blue poly versions (presumably the Super Pro units). My car is a 69 and I have had no problem setting factory specs for castor and camber on my particular car, though from memory the tech had a few goes at getting it right.

    Given that your car is a 68, Chris' advice might be pertinent...

    Given that I have a 68 and a 69 in my garage, I'll go have a good look and see what the differences are for you.
    John Forcier
    EarlyS #1987
    1968 911 Race Car "Grun Hilda"
    1969 S/T interpretation "Blau Healer"
    Restoration Saga

  4. #4
    John,

    When was your 1969 car built? and how much caster are you setting?





    These diagrams show the difference in angles which according to the Workshop Manual took place in 1970.

    The later camber plates have the bush shown below



    The earlier bushes are shown below on and are on the left side.

    The bushes on the right side are standard Koni bushes.




    These are the differences in camber plates between 69 and later cars.

    We have found it difficult to set caster at more the 4.5 degrees with the later plate in the early bodyshell.


  5. #5
    Senior Member Fishcop's Avatar
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    Hi Chris (and Merv)

    I don't have my settings handy, it was set up 'aggressively' for track work at the time with strong negative camber. I've definitely got the 'later' one piece. My T chassis is 0145, so presumably fairly early (August/Sept 68 I think). It's quite possible the plates were changed out by a PO.

    Thanks for the photos of the differences - they are considerable!
    John Forcier
    EarlyS #1987
    1968 911 Race Car "Grun Hilda"
    1969 S/T interpretation "Blau Healer"
    Restoration Saga

  6. #6
    Senior Member Fishcop's Avatar
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    Merv, when I got new (NOS) Koni struts for my car, they came with a new set of the bushes shown in the bottom photos from Chris - so maybe you've got the same in the kit and don't need to source new bushes?
    John Forcier
    EarlyS #1987
    1968 911 Race Car "Grun Hilda"
    1969 S/T interpretation "Blau Healer"
    Restoration Saga

  7. #7
    Senior Member Merv's Avatar
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    Many thanks John and Chris. This is great info and thanks for the time to respond. Seems I have asked a question without a perfect/easy answer. My existing bushes, in the original camber plates/retainers from '68, are a bit tatty around the edges on the top, but seem solid enough. So from what you say, the later (first of your pics Chris) ones look like the Elephant racing ones and are NOT suitable (and also the poly ones). AND the bushes that came with my new Koni inserts (as in the second photo) could do the job? The alternative is to leave the ones in there that I have.

    4.5 degrees of caster if achievable should be plenty for road use?
    Merv

    Member # 2633
    Cars:
    Porsche '68 - 911N (Sold)
    Porsche 356B (T-6) S Coupe
    Porsche 2008 C2 997 Cabriolet (Sold)
    Porsche 2010 Gen.2 Boxster S

  8. #8
    The Koni bush is almost right and will fit and 'do' the job but it isn't 100% correct if originality is vital.

    Caster for early cars (65) was nominally 6degree 45minutes. +/- 45 minutes

    For the 1967 911S this value was amended to 7degrees and 45minutes

    The SWB 911T was also specified with 6 degrees and 45minutes.

    I think 4 1/2 degrees will affect turn in behaviour but it will lighten the steering.

    We set our SWB cars to 6.5 minimum but prefer 7.5 degrees which was, I believe, also used on the 911R.

    As tyre widths increase caster reduced until the SC when it became 4.5 and I don't think IB cars steer as well as early cars but that's a whole new can of worms.
    Last edited by chris_seven; 08-15-2013 at 03:27 AM.

  9. #9
    Senior Member Merv's Avatar
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    Thanks again Chris. My steering is reasonably light now, but still stable at speed over bumps. So when I get the new Koni inserts fitted (I have also installed new ER bushes on the A arms), I could increase the caster a bit and lose a tad of the turn-in and lightness without problems. Is it possible to increase the caster on the the 68 with the standard set up ( I have 15x6 wheels)?
    Merv

    Member # 2633
    Cars:
    Porsche '68 - 911N (Sold)
    Porsche 356B (T-6) S Coupe
    Porsche 2008 C2 997 Cabriolet (Sold)
    Porsche 2010 Gen.2 Boxster S

  10. #10
    You should be able to set 7 degrees without problems as long as you have the correct early style camber plate. The turn in should improve with increasing caster.

    I would say increased caster should provide the following benefits:

    Increased dynamic negative camber in turns
    Improved high speed stability
    Improved road feel, steering feedback and sensitivity
    Improved steering turn-in response during corner entry

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