68L USA front strut and caliper updates

[1968L]

I have 68 L-USA model that needs lots of TLC to get it back on the road. I am considering installing 1969 or later front Koni struts to carry the 69S or later calipers. Does someone have know if this upgrade is simply swapping the parts or if there are major issues involved, assuming I can find and afford the parts. This is my first post on this board and its been a long, long time since i was completely up to speed on the technical details of hot rodding my 911. But I do remember at Willow Springs i wanted better front brakes.
Thanks, 1968L
Member # 470

[chris_seven]

If you fit a 1969 Strut then unless you find some from a 911S the Brake Caliper mounts will be 3" Centres and will use the same calipers as the 68 car,

A 69S would have 3.5" caliper mount centres and would have used the Aluminium Caliper but the later SC has a cast-iron caliper with the same mounting centres.

Piston diameters are the same 48mm for all front calipers but pads are a bigger area on the S and SC caliper.

You will also need to change the front control arms as the ball joint on the 69 strut will be different to the 68 strut and they are not interchangeable.

[1968L]

Hi Chris,

Thanks for the response. So if i understand correctly, mounting the 69S Koni Struts, will require 69 control arms. Okay, I found both of those available. i think I understand that the caliper hole spacing is 3.5 inches, whereas my calipers have a 3 inch mounting hole gap.

I wonder if the 69 control arms are a direct bolt on part to my 68 chassis, or if more modifications would be necessary.

I believe the main point of the upgrade is to be able to use the larger brake pads of the 69S or later Aluminum caliper for a lighter unsprung weight. Those 69S aluminum calipers are proving a little harder to find so far. Assuming i can find the aluminum calipers, or if not, decide instead to get the heavier cast iron SC calipers, do you think my overall suspension geometry would change due to wheel spindle position, or the angle of the struts compared to the 1968 versions on the SWB cars?

i am not so sure i would want to start the domino effect of a brake upgrade, requiring suspension components changes to lead to an even longer list of other necessary upgrades to make the car drivable and handle as well as it did when i parked it last. i would just like bigger brakes that are less prone to fade than the 1968 stock brakes do.

Any more suggestions, opinions, or guidance from anyone would be greatly appreciated.

Thanks,

1968L
Kurt Kinzel, Altadena, Ca. Member # 470

[chris_seven]

The control arms will bolt straight onto your car without any issues.

The camber plate on the strut top, if it is a correct 1969 part will be compatible with your 1968 shell as the strut mounting area angle didn't change until around May 1970.

If the 1969 911S struts have been fitted with the later camber plates with the one-piece rubber bush then the available range of adjustment will be affected and I would suggest that you use the Camber plates from your 1968 struts which have two bushes per plate. If you use the later camber plate it is likely that the amount of Caster that you can set would be affected an this would have a negative impact on turn-in and feel.

The bushes for the early camber plates are NLA from Porsche but some aftermarket bushes are available. The most commonly available bush is modelled on the Koni Shock Absorber bush which does fit but isn't quite correct.

We have recently re-manufactured the correct bush in an uprated HNBR material complete with the Plate Washers, Tab Washers, Inner Sleeves and Grade 8 Hex Nuts.



The 69S caliper was used on the 911E and cars with Sportomatic Transmissions, early Turbos and the Carrera RS. There are a couple of versions, some stamped with an X which indicates a difference seal clearance.

The Calipers have just been re-manufactured by the JP Group but I believe that the bodies are now cast rather than forges as was the case with the originals.

The do crop up from time to time and parts are available to rebuild them.

We make a 6AL4V Titanium Piston for these calipers. They are Ti carbide coated to reduce seal friction. This type of Titanium alloy has a much lower hat transfer coefficient that steel and helps to control brake fluid temperatures.

[Harvey Weidman]

I think it would be less work to put on some of PMB's new big brake alu calipers on your old struts...
Or.... BMW steel with the3.0 spacing and larger pads....
JMHO
H

[1968L]

Hi Guys,

Thank you both for the recommendations.

Chris, thank you for the detailed info that i may need to use if I go with the strut change and 69S style calipers. When you say we manufacture the correct bushes, can you tell me the name of your company?

However, before I go further toward that process i would like to explore Harvey's idea about just getting better calipers that fit my current struts. I sent a request for information to PMB today to inquire about lightweight calipers with larger pad areas that fit the 3 inch spacing of my struts and my vented discs. Thank you Harvey!

I will post what i find out from PCB.

1968L

Kurt Kinzel
Member #470

[304065]

Kurt, if your race rules permit, get the entire front end from an 84- Carrera with the thicker rotors. Crossmember, steering arm, control arms, struts, brakes, steering box, turbo tie Rods. Take the entire 68 suspension off and store it in a box for when you restore/transfer ownership of the car.

Grady Clay (RIP) did this MANY years ago with his 68 and reported great success and the parts are (relatively) cheap. You can also get the Elephant decambered ball joints etc. to really trick it out if you are into that sort of thing. Don't forget the baseball bat front ARB, I used a 31mm on my 71, felt like power steering.

[chris_seven]

There are some subtle differences if you change the entire front end to that of the later car.

The Steering Rack is longer by 16mm which is not an issue when you change all of the associated parts but whenever we have done this mod we have fitted the early strut to camber plate otherwise it may be difficult to adjust camber.

The centreline of the rack is 3mm higher in relation to the front axle and this will influence the bump steer curve but again is probably not significant.

The steering ratio also changes and the number of turns from lock to lock increases from 2.75 to 3.1 and this is the one aspect of the change that blunts my enthusiasm.

[1968L]

Hi Guys,

Sorry for the tardy response, but i had unexpected biz travel and a crazy jet lag schedule for several days. I really do appreciate all of your valuable feedback and suggestions and very appreciative that the registry provides this forum for us to learn from.

I should probably make one point clear about my intentions with the car. Its not a race car, it never was and probably never will be. i have owned this car since August of 1970 and it had one owner before me. My intention is to get it in shape to put back on the road and hopefully join in on some of the various Porsche clubs tours and gatherings, as well as a possible DE event once in a while. When I ran at Willow Springs it was my first DE event many years ago and the first time the car was driven all out, other than several years of auto-crossing when i lived in Atlanta that included several class wins and a championship. At Willow the car handled great with just my Koni's dialed in, the right tire pressures, and removing some unnecessary pieces to lighten the load a bit. After a full day of all the run groups i ran in, the brakes were the major weak point. That is why i want to upgrade from the standard brakes now. While it is a very interesting suggestion, i would really rather not replace the entire front suspension with later model parts and learn how to dial it all in correctly from scratch again.

Following up on Harvey's suggestion i contacted Eric at PMB Performance Brakes. Eric recommended the Brembo AM Calipers that are a direct bolt on replacement for my original ones. They are aluminum, 4lbs lighter, and have nearly the same pad area as the original 69 S calipers (only 2mm less in width, but longer) and they will not stress the original rotors or replacement rotors of the same size.

By going with these brakes i can keep my original struts, control arms, anti roll bar, etc., and perhaps just replace some bushings. That helps me provide more available funds for everything else the car needs, body work, re-paint, interior refresh, engine refresh and anything else that my "resto-mod" requires.

I am meeting Eric and taking a look at their brake systems at the Rennsport Reunion in a few weeks up at Laguna Seca. Not to date myself too much, but I spent a fair number of weekends at the old turn 9 during the heyday of the Can-Am and Trans-Am series when i was in high school in Palo Alto. Seeing Jim Hall's Chaparrals and the 917-10 and eventually Mark Donahue in the 917-30s do battle with likes of the ground shaking Maclaren's of Peter Revson and Denis Hulme was a real thrill.

Thanks again to you all for your help. I have no doubt that I will run into at least a few more mysteries during the process of getting the car back on the road.

[304065]

Kurt,

Race car or no, you will be far better off going with the cheaper modern alternative both in the immediate future and the long run. I've assembled and disassembled both: the original SWB pieces in my '66 and the "modern" suspension in my '71.

The original SWB pieces are a LOT more expensive to obtain, more complicated to put together and offer far less adjustability for "dialing in" than the modern bits. A few illustrations: SWB ball joints are integral with a piece of the lower control arm that slides into the arm itself, and are captured, along with the bracket for the ARB, by a pair of M12 bolts and castle nuts with cotter pins. There is no adjustability for camber built into this assembly by the factory (although you do hear about people elongating the holes in the arm, which frightens me.) The ball joints are like $200 per side. The factory bushings for the aft end of the original control arms are like $250 per side, and you have to use an air chisel to get the old ones off. The original tie rods have a lot of play in the rubber bushings, unlike the turbo tie rods which have a ball joint at each end. There are also brackets for the steering damper which are mercifully not present on your '68 but the vestigial bits are there.

Not trying to beat a dead horse and to each his own, but what makes an SWB car fast is not the brakes, it's the suspension. Also. . . if you want to convert to a 23mm master cylinder which I HIGHLY recommend with any modern brake setup, the larger cylinder will hit the crossmember, so you would typically change to an aluminum crossmember for clearance. . . as in the modern setup.

Good luck whatever path you choose and be sure to share photos of your progress!