jlkline

I'm trying to find out if there are any 4 piston calipers available that anyone knows of, which can be used with my '74 Boge struts (3" caliper mounting bolt spacing)and require minimum modification.

Steve Weiner-Rennsport Systems

Hi:

AFAIK, there are no 4-piston Porsche calipers that will bolt onto, or have readily available billet adapters, that will permit you to bolt on any of the currently used 930, S4, Big Red or even Boxter & 996 brakes onto your Boge struts.

There possibly might be some AP, Alcon, or other Brembo caliper that has 3" bolt spacing you can use, but there are so many pitfalls in this approach that I would mention a caveat emptor on this route.

I would suggest that you locate and install a good usable pair of used or new Bilstein, or Boge struts that allows you to bolt on any caliper that will fit inside your current wheels.

jlkline

Thanks Steve. At least I now have the definitive answer on that one.....

I guess my next question would be then....What would be the street pad would give me the best stopping power?

Howard

Jlk,

I have TT calipers and rotors on my '78 sc mounted to the stock Boge struts. The caliper adapter and adapter hat was mfg by Wrightwood Racing, the makers of the Charlie bars. Quality is very high and all parts are anodized, trouble is you need to purchase from a distributor. If you give Wrightwood a call they can direct you to one of their distributors, I dealt with Steve Alarcon at Johnson Alignment in Torrance, Ca.

Good luck !

Steve Weiner-Rennsport Systems

Hi Howard:

Given that Boges made struts with both 3" and 3.5" caliper mount spacing, it might be helpful to point out exactly which Boge ones you have.

All SC and Carrera Boge struts will accept any of these brake calipers, some needing an axial-to-radial caliper adapter like the S4 & TT ones.

I am one of Charlie's (Wrightwood Racing) distributors and AFAIK, he only makes brake kits for the 3.5" struts.

AES

Steve, didn't all of the 78 on SC or Carrera have 3.5" ears stock, regardless of insert?

Steve Weiner-Rennsport Systems

[quote]Originally posted by AES:
<strong>Steve, didn't all of the 78 on SC or Carrera have 3.5" ears stock, regardless of insert?</strong><hr></blockquote>

Yessir, they did,........Porsche used Boge, Woodhead, and Bilstein struts on these cars.

Tom Tweed

There was a 914 guy in Texas I found a couple of years ago who was making kits for the early struts to convert to a Girling 4-piston caliper w/ a 12" Coleman rotor. These would fit 914s or early 911 w/ 3" caliper bolt spacing. Here is a copy of my correspondence with him at the time. Don't know if the contact info is still current, but you might try if you're interested. I sold the '66 911 I was considering this for and got a '73, so it was not something I pursued.

--------begin included message----
From: A914GUY@aol.com
Date: Mon, 16 Aug 1999 19:43:51 EDT
Subject: Re: "M" strut, Girling caliper upgrade (four piston)

Thanks for the interest.

Several months ago I started to investigate the possibility of making a big brake upgrade for the "M" strut found on early 911s, 914-6s and 914-4s that have been upgraded to the five lug suspension.


The interest I had was to come up with an alternative front brake system that was a significant upgrade for these cars, use as many common parts I could find and make it a bolt-on, reasonably priced kit.

The caliper is a common four piston, steel, OE, Girling caliper. It uses a common pad the size of the 930 pad, has a set of pistons that rival the 930s. It weighs about the same as a Carrera "A" caliper and will fit under most
(if not all) of the 15 inch wheel sets we are using on our cars.

The caliper mounting bolt pattern is a perfect match for the 3 inch "M" strut's spindle. Mounting bolts and spring washers can be reused from the old ATE sets.


These calipers used a twin circuit mastercylinder in their previous life so I had a 2-1 adapter block made up to simplify the installation on the Porsche single line fluid connection. The block is a CNC built assembly with twin banjo bolts to make the 2-1 step.

The rotor is made by Coleman. It is a ompetition quality, straight vane, vented rotor that has a 12 inch outside diameter and is 23mm thick. This is very close to the spec. of the Carrera (11X24) rotor, adding 1 inch in diameter and dropping 1mm in width. Replacement prices are comparable to the retail cost of the Zimmerman OE Carrera rotor.

The rotor adapter (commonly referred to as a rotor "HAT") is another CNC built part that provides for the mounting of the rotor while serving double duty by adding the offset to center the rotor inside the caliper. The
adapter was made from billet aluminum in a grade suitable to outlive the life of your aluminum hubs. All of the hub and rotor mounting hardware is provided in the kit.


Three cars are currently using the setup. I'll know more about use over the next few weeks. One of 911 owners has move the existing front caliper to the rear to gain some piston size out back. A slight turning of the rear rotor hat was required to clearance the larger pistoned ATE fronts out back.

Cost is $750.00 for the complete package. Calipers (rebuilt), rotors and adapter, all the mounting hardware and pad set (semi-metalic street pads).

Let me know if I can help.

Rich
(972) 398-9146