23 m m master brake cylinder upgrade questions

[gwilliams]

what all is involved in installing a 23 mm master brake cylinder in a 1971 911 t with turbo brakes is this just a bolt up is there any cutting of the car what is the best master cylinder to use mercedes whats the part number and do you need any adapters where do you get the correct parts and why do you need the aluminum cross member can anybody respond in easy terrms with photos and also if i leave the standard master cylinder in it is that a bad ideal what is the correct way with out screwing the car up or devaluing the car thanks photos please

[Todsimpson]

I recommend you buy the complete kit from VCI. http://www.vehiclecraft.com. Since they are selling you the kit, I am sure they can answer your questions.

Here's what I know from when I did the upgrade.

You want the "kit" because it comes with the new pushrod you will need, along with the 90 degree feed line. (I suppose you could piece it together for less but it saves time and gives you someone to call for tech support.)

One of the hard lines needs to be replaced as well, I think on the drivers side. I removed the existing line, measured the length and bought a new hard line and bending tool at the local auto parts store. They usually sell hard lines in all sorts of lengths and you have to be sure to match the metric thread pitch and "bubble" flare style.

I had already put the aluminum crossmember in, so I can't help you there....I've heard steel "can" and "can not" work.

Other than that, it is a bolt in. I'd consider pulling the pedal cluster and doing all the bushings while you're in there, and it's also a great time to clean that area and treat any rust. I don't think you are screwing up the car in any way, and the larger MC is a good idea because your new calipers require more fluid to move the pads.

Here's a shot of the original and the Mercedes MC....sorry, no other pictures.

[John Z Goriup]

some shots of the Mercedes master-cylinder you're referring to and the aluminum cross-member I installed when I was assembling Ruprecht.

The only required modification to the non-standard crossmember was the small notch to allow installation of the cylinder. No cutting to install the cylinder, but I did fabricate a complete new set of brakelines and used new fittings throughout.

I know you didn't ask for opinions, but I am strongly of the opinion that turbo brakes are simply too much brake for any longhood 911. Brembo C2 / Boxster / 951 4-piston calipers are perfectly adequate, since they are reliably capable of locking up the biggest, stickiest racing tires available today..........over & over. On my '70 T with rebuilt 951 4-piston calipers all around and Zimmerman rotors it makes for a very balanced & effective brake system, resulting in a huge improvement in drivability..........a most worthwhile modification.

[gwilliams]

please any photos

[ttweed]

I know you didn't ask for opinions, but I am strongly of the opinion that turbo brakes are simply too much brake for any longhood 911. Brembo C2 / Boxster / 951 4-piston calipers are perfectly adequate, since they are reliably capable of locking up the biggest, stickiest racing tires available today..........over & over.

John-
I have never driven a Porsche that wasn't capable of flatspotting any tires you put on it with the stock brakes, even the early SWB cars with their tiny calipers. Stock brakes are fine for any spirited street driving you might do, and with adequate cooling, fresh hi-temp fluid and pads, you might be OK for light track duty w/o any other upgrades. Where I would quibble with your "turbo brakes are simply too much brake for any longhood 911" statement would be if the car is going to be subjected to heavy track usage in high-temperature (100F+) conditions. At some point, dissipating heat from constant heavy braking will become an issue, and brake fade will rear its ugly head. More than the size or clamping strength of the calipers, it is the mass of the rotors acting as a heat sink that is responsible for shedding this heat. The ability of the 930 brake package to fit massive rotors under a 15" wheel can make it a sensible upgrade for some early 911s subjected to such extreme conditions, IMHO. You pay a price in increased un-sprung weight and rotational inertia, but not having the pedal go to the floor in a critical braking zone can be priceless. Have you held a Boxster rotor next to a 930 rotor? Not in the same league...

BTDT,
TT