wondering if a brake booster is necessary, if you use one in your 914.....post your opinion.

thanks

Not required unless you have muscle issues.

If the brakes are in working order, you can stop on a dime.

If your system requires more force than you think it should, start with replacing the rubber brake hoses at each caliper, then look at replacing the mater cylinder.
Rebuilding your pedal cluster is always a good thing to do after 40 years of grunge and dirt to make that move more freely.

From there, it would be caliper rebuilds if you still feel its to hard.

Stick with the 17mm master cylinder to keep the foot pressure as low as you can.
Then tune up the system to perfect before you judge what it feels like....

Rich

If you have to ask, there is something wrong with your brakes or your leg.

HA ! I was thinking the same thing.

I was just asking since my brakes are new but soft, I feel I have to push the pedal thru the floor.
thanks...I will check and follow the replies.

It possible that they just need to be bled again and/or the pads/rotors should be bedded in some more. Which brake parts were replaced?

Did you set the rear venting properly?
Might want to check that

It depends upon what calipers you're running. If you go for much larger calipers, with larger pads and pistons, and perhaps more of the latter (4 vs 2), you need more fluid displacement to move the pads into contact with the rotors, and that requires a larger bore master cylinder if you want to keep the pedal stroke and the mechanical advantage the same. But even if you do that, you will need more force on the pedal to get the braking force that you went with the larger calipers to get, because you need to get back to the same pressure, in pounds/sq inch, at the pad/rotor interface, and the square inches have increased due to the larger pads.

I have 930 rotors front and rear on my car, with 930 front calipers and 965 rear calipers (very similar to 930 rears, but made by Brembo and consequently cheaper and more available). To get back to essentially the stock stroke with this combination I needed a ~23mm dia. master cylinder. That configuration figures out to require about 83% more force on the pedal to get to comparable braking. The stock 914 has excellent brakes, but I've never considered the force required to get maximum braking to be light. Consequently, I stayed with the factory combination for the brakes I have, the same vacuum boosted master cylinder used in the 930 model that had my brakes. I mounted the vacuum booster and master cylinder, together with the casting and lever used in the 911/930, in the front trunk to the driver's extreme side and hooked up the brake pedal with a mechanical linkage. The result looks like this:

Click to view attachment

You should ignore the other bits and pieces that are part of my AC system that has yet to see the light of day.

Is it necessary? Certainly not if you stay with the stock calipers or even the somewhat larger normal 911 single piston calipers. As soon as you start putting larger tires and bigger calipers with increased pad area on your car, however, the pedal force required to get the brakes to feel like they're giving you the same stopping power will go up. I've seen many posts from people who've just completed such a modification, expecting a major subjective increase in braking, and are amazed and disappointed that it doesn't seem to be so. My system still only about gets back to the stock feel as far as subjective braking force is concerned. It will produce a lot more ultimate braking force, and stand up to heavier use without fading, but the subjective feel for everyday use is only about the same as the stock brakes with the stock size tires.

I have 930 brakes, front & rear. I use a standard 23mm master without a booster. I can stop just fine. I don't struggle at all and the car stops on a dime.

The original post states the pedal is soft and brakes are new. You have a mechanical problem somewhere. Your brakes should not be soft. Fix them!