914 brake upgrade options Options

[Chris H.]

Can't believe we're talking about braided stainless steel brake hoses and the Cap'n hasn't chimed in. Is he OK (IMG:style_emoticons/default/confused24.gif) ? Someone check on him.

[race914]

19mm reduces stopping power. It was used with the larger pistons on 911 brake calipers. SS brake lines are also a downgrade compared to dot rubber hoses. All stock oem is your best bet unless you spend big $.

If I follow your though process, your 914-6 GT will have 17mm master ?
Bdstone's advice is spot on.

No, my gt has brake calipers with larger pistons, just like Porsche did on the real 914-6. I'm not an engineer but I do know fluid pressure will decrease when you increase the mc piston diameter. Try going to a 23mm mc on your otherwise stock setup and tell me what happens. There isn't a big difference going to a 19mm mc but there is some, otherwise the pedal "feel" would stay the same. A 15mm mc would provide even greater pressure to the calipers but at the expense of softer pedal and greater travel. As jake would say- or Eric, it's all in the combo.
I'll stand by my statement that a larger mc is a downgrade.

Ok, I just have to ask....

Why would Porsche Engineers specify a down graded, larger 19mm Master Cylinder in the 914-6 build specs?

I'm open to all opinions, I'm just trying to understand the logic that underlies your statement...

[mepstein]

19mm reduces stopping power. It was used with the larger pistons on 911 brake calipers. SS brake lines are also a downgrade compared to dot rubber hoses. All stock oem is your best bet unless you spend big $.

If I follow your though process, your 914-6 GT will have 17mm master ?
Bdstone's advice is spot on.

No, my gt has brake calipers with larger pistons, just like Porsche did on the real 914-6. I'm not an engineer but I do know fluid pressure will decrease when you increase the mc piston diameter. Try going to a 23mm mc on your otherwise stock setup and tell me what happens. There isn't a big difference going to a 19mm mc but there is some, otherwise the pedal "feel" would stay the same. A 15mm mc would provide even greater pressure to the calipers but at the expense of softer pedal and greater travel. As jake would say- or Eric, it's all in the combo.
I'll stand by my statement that a larger mc is a downgrade.

Ok, I just have to ask....

Why would Porsche Engineers specify a down graded, larger 19mm Master Cylinder in the 914-6 build specs?

I'm open to all opinions, I'm just trying to understand the logic that underlies your statement...

Because the 914-6 has larger pistons in the calipers to maintain a similar ratio with the larger mc.

Funny thing is, back when I ran a bike shop, I used to set up the brakes to have a firm feel at the lever because thats what buyers liked for the parking lot test ride. I set my own bikes to have a very soft (some said spongy) feel at the lever but a high mechanical leverage at the rim or disk so it took a light effort to stop. Not only was the effort less, but it was easier to modulate. There is more to braking than just being able to lock the wheels. Modulation is the amount of force you have to work with before the brakes lock up. Maybe not a big deal for straight line stopping on a dry road but throw in slippery conditions and the ability to modulate your brakes more than an on/off switch becomes very important.

...and saving $30 isn't a very good reason to go with a lesser performing part (IMG:style_emoticons/default/shades.gif)

[brant]

(IMG:style_emoticons/default/beer3.gif)
hardly

heartily.

[Eric_Shea]

I actually think a 19 performs better on a stock Teener. I like the harder pedal feel and don't notice any extra effort.

[mepstein]

I actually think a 19 performs better on a stock Teener. I like the harder pedal feel and don't notice any extra effort.

Right, you like the feel. And you don't notice the extra effort but you do have to press harder on the pedal to get the same stopping performance as the smaller mc. Maybe just 12 percent more. Not a big deal. But not everyone wants to "upgrade" to a less powerfull braking system. Its sort of like a loud Monza muffler. Sounds/feels better using the butt dyno but in reality it make less power.

[Dave_Darling]

It's 25% more, BTW. also 20% less distance traveled by the pedal.

19^2 / 17^2 ~= 1.25

--DD

[race914]

It's 25% more, BTW. also 20% less distance traveled by the pedal.

19^2 / 17^2 ~= 1.25

--DD

Finally some actually facts!! Thanks Dave...

The 19mm is not a downgrade, and certainly not "lesser performing part"

I think the incorrectly perceived issue of "lesser performance" is due to the fact the 19mm requires more pedal pressure to achieve the same effective braking force (fluid displaced from the Master Cylinder to the Calipers) as compared to the 17mm. At the same time, the 19mm has shorter pedal travel than the 17mm. They can both apply the same pressure to the Calipers.

A good layman's analogy is Harbor Freight Floor Jacks. The basic model takes many 'easy' pumps of the handle to raise a 914 off the ground, while the 'racing' version takes 6 'hard' pumps. Sure the racing version handle is harder to push down, but they both can raise the car up. The racing version is not a downgrade or "lesser performing part".

It's Basic Fluid Mechanics. Same applies to Master Cylinders.

That being said, I also agree 'feel', and the ability to control brake pressure modulation is very important. And with that in mind, I'm in agreement and would not put a 23mm Master cylinder in a 914 with stock brake calipers.

I just don't agree that the 19mm is a downgrade or "lesser performing part" with stock 914 brake calipers, just because of the additional pedal pressure.


Now after all of this, back to the original topic

I agree with everyone else who states that the stock 914 brake system is very good, and performs very well. Also agree that if it is in good mechanical condition, and has fresh upgraded fluid such as ATE, Motul, etc, Good Pads such as Porterfields, and good tires, there might be no need to upgrade at all, especially if it is primarily a street car.

The only reason I upgraded my fronts to 911 M Calipers is because 25 minute run sessions at Laguna can really be hard on your brakes and despite good fluid, good pads, and adding cooling scoops, removing the splash shields, etc I could still easily overheat the 914 brakes to the point they would fade horribly. If I wasn't doing regular track days I probably never would have upgraded the stock 914 brakes.

[Brian_Boss]

If you can lock up your brakes, they have done everything they can for you in that application.

This ought to be on some universal mandatory reading list right up there with "righty - tighty, lefty - loosy" and "always assume a gun is loaded".

[Dave_Darling]

However, Greg just (indirectly) pointed out the major shortcoming in my statement. I said "in that application". Greg mentions Laguna, which is notoriously hard on brakes. As in, puts a lot of heat into them, without a whole lot of cooling time available.

When you are putting a whole lot of heat into the brakes, and they don't have much chance to cool down, larger brakes can help. Physically larger rotors give you more heat sink, plus more area to radiate heat away. Ventilated brakes run air through the middle, carrying heat away faster. Larger calipers have more mass and more fluid, meaning more heat sink again.

But about the only people who use their brakes in that sort of fashion are doing it on the Big Track.

--DD

[Eric_Shea]

Like I said... way too much Internet yak, yak, yak, I'm right, you're wrong talk about this IMO.

17 vs. 19, it really doesn't matter. I don't really care what it pans out to in volumetric equations, it's negligible when you put your foot into it.

I never said a 19mm was an "upgrade" in the performance of the brake system. I simply like it better than the 17mm and, the fact remains as Dave pointed out; if you can lock your calipers they've "done all that they can do." If you can't (lock stock calipers) then the next thing I'd do is go through your brake system. (IMG:style_emoticons/default/wink.gif)

The only "real" way to upgrade a stock 914 brake system is to $pend thou$and$. Probably more than you spent on your actual 914. Then we have to go back to the point; if you can lock your calipers they've "done all that they can do." That would be "thou$and$ wasted. (IMG:style_emoticons/default/wink.gif)

The fastest 914's I've ever seen are using S-Calipers up front and 911/914-6 calipers in the rear on 20mm rotors. They drive faster than you, harder than you and longer than you (unless your name is Frank Beck). (IMG:style_emoticons/default/wink.gif)

[Brian_Boss]

However, Greg just (indirectly) pointed out the major shortcoming in my statement. I said "in that application". Greg mentions Laguna, which is notoriously hard on brakes. As in, puts a lot of heat into them, without a whole lot of cooling time available.

When you are putting a whole lot of heat into the brakes, and they don't have much chance to cool down, larger brakes can help. Physically larger rotors give you more heat sink, plus more area to radiate heat away. Ventilated brakes run air through the middle, carrying heat away faster. Larger calipers have more mass and more fluid, meaning more heat sink again.

But about the only people who use their brakes in that sort of fashion are doing it on the Big Track.

--DD

Dave - You're statement still holds true in that scenario. In heavy track usage, stock brakes will overheat, fade, and then you will not be able to lock them (at least not with out excessive pedal effort). Maybe some elaboration/clarification is useful to apply it to certain real world situations but your statement is pretty much axiomatic.

[patssle]

So to sum it up...if you're not tracking the car - there is really no point of putting on bigger brakes? How about even for a 6 conversion?

[ClayPerrine]

So to sum it up...if you're not tracking the car - there is really no point of putting on bigger brakes? How about even for a 6 conversion?

I always upgrade the brakes on a six conversion. The extra weight and horsepower in a six makes the solid disk brake rotors marginal.

I did overkill for the brakes on my six, but a set of M calipers from a 911 on the front, and 914/6 calipers and vented rotors on the back would be good for a mild six conversion.

[0396]

So to sum it up...if you're not tracking the car - there is really no point of putting on bigger brakes? How about even for a 6 conversion?

I always upgrade the brakes on a six conversion. The extra weight and horsepower in a six makes the solid disk brake rotors marginal.

I did overkill for the brakes on my six, but a set of M calipers from a 911 on the front, and 914/6 calipers and vented rotors on the back would be good for a mild six conversion.

Wise advice....how about 993 Big Reds on the whole car (IMG:style_emoticons/default/piratenanner.gif)

[ClayPerrine]

So to sum it up...if you're not tracking the car - there is really no point of putting on bigger brakes? How about even for a 6 conversion?

I always upgrade the brakes on a six conversion. The extra weight and horsepower in a six makes the solid disk brake rotors marginal.

I did overkill for the brakes on my six, but a set of M calipers from a 911 on the front, and 914/6 calipers and vented rotors on the back would be good for a mild six conversion.

Wise advice....how about 993 Big Reds on the whole car (IMG:style_emoticons/default/piratenanner.gif)

That would certainly be an option. But consider this:

A 993 Carrera weighs 3020 lbs. a Boxster weighs 2880 lbs. A 914 weighs 1984 lbs. The brakes on the Carrera are balanced for a rear engined car. The brakes on a Boxster are balanced for a mid engined car. Considering that the weight differential between a Boxster and a 914 is almost 1000 lbs, and the Boxster brakes are easier to find and much cheaper than 993 Carrera brakes, and you can buy a bolt on kit for them, I think the Boxster brakes are a much better solution for big brakes on a 914.

[brant]

No need for vented rear rotors. Even on the track. Wasted weight

[OlymOwen]

My first post. It’s to a nine year old thread. Not expecting anyone to notice, but more of a practice post. It looks like if I want to have really good breaking on my project 914/4, stroked and bored to 2.4L, I will just rebuild the stock system. I want to retain the stock 4 bolt pattern. Since there are lots of low cost brake upgrade options for my old air-cooled VWs, many of us, like myself, figure there must be something out there we don’t know about to help stop. However, those upgrades are usually from drum to disc brakes. It makes sense that if you can lock it up you are already good to go. Thanks for the clarification here!