Hi,

I recently bought a nice '76 2.0 that I would like to give some extra goodies. One of the projects I'm looking at is doing a 4-5 lug conversion. I read most of the articles describing the process of doing so and I think the route with a 911 front suspension is the way to go.

So I found these parts of a (supposedly) 3.2 911 online but then the questions start popping up. The missing parts are break callipers and master cylinder. As I understand 3.2 breaks also use a break booster. Is that also needed or would a 19mm master cylinder also work fine? What breaks should I search for? What will work and is doable for a newbee 914 fan?

Anyway, thanks in advance for helping my with my shopping list.

Thierry

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You have everything you need there. But buy new rotors, and I would suggest finding a set of Boxster calipers and adapters for the brake calipers. They work great, and you can use a 19mm 914 master cylinder with them.

Clay

+1 on not needing a booster.

Yep when i did boxster calipers on my conversion did not need a booster. Rears you can do standard Carrera (if i remember right) without brake bias adjuster as well. Boxster brakes will let you handle almost anything power-wise you throw at it. I had a 2.5 ltr 6 and that was way more brake than i needed (but that is almost never a bad thing).

I would splurge and get a set of 911S calipers. Send them to PMB if you need them rebuilt. They will bolt on and help offset the weight increase of the Carrera rotors. No adaptors are needed and they should fit under almost any wheel.

Thank you for your help Clay,

So you boxter brakes won't work with these rotors you mean? Any Boxter year breaks and adapter supplier you can recommend?

Best regards,

Thierry

With Boxster brakes, you use Carrera rotors and early, non S Boxster calipers. Adaptors are available from Rich/a914guy@aol.com, Stompski racing, Cliff at Rebel racing and probably some others.

Make sure they will fit under your choice of wheels and they don’t overpower your rear brakes.

You will need to bend up your own hard lines.

I’m pretty sure M & SC rotors are 20mm and Carrera’s are 24mm wide.

Great modification re the 5 -lug. I 100% agree with @mepstain. Upgrade to the early S aluminum calipers in the front (PMB is the way to go) and a set of new rotors and call it a day. Then go ahead and use the 19mm master cylinder. I would replace your soft rubber lines with new rubber lines while you are at it. Then flush and bleed the whole system. BTW, if you talk withPMB, they can hook you up with everything you need for that project. One stop shopping and you will get expert advice.

The key word here is "Almost". I am in process of putting 991 C4S Calipers on the front of the 4.0L car. The Boxster brakes are not quite enough with the available HP in that engine.

Going to send the Boxster fronts to PMB to be rebuilt and painted to match the Red C4S calipers. They will go on the rear of the 4.0L car.

Remember, brakes just slow you down

How much power is the OP going with ? I ran 80's Carrera 3.2 brakes front and rear on my 70 with a 2056 engine (120hp) for DE and AX for many years and I never ran out of brakes. Considering these brakes come from a 2800lb car (plus driver/passenger) with 230hp (euro), they might just be enough brake as is.

There are definitely some outliers that is for sure! Not getting the sense that the OP is going high HP. Thierry what are the powerplant plans?

In the late say 1979 I ran stock fresh 911SC full front suspensions from a wrecked car that was only a couple of years old. The full suspension also with the under the aluminum rack sway bar. I was running 5 lug factory magnesium wheels so the weight was low on the wheels on this stock body 1974 car. It was a Turbo 2.0

So, with 2-year-old suspension, the car handled great and the breaks stopped very well.

The difference between stock 914 stock brakes and the 911sc brakes was a huge difference.

I never raced it on a track but I used to run it hard on Mulholland Highway and it was a great runner for me. If you do not have a front sway bar this is very nice and you will not need to remove your gas tank to mount the sway bar


Bob B

Mulholland Highway
Road in Los Angeles County, California
Description
Description
Mulholland Highway is a scenic road in Los Angeles County, California, that runs approximately 50 miles through the western Santa Monica Mountains from near US Route 101 in Calabasas to Highway 1 near Malibu at Leo Carrillo State Park and the Pacific Ocean coast – at the border of Los Angeles and Ventura Counties.

No matter how much power you put in a 914 (or any car) as long as the brakes can lock up the wheels, braking power is "sufficient". Brake "endurance", like challenged during hard on-track racing, is another thing.

(And brake "sex appeal" is a whole other category.)

Agreed, with a 2 liter 4 I think you’re being lead down the way overkill path. If you like the bling or plan on going big 6, then look towards the boxster caliper.

A or S calipers on the front and Ms in the rear are more than enough. That’s what I have in my track car (150ish hp to the wheels) with RE71 205 tires and 19mm MC. I had zero problems locking them on command, and didn’t see any fade in 20-30min track sessions.

Only thing I might do different for a street car is splurge on 914-6 rear calipers and keep your parking brake setup.

Most cost effective IMO are A calipers in the front with at street pad and a soft high friction pad in your existing rear calipers.

Horsepower means nothing when it comes to braking. Only mass and velocity.

+1 on 986 calipers up front.

Light, rigid, four pistons for even pad application, and a lot less expensive than S calipers, nice as the latter look. Some say the alloy S calipers flex, and I've heard it both ways from people I trust—but I've never heard anyone speak about caliper flex with 986 calipers.

Now, if we just had a trailing arm that allows the 986's matching setup for the rear—with five-lug hubs, rotors, calipers, and parking brakes—to be bolted onto a 914…

The 'power plan' at this point is stay with standard FI 2.0L. But hey, you never know...

but will add the other important factor is tire friction (mu). And a slight correction -- what matters is acceleration (deceleration). Acceleration is the change in velocity per unit of time.

You don't need big brakes if your going 60 mph but have miles and miles to stop. If you want to stop in 130 feet, that will take some bigger brakes.

To elaborate on Mark's math:

Force = mass x acceleration

So where does the Force side of the equation come from? The tires!

Force = Tire mu x weight on the tire is the equation that defines tire force.

So the entire system is governed by:

Tire mu x weight on the tire = mass x acceleration.


Mass is set by the vehicle itself and acceleration (deceleration) is determined by the driver.

Therefore, Braking distances are determined by braking forces over a period of time, but, are ultimately dictated by what the tire can deliver. . We won't go down the path of the math to determine braking distance.

Giant brakes on hard rubber and/or skinny 4.5" tires of the 60's and 70's will still have terrible stopping distance.

Braking endurance is determined by the size of the components which provide thermal mass to keep fade at bay as previously pointed out.

Yeah, there is a lot more to brake sizing (balance, effectiveness, pedal feel, etc.) but I find most folks don't really appreciate that stopping distance is set by the rubber.

So when you say you need bigger brakes, the question is to really ask why? If you can lock up the brakes, what you really need is better tires. When you have so much tire that you can no longer lock up the brakes, now it's time to mess with the brakes.

What this should say is if you can lock up the tires you have enough brake, if you want to stop faster you need more/better tires...

This is why I mention the tires and widths, if sticking with the standard body, you’re not going to get any more than a 205, and an re71 is a really sticky tire...

Please do some research on properly upgrading brakes, if going with boxster fronts, you should have boxster rears to balance out the equation. If going with S or A up front you should have Ms or 914-6 rears... balance your setup otherwise you are limited to the weakest link, your rear calipers, and not taking full advantage of the setup.

S calipers go for 400-500 in usable shape or 800-1000 completely rebuilt, As go for 250-300 and Ms are cheap, pick those up for 100-200 on the bird all day long. Use your existing rotors and I can’t see that being more expensive than boxster brakes rotors and adaptors and custom lines...

Nobody here is going to notice S caliper “flex” that is mentioned, nor will we ever notice the weight difference between the S and A calipers. You’re talking about guys trying to save ounces on race cars, and pushing all components, including brakes to the max.

Am I missing something?

-- word smithing is not a strength of mine.

All true - but - sometimes having bigger brakes results in a better pedal feeling or sense of braking power. Some prefer that.

Keeping weight down however is a key consideration.

Not quite correct.

Pedal feel is intertwined with hydraulic displacment at the master cylinder vs. the displacment requirements of calipers. It has little to do with "bigger" brakes whatever that term may refer to (size of calipers, size of rotors, or both).

Pedal feel is also greatly affected by brake pad compressability which varies widely from compound to compound. Quite often bigger brake pads with high compressability result in even more fluid displacment which degrades pedal feel for those that prefer force modulation.

To compound matters, there is no ideal. Some people prefer travel modulation, others prefer force modulation. Some prefer the Goldilocks version in between.

Mixing the idea that bigger brakes results in better pedal feel will lead you astray.

I am with Tdskip on the premise that I’d rather use big powerful brakes lightly than all in with just adequate brakes. I like to modulate with pedal travel. It’s a holdover from my bike riding and racing. The stronger the brakes, the less hand fatigue.

I have PCCB on four cars. Takes a while to learn how to drive with them. Will say that when it comes time for DE they are a blast. I like having all the brakes I can get. One car does 0-60 in 2.3, 60-0 in 91 feet.

I get the point and I generally agree with the premise.

However, I can make your "big powerful" brakes feel like or great by varying parameters like master cylinder size, pedal ratio, pad compressability, and in stop mu characteristics of the pad compound.

The flip side of "big powerful" brakes is that they can also become extremely difficult to modulate in low friction conditions (rain, snow, sand, gravel).

Pedal feel really doesn't have much to do with stopping distance performance and/or thermal fade is the point. Not completely independent but able to be tuned seperately of stopping distance to a large degree. A brake booser system only adds further tunability of feel though it doesn't apply to 914's. Newest Electronic Brake Boost systems almost completely decouple feel from performance by using pedal feel simulator to provide brake pedal feel while all actuation is done by wire.

This isn't said often enough.

So many cars get an upgrade up front and make do with whatever they had in the rear, or something "close enough."



^ Great post.

There is more to brake performance than stopping distances or the ability to lock the wheels up. Brake balance, modulation, pedal feel, and resistance to fade are other parameters—all of them are important to control and driver confidence—with perhaps fade resistance being the most important to me.

I've encountered fade on the track and on the road, for very different reasons: Circuits work brakes harder but tend to give them a chance to cool at speed where some mountain roads never give them a break, and don't offer much in the way of speeds sufficient to cool the rotors before the next pounding. Having to drive around the brakes (or even the mere smell, a clear signal of where things are headed if you don't adjust your style and/or speed) is distinctly unfun and shakes confidence in the car not just for that drive, but future drives.

This ad deals with the issue of fade really well:

http://www.vehiclecraft.com/Brakes/930_upgrade.htm

Why the 930 Upgrade? Why not the "Boxster" or 964 calipers?

The main part of a braking system that has to deal with the heat absorption and dissipation is the brake rotor - not the calipers. So their size and mass is the main factor in choosing and upgrade. Simply put the 930 upgrade offers the largest rotor size available that will fit inside stock wheels and narrow body of most 911's and 914's. The Boxster and 964 upgrades that are being sold are based on a stock size 911 carrera rotor (24 x 289mm). While the calipers are noticeably larger, and provide more stopping power than the original small steel calipers, they actually make the main problem worse!Putting more heat energy into the same small rotor dose not solve problems, it makes them worse.
This is where the 930 Upgrade really does the job. The rotor size is 12.0" x 1.25" front (300 x 32mm) and 12.18" x 1.10 rear (310 x 28mm). This is about double the heat-sink capabilities of the original rotors! Of course along with those rotors come the 4-piston 930 calipers also about doubling your stopping power. To put it in perspective, this rotor size/mass is about 85% of what a Big Red rotor upgrade is

While I agree that rotor size is too often skipped over, I can't see the OP needing anything larger than the rotor in his pic with a 2.0-liter Type IV. Suspect that rotor is probably just fine up to 200 hp in most use cases. If the OP is going to keep the stock rear brakes, I'd aim for the best front caliper to match them that will work with those 911 rotors. I've been running the "Alfa" aluminum two-piston Brembos made popular in recent years and like the setup, but have been eyeing 986 calipers all around.