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Sun Mar 24, 2019 1:53 pm

So I'm ready to take the next step on my buggy. Brakes! As we all know our buggies are never done and in a lot of cases take on a life of their own. This seems to be the case with mine.
My original build I went with a very nice 1776. I have installed all new componants/drum brake system. Stainless steel lines at the wheel cylinders, dual master cylinder. One thing I never did was swap wheel brake cylinders front to back so my fronts locked a little to easily. But for the most part the drums were sufficient.
Fast forward, the 1776 has now been replaced with a type IV 2 liter 914 Porsche that was sent down to Fat Performance and transformed into a 2650cc beast.
Drum brakes have got to go and disc brakes should have been installed before the new stroker motor.

Now I think I've made my decision on the brake kit, and that is the Willwood kit from Airkewld. Do I need Willwood, no. It's overkill but so is the rest of the car with the chassis I built, 10 point cage and most recently the big cc motor. I also like the Airkewld kit because you can change your bolt pattern later down the road.

So why am I asking for help. Well I know nothing about disc brakes and how to set the brake bias. I'm thinking I'm going to need a 60% rear with 40% front application due to the lite front end and small smart car tire size I have on the front. So would I go two piston calipers on the front and four piston on the back? I realize Willwood does not have an emergency brake and that's fine.

Not that this makes much difference but I'm running 2" drop spindles on a link pin front suspension and IRS rear set up.

https://www.airkewld.com/Classic-VW-Front-Disc-Brake-Conversion-Kit-4151-p/4151.htm

Sun Mar 24, 2019 3:13 pm

Yes disc brakes are a good idea with the power you have available.
I would use a 4piston caliper with 4in pad 10in or 11in diameter rotor in the rear and a 2piston caliper with 2in pads 10in diameter rotors in the front. You need to install a brake bias valve to be able (reduce) to adjust pressure to front calipers.
A 19mm (3/4in) master cylinder will work.
As for a Emergency brake, Wilwood makes mechanical Spot calipers that would work, you just have to make your own mounting brackets.

A friend just converted his buggy to rear disc brakes using JaMar brakes and Wilwood mechanical calipers for the E-brake.
He used Wilwood #!20-12069-BK and #120-12070-BK using brackets he made to mount them.

Sun Mar 24, 2019 6:09 pm

Timely post for me Brent as I am about to embark on changing my Buggy from swing axle to IRS. My donor car is an '86 944 for the trailing arms etc. and just happens to come with disc brakes. I am hoping to use the fronts too so am very interested in balancing the package as a whole too.

At this point I am very sceptical about using anything that limits braking power to the front as you NEVER want the rears to lock first under any condition for the street!

Your tire radius difference front to rear is huge, much larger than mine so that will play a big part in the equation.

Mon Mar 25, 2019 10:45 am

whatever the weight distribution or the width of the tires the front brakes do most of the work,therefore the front brakes must be more powerful than the rear brakes

Mon Mar 25, 2019 3:24 pm

For brake bias I would recommend weighing the buggy front and rear. Then, as a good starting point, set up the front about 20% higher to account for the weight transfer under heavy braking. Tire sizes, seating position(s), and center of gravity all impact the best bias some. So, if the weight comes in at 340 lb. front and 760 lb. rear you want about a 53% front bias.

This is easy to calculate with stock 1968 up US spec Bug brakes because they are the same size front and rear. A comparison of wheel cylinder bores can determine the brake bias. With other systems this could require a bit more math and some manufacturer info.

I'm eyeing early Porsche 924 rear wheel cylinders (3/4 inch bore for 40mm wide brakes) for the front of my buggy. I have the older 30mm wide rear brakes with 3/4 inch wheel cylinders. That would make the braking nearly 50/50 with a slight front bias. I know stock Bug brakes clearly lock the front too early. With only 50 horsepower and a significant reduction in weight drums are good for my buggy.

Mon Mar 25, 2019 7:28 pm

Common practice with a IRS rear suspension and a dual master cylinder is to switch front to rear wheel cylinders.
Front 22mm to the rear and the 17mm rear wheel cylinders to the front.
This is with the wide shoes front and rear.
I have used this setup in my short wheelbase Manx since 1970 and has as worked well even in panic stops where it will lock up all 4 wheels at the same time.
This has worked with either using 165-15 and 205/70-15 tires in the front.
There was a article in a 1970 issue of Hot VWs magazine about it.

Tue Mar 26, 2019 9:53 am

Be careful when ordering the Wilwood brakes. Some callipers are set up for racing only pads, which are super nice on the course, but absolutely suck on the street. The race pads only function decently when hot. Sounds good? Yea! I stop hard and need them to stop and they will be warm after all my hard driving!!!

Well, what happens up to the point they get hot? They barely work. So driving around the city getting out to where you can "use" them, they are cold. What happens if they cool down while on an extended high speed run? The go back to suck mode. Yes, they will stop a buggy when cold, but they will chatter, sometimes making your wheels hop as the pad itself grabs/releases. Oh, and they tend to chew through rotors quicker than normal pads.

I had Wilwoods on my heavy El Camino, with race pads, and they worked very well because of the weight. I put them on a buggy, (2000 pound) and they cause all the problems I mentioned above. Here in the "Wet" East US, having the separate mechanical calliper for a parking brake was a maintenance issue too. Since they did not cycle through heat/cool like the main calliper, they do not dissipate the moisture and tended to freeze.

On buggies/VWs I have used EMPI, AC Industries, Wilwood, adapted Toyota and Honda, Stock VW, some modular unknown kits, all kinds of drum combinations/wheel cylinder/brake pad switches/master cylinder types. I live in the mountains, I drive very aggressive, I wear out brakes on my Jeep and Pickup at least once per year and often sooner. I have done a lot of racing with VW and other vehicles. So, when I build my buggies now, I keep coming back to EMPI and AC Industries.

Another Canadian has over 100,000 miles on his buggy, built it with EMPI Brakes, and still has the original pads on it. You drove with him Brent. The expensive brakes are very cool, and look good, fun to talk about, but to me, do not perform better than the cheap units I have driven.

Like everyone else, that is just my opinion. It means really nothing except to me.

Lastly, Pete at AK is fantastic to deal with, and I highly recommend him. He has helped me solve problems before.

Tue Mar 26, 2019 10:09 pm

I have the Empi cheapo brakes on all four corners on my buggy.

200 whp and it slows it down well.

While they are not quite a simple bolt on experience and might be heavier than the other competing brands.....they work well for my intended use and stop me in a hurry.
I have never had such a firm pedal in the 14 years I have driven my buggy as when I installed all four disc brakes.

There are some tricks to getting them to mount well but most kits seem to have a few challenges.

I built my buggy to be driven...it's not a trailer queen nor is it a show car. I'm sure there might be lighter brakes and better fits but in the end you can't really complain about the Empi brakes.
They do give a little offset...front and rear.

Take your time installing them and make sure nothing rubs and they are shimmed correctly....and they will give you good performance....for a total of about $600.00 front and rear.

I did pay a local machine shop to drill and install the press in studs... that cost a few bucks but well worth it.

Wed Mar 27, 2019 1:55 pm

Another thing to consider is that Wilwood calipers don't have dust seals on the pistons so dirt and dust can kill the seals easily. You've seen my build and know that I just run Empi brakes. I run them on all my cars. My race car is heavy almost 1800 pounds with me in it and I stop the car from 130mph in only 3/8 of a mile with only rear disks.

On my orange buggy I have the bias valve closed off all the way and it's still almost too much front brake. I'd say the fronts only do about 20% of the braking on my car.

brad

Wed Mar 27, 2019 7:07 pm

Fantastic!! This is the info I'm looking for! thx guys. I have some homework to do!

Wed Mar 27, 2019 8:13 pm

Just wondering if you fellows have a link the the bias valves you are using as I understand they are not all created equal?

Also are you using them with a single chamber master cylinder or dual?

Is anyone set up with 2 single master cylinders and a balance bar?

Wed Mar 27, 2019 8:49 pm

My Manxter Dual Sport that I built I used the CNC dual master cylinder setup with balance bar. It works very well for adjusting bias.
The common Proportioning valve is made by Wilwood and use a knob to adjust bias.
Wilwood also make one that has a lever and multiple position to use for adjustment. Lever has detents so it stays in the position you move it to.
A friend has the lever type of proportioning valve and can adjust bias on the fly for on and off road driving. It works great.
Look at Speedway Motors and you can see the different available. Speedway has their own brands, they look just like Wilwood just different colors.
I have used Wilwood and Wilwood copies for over 10 years on my own stuff and have never had a caliper ever rust or freeze up. And this includes them being completely underwater, in snow with salt all over the road, in the sand, silt, and many other places.
Also Speedway Motors carries brake pads for all kinds of disc with different compounds for different driving conditions.
I like using disc rotors that have a steel hub axle spline. The iron rotor that are available are really to soft for any high torque situations in the spline area.
A big tire and wheel can be alot of weight compared to using a stock size tire and wheel when trying to slow it down.

Thu Mar 28, 2019 4:11 am

I know how a balance bar works but what about these proportioning valves. Do they change the pressure throughout the range or do they supply equal pressure up to the set point and then limit it from there on?

Thu Mar 28, 2019 4:56 am

Note that Wilwood does now have calipers with dust boots on several models. Also just looked and their integral E-brake rear caliper is now available to fit 0.81" wide rotors (like a solid 914 or similar rear rotor).
Vdub Engineering has brackets to adapt Wilwood calipers to VW spindles using standard Ghia rotors (and lots of other options using Porsche based calipers & rotors).
http://vdubengineering.com/

If you want to keep the wide-5 lug pattern (and nice wheels!) then your choices are a bit more limited.
Jeff

Thu Mar 28, 2019 8:41 am

A proportioning valve works like a restriction in the circuit, it slows to fluid down so there is less pressure at first, eventually pressure will be equal in system when brake pedal is held down.

Thu Mar 28, 2019 12:37 pm

This picture is about the best I can find that shows how the common style aftermarket proportioning valve works. You will see the inlet and outlet on the sides arranged in a familiar fashion. The adjusting knob is where the yellow end plug is shown and it presses down on the springs. The green piston is larger on one side than the other so it will push back against the spring when there is pressure in the system. When the pressure is high enough to overcome the spring it will move left and the small inner valve will close, limiting brake pressure. The small spring assists the closing of the small blue inner valve when the larger green piston moves back allowing it to do so. When you release the brakes both pistons move left and the fluid returns. When the pressure lowers enough the large spring pushes the green piston right and it holds the small inner valve open.

Thu Mar 28, 2019 1:15 pm

If you are considering a proportioning valve, consider this one - https://www.pegasusautoracing.com/productdetails.asp?RecID=4889 you won't need adaptors to mate up with the VW brake lines. Tom

Thu Mar 28, 2019 7:35 pm

Thanks for the info! I am leaning toward a twin MC and balance bar but will give that cut-a-way diagram some serious thought.