Disc Brakes on Buggy

[James Stevens]

I am thinking about putting disk breaks on my buggy ether front or back. I mainly use it off road but it is street legal. Should I go with front disk breaks or back? I know the front would be better on street driving but it seems like the back would be better on dirt driving. Any thoughts?

[BL3Manx]

Buggies are 400#s or more lighter than a VW sedan. Typically the front axle weight is half the rear. Stock VW front drum brakes (not breaks and spelling does matter because there is a great search feature on this site which is totally defeated by misspelling key words) will lock up the front wheels of a buggy and cause them to skid uselessly when applied hard.

The rear brakes are not powerful enough especially with the larger rear tires buggies typically use.

Putting disc brake on the front makes a bad situation worse. Putting them in back is a definite improvement however you will need to ensure the calipers you use have a working emergency/parking brake and if you already have 5 wide wheels, most rear disc brakes don't have that pattern.

There are numerous threads in the archives on this subject you should search for and read but for the money I always recommend upgrading the power of your rear drum brakes and actually reducing the fronts

[Skulptorchaz]

Good post James!! I had been thinking about this as well.
And thanx for the info BL3!! I too, would have thought to put discs on the front first (because in MC's, that is 75% of your stopping power).
That is great to know!! But what about a bug in general?? A couple buddies have "Volksrods" and are contemplating it as well.
I also have the wide five pattern so I would need to do some searching for appropriate discs. I wouldn't worry much running disc's but I want to race mine a little. (Dirt drags and Autocross)
Thanx again!!
Chaz

[slalombuggy]

I have 4 wheel disk brakes on my buggy and my 57 Bug. I will never go back to drum brakes especially on race cars. When I autocrossed my buggy I had nothing but problems getting all wheels to stop evenly and always had a pull in the front no matter what I did, and I did a lot of experimenting. With regular street tires it was never really a problem, but once I went to racing slicks and "R" compound tires the problems got worse exponentially. I once came into the stop box and did a 180 instantly when one front wheel locked up and the others didn't..

The only thing I did to run disk brakes on my buggy was to install a brake bias valve on the front circuit to cut down the brake pressure to the front calipers. Once I did this braking was easily balanced and far superior to drums. The car always stopped straight and I never had problems with brake fade on longer courses.

As far as 5 bolt disks, many companies make them CB, EMPI, CSP Airkewled and others. I have always used EMPI brakes. Yes they are heavier than others but have never had a problem with them stopping cars, even from very high speeds. Slowing down from 120 mph on the loose surface of the salt flats can be tricky, but I've never had a problem in my buggy or Beetle.

brad

[vincent9993]

I'm not going to claim to be a subject matter expert here but I've always challenged the "Accepted" recommendation that you should put discs in the rear as opposed to the front on a Dune Buggy.

I'm going to base my answer on actual experience of driving our Kick-Out over 45,000 miles on the road (and having driven our Berrien over 85,000 miles).

The Berrien has 4 drum brakes and the Kick-Out has discs up front.

The 1st thing, in my book, one needs to ask themselves when thinking of converting from drum to disc (note I did not use the term 'upgrading' here) is: what are they trying to achieve? One could argue that the stopping power of either disc or drums is pretty close (when comparing VW disc conversion). The main advantage of going to a disc setup will be better cooling capabilities for repeated brake use. This means that if you plan to track or auto-x your buggy, then you 'may' have a case for converting to disc brakes.

When it comes to discs on the front vs the back discussion, I'm again going to draw on the experience of our 45,000 miles in our Kick-Out. Let's 1st look at the center of gravity of a buggy. In our Kick-Out, the COG is just in front of the inspection plate (shift coupler). Once you add 2 adults, the COG is not far from 50/50. On hard braking, most of the weight is transferred to the front wheels. In a properly calibrated braking system, even with front disc and rear drums, you should not experience a substantial wheel lock difference (at least we don't in the Kick-Out). Remember, the braking force of drums and discs should be very similar.

For us, we did not want to have to mess with E-Brake complexity and opted to only run discs up front. Our motivation were mainly because we needed to have a specific bolt pattern and for the 'cool' factor.

As you can see, I'm not commenting on off-road application as we do not have enough experience to comment on that. Maybe there are practical reason to run discs for off-road purpose but I don't see what it would help with.

One thing I can tell you is that disc brake calipers were hard to properly bleed. We ended up using my pressure bleeding system to get all the air out of the system, no amount of pedal bleeding process would actually get all the air out.

[joescoolcustoms]

I run drums on my Manx, wide 5 front and rear. Thing drums on the front with the later model shoe, and type three on the rear. They are OK, but my buggy is heavy at 2000 pounds. On the recent trip with Vincent across the US and back, mine performed fine and only experienced fade one time on Lombard Street in San Francisco. I do want to change to Disc, but have a problem with off sets and justifying the $ when what I have has worked for 20,000 miles.

I also helped David build his buggy and he used EMPI disc's front and rear with the E-Brake option on the rear. I have driven this buggy, hard, and braked hard. It has the best balanced brakes of any buggy I have built or driven. He did order the Disc Brake Master Cylinder from I think Cip1 and he installed a proportioning valve on the front, but has yet to use it. As with typical EMPI parts, he did have to clearance the rear calipers to keep them from rubbing the rotor.

David too crossed the US with Vincent and has not had a problem with them and now has about 7600 miles on his Moss Green buggy.

EDIT: David ordered a 5 lug pattern on the disc rotors and eliminated the need for adapters.

If I were to suggest for off road, I would go to the rear first with the disc's. The dirt has less friction than asphalt and locking the front wheels is much higher with the clamping pressure the disc has.
From what off road experience I have, my drums always filled with dust or mud/water and initially did not work until the debris cleaned itself off of the brake surface when running longs runs without using the brakes. Disc brakes would not hold water/dust/mud and work quicker on demand.
_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[Glasser]

Put them on the back!!
I ran an off road Rail for YEARS.... I was running a 31" Terra tire with a huge amount of grip on the back. This was an off road car only. I never ran front brakes at all. They locked up way to easy (I had triple rib tires on the front, no tread) If I hill climbed a hill and didn't make it coming down backwards with front brakes was a death trap. They were always locked and I was a dart going backwards.
I went with rear disc brakes with cutting brakes.
I would not recommend no front brakes for street . The rear disc brakes were a HUGE upgrade especially when going through water. You always had brakes unlike drum brakes when they get wet.

Lots of time the front tires were never on the ground anyways LOL

_________________
Brent
My build up http://www.thesamba.com/vw/forum/viewtopic.php?t=265364&postdays=0&postorder=asc&start=0
Project#2. Neighbors build up. http://www.thesamba.com/vw/forum/viewtopic.php?t=327008

[IowaRedManx]

10 years ago I put front & rear disc brakes on my buggy. I used the no hole option with an E-break on the rear. Had the rotors drilled for a custom to match the wheels I planned to use.

It was on of the best decisions I made during the build.

[herkster]

we are running 4 wheel disc and with a bias valve. action is very good. we are running large tires all the way around which helps with traction for all wheels.

[1madmanx]

[joescoolcustoms]

Hey Bud!

Here is the proportioning valve I have used on two buggy's I have built.

http://www.summitracing.com/parts/ssb-a0707-1

The function is simple, twist inward and it restricts the fluid pressure going through the line. Twist outward and it increases the pressure that flows through the line.

To isolate the front brakes on a typical dual master cylinder buggy, the front brakes have to come off the front master cylinder with one line and into the Proportioning Valve. Then the exit of the valve needs routed to a Tee fitting splitting off to each front wheel. Very simple, but does take some customizing the brake lines. Also, one port on the Master Cylinder will need to be plugged where as it will not be used.

Here is the best photo I have of the unit I installed on the Blue Buggy I built in 2013. It is not totally completed, but you can see the routing of the brake line to the PValve and then onto the Tee fitting. This buggy recently sold and is near Paul in New Jersey now. Maybe it may make it to MOTB '15.

_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[1madmanx]

[EVfun]

I see two ways to balance brakes, with a purportioning valve or by changing bore sizes. The bore size is easier with drum brakes, but with all the disc kits out there some choices should effect balance.

What are the pros and cons of each method? The purportioning valve allows fine adjistments. It seems to block any brake action at the end it's installed on until you go over the pressure set point.
_________________

[joescoolcustoms]

When I built my buggy, (I like to experiment with different things, sometimes you stumble onto a good idea, sometimes you ruin parts) I reversed the master cylinder. No, I did not put it on backwards, I just installed the lines backwards.

I also switched around the wheel cylinders to match. The front brakes have late model rear wheel cylinders and the rear brkes have type three wheel cylinders, (which are the largest that will fit a type one style rear brake). And since the wheel cylinders are switched, why not match up the MC? Well, it works.

That is one way to restrict the fronts, by placing them on the less pressure rear cylinder section of the Master Cylinder. And conversely, it put more pressure on the rear with the front, higher pressure cylinder section of the Master Cylinder.

With a very hard stop, all 4 wheels lock up at about the same exact time.
_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[slalombuggy]

Here's my front lines with the T fitting

I mounted my bias valve inside the buggy so I can adjust the brakes depending on what front tires I'm running (race or street) I also have a mechanical line-loc to make tire changes easier

brad

[EVfun]

[joescoolcustoms]

The rear chamber of a dual circuit MC has less pressure due to the push rod that is inside the chamber pushing the front chamber reducing the area of the cylinder. This volume reduces the square inches of the rear chamber available to generate the pressure.

PSI = pounds X square inch

The front chamber does not have the push rod reducing the area of the cylinder.
_________________
Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race

Everyone is gifted. Some just do not open the package.

Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone

[BL3Manx]

[James Stevens]

Thanks for all the good information on disk brakes. I think I will try to go with the rear disk brakes. I am not totally done with my fiberglass buggy build, but what little I have drove it the brakes are not good enough. I do want to stick with the wide 5 with e- brake. I already have a dual master cylinder. I hope it is big enough. I think I will not put on a brake bias valve to start with. If I need to add it later I will.
I wonder if you can put cutting brakes in line going to the back brakes. Or would that cause more trouble than it's worth?
I guess now I can start looking for rear disk brakes. If anyone has any other advice on where to ordering and installing them let me know. I do not know if all kits are the same.
thanks again for all the help

[jsturtlebuggy]

In the Without Guesswork spec book 1971-1974 it shows the specs for the dual master cylinders.

From chassis #111 2 000 001,
Front circuit stroke 17.5mm, Rear circuit stroke 11.5mm
This a Super Beetle with 9 3/4in front drums and 23mm wheel cylinders and 9in rear drums with 17mm wheel cylinders.

Model 111 from 117 000 001 and Model 14 from 144 2 000 001
Front circuit stroke 15.5mm, Rear circuit stroke 12.5mm
This would be with 9in drums front and rear. 22mm front and 17mm rear wheel cylinders.

Model 14 from 147 000 001
Front circuit stroke 14mm, Rear circuit stroke 14mm

A model 14 is a Ghia that came with disc brakes in the front in the USA.

My own personal experience with switching wheel cylinder on the Buggy my Dad first built (the one that is the Kick Out now) in 1970 with a 1969 IRS chassis the wheel cylinders were switch and it made a big difference in stopping. Master cylinder connections are in stock location. I have never measure the circuits stroke length in the replacement master cylinder that is on it now.
_________________
Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960