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66bugguy
Samba Member
Joined: October 03, 2021
Posts: 44
Location: Oregon
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 Posted: Wed Jun 04, 2025 9:51 pm Post subject: Brake Performance '66 beetle |
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I have EMPI disc brakes installed on my 66, but the pedal it feels like I have to press it like 4.5 inches before I get any braking, and most of the brake dust is on the rear wheels and not the fronts, which seems opposite to how it usually should be biased. The brakes have been bled, I'm not sure if this is just the brake performance to expect or if I have something wrong with my car.
Thanks |
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VW_Jimbo 
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Joined: May 22, 2016
Posts: 11111
Location: Huntington Beach, CA
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| Posted: Wed Jun 04, 2025 10:28 pm Post subject: Re: Brake Performance '66 beetle |
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Something wrong. How much freeplay at the pedal?
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Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
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scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 3342
Location: Memphis
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| Posted: Thu Jun 05, 2025 2:02 am Post subject: Re: Brake Performance '66 beetle |
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That much pedal movement sounds like a bad master cylinder or a circuit with air still in it
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Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
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runamoc
Samba Member
Joined: June 19, 2006
Posts: 6086
Location: 37.5N 77.1W
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| Posted: Thu Jun 05, 2025 6:12 am Post subject: Re: Brake Performance '66 beetle |
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| disc brakes installed |
Disc brake MC have larger bores so that more fluid is 'pumped' out when pressed. Do you have a MC made for disc brakes?
https://www2.cip1.com/c31-611-015-000/
_________________
Daily driver: '69 Baja owned 45 yrs - Plan B: '72 Ghia
Yard Art: 2 Sandrails
Outback: '69 Ghia - '68,'69,'70,'72 Beetle - '84 Scirocco, GTI - Pair of '02 Golfs- '80 Rabbit Diesel
VW Wiring = It's just wires |
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slave1pilot
Samba Member
Joined: February 22, 2010
Posts: 1107
Location: Yuba City CA
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| Posted: Thu Jun 05, 2025 6:19 am Post subject: Re: Brake Performance '66 beetle |
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it would also help to know if its 4 wheel disc or front disc/rear drum
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Currently:
1959 pan with a 64 body and a 63 ragtop grafted in Herbie replica
Previously:
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1968 Beetle
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Bobs67vwagen
Samba Member
Joined: March 27, 2005
Posts: 242
Location: Eastern north carolina
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| Posted: Thu Jun 05, 2025 7:25 am Post subject: Re: Brake Performance '66 beetle |
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| If you have 4 wheel disc brakes you probably need a brake proportioning valve to adjust the ratio between front and rear. If you have only front discs it is common to have more pedal travel than 4 wheel drums with a peak adjustment. The original master cylinder with a front disc brake karmann Ghia had an internal valve that metered the pressure between the front and the back. When I did a front disc conversion on a 72 bug about 40 years ago I tried to get a Ghia master cylinder replacement and could not find it anywhere. NOS might be the only source for that. I hope this helps-bob |
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runamoc
Samba Member
Joined: June 19, 2006
Posts: 6086
Location: 37.5N 77.1W
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| Posted: Thu Jun 05, 2025 9:21 am Post subject: Re: Brake Performance '66 beetle |
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| Quote: |
| 4 wheel disc brakes you probably need a brake proportioning valve |
I put discs all around on my Ghia and used this MC without any valve
https://www2.cip1.com/c13-16-9554/
_________________
Daily driver: '69 Baja owned 45 yrs - Plan B: '72 Ghia
Yard Art: 2 Sandrails
Outback: '69 Ghia - '68,'69,'70,'72 Beetle - '84 Scirocco, GTI - Pair of '02 Golfs- '80 Rabbit Diesel
VW Wiring = It's just wires |
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viiking
Samba Member
Joined: May 10, 2013
Posts: 3130
Location: Sydney Australia
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| Posted: Thu Jun 05, 2025 5:26 pm Post subject: Re: Brake Performance '66 beetle |
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| Bobs67vwagen wrote: |
| If you have 4 wheel disc brakes you probably need a brake proportioning valve to adjust the ratio between front and rear. If you have only front discs it is common to have more pedal travel than 4 wheel drums with a peak adjustment. The original master cylinder with a front disc brake karmann Ghia had an internal valve that metered the pressure between the front and the back. When I did a front disc conversion on a 72 bug about 40 years ago I tried to get a Ghia master cylinder replacement and could not find it anywhere. NOS might be the only source for that. I hope this helps-bob |
The original OEM ATE disc brake introduced in Europe on beetles (and Ghias in the US) did not have any special valve. Yes it had specific drillings internally but not a valve per se.
The pedal stroke and therefore the volume of fluid displaced was 28mm at 19.05mm bore.
The drum brake dual circuit master cylinder split this displacement to 15.5mm front and 12.5mm rear.
The disc brake dual master cylinder split this displacement evenly at 14mm/14mm.
The two MC's were therefore NOT the same i.e drum v disc.
This difference was to compensate for the differing volumes required to provide full travel of either the brake cylinder or the calliper piston. Of course using different or aftermarket discs, or drum v disc MC's may require a rethink of how much volume is require per a full stroke application of the pedal. Hence it is critical to match the MC to the disc brake set up. Only knowing the requirement of both will allow you to not suffer having a "long pedal" as the OP has stated.
Unfortunately, I'm not sure how much of this information is ever provided by the vendors selling the MC's or disc conversions. The maths is pretty simple to determine the volumes required from the volumes of the calliper and brake cylinders if fitted. That's why I try and use OEM replacement parts which in my case is ATE. A lot more money but worth it in having less hassle.
If the MC does not have enough volume to expand the calliper piston and the brake cylinder(master) in BOTH of the separate circuits you will get the scary feeling of the excessive pedal travel. A second pump should bring the pedal up to a more normal pedal height. If it doesn't there are other problems. Yes other issues such as brake rod adjustment or air in the system can also be the reason.
| runamoc wrote: |
| Quote: |
| disc brakes installed |
Disc brake MC have larger bores so that more fluid is 'pumped' out when pressed. Do you have a MC made for disc brakes?
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Yes but a bigger bore MC actually reduces the pressure developed for the same pedal effort. Excessively large bores do not necessarily improve brake performance and why vacuum boosters are fitted to more modern vehicles to reduce brake effort.
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1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3
Last edited by viiking on Sat Jun 07, 2025 4:24 pm; edited 1 time in total |
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66bugguy
Samba Member
Joined: October 03, 2021
Posts: 44
Location: Oregon
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| Posted: Fri Jun 06, 2025 12:03 am Post subject: Re: Brake Performance '66 beetle |
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| scrivyscriv wrote: |
| That much pedal movement sounds like a bad master cylinder or a circuit with air still in it |
Its a 67’ dual circuit one i installed instead of the single 66 one, i guess bleeding the brakes again wouldn't hurt. |
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66bugguy
Samba Member
Joined: October 03, 2021
Posts: 44
Location: Oregon
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| Posted: Fri Jun 06, 2025 12:04 am Post subject: Re: Brake Performance '66 beetle |
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| runamoc wrote: |
| Quote: |
| disc brakes installed |
Disc brake MC have larger bores so that more fluid is 'pumped' out when pressed. Do you have a MC made for disc brakes?
https://www2.cip1.com/c31-611-015-000/ |
No, its a stock 67 dual circuit one. |
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66bugguy
Samba Member
Joined: October 03, 2021
Posts: 44
Location: Oregon
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| Posted: Fri Jun 06, 2025 12:05 am Post subject: Re: Brake Performance '66 beetle |
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| slave1pilot wrote: |
| it would also help to know if its 4 wheel disc or front disc/rear drum |
4 wheel EMPI disk brakes all around |
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Bobs67vwagen
Samba Member
Joined: March 27, 2005
Posts: 242
Location: Eastern north carolina
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| Posted: Fri Jun 06, 2025 3:37 am Post subject: Re: Brake Performance '66 beetle |
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| Viking that was very educational information that you posted. In the US , I have never seen a vendor selling the karmann Ghia disc brake master cylinder. Do you have a part number and a source for the ATE Ghia master cylinder? Also since the original poster has now stated that he has 4 wheel disc brakes do you agree that a proportioning valve could be set to regulate front and rear pressure for this setup? Thanks Bob |
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viiking
Samba Member
Joined: May 10, 2013
Posts: 3130
Location: Sydney Australia
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| Posted: Fri Jun 06, 2025 9:32 pm Post subject: Re: Brake Performance '66 beetle |
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| Bobs67vwagen wrote: |
| Viking that was very educational information that you posted. In the US , I have never seen a vendor selling the karmann Ghia disc brake master cylinder. Do you have a part number and a source for the ATE Ghia master cylinder? Also since the original poster has now stated that he has 4 wheel disc brakes do you agree that a proportioning valve could be set to regulate front and rear pressure for this setup? Thanks Bob |
Unfortunately mine is a RHD disc brake car so it won't fit yours. It was originally VW number 114 611 017E. The RHD are much harder to find but my original source was here:
https://www.heritagepartscentre.com/us/catalogsearch/result/?q=ate%20master%20cylinder
There you can see a RHD and a German LHD (not necessarily ATE) available too.
As far as I can see from the original German documentation the LHD MC numbers were:
113 611 017, and the suffixes determined the year models. These were suitable for both the Beetle and the Ghia.
If you can tell me the VIN number range I can give you a more accurate answer.
Re the proportioning valve, I have seen posts from various people that support with or without. I can't comment either way other than my own experience with OEM disc up front and drum at rear. However if the stroke volume of the MC is known and the calliper volumes are known then I would think there would be no need for a proportioning valve as the MC takes care of that to a great extent.
Also IMO the need for 4 wheel discs on a car that is less than 1 tonne with weight distribution as it is, is unnecessary and is unlikely to provide better braking than what is available with the disc - drum set up. There are other VW solutions to improve braking including wider drums and brake shoes from other VW types.
As I indicated in the earlier post, you really have to look at what combination of components you are using. Unfortunately many people do not realise that there are nuances with the parts that they buy and (in general) the vendors just seem to sell "one size fits all" parts that may or may not be compatible.
Going on the ATE website gives this answer for Ghias 64-74. There are other year ranges so you could perhaps fill in for different years.
https://web.tecalliance.net/ate/en/parts/cars/part...groups:258
Pumping that number into google gives lots of hits. They appear to be mostly in Europe so you can search for other places. Here is just the first one that came up on my search.
https://spareto.com/products/ate-brake-master-cylinder/03-2119-8511-3
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1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3 |
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Bobs67vwagen
Samba Member
Joined: March 27, 2005
Posts: 242
Location: Eastern north carolina
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| Posted: Sat Jun 07, 2025 7:27 am Post subject: Re: Brake Performance '66 beetle |
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| Great info viking-thanks for posting it. I am sure that I am not the only person in the US who over the years has thought of getting the correct master cylinder for a Ghia front disc setup with standard rear drums. Much appreciated-Bob |
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Cusser
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Joined: October 02, 2006
Posts: 33019
Location: Hot Arizona
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| Posted: Sat Jun 07, 2025 9:48 am Post subject: Re: Brake Performance '66 beetle |
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| Bobs67vwagen wrote: |
| I am sure that I am not the only person in the US who over the years has thought of getting the correct master cylinder for a Ghia front disc setup with standard rear drums. |
That's actually a very good idea !
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EVfun
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Joined: April 01, 2012
Posts: 6129
Location: Seattle
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| Posted: Sat Jun 07, 2025 3:06 pm Post subject: Re: Brake Performance '66 beetle |
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| 66bugguy wrote: |
| scrivyscriv wrote: |
| That much pedal movement sounds like a bad master cylinder or a circuit with air still in it |
Its a 67’ dual circuit one i installed instead of the single 66 one, i guess bleeding the brakes again wouldn't hurt. |
It is doubtful that you have a US spec ‘67 master cylinder, more likely a ‘67 up replacement. I say this because you didn’t have your disc brakes running HOT. Here is a picture of a ‘67 master cylinder, complete with the external residual pressure valves:
Most likely you have the “universal” replacement master cylinder sold in the US. It has restriction drillings so drum brakes don’t release too fast instead of residual pressure valves that would leave disc brakes dragging.
If your brakes start halfway down the travel you have a serious brake problem! Since you see noticeably more wear at the rear my guess would be either serious air in the front brakes or the front half of the master cylinder doesn’t work. Even stock, the ‘60’s Beetles had brakes that bettered many American cars of the era.
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viiking
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Joined: May 10, 2013
Posts: 3130
Location: Sydney Australia
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| Posted: Sat Jun 07, 2025 4:39 pm Post subject: Re: Brake Performance '66 beetle |
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...and following on from EVfun and my diatribe explanations above Bentley states:
"Caution -
The tandem master cylinder for disc brakes is not interchangeable with tandem cylinders for drum brakes".
So if 66bugguy has an existing dual circuit drum brake master cylinder fitted with residual pressure valves on a new Empi brake setup, this may be part of the problem.
So if you originally had drum brakes or you have bought a new brake master cylinder you are more likely in the US to NOT get a MC that has the correct internal drillings and variations in the stroke. This more likely leads to the many issues that we see with people blaming the MC for poor brake performance.
As most (not all) Beetle models sold outside of North America came with discs as standard from the mid-late 60's the search for MC's perhaps would yield better results from Europe.
Perhaps our European or more specifically German members could comment further on what their understanding is on the correct MC's available for LHD.
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1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3 |
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EVfun
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Joined: April 01, 2012
Posts: 6129
Location: Seattle
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| Posted: Sat Jun 07, 2025 8:04 pm Post subject: Re: Brake Performance '66 beetle |
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| viiking wrote: |
...and following on from EVfun and my diatribe explanations above Bentley states:
"Caution -
The tandem master cylinder for disc brakes is not interchangeable with tandem cylinders for drum brakes".
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I understand, and showed an original Bug dual circuit master cylinder. The original dual circuit master cylinder used those external residual pressure valves for drum brakes, and also had a slightly different stroke length in each half between disc and drum cars. We have been using a universal replacement for years. I have one in my buggy with 4 wheel drums and no residual pressure valves.
Here is look at the common options for master cylinder replacement today:
CIP
JBugs
Mid American Motorworks
Heritage Parts Centere
Note that they are for the Bug and Ghia. The later Ghia's covered have front disc brakes in US trim. Can you even find the originally correct disc/drum and drum/drum master cylinders?
If all your brakes are aftermarket based on some Golf parts, or whatever, you need to consult whoever made your braking system. If it isn't using stock parts at the wheels it may not be appropriate to use a stock master cylinder of any year.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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Schnitzelfuss
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Joined: September 18, 2024
Posts: 118
Location: North Alabama
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| Posted: Sun Jun 08, 2025 12:50 am Post subject: Re: Brake Performance '66 beetle |
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| What is a “residual pressure valve” and where is it located in or on a vintage VW brake master cylinder? Just trying to understand what I’m looking at in that picture of a dual circuit cylinder above. Those external protuberances with electrical connectors look like hydraulic brake light switches to me. |
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EVfun
Samba Member
Joined: April 01, 2012
Posts: 6129
Location: Seattle
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| Posted: Sun Jun 08, 2025 7:24 am Post subject: Re: Brake Performance '66 beetle |
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| Schnitzelfuss wrote: |
| What is a “residual pressure valve” and where is it located in or on a vintage VW brake master cylinder? Just trying to understand what I’m looking at in that picture of a dual circuit cylinder above. Those external protuberances with electrical connectors look like hydraulic brake light switches to me. |
You have spotted the brake light switch. If you look at the right hand brake light switch you can see a piece of metal brake line still attached to the master cylinder. You can see the bubble flare nut attaching that line to the master cylinder. If you look closely you will see that the brake line doesn't screw directly into the master cylinder. There is another larger nut screwed into the master cylinder that the brake line attaches too. That is the residual pressure valve for Bugs with dual circuit master cylinders. There is one in the front circuit as well, with no brake line is attached to it.
A Ghia with disc brakes would not have had the front residual pressure valve and the location of that screw in the top would have been a couple millimeters different.
On modern replacement dual circuit master cylinders for Bugs and Ghias the brake lines screw directly into the master cylinder above the brake light switches. If you look inside those holes you will see that the fluid has to pass through a small drilling to get into and back from the brakes. This is the restriction drilling that eliminates the need for residual pressure valves on stock Bugs with drum brakes.
The single circuit master cylinder is completely different. The residual pressure valve is internal to it, attached to the end of the internal piston return spring. When disc brakes are used with a single circuit master cylinder that will need to be removed and an external residual pressure valve should be used if rear drum brakes are retained.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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