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blackivory69 Samba Member
Joined: April 08, 2013 Posts: 309 Location: California
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Posted: Tue Jun 19, 2018 4:38 pm Post subject: Empi Disc Brake conversion |
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Hi everybody. It’s been a long time since I post but I got bitten by the bug again so here I am. I’m currently converting my 70 Crew Cab from drum to disc using the Empi disc conversion kit. I know, why Empi, but that is all I can afford.
Everything is well until it’s time for me to replace the master cylinder. The MC in the kit is exactly what’s in the picture which I think it’s for 1971 and later because it meant to be installed with a booster. I have a few options. The ports of this new MC is different from the original, so if I’ll use this I have to re-route my metal brake lines. And then since the reservoir is sitting on top of the MC, I have to make a hole on the floor so that I can refill the reservoir when needed. I cringe just thinking of cutting a hole on my floor. That’s my 1st option. My second option is to buy a 1971 MC and a booster and do some cutting underneath for the booster installation, but to tell you the truth, I don’t really need or want a booster because my legs are strong enough. Now, my last option is to use my existing MC but someone told me that I have to disassemble it and take off some kind of a small valve inside the MC or I’ll run the risk of locking up my disc brake. I like the 3rd option but could someone please verify me if I have to modify my OEM MC (take off that “valve”) or I can use it AS IS for my converted disc brake? Thank you very much in advance. _________________ 1970 Double Cab. Stock engine (1600 SP)
1973 Thing (Mexican Safari)
1970 Karmann Ghia Convertible
1969 Buggy |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Tue Jun 19, 2018 4:52 pm Post subject: Re: Empi Disc Brake conversion |
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Good to see you back here!
Disc bus brakes without a booster are SIGNIFICANTLY harder to press than a four wheel drum brake bus. The physics involves the double leading shoe design where both shoes “energize” themselves from being pulled out into the drum, like the front shoe does by itself without the help of the rear shoe back in the rear brakes on every bus. No other vehicle on the road utilized double leading shoes like VW did to my knowledge. Because of this designed-in mechanical advantage of stock bus drums, you will likely not be able to lock the front discs with your stock master cylinder, even if you did take the residual valves out like you mentioned in option number three.
Any time you change the stock brake balance, you’ll also want a proportioning valve to avoid prematurely locking the rear tires in a hard stop. Also, when the balance is altered, the master cylinder bore displacement has to match the requirements of the front/back systems.
Good luck!
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21474 Location: Oklahoma City
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Posted: Tue Jun 19, 2018 10:38 pm Post subject: Re: Empi Disc Brake conversion |
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asiab3 wrote: |
Good to see you back here!
Disc bus brakes without a booster are SIGNIFICANTLY harder to press than a four wheel drum brake bus. The physics involves the double leading shoe design where both shoes “energize” themselves from being pulled out into the drum, like the front shoe does by itself without the help of the rear shoe back in the rear brakes on every bus. No other vehicle on the road utilized double leading shoes like VW did to my knowledge. Because of this designed-in mechanical advantage of stock bus drums, you will likely not be able to lock the front discs with your stock master cylinder, even if you did take the residual valves out like you mentioned in option number three.
Any time you change the stock brake balance, you’ll also want a proportioning valve to avoid prematurely locking the rear tires in a hard stop. Also, when the balance is altered, the master cylinder bore displacement has to match the requirements of the front/back systems.
Good luck!
Robbie |
He will be able to lock the brakes just fine. The lack of a booster does not change the output pressure of the MC. It just increases the effort to produce it. Diameter and stroke is diameter and stroke. Plenty of bigger and heavier vehicles without power boosters worked fine.
But.....if not using power.....it WILL be somewhat easier to go to a non power MC. Ray |
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richparker Samba Member
Joined: November 24, 2011 Posts: 6936 Location: Durango, CO
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Posted: Tue Jun 19, 2018 10:56 pm Post subject: Re: Empi Disc Brake conversion |
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raygreenwood wrote: |
asiab3 wrote: |
Good to see you back here!
Disc bus brakes without a booster are SIGNIFICANTLY harder to press than a four wheel drum brake bus. The physics involves the double leading shoe design where both shoes “energize” themselves from being pulled out into the drum, like the front shoe does by itself without the help of the rear shoe back in the rear brakes on every bus. No other vehicle on the road utilized double leading shoes like VW did to my knowledge. Because of this designed-in mechanical advantage of stock bus drums, you will likely not be able to lock the front discs with your stock master cylinder, even if you did take the residual valves out like you mentioned in option number three.
Any time you change the stock brake balance, you’ll also want a proportioning valve to avoid prematurely locking the rear tires in a hard stop. Also, when the balance is altered, the master cylinder bore displacement has to match the requirements of the front/back systems.
Good luck!
Robbie |
He will be able to lock the brakes just fine. The lack of a booster does not change the output pressure of the MC. It just increases the effort to produce it. Diameter and stroke is diameter and stroke. Plenty of bigger and heavier vehicles without power boosters worked fine.
But.....if not using power.....it WILL be somewhat easier to go to a non power MC. Ray |
You just got “Airschooled”. 🤓 _________________ __________
’71 Westy build
Adventure thread
’65 Deluxe Build |
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curtp07 Samba Member
Joined: November 28, 2007 Posts: 874 Location: Mass
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Posted: Wed Jun 20, 2018 3:42 am Post subject: Re: Empi Disc Brake conversion |
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Airschooled...hahahah. _________________ Subaru |
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Davydomes Samba Member
Joined: August 28, 2013 Posts: 110 Location: North West England (Savoury Pie Country)
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Posted: Wed Jun 20, 2018 4:51 am Post subject: Re: Empi Disc Brake conversion |
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On our 69 we did a conversion to Crossover/Late Bay Discs. We don't have a servo booster and it stops fine. But a lot of owners on the EarlyBay forum say that having the servo booster is one of the best upgrades they have done. _________________ I only went to look at it!
"Mum, Dad ………. I'm Bay"
Patience is bitter, but its fruit is sweet. Jean-Jaques Rousseau |
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VWsArent4Hippies Samba Member
Joined: April 13, 2005 Posts: 3076 Location: The Bull City
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Posted: Wed Jun 20, 2018 6:26 am Post subject: Re: Empi Disc Brake conversion |
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asiab3 wrote: |
Disc bus brakes without a booster are SIGNIFICANTLY harder to press than a four wheel drum brake bus. The physics involves the double leading shoe design where both shoes “energize” themselves from being pulled out into the drum, like the front shoe does by itself without the help of the rear shoe back in the rear brakes on every bus. No other vehicle on the road utilized double leading shoes like VW did to my knowledge. Because of this designed-in mechanical advantage of stock bus drums, you will likely not be able to lock the front discs with your stock master cylinder, even if you did take the residual valves out like you mentioned in option number three |
Having put many, many miles behind the wheel of a non boosted euro disc brake bus, I couldn’t disagree any more _________________
aeromech wrote: |
in my opinion you don't know shit |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Wed Jun 20, 2018 8:42 am Post subject: Re: Empi Disc Brake conversion |
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VWsArent4Hippies wrote: |
asiab3 wrote: |
Disc bus brakes without a booster are SIGNIFICANTLY harder to press than a four wheel drum brake bus. The physics involves the double leading shoe design where both shoes “energize” themselves from being pulled out into the drum, like the front shoe does by itself without the help of the rear shoe back in the rear brakes on every bus. No other vehicle on the road utilized double leading shoes like VW did to my knowledge. Because of this designed-in mechanical advantage of stock bus drums, you will likely not be able to lock the front discs with your stock master cylinder, even if you did take the residual valves out like you mentioned in option number three |
Having put many, many miles behind the wheel of a non boosted euro disc brake bus, I couldn’t disagree any more |
Didn’t those buses use a different master cylinder? My point is the brake system is just that, system, and everything has to match.
There are enough people texting and driving; we don’t need to add mismatched brake components to the soup.
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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OB Bus Samba Member
Joined: February 09, 2003 Posts: 2531 Location: Ocean Beach in Beautiful BLUE California
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Posted: Wed Jun 20, 2018 8:43 am Post subject: Re: Empi Disc Brake conversion |
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Is your original master cylinder OK? If so, search “residual valve” on this forum. You might be able to just use your current master cylinder. _________________ Larry in OB
Stop dead photo links! Post your photos to The Samba Gallery!
69 Westfalia and 2002 Eurovan Camper. |
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blackivory69 Samba Member
Joined: April 08, 2013 Posts: 309 Location: California
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Posted: Wed Jun 20, 2018 8:32 pm Post subject: Re: Empi Disc Brake conversion |
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Thank god you VW Gurus are still here at Samba. Some people will not know what to do with out you guys and that includes me.
OB Bus; Yes I believe my MC is still in good condition.
Now that I have guidance from you guys, my game plan will be to try to run it with my original set up and see if it’s going to bind. I rotated the wheels after bleeding the system and the wheels are turning. And this was after pumping the pedal a few times, I can feel the resistance of the pad but I think that’s how it supposed to be. So it’s a good sign. If it binds, then my next step is to open the cylinder and bypass that residual pressure valve.
I didn’t have the chance to road test it coz I need to go to work. So tomorrow will be the day and I’m excited. After a 2 year (or so) hibernation, she’ll awake tomorrow. Can’t wait 🙂 _________________ 1970 Double Cab. Stock engine (1600 SP)
1973 Thing (Mexican Safari)
1970 Karmann Ghia Convertible
1969 Buggy |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Wed Jun 20, 2018 8:48 pm Post subject: Re: Empi Disc Brake conversion |
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You shouldn’t need to open the cylinder to remove the residual valves; they should unscrew directly from the master. The question is: are the MC residual valve bores the same thread as the stock brake lines? I don’t know.
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Wed Jun 20, 2018 9:25 pm Post subject: Re: Empi Disc Brake conversion |
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Removeing the internal parts of the residual valve for the front disc brakes.
Disc Brake Conversions |
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blackivory69 Samba Member
Joined: April 08, 2013 Posts: 309 Location: California
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Posted: Wed Jun 20, 2018 9:37 pm Post subject: Re: Empi Disc Brake conversion |
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asiab3 wrote: |
You shouldn’t need to open the cylinder to remove the residual valves; they should unscrew directly from the master. The question is: are the MC residual valve bores the same thread as the stock brake lines? I don’t know.
Robbie |
Hi Robbie. Long time no see. I hope you still remember me. I’m the guy with the red 71 Small pop top reviera.
You are absolutely right Robbie. After some reading here, I found out that residual pressure valve is built in to the fitting. So judging from the photo below, it looks like I don’t have one. Do I?
_________________ 1970 Double Cab. Stock engine (1600 SP)
1973 Thing (Mexican Safari)
1970 Karmann Ghia Convertible
1969 Buggy |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Wed Jun 20, 2018 9:50 pm Post subject: Re: Empi Disc Brake conversion |
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Of course I still remember your beautiful custom interior and bespoke roof rack system!
Check out those silver looking 19mm~ish fittings where the brake lines fit into the MC. As shown in Tcash’s link, those are residual valves that should be removed for disc brake operation.
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21474 Location: Oklahoma City
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Posted: Wed Jun 20, 2018 10:19 pm Post subject: Re: Empi Disc Brake conversion |
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asiab3 wrote: |
VWsArent4Hippies wrote: |
asiab3 wrote: |
Disc bus brakes without a booster are SIGNIFICANTLY harder to press than a four wheel drum brake bus. The physics involves the double leading shoe design where both shoes “energize” themselves from being pulled out into the drum, like the front shoe does by itself without the help of the rear shoe back in the rear brakes on every bus. No other vehicle on the road utilized double leading shoes like VW did to my knowledge. Because of this designed-in mechanical advantage of stock bus drums, you will likely not be able to lock the front discs with your stock master cylinder, even if you did take the residual valves out like you mentioned in option number three |
Having put many, many miles behind the wheel of a non boosted euro disc brake bus, I couldn’t disagree any more |
Didn’t those buses use a different master cylinder? My point is the brake system is just that, system, and everything has to match.
There are enough people texting and driving; we don’t need to add mismatched brake components to the soup.
Robbie |
Understand.....the power brake booster does NOTHING....to increase hydraulic pressure in the MC. You have X diameter by Y stroke. It creates Z pressure.I
If that cylinder can create the volume required for the pressure your brakes require.....there is nothing that can increase that.
All the booster does.....is allow your leg to create the same pressure its going to create no matter what......using less EFFORT.
Its an ASSIST. Air rushes into a vacuum chamber whem you push the pedal ....giving between 2.5 and 3+ X whatever pressure you put on that pedal (it varies from vehicle to vehicle).
In other words it cuts YOUR effort down....to produce the same pressure....it was going to make in the first place.
I fully agree....do not start swapping cylinders around because the port spacing for each circuit....and the internal spring pressure on each piston set....is what sets your brake BIAS.
However.....if your booster is dead but otherwise you keep the same MC in there.. it WILL stop just as well.....if you learn to put your foot into it. Ray |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Thu Jun 21, 2018 6:42 am Post subject: Re: Empi Disc Brake conversion |
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Removeing the internal parts of the residual valve only for the front disc brakes.
Disc Brake Conversions |
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Davydomes Samba Member
Joined: August 28, 2013 Posts: 110 Location: North West England (Savoury Pie Country)
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Posted: Thu Jun 21, 2018 11:44 am Post subject: Re: Empi Disc Brake conversion |
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Davydomes wrote: |
On our 69 we did a conversion to Crossover/Late Bay Discs. We don't have a servo booster and it stops fine. But a lot of owners on the EarlyBay forum say that having the servo booster is one of the best upgrades they have done. |
Not a vanity trip, just remembered! We changed the master cylinder because I think (not entirely sure because it's a few years back) the bore is slightly bigger by 2mm diameter on the later ones.
Probably get schooled now
We also fit the pressure regulator valve that stops the back wheels from locking up causing the bus to snake. I don't think everybody fits these. _________________ I only went to look at it!
"Mum, Dad ………. I'm Bay"
Patience is bitter, but its fruit is sweet. Jean-Jaques Rousseau |
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blackivory69 Samba Member
Joined: April 08, 2013 Posts: 309 Location: California
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Posted: Thu Jun 21, 2018 12:40 pm Post subject: Re: Empi Disc Brake conversion |
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So I ended up bypassing the residual pressure valve. Bleeded the system again and put it back. I just finished the road test and holy cow! Big difference from my drum. Just a little pressure and I will lock both front wheels. I can’t feel any binding as well. I need to get used to it coz I’ll end up locking my front wheels every time I brake.
Now my question is, since I need just a little pressure for my front disc, is my back drum brakes working when I brake? I’m thinking it is just because it still has that residual pressure valve in there. That’s actually a check valve so it means that the fluid between my master cylinder and wheel cylinder stays there every time, so it should be working. Right? _________________ 1970 Double Cab. Stock engine (1600 SP)
1973 Thing (Mexican Safari)
1970 Karmann Ghia Convertible
1969 Buggy |
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lastchancevw Samba Member
Joined: August 26, 2008 Posts: 190 Location: Southeastern Mass
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Posted: Mon Sep 17, 2018 7:29 pm Post subject: Re: Empi Disc Brake conversion |
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Aw cool.. I'm thinking of getting the same kit for my 70 kombi. I put the thing back on the road for the first time in 45 years and well, of course the original brakes leak everywhere, so I could either spend a bit constantly switching out failing original parts (and I do mean original!) or just spring for a kit like this.
As I do need a MC anyway , the empi kit seems the best bang for the buck as it comes with it. I'm none to happy about the filler cap for the reservoir requiring you to cut an access hole under your seat. for realz? What? You can't rig up the original hoses and use the original reservoir under the dash? WTF?
-Tara _________________ 1970 Commercial Kombi
1971 rusty Westfalia (retired for now)
1971 ghia (waiting)
1974 super beetle (2, maybe can be made into one)
1969 delta blue deluxe bus, half-camperized and being worked on |
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hoss Samba Member
Joined: May 01, 2003 Posts: 788 Location: San Jose, CA
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Posted: Thu Jul 25, 2019 11:58 pm Post subject: Re: Empi Disc Brake conversion |
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Bumping this up from about a year ago.
Just installed these on a '70 Westy. I ended up keeping the original master and I removed / modified both residual valves. I think I was only supposed to modify the front one. Can somebody confirm that is the case? Is there any place these are available for purchase? I looked a little bit and couldn't find one.
2nd issue.. the brake light on the dash is on and doesn't go away. Is that normal after this?
Otherwise, they really do work great. I need to bed the pads a little bit more as it takes a bit of force to get the bus to stop. _________________ '54 Kombi | '57 356 Coupe | '57 Samba | '62 Notchback | '63 Beetle (36k Original Miles) | '66 Pigalle Sunroof Squareback | '70 Westy |
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