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Sofia74
Samba Member
Joined: August 30, 2015
Posts: 565
Location: WV
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 Posted: Mon Oct 09, 2017 1:58 pm Post subject: Rear Disc Brake Conversion - seen conflicting answers |
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Yes, I know this has been covered and I have read many posts but I wanted to verify a couple things since I have read some answers or opinions that seem to conflict.
Looking at CB Performance rear disc brake conversion with parking brake for a 1974 KG Coupe. Plan is to keep the front discs and add discs to the rear.
My questions:
1. What master cylinder? I will be getting a new one – stock size or go the larger 20.6 mm as I have seen recommended?
2. Do I need a Residual pressure valve? The CB Performance website says: "Vehicles with four wheel disc brakes using a 67-later master cylinder are recommended to install a 4 lb. Residual Pressure Valve." I have seen other answers on this site that seem to conflict...
3. Wheel bearings? Which to use? I haven’t heard this addressed yet and CB Performance should have a recommendation. Just thought I’d ask since I was here…
Thanks,
Matt |
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9143
Location: Canada
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| Posted: Tue Oct 10, 2017 11:25 am Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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yes, get the larger master, you will need it to move enough fluid for the larger pistons on all 4 wheels.
Yes put in a valve, it will help keep the pedal firm, you can run without and they will work fine, but the pedal will feel spongy all the time.
I prefer FAG or KOYO bearings, anything but white box cheap stuff.
brad
Last edited by slalombuggy on Wed Oct 11, 2017 11:09 am; edited 1 time in total |
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Lo Cash John
Samba Member
Joined: February 06, 2004
Posts: 2246
Location: Jacksonville, FL
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| Posted: Tue Oct 10, 2017 11:53 am Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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Click on the link below and about halfway down is another very good option for 4 wheel disc brakes.
http://www.coolrydescustoms.com/coolstop-brakes.html
This MC will work with right hand drive or left hand drive cars since the ports exit upwards.
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Sofia74
Samba Member
Joined: August 30, 2015
Posts: 565
Location: WV
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| Posted: Tue Oct 10, 2017 3:39 pm Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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Slalombuggy - thanks. Any advice on where the best location for the valve?
Also, I try to buy FAG bearings when I can. My dad worked for FAG for years. They might have put me through college. 
Lo Cash John - 23.8mm MC, that's a pretty big increase over stock, isn't it. Would that lock up the brakes pretty easily? Too easily?
Matt |
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Era Vulgaris
Samba Member
Joined: August 22, 2012
Posts: 1672
Location: Raleigh, NC
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| Posted: Tue Oct 10, 2017 4:42 pm Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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| Sofia74 wrote: |
Lo Cash John - 23.8mm MC, that's a pretty big increase over stock, isn't it. Would that lock up the brakes pretty easily? Too easily?
Matt |
Everything else staying the same, going to a bigger MC will create a stiffer pedal feel, but will actually require more pedal effort to stop the car.
This is a common occurrence on the 914, when people swap the stock 17mm MC for a similar-era 911 19mm MC and keep the stock 914 calipers.
However, the coolrydes brake kits are 4 piston front and 4 piston rear (stock VW are 2 piston front), so you'll need a sizable increase in MC to accommodate that.
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Currently own:
66 Karmann Ghia, L390 Gulf Blue, under construction, here: www.thesamba.com/vw/forum/viewtopic.php?t=760505&highlight=
99 Mazda MX-5 10AE, Sapphire Blue Mica, 6 speed, LSD
Previously owned:
98 Porsche Boxster, silver, 2.5L -- 67 Karmann Ghia, Black, 1500sp -- 98 BMW Z3, Atlanta Blue Metallic, 2.8L I6 -- 75 Porsche 914, Laguna Blue, 2270cc -- 72 Porsche 914, Signal Orange, 1.7 FI -- 74 Karmann Ghia, Black, 1600dp -- 74 Triumph TR6 with O.D., sapphire blue |
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Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 76884
Location: Sneaking up behind you
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| Posted: Tue Oct 10, 2017 5:16 pm Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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Don't waste your money. 70% of braking is done by the front and adding rear disc is not needed.
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
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CiderGuy
Samba Member
Joined: December 23, 2013
Posts: 1351
Location: Bucks County, Pa
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| Posted: Tue Oct 10, 2017 5:54 pm Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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| Glenn wrote: |
| Don't waste your money. 70% of braking is done by the front and adding rear disc is not needed. |
Agreed, but I thought it was 80%
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Cars Currently Owned:
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Era Vulgaris
Samba Member
Joined: August 22, 2012
Posts: 1672
Location: Raleigh, NC
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| Posted: Wed Oct 11, 2017 6:40 am Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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| Glenn wrote: |
| Don't waste your money. 70% of braking is done by the front and adding rear disc is not needed. |
Especially not needed on a car this light! That coolrydes stuff is insane overkill for a stock engine car. I think his stuff is more geared toward people with subaru conversions or high hp motors.
My only temptation for even considering rear discs would be reduced maintenance. Maybe some people don't mind, or possibly might even enjoy, adjusting drums...but if I never had to do it again I definitely wouldn't miss it.
_________________
Currently own:
66 Karmann Ghia, L390 Gulf Blue, under construction, here: www.thesamba.com/vw/forum/viewtopic.php?t=760505&highlight=
99 Mazda MX-5 10AE, Sapphire Blue Mica, 6 speed, LSD
Previously owned:
98 Porsche Boxster, silver, 2.5L -- 67 Karmann Ghia, Black, 1500sp -- 98 BMW Z3, Atlanta Blue Metallic, 2.8L I6 -- 75 Porsche 914, Laguna Blue, 2270cc -- 72 Porsche 914, Signal Orange, 1.7 FI -- 74 Karmann Ghia, Black, 1600dp -- 74 Triumph TR6 with O.D., sapphire blue |
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9143
Location: Canada
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| Posted: Wed Oct 11, 2017 11:08 am Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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| Sofia74 wrote: |
Slalombuggy - thanks. Any advice on where the best location for the valve?
Also, I try to buy FAG bearings when I can. My dad worked for FAG for years. They might have put me through college.
Lo Cash John - 23.8mm MC, that's a pretty big increase over stock, isn't it. Would that lock up the brakes pretty easily? Too easily?
Matt |
Put the valve at the rear before the "T" and it makes for a nice clean install. Put it just off the master if you're worried about access. Either will work.
Once you've gone to 4 wheel disks you'll never go back to drums. At least that's my personal experience on the 3 cars I've built.
brad |
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jpjohns
Samba Member
Joined: May 03, 2014
Posts: 882
Location: Harrisonburg, VA
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| Posted: Sun Oct 15, 2017 2:39 pm Post subject: Re: Rear Disc Brake Conversion - seen conflicting answers |
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Yeah but rear discs look cool as hell! My question is the lug pattern. 4-lug, 5-lug porche or wide 5?
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"Scrapyards are for quitters" - Beetlenut (a Samba member) |
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