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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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 Posted: Sun Oct 16, 2011 7:22 am Post subject: So are EMPI rear disc conversions OK? |
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| I see that CB performance is out of stock... I'd like to ditch the rear drums. I see that EMPI has a kit. I've read some pretty good and bad things about their rear kit. I have also read some people that have had good luck. Are there any other options that supply ebrake cables, etc too? |
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owdlvr
Samba Member
Joined: June 23, 2008
Posts: 686
Location: Squampton BC
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| Posted: Sun Oct 16, 2011 10:02 am Post subject: |
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50,000 miles on mine, no problems at all. My replacement rotors weren't true and needed to be turned down, but the first set were great.
-Dave
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Instagram: @DaveHord
1971 1302s - Salzburg Tribute the #RallyBug
1958 Beetle
1975 Beetle
1973 Super Beetle
1993 C3500 with Cummins swap
1967 MGB
1963 MG Midget |
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'69Custom
Samba Member
Joined: September 16, 2008
Posts: 2497
Location: Ventura, California
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| Posted: Sun Oct 16, 2011 12:49 pm Post subject: |
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You're right: some people have good experiences, but others bad. I'm a firm believer that you'll live a happier and less stressful life with your VW if you practice the philosophy assuming all EMPI products are garbage. That way, you don't have to play games with Murphy or the Law of Averages. If enough people did so, we might just put them out of business and some new manufacturer may fill the void with better quality parts we can rely on.
I call my philosophy "FUMP." Just spell it out.
My advice: be patient and wait for CB to restock.
_________________
-Tim
1969 Frankenbug
1965 Ford Mustang
:2gunfire: F-U-M-P!
~"I thought I was wrong once, but I was mistaken." ~The Boss
Please excuse any typos as my iPhone doesn't speak English very well.
| tham64 wrote: |
Why tune a big round again and again????? For me.... 1 hour will solve the case  |
www.endlesscustomz.com |
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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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| Posted: Sun Oct 16, 2011 1:02 pm Post subject: |
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| owdlvr wrote: |
50,000 miles on mine, no problems at all. My replacement rotors weren't true and needed to be turned down, but the first set were great.
-Dave |
Do you have a soft pedal or caliper flex symptoms? |
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zadieman
Samba Member
Joined: July 10, 2011
Posts: 426
Location: ERIE CO
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| Posted: Sun Oct 16, 2011 1:26 pm Post subject: |
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| Went to a VW show yesterday and was talking to a VW shop owner. He was telling me that to use the 4 wheel disk properly you should replace the master with a Jetta master because of the much larger size diameter of the piston. There is one guy out there making an adapter because of the tilt of the master. I am doing more research and will let you know what I find. I have 4 disk brakes but have not put it back on the road yet. |
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BenJAMin
Samba Member
Joined: February 01, 2004
Posts: 520
Location: Michigan
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| Posted: Sun Oct 16, 2011 6:31 pm Post subject: |
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| I got both front and rear discs from Aircooled.net and have the stock master for my car, '74 Super, and have had no problems. I have the kit with the e-brake. |
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pbullblue
Samba Member
Joined: June 16, 2007
Posts: 158
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| Posted: Sun Oct 16, 2011 6:40 pm Post subject: |
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| zadieman wrote: |
| Went to a VW show yesterday and was talking to a VW shop owner. He was telling me that to use the 4 wheel disk properly you should replace the master with a Jetta master because of the much larger size diameter of the piston. There is one guy out there making an adapter because of the tilt of the master. I am doing more research and will let you know what I find. I have 4 disk brakes but have not put it back on the road yet. |
Not true. A larger piston pushes more volume at a lower pressure. What you want is more PSI, Think of your thumb over the end of a garden hose. A stock master works great. |
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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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| Posted: Sun Oct 16, 2011 7:19 pm Post subject: |
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| pbullblue wrote: |
| zadieman wrote: |
| Went to a VW show yesterday and was talking to a VW shop owner. He was telling me that to use the 4 wheel disk properly you should replace the master with a Jetta master because of the much larger size diameter of the piston. There is one guy out there making an adapter because of the tilt of the master. I am doing more research and will let you know what I find. I have 4 disk brakes but have not put it back on the road yet. |
Not true. A larger piston pushes more volume at a lower pressure. What you want is more PSI, Think of your thumb over the end of a garden hose. A stock master works great. |
Not exactly true. A small master is less volume. If your "new calipers" are 2 piston calipers use more fluid to move the pad that the stock drum wheel cylinder. So, pressure isnt always what you are looking for. Small bores = more line pressure. Large bores= more volume.
I set up a NASCAR late model recently that had huge 6 piston calipers in the front, and 4 in the rear. The dual 7/8" master bores. With everything bled, there was not enough volume. It was a very easy pedal though. We put 1 1/8" masters and it had enough volume to build the necessary line pressure . Now, we had volume, line pressure, but unreal pedal effort. 400 lbs of foot pressure to lock them up. So a longer brake pedal with the master rod clevis closer to the hinge pin did the trick. You can't get volume and psi without compromise. |
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pbullblue
Samba Member
Joined: June 16, 2007
Posts: 158
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| Posted: Sun Oct 16, 2011 7:32 pm Post subject: |
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| Mopar92 wrote: |
| pbullblue wrote: |
| zadieman wrote: |
| Went to a VW show yesterday and was talking to a VW shop owner. He was telling me that to use the 4 wheel disk properly you should replace the master with a Jetta master because of the much larger size diameter of the piston. There is one guy out there making an adapter because of the tilt of the master. I am doing more research and will let you know what I find. I have 4 disk brakes but have not put it back on the road yet. |
Not true. A larger piston pushes more volume at a lower pressure. What you want is more PSI, Think of your thumb over the end of a garden hose. A stock master works great. |
Not exactly true. A small master is less volume. If your "new calipers" are 2 piston calipers use more fluid to move the pad that the stock drum wheel cylinder. So, pressure isnt always what you are looking for. Small bores = more line pressure. Large bores= more volume.
I set up a NASCAR late model recently that had huge 6 piston calipers in the front, and 4 in the rear. The dual 7/8" master bores. With everything bled, there was not enough volume. It was a very easy pedal though. We put 1 1/8" masters and it had enough volume to build the necessary line pressure . Now, we had volume, line pressure, but unreal pedal effort. 400 lbs of foot pressure to lock them up. So a longer brake pedal with the master rod clevis closer to the hinge pin did the trick. You can't get volume and psi without compromise. |
Agreed But we're talking single piston calipers used in the VW hobby. |
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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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| Posted: Sun Oct 16, 2011 7:42 pm Post subject: |
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| What cc is the single piston caliper and how many cc's does that wheel cylinder hold? You can't just guess... It's math.... So yeah it's relative. |
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pbullblue
Samba Member
Joined: June 16, 2007
Posts: 158
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| Posted: Sun Oct 16, 2011 7:54 pm Post subject: |
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| Mopar92 wrote: |
| What cc is the single piston caliper and how many cc's does that wheel cylinder hold? You can't just guess... It's math.... So yeah it's relative. |
No guessing needed. Stock master works with 4 discs. Many have done it. A proven combo. If you feel differently and want more volume, have at it. Enjoy that pedal travel. |
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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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| Posted: Sun Oct 16, 2011 8:07 pm Post subject: |
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| pbullblue wrote: |
| Mopar92 wrote: |
| What cc is the single piston caliper and how many cc's does that wheel cylinder hold? You can't just guess... It's math.... So yeah it's relative. |
No guessing needed. Stock master works with 4 discs. Many have done it. A proven combo. If you feel differently and want more volume, have at it. Enjoy that pedal travel. |
Uhhh.... You mean if I put a larger bore master on, I will have more travel... I think not. Small bore= more psi and pedal travel. So, yeah, I will enjoy a rigid pedal, as opposed to 4" of travel. Thanks. |
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pbullblue
Samba Member
Joined: June 16, 2007
Posts: 158
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| Posted: Sun Oct 16, 2011 8:17 pm Post subject: |
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Last edited by pbullblue on Sun Oct 16, 2011 8:24 pm; edited 2 times in total |
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pbullblue
Samba Member
Joined: June 16, 2007
Posts: 158
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| Posted: Sun Oct 16, 2011 8:21 pm Post subject: |
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[quote="pbullblue"]
| Mopar92 wrote: |
| pbullblue wrote: |
| Mopar92 wrote: |
| What cc is the single piston caliper and how many cc's does that wheel cylinder hold? You can't just guess... It's math.... So yeah it's relative. |
No guessing needed. Stock master works with 4 discs. Many have done it. A proven combo. If you feel differently and want more volume, have at it. Enjoy that pedal travel. |
Uhhh.... You mean if I put a larger bore master on, I will have more travel... I think not. Small bore= more psi and pedal travel. So, yeah, I will enjoy a rigid pedal, as opposed to 4" of travel. Thanks. |
Makes sense to me.... as the harder something is to push the farther you can push it!!!
Have fun |
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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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| Posted: Sun Oct 16, 2011 8:39 pm Post subject: |
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| You are pushing more fluid with a bigger bore at the expense of pedal effort. |
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torsionbar
Samba Member
Joined: December 11, 2010
Posts: 2215
Location: earf
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| Posted: Mon Oct 17, 2011 11:17 am Post subject: Re: So are EMPI rear disc conversions OK? |
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| Mopar92 wrote: |
| I'd like to ditch the rear drums. |
why? what are you trying to solve by doing that?
_________________
| Max Welton wrote: |
[air cooled vw's] are no longer suitable for the general public. The owner has to be be able to maintain the car. And that is after fixing all the deferred maintenance items and ill-conceived modifications. If you can't do those things you are pretty much screwed. |
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torsionbar
Samba Member
Joined: December 11, 2010
Posts: 2215
Location: earf
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| Posted: Mon Oct 17, 2011 11:20 am Post subject: |
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is that how these kits really look? man, that is ugly! that's a frightening mess of fittings and adapters.
i'm keeping my drums until someone develops a proper solution using a fixed caliper and parking brake inside the rotor hat.
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| Max Welton wrote: |
[air cooled vw's] are no longer suitable for the general public. The owner has to be be able to maintain the car. And that is after fixing all the deferred maintenance items and ill-conceived modifications. If you can't do those things you are pretty much screwed. |
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Mopar92
Samba Member
Joined: August 16, 2011
Posts: 217
Location: Tn
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| Posted: Mon Oct 17, 2011 11:23 am Post subject: Re: So are EMPI rear disc conversions OK? |
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| torsionbar wrote: |
| Mopar92 wrote: |
| I'd like to ditch the rear drums. |
why? what are you trying to solve by doing that? |
I autoX the car and the drums are getting very hot on mountain drives etc. My brake force is very close to 70% front 30% rear. So it's not like the bias is way off. Drums are old tech and just don't cool well. For the street they actually work quite well I admit. |
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torsionbar
Samba Member
Joined: December 11, 2010
Posts: 2215
Location: earf
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| Posted: Mon Oct 17, 2011 11:33 am Post subject: Re: So are EMPI rear disc conversions OK? |
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| Mopar92 wrote: |
| torsionbar wrote: |
| Mopar92 wrote: |
| I'd like to ditch the rear drums. |
why? what are you trying to solve by doing that? |
I autoX the car and the drums are getting very hot on mountain drives etc. My brake force is very close to 70% front 30% rear. So it's not like the bias is way off. Drums are old tech and just don't cool well. For the street they actually work quite well I admit. |
ok fair enough. whichever calipers you end up using, make sure the bias ends up correct. i don't know what the ideal bias is for a beetle, but for an air cooled porsche 911, it's 1.6 to 1. higher than this and the car is too front biased. lower than this and the car is too rear biased. if the car is too rear biased, you must add a proportioning valve to correct it. if the car is too front biased, well, you're screwed and you need to find different calipers (or use different front/rear pad compounds).
does anyone know what the factory bias ratio is for a beetle?
_________________
| Max Welton wrote: |
[air cooled vw's] are no longer suitable for the general public. The owner has to be be able to maintain the car. And that is after fixing all the deferred maintenance items and ill-conceived modifications. If you can't do those things you are pretty much screwed. |
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jhoefer
Samba Member
Joined: May 19, 2011
Posts: 987
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| Posted: Mon Oct 17, 2011 11:43 am Post subject: |
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| pbullblue wrote: |
| Mopar92 wrote: |
| pbullblue wrote: |
| Mopar92 wrote: |
| What cc is the single piston caliper and how many cc's does that wheel cylinder hold? You can't just guess... It's math.... So yeah it's relative. |
No guessing needed. Stock master works with 4 discs. Many have done it. A proven combo. If you feel differently and want more volume, have at it. Enjoy that pedal travel. |
Uhhh.... You mean if I put a larger bore master on, I will have more travel... I think not. Small bore= more psi and pedal travel. So, yeah, I will enjoy a rigid pedal, as opposed to 4" of travel. Thanks. |
Makes sense to me.... as the harder something is to push the farther you can push it!!!
Have fun |
A larger bore MC moves more volume of fluid than a smaller bore for the same stroke length. So if we assume the brake piston size and pedal pivots are the same:
Larger MC Bore: Less pedal movement, more pedal effort
Smaller MC Bore: More pedal movement, less pedal effort
In this case, both systems move the same volume of fluid because the brake pistons are the same and thus move in and out the same distance. It's the pedal stroke length that changes to account for the different bore sizes in order to keep the volume the same.
If the brake pistons are the same and it takes X PSI to fully engage the brakes, the PSI required to fully engage the brakes is the same regardless of MC size. And from Pascal's law, (Mechanical advantage = Abrakes / Amaster) so a larger MC bore means less mechanical advantage so your pedal effort increases.
If your bore is too small, you can't move enough fluid with the pedal travel you have to fully engage the brakes. If your bore is too big, you can't push the pedal hard enough to fully engage the brakes. |
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