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tattooed_pariah
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Joined: April 24, 2006
Posts: 2047
Location: El Cajon, CA
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 Posted: Mon Apr 15, 2019 8:22 am Post subject: Varga C34 disc brakes |
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So I did some googling (and searching here) but didn't really come up with too much helpful..
back in 2007 I had a friend put Varge C34 disc brakes on the rear of my bug while I was out of country.. Neither one of us can remember what parts the kit alleged to use.
I think I screwed up some kind of adjustment or something (I know beetle drums, but never worked with discs on any car prior to last week when I did my daughter's 280zx's brakes.. and well, now it has a similar problem, so I think I must be the cause of the issue..)
Basically, the driver rear inboard pad is rubbing the caliper.
on my bug, it's rubbing bad enough (and I don't inspect often enough) that it's ground away a significant portion of my caliper. So now I want to put in a new rotor and pads, but have no idea what I need to order
Does anyone else have this kit and know what direction I should be looking? my buddy thought he remembered it being a golf or jetta, but all the newer kits seem to use 914's..
_________________
-pariah (just a novice from "that other VW site")
'72 Volksrod "Effigy"
"Never worry about stepping on people's toes. People who get their toes stepped on are either sitting down, or standing still on the job."
-Admiral Arleigh Burke, USN(ret.) |
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jason
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Joined: August 07, 2002
Posts: 3445
Location: Garage
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| Posted: Mon Apr 15, 2019 11:23 am Post subject: Re: Varga C34 disc brakes |
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| Calipers float. Maybe the caliper wasnt centered and cant move away enough. Your master cylinder changed, residual pressure valve still used? |
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FreeBug
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Location: deepest, darkest Switzerland
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| Posted: Mon Apr 15, 2019 12:04 pm Post subject: Re: Varga C34 disc brakes |
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| jason wrote: |
| Calipers float. Maybe the caliper wasnt centered and cant move away enough. Your master cylinder changed, residual pressure valve still used? |
I was thinking the same thing..those are floating calipers, are the shafts stuck? The mobile part of the caliper should move pretty freely..and self-center.
It all looks quite rusty. Start by disassembling and maybe rebuilding stuff, but definitely get stuff freed up. |
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Kauai/5
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Joined: August 16, 2016
Posts: 76
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| Posted: Mon Apr 15, 2019 12:58 pm Post subject: Re: Varga C34 disc brakes |
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Yes, those look like the 914 rotor hat conversion with a pair of floating calipers with built in parking brake.
As others have said, these calipers are designed to “float” versus a hard fixed mount, so shimming is not as critical although I still like to center mine.
Regarding the issue you are having, check to make sure the calipers can still float as others have suggested. Those rubber accordion looking things are covers for the guides. The guides allow the whole caliper body to float (ride along guid pins) independently of the mount so that the caliper can move in and out centering itself as it applies pressure. Important to note that the caliper needs to be mounted perpendicular to the face of the rotor otherwise you will get uneven pad ware and poor performance. This is where shimming at the two mounting bolts where the caliber assembly mounts to the hub adapter comes into play.
The other and more likely culprit is corrosion in the caliper is causing it not to retract which can cock the piston causing one side of the pad to rest more closely against the rotor. It doesn’t take much and brake fluid is really good at absorbing moisture. You’re really supposed to change it frequently to combat it, but most don’t. Eventually it makes its way into the calipers where it find a nice home in the piston and causes the piston not to retract fully. Sometimes this doesn’t cause problems for a long while as the pads ware instead, but then when you go to try to fit a new set of pads (asking the pistons to return home) and then drive around the block, it feels like a freight train is attached to the car, and ohhh the smell! Or everything seems fine until the next day when you try to drive the car and find the calipers dragging or locked.
So, you have two options if you find the caliper pistons not fully retracting -you can try to rebuild them, or just buy a new pair.
Fortunately a brand new pair (not Varga but same design) can be purchased from CB Pergormance or on EBay for less than $100 loaded with new pads. Be sure to flush and fill the system with new fluid after replacing. CB also sells the rotors as well as multiple suppliers on EBay. They are basically 914 rotors with the 4 lug (4x130) deep hat design. |
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Kauai/5
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| Posted: Mon Apr 15, 2019 1:11 pm Post subject: Re: Varga C34 disc brakes |
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And I just looked at your photo more closely and can clearly see one of the spring keeper/guides for the pad coming through the slot in the body of the caliper. There are two. They look like butterfly wings and they keeps the pads in the right spot.
With one in the slot (unless bad camera angle), it means the pad is not riding in the slot and is out of position which would certainly cause problems. |
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raygreenwood
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Location: Oklahoma City
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| Posted: Mon Apr 15, 2019 3:52 pm Post subject: Re: Varga C34 disc brakes |
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Right off the bat....I would say that is not the right caliper for that caliper bracket with that 914 rear rotor.
1. Look at the pad path on both the front and back picture of your rotor. It sweeps only about 60% of the rotor area and it should sweep to within about 3mm of the inner ledge next to the hat.
So...you are losing about 30% of your braking capacity.
2. It does appear...that the rotor is literally grinding on the caliper. There should be several millimeters of gap between rotor and caliper.
Pull the caliper loose and make sure that when installed...someone did not oval out the holes just to get too small of a caliper to fit.
Ray |
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Kauai/5
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Joined: August 16, 2016
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| Posted: Mon Apr 15, 2019 11:43 pm Post subject: Re: Varga C34 disc brakes |
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| raygreenwood wrote: |
Right off the bat....I would say that is not the right caliper for that caliper bracket with that 914 rear rotor.
1. Look at the pad path on both the front and back picture of your rotor. It sweeps only about 60% of the rotor area and it should sweep to within about 3mm of the inner ledge next to the hat.
So...you are losing about 30% of your braking capacity.
2. It does appear...that the rotor is literally grinding on the caliper. There should be several millimeters of gap between rotor and caliper.
Pull the caliper loose and make sure that when installed...someone did not oval out the holes just to get too small of a caliper to fit.
Ray |
The contact patch looks about right to me, maybe a little narrow, but the rotors he is running appear to have a flat surface all the way to the hat whereas stock 914 rotors have a recessed groove in them on the inboard where the join the hat for dust to collect in and clear away which give the appearance of a larger contact area. You can see that the gap between the outer diameter edge of the rotor and the two caliper halves is about right, maybe a little bigger than necessary, but being that these are disc brakes on the rear maybe the adapter manufacturer figured it was good enough.
He describes the problem as being “the inboard pad rubbing the caliper” but I think he probably means the inboard pad is rubbing the rotor.
And so I think the real issue is the inside pad not being loaded properly. With that one spring tab sticking through the slot it’s probable it’s metal backing plate is not sliding within the body and not fully retracting, and that pad is probably cocked and not perpendicular to the rotor face causing uneven ware and possibly even dragging. When the brakes are pressed, the inside pad which is the one that is directly activated by the piston is working harder doing most the stopping power and the body isn’t floating as evidenced by the different wear on the inside and outside of the rotor.
Looking at the photos, you can see evidence that the inner pad is engaging the rotor surface more so than the outer based on there being less rust on the surface and deeper grooves in it. You can also see that the outer pad appears to only make partial contact during the rotation based on the uneven rust ware pattern around its circumference, as if the body is not evenly floating perpendicular to the rotor and the outside pad is only contacting in the high spots. These rotors can have quite a bit of run out.
This is all of course based on the photos which can be deceiving, but I can tell you that at least one pad is not loaded properly and that with a floating caliper the outside pad should be held in place in its proper position by those springs keeping it perpendicular to the rotor surface, and that the inside pad is the one that travels. As it travels and makes contact, the whole body should then “float” along the guides to clamp the rotor and distribute the squeezing pressure between both pads. If the pads aren’t properly loaded or are unevenly worn, all bets are off on a balanced application of stopping power.
To me when looking at the photo, the piston is clearly in the extended position but that may be because the parking brake is on.
And there’s still of course the possibility that the caliper body isn’t floating, and/or that the calipers need to be shimmed so that the rotor is centered in the caliper body when at rest, and that it might even need to be shimmed top to bottom so that the caliper is perpendicular to the rotor face if the adapters are poor quality or bent.
Here’s a photo of a similar floating caliper design. The slots are guides for the pad springs to slide along. If the springs aren’t in this slot, the metal backing plate will be scraping along the caliper body and eventually the backing plate could get stuck or cocked, then it would remain in contact with the rotor dragging, which could then heat the piston seal and cause it to start leaking, etc..
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tattooed_pariah
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Location: El Cajon, CA
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| Posted: Tue Apr 16, 2019 6:10 am Post subject: Re: Varga C34 disc brakes |
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Wow, lot of good responses, thank you guys! I'll try and hit them in order 
Jason: MC stayed the same, that could be part of the problem as to my limited understanding, disc require a different MC to work 100% properly, and should have a residual pressure valve which I don't think I have..
FreeBug: stuck shafts could be the case.. Unfortunately, the car has only had about 6000 miles put on it since 2007 due to other unrelated engine issues, and it becoming an extra car instead of a primary daily driver.. :/ It's not actually too rusty, all that red dust on everything is material from the rotor.. it's coating the entire fender well..
Kauai/5: This makes me feel a little better, maybe it wasn't my mechanical skills screwing something up so much as the environment in Virginia where both cars spent a lot of time parked.. The bug got minimal use and the 280zx was used by my daughter who doesn't go out much.. we also had another car she drove more than her Z, so maybe it all just got that nasty sea-air gumming things up and the pistons are stuck.. It's probably best to just replace the rear calipers at this point as rebuilding things seems to be more expensive these days.. Good catch on the clip! like I said, I know drums, but not much about discs, so I never would have known that clip is not positioned correctly..
raygreenwood: again, I don't know discs at all, but what you said about sweep makes sense.. the rotors do stop on a dime, so I guess they are sufficient, but that doesn't mean it's not wrong.. and yes, the inboard pad is straight up grinding the rotor.. there is a ton of material left, but the rotor has been "turned down" by at least 1mm on the inside.. :/
kauai/5: yes, i meant the pad is rubbing the rotor..
at this point, I feel like my options are to attempt to rebuild a cheap caliper, and buy at least one rotor (the inside of this one is seriously ground down..) or just spend a little bit more and buy a new rear disc kit with new rotors, calipers, pads, etc, and install it and save this set up for spare parts..
_________________
-pariah (just a novice from "that other VW site")
'72 Volksrod "Effigy"
"Never worry about stepping on people's toes. People who get their toes stepped on are either sitting down, or standing still on the job."
-Admiral Arleigh Burke, USN(ret.) |
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tattooed_pariah
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raygreenwood
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Location: Oklahoma City
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| Posted: Tue Apr 16, 2019 8:27 am Post subject: Re: Varga C34 disc brakes |
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| Kauai/5 wrote: |
| raygreenwood wrote: |
Right off the bat....I would say that is not the right caliper for that caliper bracket with that 914 rear rotor.
1. Look at the pad path on both the front and back picture of your rotor. It sweeps only about 60% of the rotor area and it should sweep to within about 3mm of the inner ledge next to the hat.
So...you are losing about 30% of your braking capacity.
2. It does appear...that the rotor is literally grinding on the caliper. There should be several millimeters of gap between rotor and caliper.
Pull the caliper loose and make sure that when installed...someone did not oval out the holes just to get too small of a caliper to fit.
Ray |
The contact patch looks about right to me, maybe a little narrow, but the rotors he is running appear to have a flat surface all the way to the hat whereas stock 914 rotors have a recessed groove in them on the inboard where the join the hat for dust to collect in and clear away which give the appearance of a larger contact area. You can see that the gap between the outer diameter edge of the rotor and the two caliper halves is about right, maybe a little bigger than necessary, but being that these are disc brakes on the rear maybe the adapter manufacturer figured it was good enough.
He describes the problem as being “the inboard pad rubbing the caliper” but I think he probably means the inboard pad is rubbing the rotor.
And so I think the real issue is the inside pad not being loaded properly. With that one spring tab sticking through the slot it’s probable it’s metal backing plate is not sliding within the body and not fully retracting, and that pad is probably cocked and not perpendicular to the rotor face causing uneven ware and possibly even dragging. When the brakes are pressed, the inside pad which is the one that is directly activated by the piston is working harder doing most the stopping power and the body isn’t floating as evidenced by the different wear on the inside and outside of the rotor.
Looking at the photos, you can see evidence that the inner pad is engaging the rotor surface more so than the outer based on there being less rust on the surface and deeper grooves in it. You can also see that the outer pad appears to only make partial contact during the rotation based on the uneven rust ware pattern around its circumference, as if the body is not evenly floating perpendicular to the rotor and the outside pad is only contacting in the high spots. These rotors can have quite a bit of run out.
This is all of course based on the photos which can be deceiving, but I can tell you that at least one pad is not loaded properly and that with a floating caliper the outside pad should be held in place in its proper position by those springs keeping it perpendicular to the rotor surface, and that the inside pad is the one that travels. As it travels and makes contact, the whole body should then “float” along the guides to clamp the rotor and distribute the squeezing pressure between both pads. If the pads aren’t properly loaded or are unevenly worn, all bets are off on a balanced application of stopping power.
To me when looking at the photo, the piston is clearly in the extended position but that may be because the parking brake is on.
And there’s still of course the possibility that the caliper body isn’t floating, and/or that the calipers need to be shimmed so that the rotor is centered in the caliper body when at rest, and that it might even need to be shimmed top to bottom so that the caliper is perpendicular to the rotor face if the adapters are poor quality or bent.
Here’s a photo of a similar floating caliper design. The slots are guides for the pad springs to slide along. If the springs aren’t in this slot, the metal backing plate will be scraping along the caliper body and eventually the backing plate could get stuck or cocked, then it would remain in contact with the rotor dragging, which could then heat the piston seal and cause it to start leaking, etc..
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No....not even close to normal. The contact patch is only about 60% of the swept area.
If that is what whoever sold that set up calls normal....dont buy it.
Those are Porsche 914 rear rotors. Even the 914's...with their barely adequate calipers...run the pad full width to within 2-3mm of the inner ring lip.
In fact...most disc brakes use 90-ish % of their rotor swept area for pad contact. If not...why bother with the worthless extra weight of a larger diameter rotor like that when you could do it with a 9" or so rotor?
I have a brand new set of Zimmerman 914 rear rotors right now waiting for install on my 412 (its a type 3 rear set up). The proper caliper even when using a sliding caliper....should have pad contact with a bare minimum of about 4/5ths of the swept area...or else its a waste and you will not even get as much braking action as the original drums had.
Compare:
Notice the swept area mark on the left corresponds to the length of the pad...which is really poor...really mismatched to the swept area of this rotor.
A correct usage is shown on the 914 on the right...but even this was barely adequate because the piston diameter of the stock 914 caliper was so small.
The combination of not enough reach out into the swept area of teh rotor...as well as this.....
From the picture he posted....note the slight dip where the rotor has ground against the caliper...and the rusted metal filings from the caliper...and his statement that:
| Quote: |
| on my bug, it's rubbing bad enough (and I don't inspect often enough) that it's ground away a significant portion of my caliper. So now I want to put in a new rotor and pads, but have no idea what I need to order |
One can only surmise that either caliper is too small for that rotor....the rotor is too big for that caliper....or even if you are willing to put up with low swept area and pad contact....the main caliper mount bracket to the rear bearing cover is the incorrect model....or the secondary caliper bracket needed for sliding calipers is mismatched to the caliper body.
Ray |
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slalombuggy
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| Posted: Tue Apr 16, 2019 8:55 am Post subject: Re: Varga C34 disc brakes |
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Before you replace everything.
How did the car stop when you had the brakes working before? IF yes then just replace the parts needed or repair them.
Quite honestly I've seen OE braking systems that had the same percentage of swept area on the brake rotor and on more than just a few makes of vehicles.
Being that the braking contact is at the outer edge of the rotor, it gives the smaller pads the best mechanical advantage for stopping. The same clamping force exerted closer to the hub would not have as great of a mechanical advantage.
While it might not be optimal, if it worked before it will work again when the issues you have are sorted out.
brad |
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tattooed_pariah
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Location: El Cajon, CA
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| Posted: Tue Apr 16, 2019 10:10 am Post subject: Re: Varga C34 disc brakes |
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| slalombuggy wrote: |
Before you replace everything.
How did the car stop when you had the brakes working before? IF yes then just replace the parts needed or repair them.
Quite honestly I've seen OE braking systems that had the same percentage of swept area on the brake rotor and on more than just a few makes of vehicles.
Being that the braking contact is at the outer edge of the rotor, it gives the smaller pads the best mechanical advantage for stopping. The same clamping force exerted closer to the hub would not have as great of a mechanical advantage.
While it might not be optimal, if it worked before it will work again when the issues you have are sorted out.
brad |
It did stop great when they were first installed... I could lock up my tires almost instantly if i stood on the brakes.. car would still slide, but the tires sure weren't spinning.. 
I'm only thinking about replacing the entire system because I fear the "snowball" effect.. I think spending a few hundred up front and getting all new parts from a matched system might be cheaper in the long run than replacing things individually and having worn out parts affecting new parts and possibly mismatching things, etc.. :/
_________________
-pariah (just a novice from "that other VW site")
'72 Volksrod "Effigy"
"Never worry about stepping on people's toes. People who get their toes stepped on are either sitting down, or standing still on the job."
-Admiral Arleigh Burke, USN(ret.) |
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raygreenwood
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Location: Oklahoma City
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| Posted: Tue Apr 16, 2019 11:11 am Post subject: Re: Varga C34 disc brakes |
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| slalombuggy wrote: |
Before you replace everything.
How did the car stop when you had the brakes working before? IF yes then just replace the parts needed or repair them.
Quite honestly I've seen OE braking systems that had the same percentage of swept area on the brake rotor and on more than just a few makes of vehicles.
Being that the braking contact is at the outer edge of the rotor, it gives the smaller pads the best mechanical advantage for stopping. The same clamping force exerted closer to the hub would not have as great of a mechanical advantage.
While it might not be optimal, if it worked before it will work again when the issues you have are sorted out.
brad |
Yes...I have seen a few that do not use the entire swept area...but lets get precise here....not by that much.
And there is no real mechanical advantage....but there are some benefits and trade offs. RPM towards the center of the rotor is higher....but swept length/diameter towards the outer edge is longer. All rotors have that differential. If you reach too far in yes...the pads can wear faster either on the inside edge or outside depending on material and pressure. It puts an angle on the pad.
The secondary problem running pads like this causes...and yes its notorious on more than a few vehicles...is noisey and dragging brakes after a basic friction rebuild.
This happens on set ups like this....because when you change the pads...unless you use the exact brand...and unless that same brand is made to a VERY precision level.... the inner groove/step worn by the short pads....can now impinge on new pads that are even .010" to .020" different.
.... and if you work on enough cars you will know that friction material placement on otherwise very similar metal pad backings...varies a bit.
More disc systems actually have slight pad overlap inside the inner ring that those that are short. While this can cause the same issue in reverse...its easier to fix than having to turn the disc.
But all of that aside whether you agree with one method or not....thats really poor pad to swept area contact....and while there may be a spring dragging for sure....his comment that his calipers are wearing away...already states that something is not correct in the caliper or bracket fit. Ray |
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Kauai/5
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| Posted: Tue Apr 16, 2019 12:21 pm Post subject: Re: Varga C34 disc brakes |
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The more expensive kit is made up of a hub that has the studs pressed through it that slips over axle end which then accepts the rotor with integral hat.
The less expensive kit uses a one piece design where the rotor itself acts as the hub similar to the front disc brakes.
Running the wrong master if it was a disc/drum should only really cause poor brake feel performance related to brake effort since the issue has to do mostly with volume. Caliper bores require more volume than drum cylinder, X4 and you need a disc/disc master. If you ran a drum/drum you’d really have issues due to volume and the valve built in for drums to keep pressure in the line and the cylinders extended so that they don’t have to extend far to engage the drum. I think since the rear caliper floats, this isn’t as much of an issue.
You shouldn’t need a residual valve. That’s probably for people who are using split brakes with a sliding lever to independently control them like a road racing or off road vehicle.
You say the rotor has been worn down 1mm on the inside, how do you know this? Did you measure or just guessing. With floating calipers it’s not as critical so long as they run true and are within manufacture ware specs. The only way this could have worn down like that so quickly is if the pad was dragging due to it not being loaded and sitting right, the caliper piston not retracting, or the caliper body not floating. From the photos it looks like the piston is extended.
Also don’t forget, when you install new brake shoes or pads and rotors, etc. you have to readjust the parking brake. If it’s been adjusted to compensate for worn tolerances, then you install new parts with thicker ware surfaces, your parking brake may not allow for this and may cause dragging especially as the parts warm up and expand.
If you end up with one brake dragging or locking and the other free on the rear end and you drive with it like that, you can kiss your differential, axle paddles, or splines goodbye because something is going to go.
Unfortunately, yes a lot of times parts are so cheap these days it easier faster and more economical to replace with new. A new set of loaded calipers are about $150 as are the rotors. I would only replace what is necessary unless you feel the system was contaminated with water or that parts of it are rust welded from sitting.
Last edited by Kauai/5 on Wed Apr 17, 2019 2:00 am; edited 1 time in total |
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Kauai/5
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Joined: August 16, 2016
Posts: 76
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| Posted: Tue Apr 16, 2019 1:00 pm Post subject: Re: Varga C34 disc brakes |
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| raygreenwood wrote: |
| Kauai/5 wrote: |
| raygreenwood wrote: |
Right off the bat....I would say that is not the right caliper for that caliper bracket with that 914 rear rotor.
1. Look at the pad path on both the front and back picture of your rotor. It sweeps only about 60% of the rotor area and it should sweep to within about 3mm of the inner ledge next to the hat.
So...you are losing about 30% of your braking capacity.
2. It does appear...that the rotor is literally grinding on the caliper. There should be several millimeters of gap between rotor and caliper.
Pull the caliper loose and make sure that when installed...someone did not oval out the holes just to get too small of a caliper to fit.
Ray |
The contact patch looks about right to me, maybe a little narrow, but the rotors he is running appear to have a flat surface all the way to the hat whereas stock 914 rotors have a recessed groove in them on the inboard where the join the hat for dust to collect in and clear away which give the appearance of a larger contact area. You can see that the gap between the outer diameter edge of the rotor and the two caliper halves is about right, maybe a little bigger than necessary, but being that these are disc brakes on the rear maybe the adapter manufacturer figured it was good enough.
He describes the problem as being “the inboard pad rubbing the caliper” but I think he probably means the inboard pad is rubbing the rotor.
And so I think the real issue is the inside pad not being loaded properly. With that one spring tab sticking through the slot it’s probable it’s metal backing plate is not sliding within the body and not fully retracting, and that pad is probably cocked and not perpendicular to the rotor face causing uneven ware and possibly even dragging. When the brakes are pressed, the inside pad which is the one that is directly activated by the piston is working harder doing most the stopping power and the body isn’t floating as evidenced by the different wear on the inside and outside of the rotor.
Looking at the photos, you can see evidence that the inner pad is engaging the rotor surface more so than the outer based on there being less rust on the surface and deeper grooves in it. You can also see that the outer pad appears to only make partial contact during the rotation based on the uneven rust ware pattern around its circumference, as if the body is not evenly floating perpendicular to the rotor and the outside pad is only contacting in the high spots. These rotors can have quite a bit of run out.
This is all of course based on the photos which can be deceiving, but I can tell you that at least one pad is not loaded properly and that with a floating caliper the outside pad should be held in place in its proper position by those springs keeping it perpendicular to the rotor surface, and that the inside pad is the one that travels. As it travels and makes contact, the whole body should then “float” along the guides to clamp the rotor and distribute the squeezing pressure between both pads. If the pads aren’t properly loaded or are unevenly worn, all bets are off on a balanced application of stopping power.
To me when looking at the photo, the piston is clearly in the extended position but that may be because the parking brake is on.
And there’s still of course the possibility that the caliper body isn’t floating, and/or that the calipers need to be shimmed so that the rotor is centered in the caliper body when at rest, and that it might even need to be shimmed top to bottom so that the caliper is perpendicular to the rotor face if the adapters are poor quality or bent.
Here’s a photo of a similar floating caliper design. The slots are guides for the pad springs to slide along. If the springs aren’t in this slot, the metal backing plate will be scraping along the caliper body and eventually the backing plate could get stuck or cocked, then it would remain in contact with the rotor dragging, which could then heat the piston seal and cause it to start leaking, etc..
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No....not even close to normal. The contact patch is only about 60% of the swept area.
If that is what whoever sold that set up calls normal....dont buy it.
Those are Porsche 914 rear rotors. Even the 914's...with their barely adequate calipers...run the pad full width to within 2-3mm of the inner ring lip.
In fact...most disc brakes use 90-ish % of their rotor swept area for pad contact. If not...why bother with the worthless extra weight of a larger diameter rotor like that when you could do it with a 9" or so rotor?
I have a brand new set of Zimmerman 914 rear rotors right now waiting for install on my 412 (its a type 3 rear set up). The proper caliper even when using a sliding caliper....should have pad contact with a bare minimum of about 4/5ths of the swept area...or else its a waste and you will not even get as much braking action as the original drums had.
Compare:
Notice the swept area mark on the left corresponds to the length of the pad...which is really poor...really mismatched to the swept area of this rotor.
A correct usage is shown on the 914 on the right...but even this was barely adequate because the piston diameter of the stock 914 caliper was so small.
The combination of not enough reach out into the swept area of teh rotor...as well as this.....
From the picture he posted....note the slight dip where the rotor has ground against the caliper...and the rusted metal filings from the caliper...and his statement that:
| Quote: |
| on my bug, it's rubbing bad enough (and I don't inspect often enough) that it's ground away a significant portion of my caliper. So now I want to put in a new rotor and pads, but have no idea what I need to order |
One can only surmise that either caliper is too small for that rotor....the rotor is too big for that caliper....or even if you are willing to put up with low swept area and pad contact....the main caliper mount bracket to the rear bearing cover is the incorrect model....or the secondary caliper bracket needed for sliding calipers is mismatched to the caliper body.
Ray |
Yes, I see what you are pointing out and understood the first time you mentioned it. Correct, the contact patch is not ideal. Does it offer better performance when properly working than a drum brake, probably. Should/could it be larger, yes. Why isn’t it? Well for one, the two components weren’t originally designed for each other. You can’t really compare the stock 914 setup since it has a different caliper design. This rear kit was put together with components that fit, allow for clearance with skinny stock 15” wheels, using parts that could be readily sourced and was not really designed with performance in mind. Heck, they are rear disc brakes on a very light car after all, and we all know how much work rear brakes do compared to the front. Now if it were the front brakes I would be concerned.
But again I will repeat that no caliper will work well if the pads aren’t being equally applied perpendicular to the face of the rotor, whether it be due to improper loading or seating of the pads, uneven pad ware, a piston that is cocked in its bore due to corrosion, bad guide pins, etc.. |
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slalombuggy
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Joined: July 17, 2010
Posts: 9143
Location: Canada
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| Posted: Tue Apr 16, 2019 8:26 pm Post subject: Re: Varga C34 disc brakes |
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Off the top of my head, I can think of a handful of cars with as little or less swept area, including the front brakes on my last Colorado. But we've already established that the brakes were more than adequate for the OPs purpose. I haul my racecar down from130mph using only rear brakes that use Ghia front calipers and the very small pads that they use. 1800#. You don't need huge pads or rotors unless your car is a lot heavier than ours or you are stopping repeatedly.
Last edited by slalombuggy on Mon Apr 22, 2019 6:12 am; edited 1 time in total |
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Kauai/5
Samba Member
Joined: August 16, 2016
Posts: 76
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| Posted: Tue Apr 16, 2019 11:17 pm Post subject: Re: Varga C34 disc brakes |
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| slalombuggy wrote: |
| Off the top of my head, I can think of a handful of cars with as little or less swept area, including the front brakes on my last Colorado's front brakes. But we've already established that the brakes were more than adequate for the OPs purpose. I haul my racecar down from130mph using only rear brakes that use Ghia front calipers and the very small pads that they use. 1800#. You don't need huge pads or rotors unless your car is a lot heavier than ours or you are stopping repeatedly |
Hey wait a second, stopping a car out at The Salt Flats doesn’t count! I mean what’s to hit out there? 😜
But to your point about knowing of a few other cars not utilizing the full rotor area as another poster had also mentioned, it is quite true. I’ve come across more than a few. You see it on motorcycles and scooters too which I sometimes think might have to do with leaving more mass to draw out the heat from the contact surface, but it is probably just a classic case of “hey we got 10 pallets of those calipers from that 2005 model left”, let’s use those with our fancy big new rotor that has the look that’s all the rage”....
Now I can’t remember the original application for the rear calipers used in these rear disc conversion kits, but I seem to remember that the vehicle may have used smaller rotors due to smaller wheels which is probably why the caliper does not make use of the 914 rotors full surface area. Also as I mentioned before, the aftermarket rotors like the OP is using don’t appear to have the step in them along inside which makes the lack of contact area look even greater.
BTW, I have two of these rear kits. I can’t make out the PO’s adapter bracket to know if it’s the same, but I can confirm the contact patch (see photo below) as I have one set with aftermarket rotors without groove, and the other set with an NOS pair of 914 rotors that I scored for next to nothing on EBay because they were in their original bags covered in dried cosmoline and looked like they had been tossed in a city sewer where they sat for 50 years. Needless to say it took more than one can of brake cleaner to clean them up! Who says you can’t polish a turd?
The photo below is a straight on shot showing the NOS 914 rotors. See the large inboard groove? Without that, like the aftermarkets the OP has, it would make the contact patch look even worse in proportion to the rotors surface area.
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tattooed_pariah
Samba Member
Joined: April 24, 2006
Posts: 2047
Location: El Cajon, CA
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| Posted: Mon Apr 22, 2019 6:47 am Post subject: Re: Varga C34 disc brakes |
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took it to the base auto shop friday so I could throw it on a lift and swap the tires.. running 185/60r15 fronts and 255/70r15 rears now, fender gap looks SOOOO much better on the rear..
that driver inner pad was gone, been metal to metal for who knows how long..
called CB, told em I have the varga c34 calipers and no idea what pads it uses. they said they are Brazilian pads and they have em in stock. They are shipping me pads and a new rotor because that one is toast, it's almost half ground through..
parts should arrive wednesday and hobby shop is open thursday-sunday, so hopefully i'll be back on the road thursday..
_________________
-pariah (just a novice from "that other VW site")
'72 Volksrod "Effigy"
"Never worry about stepping on people's toes. People who get their toes stepped on are either sitting down, or standing still on the job."
-Admiral Arleigh Burke, USN(ret.) |
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ach60 
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Joined: May 14, 2001
Posts: 4139
Location: Santa Maria
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| Posted: Mon Apr 22, 2019 5:34 pm Post subject: Re: Varga C34 disc brakes |
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| tattooed_pariah wrote: |
took it to the base auto shop friday so I could throw it on a lift and swap the tires.. running 185/60r15 fronts and 255/70r15 rears now, fender gap looks SOOOO much better on the rear..
that driver inner pad was gone, been metal to metal for who knows how long..
called CB, told em I have the varga c34 calipers and no idea what pads it uses. they said they are Brazilian pads and they have em in stock. They are shipping me pads and a new rotor because that one is toast, it's almost half ground through..
parts should arrive wednesday and hobby shop is open thursday-sunday, so hopefully i'll be back on the road thursday.. |
If you could take photos of the box & part numbers on the box, and parts.
May be we could figure out what vehicle make & model these calipers come from?
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Good Luck
Al |
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Kauai/5
Samba Member
Joined: August 16, 2016
Posts: 76
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| Posted: Mon Apr 22, 2019 11:33 pm Post subject: Re: Varga C34 disc brakes |
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| ach60 wrote: |
| tattooed_pariah wrote: |
took it to the base auto shop friday so I could throw it on a lift and swap the tires.. running 185/60r15 fronts and 255/70r15 rears now, fender gap looks SOOOO much better on the rear..
that driver inner pad was gone, been metal to metal for who knows how long..
called CB, told em I have the varga c34 calipers and no idea what pads it uses. they said they are Brazilian pads and they have em in stock. They are shipping me pads and a new rotor because that one is toast, it's almost half ground through..
parts should arrive wednesday and hobby shop is open thursday-sunday, so hopefully i'll be back on the road thursday.. |
If you could take photos of the box & part numbers on the box, and parts.
May be we could figure out what vehicle make & model these calipers come from? |
They are Brazilian for Chevy GSI application, but the same design has been copied and used by many makes and models over the years including Ford, Mercury, VW, etc.. The C34 designation is for that particular casting, but I’ve had pairs that are identical with a VF casting number. I think they were even used on early Mustangs before performance became as much about show as go.
Just Google Ford/Varga calipers for example and you’ll see photos of the same calipers with the same small contact ware pattern on the rotor.
To the original poster: make sure you load the pads properly and verify that the caliper’s piston is extending and retracting, then make sure the guide pins are not seized and that the caliper will float, otherwise you might end up with same problem. Just swapping new parts on without finding out what caused the problem in the first place is a pretty foolish way to go about “fixing” something -especially brakes! |
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