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Author Topic: Bigger Brakes  (Read 19455 times)

Reply #15May 08, 2005, 11:05:22 am

racer_x

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« Reply #15 on: May 08, 2005, 11:05:22 am »
Well, I'll jump in here. I don't think any diesel or Turbo diesel A1 or A2 needs anything larger than the 9.4" fronts, and the stock rear drums. In my experience, the stock VW brakes in various sizes and configurations are excellent for the cars they were delivered on, and good for a bit more performance. Here's the way it generally breaks down:

9.4" solid front rotors with 180mmx30mm rear drums: These are the lightest weight, and with proper pad selection they can handle any car up to 2400 pounds or so gross weight at speeds up to about 100mph. They do tend to fade a bit toward the end of a 70mph stop, especially with cheap pads. But they are excellent when used with good performance pads selected to match the driving conditions you will encounter.

9.4" vented front rotors with 180mmx30mm rear drums: These were on the Rabbit GTI's and 8V Sciroccos. The vented front rotors were also used on a lot of the A2 GTI's. These can handle higher speeds, and if you use them hard at higher speeds, you need high performance shoes for the rear drums and better front pads. These are excellent for up to 2400 pounds gross weight at speeds up to about 125mph.

9.4" vented front rotors with rear discs: This was the setup for the early A2 GTI's. They are good for about the same loading and speeds as the 9.4" vented fronts/180mmx30mm rear drums. They are excellent for up to 2400 pounds gross weight at speeds up to about 1250mph. In the mid 1980's, when friction material technology was limited, the rear discs were good for fighting rear brake fade in extreme use. Today, with Porterfield R4-S (street) and R4 (race) compounds available on the 180mm shoes, that's less of an issue (provided you use good shoes in the rear drums).

Proportioning for the rear discs is a big challenge for the A1 chassis. The A2 proportioning setup is good for A2 cars and makes rear discs much easier on an A2. Also, the VW calipers have very unreliable parking brake mechanisms and they weigh about 6 1/2 pounds more than the drum setup. The added weight is unsprung (actually unsprung, beyond the wheel centerline, so it's about 8 pounds of load on the springs and shocks). You do get slightly less rotating inertia with the rear discs, so acceleration is slightly better.

10.1" vented front rotors with rear discs: This was the stock setup on the 16V Sciroccos, and on the 2.0L 16V Jetta GLI's and B3 Passat 16V's. You have to use the 22mm master cylinder with these, and proportioning is an issue for the A1 chassis. Also, 14" is the smallest wheel that will clear the front calipers. These brakes will handle up to 2500-2600 pounds gross weight at speeds up to 135mph-140mph.

10.1" vented front rotors with 200mmx40mm rear drums: This wasn't stock on anything, but for an A1, these match up well. You can use the drum brake proportioning valves with this setup, and the balance is pretty good. Good for up to 2500 pounds gross weight at speeds up to 135mph or so. High speeds require high performance shoes for the rear discs to avoid fade issues at the rear.

I won't go any larger than that because it's not very applicable to diesel powered cars.

The big weight penatly with the larger brakes is in the wheels and tires. With light 13" wheels and light tires, it's possible to get the wheel and tire package down to 25 pounds or so. With 14" wheels and tires, getting under 35 pounds per corner is difficult, and the lightest I've seen is about 30 pounds per corner. 2 pounds on each wheel is about the same for acceleration as a pound on the flywheel. The added inertia from the larger wheels and tires is very significant.

On my 1984 diesel I run the vented 9.4" front rotors, and I actually have rear discs that I've been screwing around with for about 6 years. I have another Jetta here and I might just go back to the rear drums on the diesel and put the discs on the other Jetta for when I sell it.

Although, with extreme mods (rotor weight reduced by about 40%, aluminum calipers from an A4 chassis car, modifications to my custom brackets for the A2 load sensing regulator, etc.), I have the rear discs to the point where they are about the same as the original stock drums in terms of handling, and acceleration is slightly better. But unless you want to do a whole lot of work for very little gains, I wouldn't recommend rear discs.

At the front, I don't see any IDI diesel needing anything more than the stock brakes. I run the vented front rotors at minimum rotor thickness (or slightly below minimum thickness) because I have worn rotors from the race car, so it's more for convenience than for any real improvement in braking. At minimum thickness, the vented rotor is about the same weight as a full thickness, new solid front rotor. The vented 9.4" rotors are a decent upgrade for a car with the 9.4" solid rotors. You get about twice the surface area for cooling air with the vented rotors.

I see at least one Quantum owner posting here, so I'll make a comment or two about that. If you have a Quantum and need larger brakes due to additional weight, the 10.1" fronts with either rear discs or 200mmx40mm rear drums might be a good choice. The Scirocco 16V/Audi 4000CS caliper carriers will bolt right up to the front of a Quantum (or Dasher or Fox, or Rabbit or A1 Jetta). But you'll need 14" wheels with the 10.1" rotors, and that adds a lot of inertia to the package, hurting acceleration.


EDIT:

Also, if you want to use an adjustable proportioning device, for a street car you need to run two separate adjustable valves, one in each rear line, or get some kind of dual channel setup. Dr. Diesel's dual prop valve setup is a good example.

This setup

works for a track only race car. It looks like he has a tee connector joining the two rear brake lines into a single adjustable prop valve, and then another tee connector splitting the combined prop valve back out to the two rear brakes. That setup is not street legal! Every vehicle made since the mid 1960's (1964 I think) is required by law to have two separate and independent hydraulic circuits. That way a failure or leak in one system will only disable the brakes on two wheels at the most. With the setup in the picture, a leak in one caliper will disable the brakes on all 4 wheels. Again, if the rules allow it, that works fine for track use, but it's not a good idea for street use.

Reply #16May 08, 2005, 05:29:20 pm

VWRacer

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« Reply #16 on: May 08, 2005, 05:29:20 pm »
Great summary of upgrade choices, racer_x. Thanks for doing all that work and sharing the results!

In the case of my GTI race car though, there is no provision for upgrade. In a fit of common sense I went to the rules for NASA's GTI Cup and reviewed the section dealing with brakes:

Quote
7.31. Brakes
All cars must use the 1983-1984 model 9.4" vented brake rotors in front. Brake pads are spec brand/model and the brake fluid is unrestricted. Brake lines may be replaced with metal braided lines. Backing plates may be removed or modified. An adjustable proportioning valve may be used to limit pressure to the rear brake pistons. The stock proportioning (biasing) valve may be removed, if an adjustable valve is used. However, no modifications are allowed to the stock proportioning (biasing) valve, under any circumstances.The master cylinder and brake booster must be stock and unmodified. Parking brakes may be removed along with the appropriate mechanisms. Air ducts may be directed at the brakes. Ducts may not go through the body. Liquid cooling is prohibited. ABS braking systems are prohibited. No drilling, slotting, or any other modification may be performed on the rotors.


I'll inquire specifically about the rear brakes.
Stan
C-Sports Racer

Reply #17May 08, 2005, 07:41:15 pm

fspGTD

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« Reply #17 on: May 08, 2005, 07:41:15 pm »
As already explained in the thread I posted a link to above, (specifically, this one on the old forum: http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=363), my GTD's braking system indeed does have dual hydraulic circuits.  It has modified hydraulic circuits to be separated based on front to rear wheels, rather than diagonal corners like the stock circuit uses.  I have not tested braking performance in the event of a circuit failure, but I can say it works great in normal operating conditions, and in theory it should still give braking on two wheels in the event of a hydraulic leak.  Unlike a dual adjustable prop valve setup, having a single adjustable prop valve controlling both rear brakes is simpler, as well as ensures that the proportioning from left to right on a given end of the car will always be equal.
Jake Russell
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Reply #18May 08, 2005, 09:26:22 pm

racer_x

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« Reply #18 on: May 08, 2005, 09:26:22 pm »
Quote from: "fspGTD"
As already explained in the thread I posted a link to above, (specifically, this one on the old forum: http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=363), my GTD's braking system indeed does have dual hydraulic circuits.  It has modified hydraulic circuits to be separated based on front to rear wheels, rather than diagonal corners like the stock circuit uses.  I have not tested braking performance in the event of a circuit failure, but I can say it works great in normal operating conditions, and in theory it should still give braking on two wheels in the event of a hydraulic leak.  Unlike a dual adjustable prop valve setup, having a single adjustable prop valve controlling both rear brakes is simpler, as well as ensures that the proportioning from left to right on a given end of the car will always be equal.
Sorry, the picture wasn't that clear. If you have a front/rear setup on the master cylinder, and only one tee connector, that will work.

Which master cylinder are you using? Most VW master cylinders won't run two front calipers from one end of the master cylinder. If you go oversized, it helps, like using a 22mm master cylinder with the stock Kelsey-Hayes 9.4" front calipers. But often the piston driving both front calipers bottoms out and any additional pressure from more pressure on the pedal goes only to the rear calipers. If the prop valve is actually a pressure regulator, with a slope of zero above the knee/cutoff pressure, then it isn't a big issue. In that case, the front piston bottoms out, the back is already cut off by the prop valve/regulator and it doesn't matter how hard you push the pedal, none of the brakes work any harder.

If there's a positive slope on the prop valve above the knee pressure, then the symptoms of bottoming out the front piston is excessive lockup of the rear wheels when pushed hard.

Reply #19May 08, 2005, 11:08:29 pm

Dr. Diesel

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« Reply #19 on: May 08, 2005, 11:08:29 pm »
Quote from: "fspGTD"
Unlike a dual adjustable prop valve setup, having a single adjustable prop valve controlling both rear brakes is simpler, as well as ensures that the proportioning from left to right on a given end of the car will always be equal.


I've found that having a car that isn't equally balanced left to right (don't have the weighing equipment neccessary) has rear wheels that lock up at different times. My simple solution: two valves! It took about an hour to install and bleed, and with the absolute tunability both front to rear and (rear) left/right allows me to extract maximum braking from my car. Sometimes I have my pit crew friend hop in the right rear seat to help balance the car, and I've already figured out what valve positions to start at for that weight distribution. No uneven rear braking. Works for me! :D
I repair, maintain and modify VW's and BMW's.
Good work done at affordable rates. Welding and fabricating, too.
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Reply #20May 09, 2005, 03:26:32 am

vwmike

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« Reply #20 on: May 09, 2005, 03:26:32 am »
I agree that unnecessarily increasing braking diameter will unnecessarily increase unsprung weight and that in most cases a diesel is just fine with stock brakes. My opinion for diesels is that an A1 ought to have vented 9.4's. There's really just no reason not to install these over the solid rotors. On my A2 I'm going to install 10.1" brakes only because I figure it's a big car and I'd like to be able to stop if someone pulls out in front of me.

My Rabbit is a different case entirely. It has those 10.1" brakes up front, but they're warped. That car will probably hit 220-225 wheel this summer so going to 11's sounds like a good idea. Moreover, this isn't simply an issue of being able to lock up the brakes on the freeway. A set of solid 9.4's can do that. It's an issue of modulation before lock up since lock up is something we're trying to avoid. Increased modulation expands the area known as threshold braking which is where I'd like to be  :D

Reply #21May 09, 2005, 11:27:13 am

fspGTD

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« Reply #21 on: May 09, 2005, 11:27:13 am »
RacerX: please read the thread containing the details on my setup I have now already linked twice in this thread.

VWMike: the main reason to run solid front rotors rather than vented is to have less rotating, unsprung weight.

Dr. D: I can see how that might work now...  very interesting!  :)
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
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Reply #22May 09, 2005, 12:32:08 pm

racer_x

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« Reply #22 on: May 09, 2005, 12:32:08 pm »
Quote from: "vwmike"
I agree that unnecessarily increasing braking diameter will unnecessarily increase unsprung weight and that in most cases a diesel is just fine with stock brakes. My opinion for diesels is that an A1 ought to have vented 9.4's. There's really just no reason not to install these over the solid rotors.
I basically agree with you there. There's twice the surface area on a vented rotor, so it comes in contact with twice as much air (theoretically) and will transfer heat twice as quickly and cool better. That's why they fade so much less than solid rotors. The weight difference is only slight, and the gain in cooling is huge.

But, let's stop for a physics break here. The function of the brakes is to turn the kinetic energy of the car into heat. No energy is lost, it's just converted from one form to another. The kinetic energy of a moving car is equal to its mass time the square of its velocity. I could give all the conversion factors, but the Google calculator is so cool about working out conversions, just type in "2000 pounds * (70 mph)^2 in calories" and it will give you the answer. To slow from 70 mph to 35 mph in a 2000 pound diesel Rabbit, you would convert the motion of the car into 159,240.735 calories of heat. To stop from 70mph, you'd generate 212,320.98 calories of heat in the brakes. It gets scary at higher speeds because of the square of the velocity thing. Slowing from 100mph to 70mph generates 220,987.142 calories of heat in the brakes. That's slightly more heat than a full stop from 70mph.

Quote from: "vwmike"
On my A2 I'm going to install 10.1" brakes only because I figure it's a big car and I'd like to be able to stop if someone pulls out in front of me.
It's not that much bigger, and it's not enough faster to worry that much.

Quote from: "vwmike"
My Rabbit is a different case entirely. It has those 10.1" brakes up front, but they're warped. That car will probably hit 220-225 wheel this summer so going to 11's sounds like a good idea.
First, unless the lugs were improperly torqued, I doubt the rotors warped. It's possible they picked up pad material unevenly and give a pulsing feel in the pedal and maybe even a bit of a shake in the steering wheel. But warped rotors are almost always caused by improper lug torque. And uneven pickup of pad material is also generally caused by bad driving habits or abuse.

I've only seen one Rabbit that needed 11" front brakes, and it was a turbo VR6 engine. That Rabbit hit over 145mph on the track, and it was just outside the envelope where I would have been comfortable with 10.1" front brakes. I've been in normally aspirated VR6's and turbo 16V's that were great under braking with 10.1" fronts.
Quote from: "vwmike"
Moreover, this isn't simply an issue of being able to lock up the brakes on the freeway.
Actually, bigger brakes do two things and only two things. They provide more torque for the same pedal pressure, and they have more thermal capacity for the heat. That's because they have more mass to absorb more heat energy without getting as much of a temperature rise. They also have more surface area and cool quicker.  
Quote from: "vwmike"
A set of solid 9.4's can do that.
If you take some stock pads (or Mintex red box) and do a quick slow down from 75mph to 15mph, then try to push the pedal hard enough to lock the brakes, it won't happen. THe pads will be overheated and fading. With vented 9.4" brakes, that's not as likely, and with 10.1" brakes it's more likely that you'll be able to lock the wheels at 15mph after slowing quickly from 75mph.

Quote from: "vwmike"
It's an issue of modulation before lock up since lock up is something we're trying to avoid. Increased modulation expands the area known as threshold braking which is where I'd like to be  :D
Actually, going too big can make the brake very difficult to drive.

If you think about the physics, you press on the pedal with a certain amount of force. The pedal is a lever that multiplies that force and applies the multiplied force to the master cylinder. So, if the pedal ratio is 4:1, and you press with 100 pounds of force on the pedal, 400 pounds of force is applied to the master cylinder piston. That translates into hydrualic pressure in the master cylinder. The force is applied to the area of the master cylinder piston, making the pressure in the hydraulic system some number of pounds per square inch. Taking our 400 pound example, and assuming a 1 square inch master cylinder piston (and I'm just making this up here, it's not what VW uses), we have 400 psi in the hydraulic lines. Now, if the front caliper has 3 square inches of piston area, then we get 400 * 3 or 1200 pounds of force applied to the caliper piston. The next thing is the cF of the pad. Let's assume 0.45 (a decent performance pad will have a cF of about 0.45). 1200 * 0.45 = 540 pounds of force applied at the piston center to the rotor. That applies torque to the rotor around the axle centerline based on the distance from the centerline of the axle to the center of the caliper piston. Let's say it's 4" from the caliper piston center to the centerline of the axle, that would be 180 ft. lbs. of torque at the axle. And that becomes reverse thrust at the tire/road interface based on the rolling radius of the tire (the distance from the axle centerline to the road). Let's say it's 11.25" rolling radius for the tire. That would make 192 pounds of reverse thrust at the road.

Bigger brakes like the 10.1" fronts for VW's increase the distance from the center line of the axle to the center of the caliper piston, which increases brake torque. And they also increase the piston diameter in the caliper significantly, which also increases brake torque. But they lose a small amount of brake torque to the requirement for a larger master cylinder. But overall, the 10.1" Girling 54's have about 50% more brake torque for the same pedal pressure as the Kelsey-Hayes 9.4" setup (assuming the same pad compound in each setup).

If you go too far, especially with street tires, the brakes get really touchy and it becomes difficult to modulate the brakes at the threshhold of tire grip. You end up with a brake pedal that's more of a skid switch than a variable braking control. The higher the grip of your tires, the more brake torque you need to lock the wheels, and the more you can use higher cF pads and bigger rotors and bigger calipers. For example, on my Improved Touring car, it's very difficult to drive it on DOT competition rubber, and nearly impossible to drive it on street tires if I use Ferodo DS-3000 Plus pads. Those have a cF of about 0.72-0.75, and they just provide so much brake grip that it's nearly impossible to avoid locking the wheels with street tires. It's a little easier to avoid locking the wheels with DOT competition rubber, and if I want to try race slicks, it just stops quicker with less pedal effort with those pads (once the tires and pads are up to operating temperature, of course). You can get into similar situations by pushing the caliper piston area or rotor size larger. The brakes can get very touchy and difficult to control.

Reply #23May 09, 2005, 12:51:57 pm

vwmike

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« Reply #23 on: May 09, 2005, 12:51:57 pm »
I understand what you're saying, but I've had some personal experience with all of the different brake sizes and haven't run into any issues with modulation or lock up even with the 11's. In fact the opposite has been true. As for my brakes, the pedal returns a bit of a pulse and the rotors don't look too spectacular either. So, if it's going to need brakes I'll probably just go up to the 11's since I have to buy new rotors anyways and the difference in cost would mostly be the adapters at ~$50-100 or whatever it is.

Reply #24May 09, 2005, 06:47:22 pm

racer_x

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« Reply #24 on: May 09, 2005, 06:47:22 pm »
Quote from: "vwmike"
I understand what you're saying, but I've had some personal experience with all of the different brake sizes and haven't run into any issues with modulation or lock up even with the 11's. In fact the opposite has been true. As for my brakes, the pedal returns a bit of a pulse and the rotors don't look too spectacular either. So, if it's going to need brakes I'll probably just go up to the 11's since I have to buy new rotors anyways and the difference in cost would mostly be the adapters at ~$50-100 or whatever it is.
If you're running 15" wheels and tires already, then just the adapters will get you to 11" front brakes. But you might have to machine the rotors down a bit or machine the pads to fit. I'm pretty sure the Corrado "Girling 54" calipers are a couple mm wider in their grip than the 10.1" "Girling 54" calipers. So it can be too tight to fit the Corrado pads and rotors in the Passat or 16V Scirocco or 2.0L 16V Jetta GLI calipers.

And if you have 14" wheels, then 11" brakes require upgrading to 15" wheels and tires. Don't forget a 15" spare. It sucks to have a puncture at the front on a rainy night and have to change the back tire to install the spare where it fits, then put the back wheel on the front to replace the flat. Don't ask me how I know this.

Reply #25May 09, 2005, 07:11:58 pm

lord_verminaard

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« Reply #25 on: May 09, 2005, 07:11:58 pm »
[flamesuit]
[sarcasm]

I think everyone will agree, all performance and physics aside, a car just plain looks cool with giant brakes jammed in the wheels.  My Camaro has factory 12 front and 12.1 rear rotors, aluminum twin piston calipers front and aluminum rears, and just for fun I added slotted/drilled rotors all around with EBC pads.  All stuffed under stock 16" wheels, barely any space between wheel and rotor.  :)

[/flamesuit]
[/sarcasm]

All joking aside, big brakes add to "bling" factor, but I think that most would agree that for racing, brake selection is a WHOLE different bag of crackers, not just big and bling.  :)

Brendan
84 Scirocco 8v
00 Camaro L36 M49

P.S. I am enjoying the discussions though, learning a lot.  :)
81 Scirocco 'S -->Soon to be m-TDI
93 Corrado SLC VR6
'86 Golf N/A Diesel  -->Wife's car
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05 New Beetle PD TDI


"I am a man, I can change... if I have to.... I guess....."

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Reply #26May 09, 2005, 07:45:44 pm

VWRacer

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« Reply #26 on: May 09, 2005, 07:45:44 pm »
No sarcasm or frustration from me, racer_x. I'm thoroughly enjoying the exchange!

Just like we get faster as racers by racing better drivers, we learn faster by interacting with persons whose experience compliments or exceeds our own.

Ya never get better hangin' with guys you can easily beat.  :!:
Stan
C-Sports Racer

Reply #27May 09, 2005, 10:07:27 pm

moosiah

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« Reply #27 on: May 09, 2005, 10:07:27 pm »
So "vw racer" stan...... I'm sticking w the big drum set for all practical reasons . . . . I think :wink:  I've read about folks w problems w rusting and sticking calipers on their rear disc setups ,,,,, and the weak parking brake complaints :cry:  further  moved the decesion to the drums ...... and I got the whole thing for about $60 .... and the rear disc conversion even at P&P cost me $100 or so  :x   the BIG problem I've had is finding good shoes...  the local parts place I go for VW stuff had 5 sets of quantum shoes that had the wrong ebrake arm on them ,, we finally got some NEW shoes from a japanese co that fit......  I'd love to know where to get higher grade rear linings. ??????  Later   :lol:
PS : Stan I grew up across the street from Sears Point and raced motorcycles ( F1 tz750 yam :twisted: ) there  for yrs
'81 Frankenbunny: part rabbit, sirroco, golf ,caddy cabrio ,jedda and ! ford teimpo! w a little more Audi and soon some Peogeot too!!!!

Reply #28May 10, 2005, 05:07:15 am

vwmike

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« Reply #28 on: May 10, 2005, 05:07:15 am »
Quote from: "racer_x"
Quote from: "vwmike"
I understand what you're saying, but I've had some personal experience with all of the different brake sizes and haven't run into any issues with modulation or lock up even with the 11's. In fact the opposite has been true. As for my brakes, the pedal returns a bit of a pulse and the rotors don't look too spectacular either. So, if it's going to need brakes I'll probably just go up to the 11's since I have to buy new rotors anyways and the difference in cost would mostly be the adapters at ~$50-100 or whatever it is.
If you're running 15" wheels and tires already, then just the adapters will get you to 11" front brakes. But you might have to machine the rotors down a bit or machine the pads to fit. I'm pretty sure the Corrado "Girling 54" calipers are a couple mm wider in their grip than the 10.1" "Girling 54" calipers. So it can be too tight to fit the Corrado pads and rotors in the Passat or 16V Scirocco or 2.0L 16V Jetta GLI calipers.

And if you have 14" wheels, then 11" brakes require upgrading to 15" wheels and tires. Don't forget a 15" spare. It sucks to have a puncture at the front on a rainy night and have to change the back tire to install the spare where it fits, then put the back wheel on the front to replace the flat. Don't ask me how I know this.


I'm already running 15" wheels and already have at least one set of girling 54's with carriers for 11's, as well as two sets of girling 60's, so it isn't like I'd really be going out of my way by putting 11's on there. Oh yeah, I also have a 15" spare in the car already.

Reply #29July 28, 2005, 12:39:44 pm

vwpieces

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« Reply #29 on: July 28, 2005, 12:39:44 pm »
I have done the full swap to 16V scirocco brakes front 10.1 & rear 8.9 disc on my 83 TD Jetta. Some things I have learned is to use the 16V scirocco 22mm master cylinder, booster & pedal assembly too. You can also use the pedal assy from any 85 & up A1 5 spd car, like cabriolet or 8V scirocco. But the 16V pedal cluster has an added spring like a mk3 assy that reduces pedal pressure, making a lighter push with your foot. Also it is possible to use a booster from the later 85 & up A1's too. Proportioning vlaves I used on the Jetta are from the 16V scirocco & mount on the master cylinder itself, staggered positions for the rear lines. If you have access to the 16V scirocco for parts get the front left & right hard lines & rear hard lines on the axle too. Makes life easier. ALWAYS replace the hoses with NEW ones. 15+ year old hoses rot from the inside out & will cause a caliper to stick. You will aslo NEED to remove the rear proportioning valve mounted on the body with the load spring to the rear axle for this setup to work properly & rerun some new hard lines back there to the hoses where the axle pivots.

My Jetta stops awesome & has a very light foot pressure for normal braking. I have let a few guys drive her & that is the first comment when they come back... "What did you do to those brakes...They are awesome."

I have also done the same swap on my 84 cabby & without the same results. I left the rear axle load proportioning valve on the cabby & it is lacking on rear stopping power. Do it ALL & do it right & in the end it will be gratifying.

Some more tips,
Used brake parts are now approching 20 years old & you may consider buying new what ever you can for the swap. I rebuilt the front calipers on my Jetta myself. It is not exactly easy, tedious work to get the dust seals seated in correctly. I also used mk3 front calipers with 16V scirocco carriers. MK3 calipers have the larger bleed screw & do not break off like the 7mm ones on the earlier cars. If you buy used front calipers make sure the bleeder opens before you buy them.
Rear calipers are noted for parking brake issues. Make sure the parking brake works & the bleed screw opens before you buy a used rear caliper.
Pedal assy, make sure the clutch tube is not cracked or broken off. & when removing from the parts car make sure you take off the retaining clip to the fire wall or you will be inside the car fighting it & most likely will break off the tube.
The later pedal assy will have the brake light switch mounted to it. So make sure you get the switch & wires. Cut off as much wire you can. Your old wires to the master cylinder switches can still be used & you will have to tape off one set.
NEVER reuse an old hose.
Bench bleed a master before you install it or you are wasting time & fluid. A completely empty brake systen is a real PITA to get fluid flowing & completely blead out.
You may also want to invest in a good flairing tool that does the bubble type flares. Metric hard lines are available from auto parts stores but are never the correct lenghts. Just cut them & re-flare the end.

I agree there is added unsprung weight with any brake up grade but the 16V scirocco setup will be the best performing for the weight. Those Girling dual piston G60 model calipers are 16 pounds each!! That will have adverse effects on an A1 suspension. I have a set with adapters & after realizing some things... NO WAY! If you are going with a manual proportioning valve like the Wilwood I would say go for the mk4 aluminum rear calipers, other wise you will not get them to work. The large piston diameter needs a master cylinder to match. I had a set I considered using at the time of build but after reading up on it it would have been too much hassle for the time I had to get it done. So I sold them.

Wheels, yes rule of thumb is 14's for 10.1 but there still are a few after market wheels in 14 that do not fit. BBS RA in 14in come to mind. I have the mk3 cabrio wheels on the Jetta, they are 45mm ET & fit. OK there is a slight rub mark on the strut housing from the tire flex but nothing to be at all worried about & I am running 195/60/14's.

well if you made it this far in the reading, sorry for the long post.

 

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