Bargain Basement Big Brakes

[wret]

Success! It took a couple of months start to finish but I finally succeeded in adapting 3000GT calipers to my Spyder. The first side took about 2 months. The 2nd side took 2 hours.

I had several goals when I started the project:
1. No wheel spacers.
2. Simple enough to be repeatable by others.
3. Affordable
4. and of course, functional.
Well, I think I got 3 out of 4. I had to space the wheels about 1mm. As it is, after the metals warm up I’ve got about enough clearance to slide a piece of paper between.

The parts for the swap:
1. Stealth TT calipers, 1992 (all four), ebay, $125 shipped
2. Audi A6 Rotors, ebay $179 shipped
3. Hardware, Mcmaster-Carr about $30
4. Adaptor plates, scrap ½ aluminum, cut by a friend, feebee.

One bonus was that the calipers arrived with usable pads and lines.

 

[DSMSpyder99]

Your Spyder gives me motavation to make mine just as bas ass as yours So those are the 4-piston calipers right

 

[ACKERSON]

Looks pretty sweet man. Would it be possible to get some dimensions and pics of those adapters?

 

[karbon]

This is great news. I'd like to see some brackets to fit larger rotors, however.

 

[ECTurboDSM]

Why Audi A6 rotors? Don't they have a 5x112 bolt pattern?

 

[wret]

Your Spyder gives me motavation to make mine just as bas ass as yours So those are the 4-piston calipers right

Yes, they are 4-piston calipers, and therein lies the biggest problem adapting them to a 2g DSM. One of my goals was to do the install without wheel spacers. I almost succeeded.

Looks pretty sweet man. Would it be possible to get some dimensions and pics of those adapters?

Sure thing. I’ll post the template. I need to make a couple modifications to the drawing I started with though. Or maybe I’ll just keep this little secret to myself and open a DSM brake adapter business. Just kidding.

This is great news. I'd like to see some brackets to fit larger rotors, however.

Same bracket with holes a little further out. Actually bigger is easier. The 2nd obstacle in making the 3000GT brake swap is that you need to use rotors that are considerably larger than stock. This is because the mounting ear positions overlap. I’ll explain more on this later.

Why Audi A6 rotors? Don't they have a 5x112 bolt pattern?

Information on brake rotors sizes is scarce. Typically people shop for rotors my vehicle model, not rotor dimension. There are a couple of brake manufactures that do list rotor dimension though incomplete; Brembo is one. The Audi A6 rotor has slightly more overall height, close to the same diameter, and the braking surface is 25mm compared to the 30mm 3000GT rotor.

The problem with 3000GT rotors is that they are basically the same height as stock DSM, though much thicker. I tried these first, but found that I would have to space the wheel out almost 10mm to fit over the caliper. I was not willing to do this.

Yes, bolt spacing is different and the center bore is slightly smaller. The bolt pattern fit is no problem because the Audi has larger studs. The center bore just fits too. The only snag was the hub flange. The Audi flange is smaller. I had to remove about 6mm of material from the diameter of my flanges. This was actually easier than I thought it would be. About 15 minutes with an angle grinder with the engine running in neutral does the trick.

I will follow up with some more specifics as I get time.

Edit: After almost 2 years running the Audi discs and having them resurfaced twice, I discovered that one side was not sitting flat. I had measured the inner diameter of the rotor very carefully, 134.8 mm, and sized the hubs the same or slightly less. Recently, while preparing new hubs for on the bench I a difficult time getting the rotor to seat properly. I rechecked all the dimensions and finally found that where the wall of the rotor hat met the hub mounting surface was not a clean angle. After beveling the edge of the hub, the rotor fit perfectly. It is also worth noting that the aftermarket hubs I used had a shoulder at the centering hub that prevented the rotor from seating. The original hubs did not have this shoulder. It was necessary to grind it down to 68mm to get the rotors to seat.

 

[wortdog]

Those of you with 1G's should note that the Audi rotor will probably not fit due to its extra height as it may hit the lower ball joint. Even the stock rotor comes close to the joint. I have not heard of anyone with a 1G getting the TT 4-pot setup to fit without spacers unless they use a wheel designed for large calipers(basically any wheel that fits a 3000GT VR4). My personal setup with Cobra 13.1" rotors and TT 4-pot calipers required at least a 3/4" spacer to get average wheels to fit, and there isn't much clearance with the lower ball joint.

 

[L2RTSiAWD]

I better see a tech article on this. Especially since I may do it also.

 

[wret]

They may fit a 1g. I'll double check but I think they are only about 2mm more height than stock. But you are right, wheel design is key. I also tried an A8 rotor of greater diameter and about the highest offset (height) of any available. The ball joint wasn't the problem. It rubbed the knuckle edges, and after smoothing them out a little, it rubbed the ABS sensor. I decided the A8 rotor was a lost cause at that point.

 

[wret]

I better see a tech article on this. Especially since I may do it also.

No prob. I'll answer questions and post some pics here, then move it over to an article.

 

[Bostedquest]

I better see a tech article on this. Especially since I may do it also.

I want to see the article for the wortdog set up...

 

[mavisky]

Awesome job, and to think I was all excited last month when I stepped up to the 2 piston brakes on my fwd although I'm assuming those would rub like a son-of-a-betch on my 16" wheels.

 

[karbon]

Yes, they are 4-piston calipers, and therein lies the biggest problem adapting them to a 2g DSM. One of my goals was to do the install without wheel spacers. I almost succeeded.

I take it the clearance issue was with the outside of the caliper. At least a few millimeters of material could be shaved off if need be though. I'm sure those letters, while looking cool, are at least a mm in height, correct?

Same bracket with holes a little further out. Actually bigger is easier. The 2nd obstacle in making the 3000GT brake swap is that you need to use rotors that are considerably larger than stock. This is because the mounting ear positions overlap. I’ll explain more on this later.

So the matter of adapting it for say, 12" calipers means you'd merely position the holes farther out on the bracket? Makes sense to me. As long as one has the rims to fit this it should work.
Will these brackets be able to be simply sawn and drilled from a 1/2" thick piece of aluminum from a template, or is there additional machining involved? This would be excellent news for those with only a jigsaw and drill to work with. I am awaiting the template with mouth watering.

 

[wret]

I take it the clearance issue was with the outside of the caliper. At least a few millimeters of material could be shaved off if need be though. I'm sure those letters, while looking cool, are at least a mm in height, correct?

I have seen calipers that have been shaved. Without knowing exactly how thick the sides are, this was not something I wanted to play around with. And mine are the Stealth TT calipers. The lettering is stenciled high-temp white spray paint.

So the matter of adapting it for say, 12" calipers means you'd merely position the holes farther out on the bracket? Makes sense to me. As long as one has the rims to fit this it should work.

The A6 rotors are about 12.25 inches. You cannot practically go any smaller do to the mounting ear overlap. It would be much easier to go bigger if you can find the rotors. Custom or 2-piece rotors are also an option. I should say some thanks to Todd TCE who gave me some advice and a quote on a 2-piece rotor. After seeing the price, I told him I didn't need a whole set. To be fair, his prices are competitive but did not fit my idea of big brakes for the masses.

Will these brackets be able to be simply sawn and drilled from a 1/2" thick piece of aluminum from a template, or is there additional machining involved? This would be excellent news for those with only a jigsaw and drill to work with. I am awaiting the template with mouth watering.

The adapter plate is cut with straight perpendicular cuts and holes. With enough time and motivation, one could probably do it with a hack saw. I gave up after about half an hour though and took mine to a local metal shop. This wasn't exactly free, I still owe him pizza.

The holes are half inch straight though with a $40 Harbor Freight drill press.

 

[wortdog]

I want to see the article for the wortdog set up...

I'll start working on an article soon, I have an engineering drawing for my specific setup that I'll probably include.

 

[Bostedquest]

I'll start working on an article soon, I have an engineering drawing for my specific setup that I'll probably include.

I always thought that the cobra 97-up brakes would work...
just the bugger would be the caliper bracket...

 

[Todd TCE]

A few comments (I hope constructive);

The larger bore calipers here coming from the TT are taken off a car with a 1 1/16MC application. The 1G has either a 15/16 or 1.0 if I recall. I'd highly suggest you look into the fit of the larger MC if you can. At least use the 1.0 model. The smaller unit will have a very soft pedal feel and long travel.

The four pots offer about 4.2sq" of piston area and is nearly the same as that of the 2G (both single and twin pot) of 4.4sq". Either of these will push bias towards the front to about 84% depending upon pads. Stock is about 75 from my spread sheet.

The next step is to increase the rear using the same twin pot off the TT if you can. This on the stock rotor alone will push that % back down to 77%. And if you run it on say a 11.75 rotor you'd be at 72% or so. This would be a very 'bitchin' set up. And affordable using the TT parts. You may however require CORES to return (of course they don't know a four pot from a single one....)

FYI; the 2G rear might work as well to about 75% on the 11.75. You might get lucky and find one of them can use an adapter like the front with some working on it.

The two piece rotor package is nice but the value of it at $500 is hard to justify if you are after a budget package. Fully understand. So far this one looks promising.

 

[wret]

The next step is to increase the rear using the same twin pot off the TT if you can.

The TT rears that I got with the package are only one pot.

Good info, Todd, I'll take it under advisement. I wouldn't exactly call the current pedal feel "soft." It feels about the same but with a huge grab at the end.

My bracket template is a little worse for wear but I made a quick drawing. Duplicate on 5 sq per inch graph paper. Tolerances should be plus or minus 1mm.

-The bottom set of dots represents the center spacing of the mounting ears on the knuckle. The spacing is 128mm or about 5.05 inches.

-The higher set of dots represents the mounting position of the 4-pot caliper with a spacing of 159mm or 6.25 inches. This set of dots should be 11mm or 0.6 inches higher than the first set for a 12.28 inch rotor. To use a larger rotor just add the difference in radius to this offset.

-The circles around the points represent the size of the holes (0.5 inches) and then the approximate area taken by the surface of the mounting ears. The overlap is in red. It is necessary to grind off the material from the mounting ears here.

-The bracket can be cut from half inch or thicker aluminum or steel. Slightly thicker is okay and will not effect the fit.

-I did not get the holes exactly right the first time so my top set of holes ended up as slots. This actually makes fitment easier but the obvious concern is that the caliper may slide upward. The current drawing is based on my estimate of the final position I ended up with.

-The shaded area at the top is excess material and may be removed.

Hardware from McMaster-Carr:
4 M12 x 1.75 60mm high strength bolts
4 M12 x 1.75 50mm serrated flange head bolts
8 M12 nuts
4 M12 flange nuts
Lock washers
0.5” ID 1” OD spacer washers

Description of rotors:
Application

2 Front Rotors (left and right)

2002-2004 Audi A4 (V6)
2002-2004 Audi A4 Quattro (V6)
1998-2001 Audi A6 (16/17" wheels)
2002-2003 Audi A6
1998-2001 Audi A6 Quattro (2.8 V6, 16/17" wheels)
2002-2003 Audi A6 Quattro (3.0 V6)
1998-1999 Audi A8
1997-1999 Audi A8 Quattro


*these rotors are 312mm in diameter (12.28"). Because people often change wheel sizes on cars, please measure your the rotors on your car to confirm these are the right parts before ordering.

Edit: I changed some lines on this drawing to leave more material. If you want to use it for a template, see the revised drawing later in this thread.

 

[wret]

Here's a picture that shows the orientation of the bracket and mounting ears. You can see where the ears interfere with each other and must be trimmed.

 

[Todd TCE]

Couple more thoughts and I'll bow out. Promise.

First; single pot or twin pot for the rear- doesn't matter. 1.5" floater is the same as opposed with regard to area. Long story, trust me.

Second; if you want help with this in cleaning it up some, why don't you give me a call. I have about half the info you need for this and you a few more bits that I'd need to help you make this a reality. You'll need a supplier of sorts if you want to move it. I'm reasonably qualified.

 

[wortdog]

Thanks for the musings Todd, I know that I need to upgrade the rears at some point, the biggest problem I've been having is finding a caliper I like with a cable actuated parking brake. It definately has too much front bias with Porterfield R4-S pads on the front and whatever came on the car in the rear.

The pedal travel is a hair softer and longer, but not alarmingly so. It does bother me enough that I've already looked into the 1 1/16 MC from the 3/S TT application. It is a direct bolt up except for one problem. One of the brake lines comes into the MC from the side(where the fender is) instead of the top like a 1G/2G and requires some clearancing of the fender along with a section of new line.

As far as the TT brakes go, there are 1G TT and 2G TT brakes. 1G TT front calipers are identical to the 2G fronts except for having longer mounting tabs to accept larger rotors. The rear calipers are quite different, with the 2G getting a nice 2 piston rigid rear caliper while the 1G got a single piston floating caliper. Both calipers have the same effective clamping force though.

 

[wret]

This picture shows the difference in size between stock and the 3000GT rotor. I didn't end up using this rotor because of the offset and thickness issues but the audi rotor is the same diameter.

 

[wret]

This is what my brackets looked like. The uneven shape was intended to leave material for a set of holes even further out, in case I later decided to try 13" rotors, I would only have to Drill out a couple of new holes. As it turned out, my calculations were off and the first set of holes were about right for 13" and I had to "slot" them inward for the 12.28" rotors. The revised template pictured above should be much closer than my original.

The reason I selected serrated head flange bolts is that they dig into the aluminum and are unlikely to shift when torqued to about 90 ft. lbs. High strength bolts were selected to mount the adapter plate to the original mounting ears separated by a very nice flanged nut to support the plate in a perpendicular position.

 

[wortdog]

Here's a link to the tech article I just posted describing my setup, hopefully someone will find it useful:

http://www.dsmtuners.com/forums/showthread.php?t=185350

 

[wret]

Nice article Eric. I have a couple of questions:

$20 for a 13 inch rotor? Is that a typo?

The holes in your adaptor plate are not on parallel lines (or concentric circles, actually). With my setup I found that they must be parallel for proper orientation of the caliper. Can you comment on this?