Project Y2k: New Stopping Power for Our C5 Corvette from DBA USA

dbaleadOur mission statement for Project Y2k, our 2000 Chevrolet Corvette, was to create a “blue collar supercar” – a competent all-around performance vehicle that excels at a wide range of different things, from the dragstrip to the autocross to Main Street on a Saturday night. We’ve already added a lot more horsepower and tightened up the handling, so it was high time to upgrade our Corvette’s stopping power to match.

Bang For The Buck

There are a lot of different ways you can go when doing a brake upgrade on a C5 Corvette, from relatively modest like a pad change up to full-race 6-piston calipers, and everything in between. Keeping our theme in mind, we wanted to retain our existing factory wheels (larger-diameter wheels and tires are one potential budget buster when contemplating a brake upgrade) and only swap out the “consumable” parts of the brake system; the pads and rotors.

y2kThe great thing about this strategy for an older “modern” Corvette is that these are the parts that are quite possibly in need of replacement anyway, having reached the service limits of the stock components. If your Vette needs a brake job, it’s easy to justify stepping up to aftermarket high performance pads and rotors while you’re at it, because the incremental additional price isn’t so bad.

To achieve our goals, we called up DBA USA, the American arm of Disc Brakes Australia, and had National Sales & Marketing Manager Yoni Kellman help us figure out what we needed. DBA specializes in replacement rotors designed to work with stock calipers, and to make things easy, DBA USA also acts as a distributor for Hawk and Carbotech pads, making them a one-stop shop for our project.

Our Corvette came factory equipped with sliding brake calipers (two piston in front, single piston out back) and vented solid discs.

Our Corvette came factory equipped with sliding brake calipers (two piston in front, single piston out back) and vented solid discs. And yes, the Plasti-Dip on the wheels needs to be touched up…

Where Do We Begin To Stop?

The first order of business was getting educated about DBA’s wide range of different choices for our application. Their product line covers an astonishing array of different vehicles, and in most cases there will be multiple designs for any given car or truck.

“Here in the US, we offer Street Series, 4000 Series, 5000 Series, and Survival Series rotors,” Kellman explains. “Street is basically an OE replacement equivalent rotor with an improved look, thanks to the slotting or drilling. It does incorporate our Kangaroo Paw cooling though, so there is a performance benefit from that. The 4000 and 5000 Series share all of the same main features, with the only difference being a one or two piece rotor, respectively. They all have Kangaroo Paw ventilation, Thermal Stability Profiling heat treatment, XG-150 High Carbon material, Thermo-graphic Temperature Monitoring heat-changing paint, Cubic Boron Nitride precision ground surfaces, and our T3 slotting or XS drilled and slotted combination.”

Kangaroo Paw Ventilation

Conventional ventilated rotors use one of two designs – straight vanes that offer the advantage of being ‘non-directional,’ allowing one part number to work on either side of the vehicle, or curved vanes that carry a theoretical edge in pumping efficiency while moving cooling air from the hub to the outer edge at the expense of only working properly when spinning in one direction.

Most aftermarket rotors are of the curved-vane variety, which leads to a design compromise when they’re slotted. In order to keep the slots from lining up with the internally-swept vanes, thus causing weak spots, these rotors have slots going the “wrong” way; when spinning, the slots sweep any debris or water towards the center of the hub, fighting centrifugal force, rather than to the outer edge and away from the friction surface.

DBA’s Kangaroo Paw internal casting structure is fundamentally different than conventional vanes. The 144 diamond and teardrop shaped “pillars” offer a claimed 20% improvement in cooling efficiency, aren’t directional so that a single part number can be used on either side, and provide better, more evenly distributed support to the rotor face.

“Survival Series is what we call any truck application,” Kellman adds. “It is available in Street or 4000 versions and has all the same options as the corresponding car applications.”

Street Series Options:

  • T2 – Slotted Only
  • X Gold – Drilled/Slotted

4000 Series Options:

  • T3 – Slotted Only
  • XS – Drilled/Slotted

5000 Series Options:

  • T3 – Slotted Only
  • XS – Drilled/Slotted

This Is Not A Drill

With rotors available in both slotted and drilled/slotted versions, we were inspired to ask what the real differences were. Per Kellman, “For most drivers, a slotted or a drilled rotor will be fine for their use, and to most people a drilled rotor says ‘racing’ to them. So, people have grown accustomed to the drilled look and many like it. We offer our drilled and slotted versions for those people.”

“But when it comes to a race application, slotting is the way to go,” Kellman admits. “There are far fewer issues with cracking when the rotor isn’t drilled. Basically, as time has gone on, we’ve learned that drilling was the right idea back in the day, but slotting accomplishes the same tasks and more, with fewer drawbacks.”

Too Much Of A Good Thing?

For our Corvette, there was no question that we wanted DBA’s top of the line rotors. But we did ask whether or not it was possible to put “too much rotor” on a car – say, a sedan that’s driven exclusively on the street, for example.

“Not really, no,” says Kellman. “As long as the rotor fits the car properly, there is no downside to using any rotor in our lineup. The 4000 Series offers a heat treating process that will increase longevity, so that is a good investment no matter what the use is. But if you want to use a 5000 Series two-piece rotor for daily commuting, there is no downside to doing that.”

DBA's 5000 series discs use a two piece design that mounts the rotors on a lightweight aluminum 'hat.' One of the big advantages of this design is that when the disc surface is worn beyond spec, it can be replaced with a new one instead of scrapping the entire thing.

DBA’s 5000 Series discs use a two-piece design that mounts the rotors on a lightweight aluminum hat. One of the big advantages of this design is that when the disc surface is worn beyond spec, it can be replaced with a new one instead of scrapping the entire thing.

Making Our Selection

Armed with the information Kellman provided, we were ready to order up our parts. For the front of the Corvette, we selected T3 5000 Series two-piece rotors with black center hats (PN DBA52994BLKS, street price $320 each), while out back we chose T3 4000 Series one-piece rotors (PN DBA42995S, street price $119 each).

Proper friction material selection is critical to braking performance. We're using Hawk HP Plus pads, which are designed for a mix of street and track use.

Proper friction material selection is critical to braking performance. We’re using Hawk HP Plus pads, which are designed for a mix of street and track use.

To match, we added Hawk Performance HP Plus compound pads (PN HB247N.575 front, $122, and HB248N.650 rear, $99) which are designed for track day and autocross use while still providing excellent street performance. We’ve used Hawk pads with this friction material before with good results – the only caveat is that they are definitely “dirty” compared to street-only ceramic pads, producing a fair amount of brake dust.

With everything we needed in hand, we began the installation process. One of the nice things about a pad and rotor upgrade is that it’s far simpler than installing aftermarket calipers, with no bleeding of the system required. We did consult with Kellman before diving in, though – he had some very useful tips.

“Believe it or not, the installation is really the most common cause of issue that we come across,” he explains. “This can be broken down into two separate issues. First, there is improper bedding of pads. This one is more common than it should be. Without properly breaking the pads and rotors in, you can get inconsistent pad transfer that causes a layer of uneven material on the rotor face. This creates a pulsing that many will attribute to a warped rotor. The truth is that due to the strength of our Kangaroo Paw internal vaning and our manufacturing processes, a warped rotor is very difficult to achieve.”

DBA's rotors feature thermo-graphic paint markings that permanently change color once the metal reaches a certain temperature.

DBA’s rotors feature thermo-graphic paint markings that permanently change color once the metal reaches a certain temperature. At 856 degrees F, the green mark will change to white, at 1022F the orange will turn pale yellow, and at 1166F the red will turn white. ‘The common misconception is that they change back,’ explains Kellman. ‘They don’t. Once they have reached a certain temperature, the color changes and they stay that way. The best use of this is to monitor the heat being transferred into your rotors to select the best pad for your use, since all pads have a sweet spot that they work best in. You can also use this to decide if ducts are necessary in sport or race applications.’

Kellman continues, “Second, there’s runout when installing, leading to disc thickness variation. This can be caused by a number of things, like a dirty hub face, a bad wheel bearing, a bent or warped hub, or an over-torqued wheel. What happens here is that due to something other than the rotor, it isn’t sitting ‘true’ and there is runout.  This isn’t usually noticeable right away, but as the rotor begins to wear, the ‘higher’ spots wear more than the ‘lower’ spots, causing the rotor surface to be thinner in some areas than others.  This leads to pedal pulsation, which again suggests a warped rotor, but it really isn’t; it’s just got a high level of disc thickness variation.”

Out With The Old, In With The New

The actual process of replacing the stock rotors and pads is straightforward – the new DBA discs go on just like factory replacements would, with attention paid to cleaning the hub faces, as Kellman suggests, and a good wipedown of the swept areas of the discs with brake cleaner to remove all traces of oil or grease.

The Corvette's stock brakes, though not as 'racy' as opposed piston caliper aftermarket pieces, still show competition heritage. It's very easy to pull the caliper and swap pads.

The Corvette’s stock brakes, though not as ‘racy’ as opposed-piston aftermarket pieces, still show competition heritage. It’s very easy to pull the caliper and swap pads. Look closely and you can see how the internal vanes have a curve to them to help actively pump air through the center of the disc.

 

Here, you can see a stock front rotor (left) compared to the new DBA disc.

Here, you can see a stock front rotor (left) compared to the new DBA disc.

 

New front rotors and pads installed - time to move on to the rears!

New front rotors and pads installed – time to move on to the rears!

In back, the brakes incorporate a separate drum-type parking brake assembly. The DBA rotors are designed to accommodate this mechanism as well.

In back, the brakes incorporate a separate drum-type parking brake assembly. The DBA rotors are designed to accommodate this mechanism as well.

A piston press is an indispensable tool when doing a brake job.

A piston press is an indispensable tool when doing a brake job.

And just like that, the brakes are done.

And just like that, the brakes are done.

When changing pads, it’s a good idea to do a cleanup pass.  – Yoni Kellman, DBA USA

It’s important to remember that just like the pads, the discs themselves are a consumable component that won’t last forever. Our fronts, which will do the majority of the work, have the advantage of replaceable rings. “The two-piece 5000 Series rotors don’t need any special maintenance, but they do need a special level of care when replacing the rings,” says Kellman. “There is a process to mounting the rings to the hats, and runout must be measured and within spec.”

As for other other brake maintenance, Kellman adds, “All of our rotors can be machined, though we recommend grinding, not cutting. But when that isn’t possible, slow cuts are best. We etch a minimum thickness into the edge of each rotor for just this purpose. There are a few reasons to machine a rotor – primarily if the bed-in process wasn’t done correctly, you can ‘start over’ by doing a quick clean-up machining. Also, when changing pads, it’s a good idea to do a cleanup pass.”

The Results

To test our results, we started off getting baseline stopping performance data with our Racelogic PerformanceBox, a GPS-based recording device that’s widely used by racing competitors as well as media types like us. We performed a series of 60-0 MPH full-ABS stops on the factory brakes, then attempted to beat them with careful threshold braking, short of invoking the antilock brakes.

We weren’t going to beat the computer when it came to short stops, because the ABS allowed us to have maximum braking effort applied almost instantly…

What we discovered was twofold – first, we weren’t going to beat the computer when it came to short stops, because the ABS allowed us to have maximum braking effort applied almost instantly, instead of trying to manually modulate it just shy of ABS activation. That meant that the anti-lock system allowed the brakes to do more work when it was needed the most, right at 60 miles per hour. We might have been able to generate better no-ABS numbers if we’d started braking at, say, 75 miles per hour and gotten things settled before we slowed to 60, but that would be cheating just to say we beat the system.

The second discovery was the subjective feeling of just how hard the ABS was working in full-panic stops. Even on the smooth, consistent pavement we were using for our test, the Corvette felt like a dog trying to stand in the back of an uncarpeted van, shifting its footing from one corner of the car to the other as the antilock brake system fought for balance. Each stop was accompanied by a quadraphonic soundtrack of brief chirps as the tires alternately slipped and gripped.

DBA brake comparisonAfter swapping the rotors and pads, and following Hawk’s recommended break-in procedure, we tested again on the same stretch of pavement, using the same methodology. By the numbers, we saw a measurable improvement in both average stopping time and distance – just under two feet and five hundredths of a second, respectively. More importantly, the “wobbly dog” feeling was greatly diminished, with our Corvette stopping with noticeably less drama. The combination of pads and rotors is far more confidence-inspiring than stock, letting us brake later going into corners without worrying that the car will still be trying to find its footing as we come off the brakes and turn in.

It also made modulation short of ABS activation easier, with better pedal feel and initial bite. Overall, we are very pleased with the improvement in braking performance, with the real limiting factor now being our tires. Since Project Y2k is part of our long-term fleet, we’ll keep you informed as to how well our new brake combo handles daily driver, autocross, and track use.

Also, did we mention they look way cool...

Also, did we mention they look way cool?

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About the author

Paul Huizenga

After some close calls on the street in his late teens and early twenties, Paul Huizenga discovered organized drag racing and never looked back, becoming a SFI-Certified tech inspector and avid bracket racer. Formerly the editor of OverRev and Race Pages magazines, Huizenga set out on his own in 2009 to become a freelance writer and editor.
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