Late Braking News

Going From "Very Good" to "Ohmigawd!" With Wilwood's New C5 Superbrakes

Bob Wallace Aug 14, 2003 0 Comment(s)

When you have a product that performs very well in as-delivered form, logical people would very likely wonder, "Why mess with it?" Most enthusiasts are not logical. We tend to want more, bigger, faster, whether it's necessary or not.

There are plenty of times and plenty of justifications for upgrading OEM brake systems, even on Corvettes. Drum brake Vettes can benefit mightily from simply using contemporary brake linings within stock appearing drums. There are numerous options for enhancing '65-82 disc brakes--everything from stainless steel sleeves and better pad materials to serious improvements like the Force 10 system we installed on Loy McKenrick's "Size Matters" '72 coupe exactly two years ago. There were quite a few changes--all for the better--made to the factory brakes on C4s during their 13 year production run, and there is still room for enhancing the stopping power of the fours; just take a gander at the Baer installation in this issue for proof.

But does a C5 need its brakes upgraded? Does a bear, well, you know? Seriously, C5s have very good braking systems installed at the factory--the latest iteration PBR two-piston calipers and 12.6 x 1.26-inch vented rotors up front, with single piston units and 12.6 x 1.27-inch vented rotors at the aft end, and a Bosch four-wheel anti-lock system. It was excellent in 1997, and it's good enough six years later to be used on all C5s including the Z06. Magazine tests on "regular" C5s have garnered 60-0 stooping distances in the range of 116 to 125 feet (on the Goodyear Eagle EMTs, i.e. run-flats), and similar tests on Z06s, with their superb (non-run-flat) Goodyear SCs and otherwise, except for red powdercoat on calipers, identical brakes show stops from 60mph in 103 to 116 feet.

Yes, C5s stop very well in real world, everyday type situations. But subject them to severe usage, like lapping sessions during an open track event or a high-performance driving school, and you will experience brake fade. That's an unpleasant (and potentially ugly) circumstance when the brake components get too hot from repeated hard applications, and it takes more and more pedal effort to get less and less brake function, right up to that orifice-puckering moment that you press the brake pedal firmly and it sinks down to the floor--without slowing down you and your four-wheeled projectile one iota. No brakes is no fun!

But what about the 99-percent of Corvette owners who probably will never run a hot lap on a racetrack. If you're a driving enthusiast, you undoubtedly want to make that very good car even better, at least within reason and without compromising its usefulness, in whatever its main capacity might be. More power is always good. So's even better-than-stock handling, as long as you don't get the suspension too stiff or reduce the ride height to the point where you drag the bottom of the car creeping over speed bumps. As for bigger-than-factory brakes? Well, even if you'll never make use of a serious upgrade, grooved and/or drilled, oversize rotors and big racy-looking calipers look way cool. And a set of super brakes is definitely good to have, just in case...

Enter Wilwood Engineering, one of the best-known manufacturers of racing and ultra-high performance braking systems. Wilwood isn't the biggest aftermarket brake manufacturer around, but their products are definitely top notch. And they are not the first company to offer upgraded brake components for C5s. But, to the best of my knowledge, Wilwood is the first company to offer complete, integrated bolt-on systems for both the front and rear ends of C5s, systems that are engineered to be 100-percent compatible with the factory ABS, with the factory drum-style parking brakes, and to not even require a custom proportioning valve or a master cylinder change. The new Wilwood C5 brakes will fit all '97-03 spindles and hubs, and will work with any '00 and newer (five spoke "star" or Z06) O.E. wheel and the factory optional N73 magnesium wheels that were first offered in 1998. These systems (I'm using the plural form because the front and rear systems are sold separately) will NOT, however, fit the '97-99 flat five spoke O.E. wheels--and that's about the only "won't work" you'll find.

All primary engineering and testing was performed on a '99 C5 convertible belonging to a member of the Wilwood management team. Because of the, shall we say lukewarm, enthusiasm for the '97-99 factory wheels by a great many C5 owners, making the system fit those wheels was not a concern. Fitting the system within the space allotted by the much more attractive '00-04 wheels and, of course, the wider Z06 wheels, without spacers or modifying wheel offsets, was deemed mandatory. My pewter '00 coupe, shod with the original equipment, silver finish factory wheels was used as a guinea pig for the '00 and newer clearance testing, and the Wilwood engineering team also made use of a pair (one each, front and rear) of N73 factory mags that are destined to be part of the rolling stock for my "C5 Shark" LS1-powered '76. Multiple measuring sessions, and test fittings on both the Wilwood exec's '99 and my '00 coupe ensured that this bolt-on system does indeed truly bolt on.

Both the front and rear systems feature new Wilwood rotors, Wilwood calipers, PolyMatrix "Q" compound (non-asbestos/non-metallic "ceramic-enhanced" formula that's engineered for better than O.E. stopping power with low noise, long wear, low dust, high fade resistance, and quick recovery) pads, and braided stainless steel flex brake lines, plus all necessary mounting brackets and hardware.

The front system, PN 140-8031-D lists for $2,548.63 and features two-piece Superlite 6 billet six-piston calipers and two-piece rotors. The Superlite 6 calipers are CNC-machined from aluminum alloy billets, weigh just a hair over 5 pounds, and feature "differential bore" stainless steel pistons in two sizes (the four leading pistons in each caliper are 1.12-inch diameter, the two following pistons are 1.62-inch diameter) for improved heat resistance, better pedal response and pad wear, and optimal distribution of clamping forces. The bleed screws (two per caliper) and fluid transfer tube rest within machined recesses for maximum protection, and are available in any finish as long as it's high-luster black anodized. The iron front rotors measure 13.06 x 1.25 inches with curved vanes and are both drilled and slotted for maximum heat dissipation, and utilize black anodized, CNC-machined aluminum "hats." The mounting brackets are also black anodized, CNC-machined aluminum and bolt up to the stock spindle bosses with aircraft-spec, grade 8 hardware, which is supplied with the kit.

The rear system, PN 140-8032-D carries the exact same list price as the front, and comes with two-piece Superlite 4 four-piston calipers and two-piece rear rotors with correct configuration internal drums that work perfectly with the factory parking brake assemblies. (Editor's note: The rear calipers used in this installation are "DynaPro" with four pistons, but their function and fit are essentially identical to the production system's Superlite 4 calipers. All other aspects of both the front and rear systems are exactly what will be in the production systems.) The Superlite 4 calipers are very similar to the Superlite 6s used on the front except for their physical size, and the number and size of the pistons. All four of the stainless steel pistons measure in with diameters of 1.25-inches. The rear rotors are 12.90-inches x 1.00 inch and, like the front rotors, feature curved vanes and are slotted and drilled.

So, the Wilwood front and rear C5 systems are bigger than stock in essentially every respect other than the thickness of the rear rotors. They should look very impressive on a C5, even shrouded within a set of stock '00-and-newer wheels. All else remaining equal, the Wilwoods should be capable of stopping a C5 in a shorter distance than the car could with OEM brakes. The Wilwoods should be much more fade resistant than the stock brakes, even with the primarily-for-the-street, "Q" compound pads. Let's find out.

Tony Porto, who handles nearly all of Wilwood's prototype installations and tests, performed the installation in Wilwood's R&D center. The entire installation, from raising the C5 on a portable hoist to backing out of the building, took less than three hours, and it was indeed a straight bolt on job.

Whenever a caliper or brake line is changed--and we swapped all four calipers and the flexible lines connecting each of the calipers to the "hard" lines on the chassis--the brakes must be bled to remove any air bubbles or pockets form the system, and we learned something quite interesting from the engineers in the R&D department. On late model General Motors anti-lock brake systems, each brake (left-front, right-front, etc.) needs to be bled three times successively, first with the ignition in a key-off position, re-bled with the ignition key in the on position, and a final bleeding in key-off. It has something to do with the ABS circuits, and if the system is not bled in both key-off and key-on, it can retain air in the lines.

After completing the installation, including the bleed, re-bleed, and bleed 'em again procedure, I rode along with Tony as he headed out towards some nearby long, straight, and relatively untraveled back roads to "bed-in" the new brakes.

Anytime you refresh (new pad, re-surfaced rotors, etc.) the brakes on a car the new package needs a break-in period. Recommen-dations as to amount of miles and/or driving cycles before the new brakes are ready to be used and abused varies with each manufacturer, and often with the projected types of usage. In most racing and high-performance circles, the break-in process is referred to as bedding-in. Bedding in is most critical in racing applications, but it's much more critical in high-performance applications than for "normal" passenger cars. Bedding in is generally also a highly accelerated procedure. A normal passenger car system's break-in might call for 150-200-miles of mixed stop-and-go and highway driving, with hard stops or severe mountain-type driving, while a racing or ultra performance system may call for a series of progressively harder stops from fairly high speeds (60 or 70-100 mph) to bring the brake components up to their intended operating temperature range in one heat cycle, before being allowed to cool completely.

Tony began bedding in the C5's new brakes by driving at a moderate speed and lightly dragging the brakes to scuff the plating off the rotors' friction surfaces. Then he started accelerating harder, to higher speeds and braking harder, without locking up the brakes or activating the ABS, and without coming to a full stop. He progressively accelerated and braked harder during each cycle, without coming to a full stop. Tony told me, "You never come to a dead stop when bedding to prevent the pads and rotors from grabbing together." As we neared a dozen or so cycles, Tony made several very hard, full stops; hard enough to create heat-generated smoke off the front brakes that was visible from the cockpit (it also created quite a stink). Then he leisurely drove back to the Wilwood plant, allowing the very hot brakes to cool to the ambient air temperature. The last couple stops were very impressive, with the car pulling down from speed extremely quickly. From the shotgun position, it felt like the car was stopping much harder than before.

The old brakes were fairly fresh. The car appeared to have had a brake service just a few thousand miles before I bought it last October, and the stock brakes worked quite well. The run-flats looked more like recent replacements with a few thousand miles rather than 3-plus years old with close to 40,000 miles. This impression of relatively unsullied parts was confirmed a few days before the Wilwoods were installed, when Assistant Editor John and I took the coupe over to our favorite local industrial side street and ran a series of 60-0 stops, using my trusty old Tesla G-Tech Pro accelerometer to measure the minimum distance required to stop from 60. We utilized the ABS, by mashing down on the brake pedal as firmly and hard as possible, and holding it down through the normal ABS pulsations to a full stop, in every stop. We performed two rounds of three consecutive stops, with a couple minutes cool down time between the two rounds, and ran the rounds in opposite directions on the same street. According to the G-Tech, all six stops from 60 mph were accomplished in 122 feet, which is right in line with the published road test results on standard C5s in magazines like Motor Trend and Road & Track. While the stops were all in the same distance, in my purely subjective opinion, it seemed to take more effort or push on the pedal in each successive stop to accomplish maximum braking, and that brake fade was accompanied by a hot and stinky aroma wafting off the front discs.

We'd originally planned on doing three stages of tests for this article--totally stock, the Wilwood system with the stock tire and wheel package, and a final series of tests with a set of wider cross-section, serious ultra high performance tires, so we could see what difference tires would make in the equation. Unfortunately, the best-laid plans don't always work out, and as of this writing, the new wheels (18 x 9.5 and 18 x 10.5 HRE 549s) have yet to arrive. When they do, we're going to wrap 'em in 275 and 295/35 ZR-18 Yokohama AVS Sport radials and run that third round of deceleration tests.

Meanwhile, we can report that the Wilwoods work quite well. Even with the limitations imposed by the stock run-flats, the double-ought coupe pulled down a series of 60-0 stops ranging from 111 to a best of 109 feet. And it did so without any sensation of fade or the stench of overworked and overheating brakes.

The Wilwood front and rear systems are not for everyone. They look great and work at least as well as they look. On the downside, these systems are expensive--it's an instance of you do get what you pay for, and you are paying for a very advanced braking system that is a "de-tuned" racing system rather than a beefed up street setup. If you drive your C5 hard, are a serious autocrosser (and the rules allow), like to participate in open track events, or just have to have an ultimate set of binders on your Corvette, these brakes are an excellent choice.

(More Late Braking News: We were just informed by Wilwood Engineering that they will have already released the systems described in this article by the time you read this--and that by October they'll also have a new 14-inch bolt-on front rotor/caliper setup. It will require using 18-inch diameter front wheels. The good news is that this setup will allow fitment of most, if not all, popular 18-inchers, including the HRE 540-series line up. We are planning to try out the new brakes, along with a couple of the more aggressive brake pad compounds, after the new tire and wheel package is installed, and will have a follow up report in the December issue.)

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Here's the stock left-front brake. The lead photo shows Wilwood's PN 140-8031-D left-front brake assembly. Quite a contrast.

And just for comparison, here are the left-front Wilwood and OEM rotors and calipers.

Tony Porto performs just about all of the Wilwood R&D Department's installations and does much of the testing of new systems...

...After removing the right-front wheel, he loosens and removes the bolts holding the stock caliper and mounting bracket from the spindle.

The two "ears" on the spindle will be the attaching points for the Wilwood black anodized, CNC-machined caliper mounting bracket...

...which Tony then bolts in place.

Next, the right-front rotor is slipped onto the hub and held in position with a pair of lug nuts.

Tony then bolts the caliper for the right-front corner up to its mounting bracket.

After slipping the PolyMatrix "Q" compound pads into the rotors and affixing the pad retainer...

...Tony replaces the original rubber flexible brake line from chassis to the original caliper with a braided stainless steel line (part of the system) that runs to the new six-piston Superlite 6 billet caliper, then turns his attention to the right-rear corner.

Here is a graphic comparison of the stock C5 rear caliper and rotor and the Wilwood PN 140-8032-D two-piece caliper (with an integral drum to work with the OEM parking brake) and four-piston caliper.

The single piston rear caliper is held in position in a manner very similar to the front, with two bolts attaching the mounting bracket to ears on the rear upright and hub assembly. Off with the old...

This is the right-rear hub and parking brake assembly. There is an integral drum inside each rear rotor, and when the parking brake is actuated, the brake shoes are pushed tightly outward against the inside surface of the drum. Other than being considerably smaller and cable actuated, the brake functions very much like the drum brakes on '53-64 Vettes.

The black anodized part is Wilwood's right-side rear caliper mounting bracket.

The four-piston rear caliper slips over the two studs and is then bolted into place.

With the caliper snugged up in place, Tony slips a pair of the "Q" pads in place...

...and installs the retainer pin.

One of the final steps is to replace the rubber flex hose with another braided stainless steel line. The braided stainless lines are much stronger and more durable than the OEM rubber hoses, and are able to handle much great line pressures than can the rubber lines.

After torquing all of the nuts and bolts to the specified levels, Tony wraps up the installation by bleeding the brakes at all four corners. ABS-equipped late models (including all C5s) require a three step bleeding procedure, which is outlined in the text, in order to eliminate all possible air pockets or bubbles in the brake system.

And here is the completed right-rear brake installation. All that's left to do is "bed-in" the new rotors and pads, then savor the incredible stopping power this system offers.

In Wilwood's R&D shop and ready to start the installation. The shop hoist is fantastic--park the car wherever you want, then roll the hoist up to the side you want to life from, carefully line it up under the car, and lift. It is also very stable. I know I can't afford it, but I really want one!

Almost all the comforts of home. With all of the components for the front and rear brake systems laid-out on a nearby worktable, Tony Porto begins work with a necessary--get the wheel(s) out of the way.

Tightening the front pad retainer.

Fitting the new braided stainless steel line to the left-front Wilwood caliper.

Moving to the rear...here's another look, from beneath and behind, of the right-rear Wilwood caliper mounting bracket.

This is the left-rear, as Tony tightens it up to the mounting ears on the upright.

Here installer Tony Porto is removing the right-rear brake line retainer clip, prior to replacing the OEM rubber hose with its braided stainless steel counterpart. Note that Tony has suspended the old caliper securely with a wire coat hanger. This prevents possibly damaging the hose or caliper, even though the hose will never be reused and the caliper certainly will never be reinstalled on this particular car.

New aircraft-spec line fittings are required to adapt the braided lines. This is (again) the right-rear corner.

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