1993 Pontiac Firebird Brake, Wheel & Tire Install - Road Race Ready!

When it comes to road racing,...        read full caption When it comes to road racing, this is the good stuff: Kumho V700 Victoracer DOT competition tires, Performance Friction carbon metallic race pads, and Performance Wheel Outlet 280 Motorsport wheels.

For a classy touch, we contacted...        read full caption For a classy touch, we contacted MBA Products and had them design some anodized billet wheel centers to match our PWO wheels. We used double-sided adhesive to attach them to the plastic centers provided by PWO.

We started out with machined,...        read full caption We started out with machined, bare unfinished wheels from PWO. Although the 280 Motorsport is available from PWO in silver powdercoat and polished aluminum, we had a more sinister look in mind. For this, we grabbed a few cans of high-temp barbecue grill paint, some high-temp clearcoat, and a gallon of thinner for $13.29.

Our skidpad results, which...        read full caption Our skidpad results, which reflect more on suspension and tire compound than brakes, revealed a tremendous increase in lateral g-force: we yanked down .94 g clockwise and .95 g counter clockwise! The big improvement came directly from the Kumho Victoracer DOT competition tires. Even more remarkable was the fact that these were full-tread, unshaved tires. We think a shaved, professionally heat-cycled set could push the lateral g mark even higher.

Don't be fooled by the "R"...        read full caption Don't be fooled by the "R" on the Kumho sticker. All Victoracer tire carcasses are built from a right-hand mold according to Kumho's David Hudrlick. The earlier rotation-specific internal splice has been changed to a uni-direction internal splice. The exterior molds and decals were never changed for cost reasons. The savings is passed on to us!

To install the Performance...        read full caption To install the Performance Friction 99 Compound carbon metallic pads on our Baer GT-P PBR calipers, we used a 15mm socket to remove the lower caliper bolt.

Just swing the caliper away...        read full caption Just swing the caliper away (leaving the upper caliper bolt in place), open up the pistons with a clamp or brake tool, and slip the pads on. Swing the caliper back over and put the caliper bolt back in.

We used this nifty brake clamp...        read full caption We used this nifty brake clamp tool to open the calipers on the front and rear--it's much easier to use than a c-clamp (stock rear caliper shown). This is a great time saver if you plan on swapping pads trackside between sessions.

For the rear, you'll need...        read full caption For the rear, you'll need to remove the top caliper bolt using a 15mm socket and a 17mm box wrench. Open the caliper, slip the pads in (pay close attention to the inside and outside pads--they're different), and replace the caliper bolt. Changing the pads front and rear takes only a half hour and can be done either at home before heading to the track, or done at the track between sessions.

With hub temperature in the...        read full caption With hub temperature in the center of the wheel approaching or exceeding 500*F under hard and continuous braking, and with 1000*F brake dust being ejected from the pad/rotor interface and fusing with the wheel surface, we needed a durable finish that would hide the carnage. Before painting, we used the thinner solvent to clean the PWO wheels of metal shaving, dirt and light machine oil.

At Englishtown, our braking...        read full caption At Englishtown, our braking tests showed remarkable improvement over our street-going rubber and stock pads. The combination of Kumho race rubber and Performance Friction race pads brough our average 70-0 braking distance down to 129.2 feet, and our 100-0 braking distance down to 273 feet (average of 5 consecutive stops).

From the outset, we have always intended for project car Operation Thunderchicken to be a triple-threat performer. The goal was to produce equally stellar results on the street, at the drags and on the road course. We've managed to do pretty well so far. On the street, we've managed a miserly 24 mpg on the highway at 80 mph with our MTI-prepared 396 LT1. Road manners are also quite nice thanks to firm--but not abusive--springs from Kenny Brown Performance. A complete Kenny Brown suspension and Street Cage have stiffened up our 7-year-old chassis to the point of feeling new again and the Street Cage even allows passengers to ride comfortably in the rear seat without the threat of brain concussion.

At the drags, we have also met our lofty goal of running 11s (11.94/117), repleat with a road-race tuned suspension and DOT-legal Mickey Thompson ET Streets. Did we mention that we did this with 92 octane pump gas through a cat-back Borla exhaust with the original single factory catalytic converter in place?

The road course, however, is a tricky measure to judge. Last fall when we attended the Kenny Brown/TrackTime driving school in Watkins Glen, Thunderchicken was among the quickest F-cars on the track, but there were a lot of Mustangs, Porches and Vipers that were faster. This state of affairs is not going to be acceptable for our return to the Kenny Brown/TrackTime driving school at Watkins Glen this October.

One thing we noticed last year is that the faster cars all had at least DOT-legal race tires and carbon metallic race brake pads. While our GM Performance Parts Durastop pads and rotors were great on the street, they really faded quick on the high-speed road course. The Goodyear F1 Steel radials were also fine for spirited driving on the road, but failed to satisfactorily hold the large girth of our '93 Firebird (some 3,675 lbs.) to the racing surface under high-g, high-speed turns. The combination of fading brakes and slippery tires meant that we were using way too much compression braking (using the engine to slow the car) in approaching a corner, and using the throttle too much to "dirt track" our way around corners. This might be fun for a short time, but it sure isn't the fast way around the track.

Plan Of Action
Clearly, there is a lot of potential improvement to be found in minor tweaking of the suspension and tire pressure, not to mention driving ability. This, however, results only from experience over time. As a long-term project car, we hope to hone our skills in this area incrementally with each track outing. But for our impending return to the high-speed circuit of Watkins Glen, we want a quick fix that will make up for our lack of tuning finesse and driving talent. To even the playing field, we decided to upgrade with the aforementioned tires, brake pads and wheels, but the selection of each item would have to take into consideration our specific needs. Your own needs may vary by budget, by usage or by sanctioning body rules.

Tires
The most glaring deficiency (other than a lack of driving skill) was in the grip department. We needed a stickier tire and we needed it yesterday. There are quite a few excellent DOT-legal road race and autocross tires out there, among them offerings from BF Goodrich (Comp T/A G-Force R1/A), Yokohama (A008RS II and A032R), Hoosier (R3S03), Pirelli (P-Zero C), and Kumho (V700 Victoracer). Out of these candidates, we were more interested in those with a hardcore slant towards competition useage, namely the G-Force R1, the Yokohama 008RSII, and the Kumho V700. The Hoosier was excluded because it's a DOT tire in name only and should not be used on the street under any circumstances. The Yokohama A032R, and the Pirelli were excluded next because they are closer to street tires and would give up some grip on a dry road course.

Which tire to choose? For help, we turned to The Tire Rack's website (www.tirerack.com) for some inspiration. It should be noted that The Tire Rack is exceptionally active in amateur road racing and autocrossing and their body of technical expertise is reflected in not only their website, but in their level of amateur racing sponsorship and their full-time staff of technical advisors. We quickly found that not only was the Kumho Victoracer V700 the most reasonably priced competition tire on the market (at $150 each, by a fair margin too), but that users of the tire have commented that it is exceptionally consistent from lap to lap and communicates its disposition to the driver quite well. One tire, the Comp T/A R1, actually grips better, but exhibits quirky behavior on corner exit in some vehicles. Considering our rank amateur skills, the R1 would not be a good starting tire for such a high-speed course. With little information available on the Yokohama, we elected to go with the Kumho Victoracer. One downside that was noted about the Kumho is that it exhibits an accelerated rate of wear on the outer edges of the front tires, a fact that was later confirmed after a few laps around our 200-foot skidpad. At some point, we would like to test the A008RSII which is also available in our 275/40R17 size, but that will have to wait until next season.

Brake Pads
In the November 2000 issue of GMHTP ("Whoa, Back!"), you may recall we upgraded our stock-sized GMPP Durastop front brakes to the Baer Racing GT-P offerings. These feature two-piece 13.15-inch vented rotors and dual-piston C5 Corvette calipers from PBR. They are in fact the largest brakes that will fit inside our beautiful 17x9.5-inch Fikse street wheels. The Baer units come with stock C5 Corvette pads from PBR and are much improved over our previous pads (see the braking results in the accompanying sidebar). And at just $1,435, the complete front kit is a down-right steal. The stock Corvette pads in the GT-P kit, however, are much too tame for our planned high-speed activity.

Fortunately, Performance Friction manufactures a carbon metallic race pad for the C5--a pad we've already had the luxury of sampling on a brand new ZR1 at the Mid-Ohio road course earlier this year. In order to slow our heavy F-car down from 140 mph repeatedly with minimal fade, we need the most aggressive race pad available, namely PF's 99 compound on the front and the 90 compound for the stock rear brakes. These pads aren't cheap as far as normal replacements go (see "Shopping Cart" sidebar, page 59), but the material is specialized for competition. The carbon metallic PF pad is a no-compromise material that bites the rotor like a pit bull with a cattle prod up its ass. As the carbon in the pad embeds itself into the surface of the rotor during the rotor seasoning process, a nearly perfect friction surface is achieved. Pad and rotor life are reduced (as is your cockpit peace and quiet), so these pads should be popped in only for racing--a street-type will be just fine for the rest of the time in the interest of rotor and pad life.

Speaking of street-type pads, Performance Friction also produces a Z-rated street pad (front, part No. 0731.10, $120.27; rear, part No. 0413.10, $67.75) designed for modest dust production and reduced noise. Stopping distance is improved over the factory PBR pad due to a more aggressive friction compound. We look forward to testing the Z-Rated pad alongside the 99 Compound race pad and the stock PBR pad sometime after the Spring thaw. These pads may turn out to be the best choice for lower speed road courses and autocrosses--we'll let you know in an upcoming test.

Wheels
We certainly can't fault the performance of our 17x9.5-inch Fikse FM/5 wheels, but it is a physical impossibility for two tires to occupy the same rim. Since swapping the Goodyears for the Kumhos onto the Fikses (and then back again) would be an unmitigated hassle, we decided to get a second set of rims for the express purpose of road racing and autocrossing. To that end, we contacted Performance Wheel Outlet. PWO not only sells wheels, they manufacture them too. Even better, they build almost exclusively for domestic cars, which means not having to wade through piles of undersized ricer wheels to get what you want.

A look at PWO's ad (and their website) reveals that most of their offerings are OEM look-alikes. PWO carries the normal stuff like SS/ZR1-style wheels for 4th gens, IROC-style wheels for the older 3rd gens, and they also do the Mustang thing with Pony rims and the Cobra R rims. Their latest GM offerings are the C5 and C5 Y2K five-spokes which also happen to fit 4th-gen F-bodies as well as Corvettes. But we weren't looking for the same cookie-cutter stuff found on other cars. Instead, we dug a little deeper into the PWO bin thanks to PWO's head machinist and tech-guru Frank Mawyer.

We expressed to Frank several criteria, specifically that the wheels fit our 5 on 43/4-inch bolt pattern, that they have the appropriate offset to fit our LT1 Firebird, that they be able to safely take a 275/40R17 tire without rubbing the brake system, suspension or bodywork, and that they be sufficiently eye-catching to turn some heads. We further piled on the consideration that (unlike the Fikse wheels) they be affordable for the average bear.

As it so happened, Frank had just finished work on an F-car adaptation of their 1995 Cobra R-style wheel. In case you've been living under a rock for the last five years, this 5-spoke wheel style is all the rage with the Mustang crowd--you can't swing a dead cat in the parking lot of a Beastie Boys concert without hitting one. As it turns out, the PWO-designed casting--called the 280 Milan--has a large enough wheel pad to accommodate the bolt circle and offset of a 4th gen F-car (something the actual Ford Cobra R item can't claim). This wheel is a 17x9-inch casting and easily accepts our 275/40R17 Kumho tires and 13.15-inch Baer rotors and C5 calipers.

PWO also offers another design based on the 280 Milan. They start with a 280 Milan and machine a total of 20 scallops into the rim. This wheel--called the 280 Motorsport--is a tad lighter than the 280 Milan and looks fabulous when mounted on a Firebird or Camaro. From the moment we trial fit the 280 Motorsport to Thunderchicken, we knew we had something that looked bitchin' that nobody else had! The icing on the cake was that the 280 Motorsport is only $150 each in unfinished form (machined, but not painted or polished).

We elected to go with an unfinished wheel because we knew that brake dust was going to be prodigious and unsightly. (We would recommend, however, that permanent street-going wheels be ordered in silver powdercoat for $10 more each.) To finish our wheels, we chose to spray paint them with high-temp flat black barbeque grill paint. We then followed up with a high-temp clearcoat. This finish was designed to hide brake dust and to withstand extremely high temperature without discoloring. When we mounted the finished product on Thunderchicken, we were blown over by the sinister look.

As if this weren't enough, Frank informed us that a 17x10.5-inch version of the 280 Milan and 280 Motorsport will be available by the time you read this. This wider rear wheel will be available in a GM 5 by 43/4-inch bolt pattern and offset, and will take a tire as wide as 315/35R17! Frank says the price should only be a few bucks more that the 9-inch wheel. If we can possibly get our hands on a pair of these for the rear, we will. (Kumho makes the V700 in a 315/35R17 also!)

The finishing touch came from MBA--custom Firebird centercaps made from engraved black anodized aluminum billet. We mounted the 23/8-inch by 1/8-inch thick caps on the generic plastic centercaps provided by PWO by means of double-sided adhesive. The MBA caps are totally unnecessary, but we couldn't resist this one cosmetic indulgence. We think you'll agree that they look incredible for the pittance of $65.

Performance Evaluation
Before booking our regular test venue--Englishtown Raceway Park--we spent a few days bedding the Performance Friction pads into our Baer rotors and heat-cycling the Kumhos. We did this on the street in the course of our normal daily commute which is what we figure most of you weekend warriors will do. Surprisingly, the aggressive pads and tires were quite manageable on the highway and around town, but with the exception of the PWO wheels, we wouldn't want to have them on the car every day. Our primary point of satisfaction was that we could put the tires and brakes on a day or two before a track event and drive to and from the track with both the tires and pads on the car. This will simplify our routine for the track and provides the option of not buying and maintaining a tow vehicle and trailer. Considering the price of the pads, tires and wheels, we think it's a bargain.

For those of you concerned about unsprung weight, we measured one of our Fikse wheel/tire assemblies and found them to weigh 48 lbs. each. The PWO/Kumho combo weighed 52.5 lbs., an increase of 4.5 pounds per wheel or 18 lbs. for the entire car. This can be significant for an all-out race car, but we will gain far more in the cornering department than we will lose from the extra weight, so the penalty is minimal. In an acceleration-specific contest like a drag race however, we would want the lightest wheel/tire possible.

On the street, our only complaint was that every time we rolled to a stop, we kept craning our necks around to find the transit bus with the squeaky brakes. Mysteriously, it was never there. Noise notwithstanding, these pads stop with a murderous force once sufficient carbon media has been transferred into the rotor surface. The tires behaved acceptably on the street too, providing sufficient wet weather traction to keep us from breaking into a sweat. Once the tires are worn down to racing depth, we may change our opinion though. On to the testing.

Our first test was 70-0 braking distance, which we measured with our trusty Vericom VC200. Initially, we thought something might be wrong with our gear because the results were so good, but stomp after stomp, the hits just kept coming. Stopping distance from 70 mph averaged 129.2 feet (five consecutive runs) with a best of 125 feet. That compares with 148.4 feet averaged with the PBR pads and Goodyear F1 Steels--a gain of 19.2 feet! That might not sound like a lot, but those readers who road race often are probably having to read this over and over again just to make sure their eyes aren't deceiving them.

Wow! So if 70-0 was so good, how would 100-0 fair? In the past, we never had enough room to get up to speed, regulate our speed with accuracy, and stop from 100 mph. Now all things were possible. We then proceeded to average 273 feet in five consecutive runs with a best run of 268 feet. Talk about major brain slosh! Our Raytek Raynger ST infrared heat gun showed rotor temperature close to 600*F several minutes after our last run from 100 mph. This isn't very scientific, but we are guessing temperatures were well in excess of 1000*F while braking was taking place. This would've obliterated most pads--even our excellent PBR factory pads. We give a very high thumbs up to Performance Friction for their Compound 99 pads! And don't forget, we had lots of help from the PF Compound 90 pads in our stock rear calipers.

We then shook the cobwebs out and proceeded to our 200-foot skidpad. We stowed the VC200 and whipped out the G-Analyst for some more cerebral deformation. In clockwise rotation with the Kumho V700s, lateral force swelled to .94 g, which compares to our previous best of .87 g with the Goodyear F1 Steels. In counter-clockwise rotation, lateral force increased to .95 g (compared to .86 g with the Goodyears). That's a huge improvement folks.

What Does All This Mean?
Experts will tell you that better braking and skidpad numbers don't always translate into better lap times or a more driveable track car, but they usually do. Specifically, better braking will allow us to brake later when approaching turns and that means more straightaway speed. More lateral g-force capability means more speed through the turns, which means more speed on corner exit, which means more speed down the straightaway--then we come full circle to the brakes.

The danger, if any, lies in driver overconfidence and under-ability. We've seen it happen before and we don't want to repeat it ourselves: Faster, better-handling cars often give their drivers more rope with which to hang themselves. As always, we move toward the Kenny Brown/TrackTime Driving School with anticipation, but restraint will be more important than ever with such performance at our disposal. We'll have a full report from Watkins Glen in the next issue of GM High-Tech Performance.
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