Sometimes things just don't go precisely as you expect, and this is especially true at the race track. My last project series, Project Z4 M, progressed perfectly, with each performance addition resulting in a machine far more capable than the bone-stock starting point, as shown by the Traqmate GPS test data.
Unfortunately, Project GT3, to this point, has encountered some testing pitfalls. Let me explain: Baseline testing of the factory-fresh 2010 GT3 started well, with lap times consistently in the high 1:24s at my home track-some four seconds faster than the completed Project Z4 M. I can tell you without a doubt that the new GT3 is a bloody fast car straight from the factory.
I had plenty of track experience with the new car at the tail end of last season, logging about 600 miles there and some 3,500 total miles on the odometer, so such excellent lap times were gladly accepted. However, once the modding started and incremental GPS testing commenced, beginning with the StopTech brake upgrade we featured in Part 2, weather was not at all on our side. Cold temperatures and a rainy spring made for a difficult time bedding the new brakes (after all, I am reporting from Calgary). Also, the StopTechs are so damn good at dissipating heat that I had to resort to blocking off the brake ducts to properly accomplish bedding for the full-race brake pads. Once this task was complete, the rains began and continued through April and May. I did have plenty of track time, but the preferred test conditions are warm sunny days on dry pavement; these are the best control conditions (as when the baseline data was collected) for incremental testing.
By the time June came along my ego was most certainly ruffled by not accomplishing much in the way of positive results for this series. On the first decent June track day I finally collected a mountain of new and desperately needed GPS data. By this time I had some 1,000 miles at the track and close to 5,500 miles on the odometer. Lap times in the fastest session of the day were in the mid 1:24s, but I was still disappointed. Something just wasn't right, but this was through no fault of the new brakes. The Stoptech STR assemblies inspire confidence with superb pedal feel, eye popping deceleration, and can be beaten on all day with zero fade.
All GPS lap testing is done "blind"; that is to say, I do not use my digital readout for lap times inside the car since I feel that the results are more effective and controlled if the driver isn't pushed by knowing his lap time may be off-pace. Afterward, a full data analysis showed a strong improvement in the braking effect that allowed for later braking, but the speed in some of the faster corners was reduced in comparison to baseline, resulting in no net reduction in lap times. I figured my OEM Pirelli Corsa System tires were likely now past their prime, resulting in the less-than-satisfactory lap times. With that, I decided to just move on to the next upgrade: a new set of wheels and tires.
The new rubber would be more than welcome, and I was fairly sure it would help me get back on track to achieving faster lap times. I selected the Toyo R888, as it is an R-compound DOT-approved competition radial ideal for track days and high-performance driving schools. It features a semi-slick shoulder area to increase cornering force and a unidirectional tread pattern with V-shaped grooves to enhance wet traction and control. The continuous center contact delivers excellent directional control during hard braking, and its stiff sidewalls and rounded outer shoulder help to maintain tire contact with the pavement. Also, the wear rating is 100, so these tires will stick to the track like Crazy Glue on a Darwin award-winner.
For wheels (see the Centerlock Wheel Buyers Guide, ec September 2010, for a range of choices), I selected a set of custom Forgeline wheels for three main reasons: the many available style and color choices, strength, and price-point. All Forgeline three-piece wheels are custom made to order, utilize forged 6061 T6 centers, forged 6061 T6 spun rim halves, and stainless steel aircraft-grade fasteners.
Forgeline's strength and durability testing begins at the design stage using advanced computer stress analysis to test each new design under a simulated load and optimize it before machining ever begins. The test wheels are physically tested beyond SAE standards, and real-life racing variables are used for such test criteria. The finished 19-inch wheel set for Project T-Rex weigh in at about 23.5 pounds (8.5x19) and 26.5 pounds (12x19), for the front and rear wheels, respectively. This saves about 3.5 pounds per corner in the rear, but gains about 0.4-pound per wheel up front. I selected the 10-spoke Performance Series ZX3S with matte titanium centers, the hidden wheel fastener option (note that this adds about a pound to each wheel over the standard exposed fasteners), and a brushed aluminum rim for an very understated, high-tech look.
8.5x19 and 23.5 pounds in front, 12x19 and 26.5 pounds in the rear.
With the new wheels and tires mounted up, the 2010 GT3 looks spectacular; much less "blingy" than the OEM setup, yet plenty purposeful and mean. I was able to scrub and sufficiently heat cycle the R888s on two separate occasions before lap testing began. Fortunately, the weather for the test day was sunny and dry, and I was able to collect some new data with the Traqmate GPS. The car felt surefooted and fast, and I also perceived less understeer in the slower corners thanks to the tight tread blocks and sticky rubber of the R888s.
These were paired with Toyo Proxes R888 R-compound rubber.
However, I did notice that I was having trouble with grip in Turn 6, a very fast left-hand sweeper. Had it gotten more slippery since initial testing earlier in the season? Was I not driving it the same way or was I now lacking in guts or confidence? I couldn't say; all I did know was that my lap times, still in the 1:24s, were still not what I was hoping or looking for. After a week of analyzing the data and thinking about the results, I ruled out my initial thoughts regarding worn tires, as the new Toyos should work better on dry pavement than the OEM Pirellis, and I also ruled out "driver issues" (i.e., me) by having my racecar driver buddy, Steven "The Bloke" Tory, drive the car with similar results. The conclusion, then, was simple: Something had to be wrong.
Next time, we'll solve the problem and get back on the track to fully demonstrate the quality of the upgrades for this project car. Look out-this GT3 is gonna fly.
Dealing With The Centerlocks
I'll be the first to admit that when I found out the new centerlock wheels were to be standard equipment on the '10 Porsche 911 GT3, I was kind of pissed off. As the car's delivery time drew nearer, and the more I read about them and how they worked, I slid further down the slippery slope of perpetual grumpiness. In the flesh, the wheels are indeed stunning if maybe a little too flash for my more conservative tastes, but I decided that I just better get bloody well used to them and learn how to deal with the locking nuts properly. Note that Porsche only supplies the special centerlock nut socket (3/4-inch drive) with your new car and no other tools to help you get the wheels off. With a set of wheels on the way from Forgeline, I figured I had better add to my toolbox arsenal, so I ordered a long 3/4-inch-drive breaker bar (rated to 1,000 ft-lb) for loosening, and a jumbo 3/4-inch-drive torque wrench (rated to 700 ft-lb) to tighten the centerlocks accurately to the specified 370 ft-lb (or 500 Nm).
However, when these industrial (MAN!) sized pieces of equipment showed up at my doorstep, I knew more tools would be necessary, because these would be near impossible to carry conveniently on a road trip or vacation in the GT3. So I then purchased a small 1/2- to 3/4-inch-drive torque multiplier (with a 3.3 to 1 multiplier ratio) and a 1/2- to 3/4-inch drive converter, to allow for a more compact (albeit not nearly as precise) method to deal the centerlocks in the middle of nowhere.
Now I have three methods to deal with the Porsche centerlock nuts (listed in order of ease and torque precision; also note that the Porsche-supplied socket is also required for each method).
Proper Method: 3/4-inch-drive breaker bar for loosening and 3/4-inch-drive torque wrench for torquing-the simplest and most straightforward method.
Emergency Method: Torque multiplier, 1/2- to 3/4-inch-drive converter, 1/2-inch-drive breaker bar, and 1/2-inch-drive torque wrench-use the torque multiplier and 1/2-inch-drive breaker bar for loosening, and then following the emergency Porsche torquing instructions. Use the drive converter and 1/2-drive torque wrench to torque the centerlock nut to 74 ft-lb (100 Nm); mark the 100 Nm point on the wheel with a pencil and tighten the nut to the "STOP" point marker (turning ~50°) with the torque multiplier and 1/2-inch-drive breaker bar. Note that you could also use the 3/4 breaker bar for loosening and tightening in this procedure-but she's a big mother to carry around.
Bare Bones Method: Torque multiplier, 1/2-inch-drive breaker bar, and 1/2-inch-drive torque wrench-use the torque multiplier and 1/2-inch-drive breaker bar for loosening, and use the torque multiplier and 1/2-inch torque wrench for torquing. Note that the torque input for the 3.3:1 multiplier is only 112 ft-lb for 370 ft-lb output; however, the error I measured was greater than +/- 10% using this method and my cheap torque multiplier.
One additional "spanner in the gears" is the centerlock nut cap/dust cover. You must very carefully pry off this cap with a small flathead screwdriver at the machined slot, and note that it is very easy to accidently bend the tight-fitting caps when they're new. They do loosen up a bit over time, so hopefully they won't start flying off by themselves. I am also very careful aligning them when putting them back on-no mini Frisbees yet. Good luck! -DN