On the Chevrolet Camaro, Do The Tires Make The Car?
The Camaro 1LE and Z/28 Swap Rubber to Find Out
Since its debut, the primary criticism leveled against the Chevrolet Camaro Z/28 has been that it's nothing more than a fancy set of tires on an otherwise poor-handling car. Put those tires on any other car and it would smoke the Camaro on a track, or so the theory goes (never mind that there's nothing stopping competing automakers from doing such a thing). But does it hold water?
As it happens, we recently had a Camaro Z/28 and a Camaro 1LE at the office for separate tests when an idea struck. What if we swapped the tires? Would the 1LE, already a car with superb handling, meet or beat the Z/28's track performance given the same tires? Is the Z/28 nothing more than a super-expensive tire and wheel package?
Here's what we're working with: The 1LE is a $3500 handling package for your standard 426-hp Camaro SS that adds stiffer monotube shocks, thicker anti-roll bars, stronger rear axle half-shafts, a strut tower brace, a number of aerodynamic aids, and, most important for this test, 285/35R20 Goodyear Eagle F1 SuperCar G:2 tires on all four corners. The Z/28, meanwhile, is a limited-edition, track-ready $75,000 car with a larger, 505-hp V-8, spool-valve shocks, stiffer springs, smaller anti-roll bars, even bigger aerodynamic aids, less weight, a strut tower brace, carbon-ceramic brakes, and again critical to this test, 305/30ZR19 Pirelli P Zero Trofeo R tires at all four corners.
Normally, a tire swap would require buying two sets of tires for each car and having a shop dismount and remount them. That would mean getting the non-stock tires for each car in the stock size, which could be difficult if either isn't offered in the other's size. It would also mean that each car would be working with different width tires than the other. The 1LE would be running 285-width Trofeo R's rather than the Z/28's 305-width Trofeo R's, and when it comes to performance, tire width can make a big difference.
Thankfully, none of this is a problem. The Camaro fans will be happy to learn that you can bolt the Z/28's wheels and tires to a 1LE (and presumably any other Camaro) with no clearance issues. No, not even at the front. How'd that happen? Stick your hand under the fender of a 1LE and you'll find that there's little clearance between the inside edge of the tire and the suspension. Chevrolet's elegantly simple solution for mounting even wider tires on the Z/28 was to jack up the wheel's offset, effectively pushing the wheel farther out from the chassis. This created extra room between the inside edge of the tire and the suspension, so Chevrolet was able to widen the wheel to fill that extra space without affecting clearances. A few fender flares and such to cover the exposed rubber (for legal and aerodynamic reasons) and you're done.
Going the other way, the 1LE's wheels fit just as well on the Z/28, though they look a little funny. The 1LE's larger diameter wheel just clears the Z/28's massive brakes. Clearances verified, we're ready to hit the track.
The Drag StripLogically, you'd expect wider, stickier tires to improve grip and therefore improve a car's launch at the drag strip, and you'd be correct. The 1LE on its stock Goodyear tires hits 60 mph from a stop in 4.5 seconds and runs the quarter mile in 13.0 seconds at 109.1 mph. Fitted with the Z/28's Pirelli tires, the 1LE hit 60 mph in 4.3 seconds and ran the quarter mile in 12.7 seconds at 111.7 mph. That's a substantial improvement.
Using the same logic, you might expect skinnier, less sticky tires to hurt a car's launch, and you'd be wrong. What? Yep. The Z/28 on its stock Pirelli tires hit 60 mph in 4.0 seconds and ran the quarter mile in 12.3 seconds at 117.2 mph. On the 1LE's Goodyear tires, the Z/28 hit 60 mph in 3.9 seconds and ran the quarter mile in 12.2 seconds at 117.1 mph, a smaller but still significant improvement.
What's going on here? Per test driver Carlos Lago, both cars were easier to launch on the 1LE's Goodyear tires. There was less risk of bogging the engine and the tires chattered nicely right on the limits of grip and right in the meat of the power band. On the Z/28's Pirellis, both cars were trickier to launch. It was either hero or zero: The cars launched nicely or they bogged down and chugged off the line. The Pirellis just aren't great drag-racing tires.
It's also worth noting that changing the diameter, width, and weight of the wheels and tires changes their rotational inertia, which affects both acceleration and braking. This isn't easily tested with our equipment, but we suspect the difference wouldn't be too significant. Additionally, changing wheel and tire diameter also alters the effective gearing, which can affect acceleration. This was noticeable on the figure eight, where the shift points changed based on which wheels and tires were on the car. As with rotational inertia, though, measuring its effect on acceleration is difficult.
Stock images of the 2014 Chevrolet Camaro SS 1LE:
BrakingWhile brakes tend to get all the credit for stopping a car, the truth is the tires are a huge factor. No matter how big the brakes are, they won't do any good if the tire doesn't have enough grip to translate that brake force into stopping power. A better set of tires can reduce stopping distances measurably without any change to the brakes.
Here, again, you would predict the wider, stickier tire would stop better, and you'd be right. The 1LE on its stock Goodyears stops from 60 mph in 101 feet. Give it the Z/28's Pirellis and it'll stop from the same speed in a seriously impressive 94 feet.
This time, the opposite is also true. The skinnier, less sticky Goodyears can't stop quite as well. On its stock Pirellis, the Z/28 stops from 60 mph in 97 feet. On the 1LE's Goodyears, the Z/28 stops in 100 feet. No special explanations here. The Pirellis simply have more grip under braking.
The SkidpadWhile the skidpad will tell you what a car's absolute steady state handling limit is, it's not much of a real-world test since you don't ever drive in continuous circles at a steady speed. Still, it's an instructive number that indicates how a car should perform at the limit in a corner. Here, again, a wider, stickier tire should have an advantage.
Fit the 1LE with the Z/28's Pirellis and you'll definitely see an advantage. With its stock Goodyear tires, the 1LE pulled 1.02 g average on the skidpad. Upfitted with the Pirellis, the 1LE pulls an even more impressive 1.05 g average. The numbers don't look big, but a 0.03g average improvement is significant.
Putting the Z/28 on the 1LE's Goodyears also makes a difference, but not the exact opposite effect you might expect. On its stock Pirellis, the Z/28 pulls 1.06 g average (0.01 g more than the 1LE on the same tires). Downgraded to the Goodyears, the Z/28 pulls 1.04 g average. Not only is that still 0.02 average g more than the stock 1LE on the same tires, the difference between the two tires' performance is smaller for the Z/28 than it is for the 1LE (plus 0.03 g average for the 1LE, minus 0.02 g average for the Z/28).
The Figure EightWhere the skidpad fails to apply to real-world driving, our unique figure-eight test picks up the slack. Consisting of two 200-foot-diameter skidpads separated by 500 feet center-to-center, the figure eight tests cornering, acceleration, braking, and the transitions between each. Here, the tires must grip under braking, hold on through the corner, and put the power down at the exit. Once again, the wider, stickier tire should have the advantage.
The 1LE, on its stock Goodyears, completes the figure eight in 24.1 seconds at 0.85 g average. On the Z/28's Pirellis, the 1LE completed the figure eight in … 24.1 seconds at 0.83 g average. Not only did it not gain an advantage, the 1LE actually recorded a lower average g figure in the corners.
The Z/28, meanwhile, was hobbled, but not as much as you'd expect. On its stock Pirellis, the Z/28 runs around the figure eight in 23.6 seconds at 0.84 g average. On the 1LE's Goodyears, the Z/28 ran the figure eight in 24.1 seconds at 0.84 g average.
What's going on here? Test driver Kim Reynolds has an answer. In stock form, Kim says, the 1LE is razor-sharp. With the Z/28's tires, it just felt mushy. The precision was gone, and for no measureable gain. Conversely, Kim says the stock Z/28 is predictable and balanced. On the 1LE's tires, it became much less predictable and much more prone to oversteer. Given there was no change in average cornering g, it's reasonable to conclude that the Z/28's diminished performance is the result of its inability to stop as quickly (despite having significantly larger brakes) or put the power down as effectively. True, the Z/28 does have a power advantage over the 1LE, but in the space of less than 500 feet, 79 hp and 61 lb-ft don't make a lot of difference (and despite what you may think, our scales say the Z/28's weight advantage over the 1LE is just 35 pounds).
ConclusionFrom this test, we can conclude that the Z/28's advantage is not simply a better set of tires. Mounting the Z/28's wheels and tires to a Camaro 1LE did not allow the 1LE to meet or exceed the performance of the stock Z/28. In fact, in half of our tests, the 1LE fitted with Z/28 tires failed to outperform the Z/28 fitted with 1LE tires, much less the stock Z/28.
Tires, then, are not the be-all, end-all of handling. They are part of the equation, and improving the tires can improve performance. However, the tire must also work with the suspension, the brakes, the steering, and the chassis. Handling is holistic, and many variables are involved. Spring rates, shock rates (both compression and rebound), anti-roll bar stiffness, bushing stiffness, suspension geometry, alignment, chassis stiffness, and more can all affect how well a car handles. While improving any one factor can increase performance, the system as a whole must be considered not only to more meaningfully improve performance, but also to retain or improve the driving experience. After all, does it matter how big the skidpad numbers are if the car is unpleasant to drive?
The Camaro Z/28, then, is not just an expensive set of tires and a wing. It's what Chevrolet promised: a serious track car that's been modified from the ground up for better performance.
|2014 Chevrolet Camaro SS 1LE||2014 Chevrolet Camaro SS 1LE (on Pirellis)||2014 Chevrolet Camaro Z/28||2014 Chevrolet Camaro Z/28 (on Goodyears)|
|0-60 MPH||4.5 sec||4.3 sec||4.0 sec||3.9 sec|
|QUARTER MILE||13.0 sec @ 109.1 mph||12.7 sec @ 111.7 mph||12.3 sec @ 117.2 mph||12.2 sec @ 117.1 mph|
|BRAKING, 60-0 MPH||101 ft||94 ft||97 ft||100 ft|
|LATERAL ACCELERATION||1.02 g (avg)||1.05 g (avg)||1.06 g (avg)||1.04 g (avg)|
|MT FIGURE EIGHT||24.1 sec @ 0.85 g (avg)||24.1 sec @ 0.83 g (avg)||23.6 sec @ 0.84 g (avg)||24.1 sec @ 0.84 g (avg)|