Mickey Thompson’s ET Street Radial and the newer ET Street Radial II are a couple of the prime choices of street and strip enthusiasts in search of a drivable, yet well-performing tire for their powerful daily drivers or weekend warriors. While each option offers exceptional performance on the road and the strip, these two tires have a design catered to a more specific use and driving style.
To illustrate the differences, we recently bolted on a set of both of these tires to our 11-second, supercharged 2011 Ford Mustang GT Wild E. Coyote and put them to the test in a side-by-side comparison to determine how they perform. In our test, we were looking not just at which performed better on the track, but how they handled out on the highway and in traffic. The truth is, you can’t go wrong with either tire…it all comes down to what your end goal is and what you need in a tire. But if you want to know how they stack up, you’ll want to continue reading.
Left: Our test bed, shown with the 295/55/15 ET Street Radial tires on a set of Weld Racing RT wheels. Right: the 15-inch ET Street Radial and the 18-inch ET Street Radial II in a 265/40/18.
ET Street Radial
The first tire we tested, the venerable ET Street Radial (295/55/15), is one of the most popular tires in use on street and strip vehicles like our 600 horsepower Mustang, and for good reason: it’s a DOT-approved street legal radial design that delivers a great ride on the street with a soft compound designed more for traction on the track. The Street Radial was also the tire to beat in Outlaw Drag Radial and 275 Drag Radial racing. Since then, M/T has produced a more hardcore, and not street recommended, 275 Street Radial Pro that took 275 Radial Racing to the next level.
The 15-inch ET Street Radial, which requires the added cost of an aftermarket wheel.
“We developed this tire a couple of years ago as a direct replacement for the old Chevelles and such, and it spilled over into the Mustang market because it’s a true 28 x 10.5, 15-inch tire. It’s a got a taller sidewall that works very well on the drag strip. There’s just no better way to sum it up than by saying it’s just an excellent-working tire,” said Mickey Thompson’s Tom Kundrik.
We developed this tire a couple of years ago as a direct replacement for the old Chevelle’s and such, and it spilled over into the Mustang market because it’s a true 28 x 10.5, 15-inch tire. – Tom Kundrik
The ET Street Radial is, however, more of what you’d call a dedicated drag racing setup inside and out. It’s got a beefier sidewall construction for launching on the strip, and low-void directional tread that handles well on dry pavement, but isn’t recommended for rain or snow driving. Mickey Thompson makes clear distinction that this is a drag racing tire for dry use only, so don’t say you weren’t warned.
One thing we discovered on our Mustang, and which is common on a lot of later-model vehicles, is that you may have to make provisions in the suspension system (the sway bar location) to fit the 15-inch wheel, or perhaps go with the 17 to 20-inch Street Radial II entirely due to fitment issues.
ET Street Radial II
The ET Street Radial II (we’re testing the 265/40/18), unlike the 15-inch Street Radial, is intended for a more all-around use. It’s no slouch at the track, but that isn’t it’s forte by design. This second-generation tire is likewise a soft compound, radial tire that’s completely DOT street legal, but inside, has a polyester ply, steel belted construction like a more typical OEM street tire for strength and long-term durability on the road. Another focus of this tire — and its 18-inch size — is to accommodate some of the large aftermarket brakes that are common on many of today’s souped-up street performers.
The 265/40/18 ET Street Radial II tire. We drove this tire for 5,000 to 7,000 miles in all type of driving conditions without a hitch.
“The ET Street Radial II is meant to be the best traction tire on the market for high horsepower Corvettes, Mustangs, and other performance vehicles. You can drive it on the street with a thousand horsepower and it will hook up. It’s far better than any original street car tire out there, and you can drive it to the race track and have a superior-performing tire there, too. You don’t have to switch back and forth between a slick and your radial to drive home,” explained Kundrik.
The 18-inch tire, as you can imagine, is going to handle better because it has a shorter aspect ratio for sidewall and thus a stiffer sidewall for less flex. It’s not an autocross tire, but it will drive and handle well.
Both the ET Street Radial and the Street Radial II use the very same compound in their construction, and in all reality, they aren’t vastly different tires, but there are some tradeoffs to one over the other. What sets them apart more than anything is their sidewall construction, which brings about differences in how they perform out of the gate at the track.
You can see the differences in the tread of the two tires in this detailed side-by-side shot. Mickey Thompson spread out the tread blocks more like that of an OEM street tire on the 18-inch ET Street Radial II to give it better driveability on the street.
Shown here are the ET Street Radial and ET Street Radial II side-by-side.
As we’ve pointed out, the 15-inch ET Street Radial is more of a drag racing-esque tire with a focus on on-track performance, and that’s where it shines. And much of this is owed to its larger sidewall depth, allowing it to squat and wrinkle when the power is applied at the starting line.
Measuring The Differences
ET Street Radial: Section Width 12.0″, Tread width 10.9″, Diameter 27.8″, Measuring Rim 9.5″
ET Street Radial II: Section Width 10.6″, Tread width 9.6″, Diameter 26.5″, Measuring Rim 9.5″
“The 15-inch ET Street Radial is going to be more forgiving at the race track, because it has more sidewall,” says Kundrik.
“The larger sidewall really lets the 295/55/15 tire wrinkle up. Most people don’t think that a radial tires wrinkles, but if you watch some of the really high horsepower cars in Outlaw Drag Radial and such, it will have wrinkles all the way around almost like a slick. But by the sixty-foot mark, it’s already back to round. Radials stay round and they’re very stable.”
Another area where these two tires differ is in their contact patch and tread pattern. The 15-inch Street Radial is roughly 1-1/3-inches wider (10.9 inches versus 9.6 inches in tread width) than the Street Radial II, providing extra real estate on the pavement for traction. It’s tread design, however, doesn’t lend itself as well to road driving, particularly in less-than-clear weather conditions.
“The first-generation tire has a more aggressive contact patch that isn’t meant to dissipate a lot of water,” says Kundrik. “It’s meant for straight-line traction and performance. The ET Street Radial II, on the other hand, is designed more for every-day use at maximum performance.”
The first-generation tire has a more aggressive contact patch that isn’t meant to dissipate a lot of water. The ET Street Radial II, on the other and, is designed more for every-day use at maximum performance. – Tom Kundrik
The Street Radial II will get the job done on everything from daily drivers-turned-dragstrip warriors to show cars and weekend cruisers. If you need to drive your car and don’t want to carry around and swap a set of tires, this tire fits the bill.
“It’s going to be better if you get caught in a little bit of rain or anything, but with it’s shorter aspect-ratio sidewall, it isn’t going to be as forgiving on the drag strip. We knew the 16, 17, and 18-inch size tires were going to be used more on weekend street-driven cars, so we wanted to make it handle better in the rain. But we definitely wanted it to perform and drive well, so we broke up the tread squares more as well,” said Kundrik.
To sum it up, “if your car is a daily driver or a weekend warrior, the 18-inch tire would be perfect. If you’re going to the race track all the time, you definitely would want to run the 15-inch tire because it’s going to be better for higher horsepower cars,” added Kundrik.
As we alluded to in our introduction, we tested both the Street Radial and Street Radial II on the street and on the track. Not surprisingly, we found the two tires to be fairly close on the dragstrip in terms of their pure sixty-foot and elapsed time potential, but there were some distinct differences in their overall consistency. After all, one is designed for the track, while the track is only a component of the other.
Testing the 18-inch ET Street Radial II at the track on the stock 2011 Mustang GT wheels.
Throughout our passes, the 15-inch Street Radial was the more consistent tire. This is particularly of emphasis if you have a stick-shift car like our Mustang, because radials aren’t generally a dump-the-clutch type of tire. Discovering and maintaining just the right amount of slip and hitting that “sweet spot” on each pass is key to making the 18-inch tire consistent, so the 15-inch gave us a little more margin for error. As it should, the 15-inch tire had noticeably more squat on the launch.
Another point to keep in mind is that the two tires are 1.3-inch difference in diameter, which will effect your gear ratio and change how the car performs down low and going down the race track. It will also, naturally, change your shift points on a clutch car.
We made four runs in total at the nearby Irwindale Dragstrip and again at Bakerfield, making one run in each lane on both tire.
We made four runs in total on two different dragstrips, two on each tire and alternated between the left and right lane. The best performance, which we expected, came from Bakersfield better-prepped quarter mile track. Our best run came on the 15-inch Street Radial (and was also our first run of the day), as we netted a quarter mile elapsed time of 11.37 at 120.54 mph, with a 1.79 sixty-foot time, which was also the best of the four runs.
On our second pass, over in the right lane, we slowed to an 11.51 and lost a tenth in the short time. We then bolted on the 18-inch ET Street Radial II’s and made a pass in the left lane, carding our slowest run of the four, an 11.546 at 121.66 mph with a respectable 1.85 sixty. Later that afternoon, we made one final run in the right lane. A 1.79 short time, just a tick off our best pass on the 15-inch tires, translated into our second-best quarter-mile numbers of the day, as the scoreboards lit up with an 11.48 at 118.33 mph.
On the left are the two passes recorded with the 18-inch ET Street Radial II tires, while the two passes on the 15-inch Street Radial (including our best run of 11.37) are shown on the right.
Naturally, comparing how the two tires drive on the street isn’t calculable like a time slip is, but rather, it’s all a seat-of-your-pants opinion. We were able to log plenty of miles on both tires, and found the stiffer sidewall of the 18-inch tire to perform similar to an OEM street tire, with the ability to not only handle well in the rain, but in a pinch in an accident-avoidance situation. The tire reacted well to the drivers motions, whereas the sidewall flex of the 15-inch tire was noticeably slower to react.
You’ve read about the two tires and you’ve seen our results. Now, which is the right pick? Well, there really isn’t a right pick. It’s all up to you. The main thing to keep in mind is the cost-to-benefit ratio and how it plays into your needs. On some newer vehicles like S197 Mustangs, you can’t install a 15-inch wheel because of the location of the sway bar. This means there are steps (particularly, sway bar relocation) that will cost you a little money and some time in order to bolt up the 15-inch tire if that’s what you choose to go with. Of course, you also have to buy 15-inch wheels. If you’ve got the money, the 15-inch tire is going to be more consistent, no question.
To get the smaller 15-inch wheel to fit, we had to relocate the sway bar on our late model Mustang. The kit we purchased from Steeda is less than $50 and takes around an hour or two to install. This is a step that you may have to undertake on your vehicle, depending on the sway bar location.
If, on the other hand, you’ve got a daily driver or just want to the cruise the street and hit occasional test and tune nights at the track, the 18-inch ET Street Radial II can be fitted to your stock wheels, and you can drive it every day. We drove on the 18-inch tire on our stock Mustang wheels for an estimated 5,000 to 7,000 miles at 75-80 mph — even in the rain — without any issues whatsoever.
At the end of the day, you can’t go wrong. Pick a tire and have fun with it.