'll never forget watching an episode of MTV Cribs, when a rap star pointed to the pimped-out chrome wheels on his SUV and enlightened the viewers with "they added these 24s for performance." I spilled Apple Jacks all over myself.
Let's face it: the majority of eurotuner readers buy a car with the intent of upgrading the wheels soon after. The problem is, most of us also buy a car for its performance, which may be sacrificed to some degree when we upgrade to larger, and usually heavier, wheels.
If you want to upgrade your wheels, but aren't interested in sacrificing ride quality, stick to the same diameter and profile. Ideally, you want a lighter wheel, which theoretically will help your acceleration, braking and turn-in response
The downside of lightweight wheels is that they're usually expensive. Fortunately, Tire Rack offered a solution for our project E36 M3 with its new SSR RS Type C wheels. Reportedly, they weigh 16 lb for 17x8" and 16.5 lb for 17x8.5." So, we ordered a set of the latter at $409 each.
Our 17x8.5" SSR wheels with...
Our 17x8.5" SSR wheels with wheel stud conversion and 235/40-17 Sumitomo tires from Tire Rack. They weigh only 39 lb combined
The wheels feature a semi-solid forged construction. Plus, they are shot-peened and heat-treated for added durability.
The next order of business was choosing tires. The best bang for our buck at Tire Rack for an all-season performer (including rain and occasional snow) was the Sumitomo HTR+ all-season.
We chose 235/40-17 all-around - the same size used on M3s for '95-only. In later years, as with our '97 sedan, BMW fattened the rears to 245/40-17 and narrowed the front to a 225/45-17 to dial in understeer, making the 3.2 liter cars a little more predictable than the older 3.0 model.
Rest assured, these inexpensive tires will provide all the performance you need for street use in dry conditions. Additionally, we've noticed they grip extremely well when wet, and surprisingly well in the snow. And with a UTQG rating of 360 AAA, we can expect good tread life, assuming the alignment is correct.
The SSR wheel and Sumitomo combo weighs 39 lb. By comparison, our 17" ten-spoke stock wheels with worn tires are 7.5 lb heavier. So, we decided to see if the weight advantage of the new wheels and tires would show up on a chassis dyno, since it measures power to the wheels.
We paid a visit to Imagine Auto, a respected Porsche tuning shop in Kansas City and strapped the M3 to its Mustang MD500 dynamometer.
A test of this nature wouldn't simply involve a couple of runs and a wheel change. First, each run had to be done with similar oil, water and air intake temperatures, which we monitored using IA's OBD2 scanner. This would eliminate power loss through heat soak.
Even though Tire Rack sent...
Even though Tire Rack sent out long bolts (top left), we decided to do a wheel stud conversion for easier wheel mounting (middle)
We set a baseline in first, second and third gears to compare power versus rpm, power over time, and even speed over time; we're most concerned with the latter when it comes to acceleration comparisons.
Our findings were interesting. We discovered that going from a well-worn 245/40 to a new 235/40 gave us around a 1% gearing reduction. In other words, at any given speed, we were seeing about 100rpm more engine speed. This in turn meant we'd see the horsepower and torque climb more quickly, but torque would drop off a little sooner. It also meant about 1mph less top speed in each gear.
In first and second gears, the acceleration differences were within 0.03sec, making the gains or losses insignificant. Apparently, the first two gears accelerated so quickly that an extra few pounds of weight weren't going to be an issue.
In third gear, however, we saw an acceleration advantage with the SSRs and 235/40 Sumitomos. Even though overall power and torque didn't really change, from 25-80mph the car gained back up to 0.19sec extra. The slight gearing change kept the power level up on the SSRs all the way to the top-end. We also found that nearly 80% of the gain happened from 25-55mph. Interestingly enough, this is during the time when the torque builds and peaks.
 Since our studs didn't have...  Since our studs didn't have a hex key to tighten them into the hub, we used a couple of nuts from another set of wheel studs. Screw the first one into the hub so there's enough thread for a second one... |  ...thread on the second nut...  ...thread on the second nut backwards. Once they press together, you'll be able to screw in the stud with a wrench. If the nuts want to rotate without the stud, you may need a second wrench to tighten the nuts against each other |  Once the studs have been tightly...  Once the studs have been tightly screwed into place, you'll need to remove the nuts. To do this, simply tighten the first nut until it breaks free of the second. Then you can just remove each nut by hand |