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Also making its way from our old E92 M3 race car to our new M4 is the wheel & tire package. We will once again be running 18×10” BC Forged RS43 wheels with Achilles GS-328 racing slicks for dry weather and the Achilles 123S for wet.Wheels & Tires are another huge part of being able to control a race car properly and once again we turn to Achilles Tire to provide us with the goods. After a successful first season with Achilles in 2015 it was a no brainer to continue using their awesome tires on the M4. The consistency of their GS-328 slick race tire over its life is exactly what we need for endurance racing and they have the speed to match. The 25 Hours of Thunderhill however is held in December in Northern California which means about the only thing you can predict on the weather is that it will be cold. In the two years we have competed in that grueling race we have seen rain at least once over the course of the weekend. Last year, half of the race was in wet conditions and gave us our first opportunity to try the Achilles 123S tire, which is our choice for wet weather. The tire blew our expectations out of the water, pun intended. Many of you have heard of the 123S as it is their flagship drift tire meaning it is a full-on passenger car street tire…albeit a high performance one. Many of you are also wondering why we don’t use a stickier GS-328 slick grooved for wet conditions and the answer might surprise you. Since it is generally so cold at the 25 Hour race, especially if it’s raining, the lower operating temperature range of a street tire proves to be more effective in full-wet conditions. It’s much harder to get and keep a set of wet weather racing tires in their operating temperature range. That, and the tread pattern on the 123S is simply phenomenal at moving water.
We wrap our Achilles tires around BC Forged RS43 18 x 10” wheels all the way around. This is the exact setup we ran on our previous E92 M3 at last year’s 25 Hour with great success. The BC Forged wheels are lightweight, strong, and very well made. Not to mention they look fantastic! The only other change we have made in this department is changing from a factory BMW wheel bolt setup to a wheel stud and lug nut setup. On our E92 M3 we had a problem early on with breaking wheel studs before eventually getting rid of the problem by customizing our hubs and brakes to accommodate thicker 14mm wheel studs as opposed to the 12mm that fit normally. On the M4 we don’t have that same problem as it comes with the ability to use 14mm wheel studs from the factory!
If this article seems like dejavu from our E92 M3 you’re right. Almost all of the components in our suspension, brakes, wheels & tires are identical or very close to what we ran on our old race car. The only changes really made were to make the parts fit the M4 specifically. The real major difference is the switch from the ZR to the DR series BC Racing coilovers. Everything is same same…but different. Why? Because it works. In the next article, we’ll get into some new things under the hood designed to add power, keep things cool, and help us win!
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