Testing Tires

Update by J.G. Pasterjak to the Volkswagen Beetle TDi project car
Aug 8, 2013

Photo by Ken Neher.

Our tire test was an interesting revelation on several levels. Not surprisingly, the slowest set was the OEM economy-biased Continentals, with the BFGoodrich Super Sport AS being faster than that and the BFG R1s being fastest of all. Again, no surprises in the finishing order.

What surprised us, though, was the differential of speeds in the tires. Around the long VIR full course, the Continentals struggled to break two and a half minutes. The Super Sports were considerably easier to drive and more confidence inspiring, and a couple seconds faster to boot. But the R1s held the car to the hot VIR surface like glue, and shaved nearly seven more seconds off our times. We had expected the spread to be a bit more even.

Most striking was the effect of the tires on the Electronic Stability Control system, which is not defeatable in our 2013 VW Beetle (not without some fancy computer work, anyway). Both sets of street tires produced plenty of ESC intervention, but it actually wasn’t too annoying. It was noticeable, however, especially when the tires were operating at high slip angles. We think this is what kept the lap times so similar. Although both sets of tires had different limits, they liked to operate at similar slip angles and produced similar yaw rates. So we think the ESC was limiting our lap times somewhat with the Super Sports.

With the R1s in place, it was a different story. The insane levels of grip resulted in much more subtle interventions from the STC. It was as though someone had changed the STC calibration to a more race-friendly setting. We felt the intervention, but it was more confidence inspiring than annoying. Honestly, we’d have to say we were more than a little impressed with the handling of the Beetle on the R1s, and so were some of our track mates.

Here’s some in-car video of the Beetle on the R1s. While we clearly don’t have the horsepower to keep up with even some of the slower cars on track, you’ll see that we have more than plenty of handling to hang with even some of the more exotic machinery.

Full results of our tire friction and lap testing in the next printed installment.

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Jerry From LA
Jerry From LA Dork
8/8/13 12:33 p.m.

Funny how the hanging wire helps give the viewer a sense of the more high-G higher body roll corners.

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