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Race Recap: 2013 Twelve Hours of Sebring, cakewalk up front, grindfest out back [w/spoilers]

This year's 12 Hours of Sebring wasn't exactly a foregone conclusion because we're still talking about racing, and anything can happen when the speeds are as high as the adrenaline and the desire. But we're still talking about Audi bringing it's two top-spec racers - and its huge budget and its nearly neurotic attention to detail - to a race that it uses as a test bed for The 24 Hours of Le Mans and as a way to open the endurance racing season with a victory.
Besides, 12 hours is a long time, especially at Sebring, and things didn't go all Audi's way. On top of that, although it was a pretty quiet race, behind the Audis things got even grimier, with plenty of battles, plenty of mechanical issues, and the new BMW Z4 GTE and Viper GTS-R being race tested. Oh, and that brand new chromed-out DeltaWing...

Is the skill of rev matching being lost to computers?

If the ability to drive a vehicle equipped with a manual gearbox is becoming a lost art, then the skill of being able to match revs on downshifts is the stuff they would teach at the automotive equivalent of the Shaolin Temple. The usefulness of rev matching in street driving is limited most of the time – aside from sounding cool and impressing your friends. But out on a race track or the occasional fast, windy road, its benefits are abundantly clear. While in motion, the engine speed and wheel speed of a vehicle with a manual transmission are kept in sync when the clutch is engaged (i.e. when the clutch pedal is not being pressed down). However, when changing gear, that mechanical link is severed briefly, and the synchronization between the motor and wheels is broken. When upshifting during acceleration, this isn't much of an issue, as there's typically not a huge disparity between engine speed and wheel speed as a car accelerates. Rev-matching downshifts is the stuff they would teach at the automotive equivalent of the Shaolin Temple. But when slowing down and downshifting – as you might do when approaching a corner at a high rate of speed – that gap of time caused by the disengagement of the clutch from the engine causes the revs to drop. Without bringing up the revs somehow to help the engine speed match the wheel speed in the gear you're about to use, you'll typically get a sudden jolt when re-engaging the clutch as physics brings everything back into sync. That jolt can be a big problem when you're moving along swiftly, causing instability or even a loss of traction, particularly in rear-wheel-drive cars. So the point of rev matching is to blip the throttle simultaneously as you downshift gears in order to bring the engine speed to a closer match with the wheel speed before you re-engage the clutch in that lower gear, in turn providing a much smoother downshift. When braking is thrown in, you get heel-toe downshifting, which involves some dexterity to use all three pedals at the same time with just two feet – clutch in, slow the car while revving, clutch out. However, even if you're aware of heel-toe technique and the basic elements of how to perform a rev match, perfecting it to the point of making it useful can be difficult.

GM recalls half-million full-size SUVs to address seatbelt issue

GM is recalling its redesigned full-size SUV models to address improperly riveted mounts securing the third-row seatbelts that may fail in the event of an accident. The population includes the 2021-2022 Cadillac Escalade and Escalade ESV, 2021-2022 Chevrolet Suburban and Tahoe, and 2021-2022 model year GMC Yukon and Yukon XL, for a total of 484,155 vehicles. "Operators at the supplier’s manufacturing plant may have not properly followed manufacturing processes and inadvertently missed the rivet forming operation," GM said in its defect report to NHTSA. "In certain of these vehicles, the rivet that retains the buckle to the mounting bracket in the left or right side third-row seatbelt buckle assembly may not have been properly formed during the manufacturing process. If the third-row seatbelt assembly is not properly riveted, it may not properly restrain occupants in a crash, increasing the risk of injury." Fortunately, the fix is relatively simple. GM service technicians will inspect the rivets on the rear seatbelt buckle assemblies and replace the entire unit if the rivets are not to spec. Dealer notifications have already been distributed; owners should receive notice start in September. Related video: Cadillac Chevrolet GM GMC Ownership Safety SUV