The Yamaha YZF-R1, or R1, is an open class sport bike, or superbike, motorcycle manufactured by Yamaha Motor Company since 1998. With the competition advancing, Yamaha made some major changes to the model. This included style updates, like an under seat twin exhaust, and performance upgrades including radial brakes, and, for the first time an R1 Ram-air intake. Furthermore, the tendency for wheelies by earlier productions was reduced by changing the geometry of the frame and weight distribution. The all-new engine was no longer used as a stressed member of the chassis, and had a separate top crankcase and cylinder block. The 2004 R1 weighs 172 kilograms (379 lb) dry. The conventional front brake calipers were replaced by radially mounted calipers, activated by a radial master cylinder. A factory-installed steering damper was also added this year. Combined with the changes to the frame, this helped to eliminate the tendency of the handlebars to shake violently during rapid acceleration or deceleration on less-than-perfect surfaces, a phenomenon known as a speed wobble or tank slapper. Motorcycle Consumer News tests of the 2004 model year YZF-R1S yielded a 0 to 60 mph (0 to 97 km/h) time of 3.04 seconds and 0 to 100 mph (0 to 161 km/h) of 5.42 seconds, a quarter-mile time of 9.90 seconds at 144.98 mph (233.32 km/h), and a top speed of 179 mph (288 km/h). John McGuinness won the senior race at the 2005 Isle of Man TT. For 2006, the swingarm was extended by 20 millimetres (0.79 in) to reduce acceleration instability. In this year, Yamaha also released a limited edition version in original Yamaha racing colors to celebrate its 50th anniversary. The model (LE/SP) had a Kenny Roberts front and rear custom Öhlins suspension units developed by the same team as the YZR-M1 MotoGP bike. Custom forged aluminum Marchesini wheels specifically designed for the LE shaved nearly a pound off the unsprung weight. A back torque-limiting slipper clutch, and an integrated lap timer rounded out the package, making the LE virtually a production racer. Only 500 units were made for the United States with another 500 units for Europe. An all-new YZF-R1 for the 2007 model year was announced on 8 October 2006. It had an all-new inline four-cylinder engine, going back to a more conventional four-valves per cylinder, rather than Yamaha's trade mark five-valve Genesis layout. It also had the Yamaha Chip Control Intake (YCC-I) electronic variable-length intake funnel system, Yamaha Chip Control Throttle (YCC-T) fly-by-wire throttle system, slipper-type clutch, all-new aluminum Deltabox frame and swingarm, six-piston radial-mount front brake calipers with 310 mm discs, a wider radiator, and M1 styling on the new large ram-air ports in the front fairing. There were no major changes for 2008. Power at the rear wheel was 156.7 horsepower (116.9 kW) @ 10,160 rpm. Motorcycle Consumer News tests of the 2007 model year YZF-R1 yielded a 0 to 60 mph (0 to 97 km/h) time of 2.94 seconds and 0 to 100 mph (0 to 161 km/h) of 5.46 seconds, a ¼ mile time of 9.88 seconds at 145.50 mph (234.16 km/h).