Technical driving report Boxer Team R 1100 S

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Technical driving report Boxer Team R 1100 S

So must be

In 1998 BMW presented the sportiest series boxer of all time. But BMW fan Romolo Liebchen from Reit im Winkel wanted more and upgraded an R 1100 S so that it can rightly be called a sports boxer.

Sachskurve, Mondays in Hockenheim, silence. Suddenly in the distance there was a dull rumble, then the blow of a freely breathing, high-revving boxer. The Boxer Team BMW R 1100 S bends deeply into the Motodrom, accelerates in the direction of the Sachskurve, lifts the rear wheel cheekily when the test driver turns on the brakes and immediately after the apex with the throttle flaps wide open, he quickly turns left and right -Combination accelerates. The stopwatch shows 1.11.64 minutes. “Not easy to drive, but 1.09 would be safe in racing,” says Markus Barth, racing driver and tester at MOTORRAD. Lap times, fantastic for any sports motorcycle, unattainable for a standard R 1100 S. How is that possible? Freed from the burden of any marketing requirements, the boxer team around Romolo Liebchen and Berthold Hauser, generously supported by enthusiastic suppliers, developed an R 1100 S into a long-distance racer with series optics.

First step: lightweight construction. The thermoplastic cladding gave way to (commercially available) carbon fiber parts from carbon fiber pope Clemens Driesch from Neustadt / Weinstrasse. A self-supporting, stable carbon fiber hump (total weight only 1.9 kilograms) replaces the rear frame, cladding and seat. The reward for the effort: a fighting weight of 202 kilograms with a full tank (with lighting system!) With a racing front-heavy weight distribution of 55 to 45 percent.

Second step: high performance with excellent durability. Helmuth Mader, tuning magician from Erding, initially increased the bore and stroke (using a lightened R 1200 C crankshaft) to 101 x 72.5 millimeters (total displacement: 1162 cm³). The crank drive, which is fairly unbalanced as standard, was finely balanced, and all plain bearing surfaces were finely machined – as narrow as possible, as wide as necessary, with optimal bearing clearance and minimal friction.
Lightweight Pankl titanium connecting rods and Mahle forged pistons reduce the rotating masses. The advantages: greater power, speed stability, reduced gyroscopic forces of the engine and thus easier handling and, last but not least, weaker vibrations (in the case of the Boxer, not caused by inertia forces, but by moments of inertia).

Not unwelcome that thanks to the short connecting rods and the lower compression height of the pistons, the cylinders could be cut by eight millimeters each, which increases the ground clearance. But the short connecting rods also result in a more radical crank ratio, which in turn promotes vibrations and reduces durability. Nevertheless, the engine vibrates noticeably less than its series counterpart. In addition, he has survived many thousands of racing kilometers without damage.
Smart solutions also in the cylinder heads, which house larger intake and exhaust valves in the racing boxer. For example, filigree "elephant feet" (articulated sliding shoes over the valve shafts) from a 125 Rotax engine replace the rustic series counterparts. Overall, the valve train lost 50 grams of oscillating and rotating masses without any loss of durability. According to Mader, the compression was "greater than 11.4: 1".

The boxer team also found their own solutions on the intake and exhaust side. Dieter Jud, map specialist at BMW in Munich, reprogrammed injection and ignition to improve performance (he also looks after PI recording). At Krontek in Neutraubling, the jagged intake path of the series boxer has been replaced by a straight guide through the aluminum tank. This increased performance just as directly as a specially pleated paper air filter. The two-in-one exhaust system made of stainless steel with the voluminous silencer (sound absorption plus reflection), contributed by MHG in Bobingen, further improves performance and power delivery. The reward for the effort: 118 hp, tremendous torque and thrilling engine characteristics.

Third step: chassis modification. The basis turned out to be good, which is why the series geometry (with BMW Sport Kit) was retained. Lightweight Sachs Race Engineering struts with aluminum damper housings take over the suspension and damping on Tele and Paralever. The elaborate suspension struts can be adjusted in rebound and compression, there in high and low-speed damping.
GThe sports boxer is braked by Brembo monoblock saddles, for which the Muller-Prazisionstechnik company in Pyrbaum manufactured adapters. While normal brake calipers are screwed together from two halves, the “monoblock” is milled from one piece of aluminum. This increases the stability, the spread under brake pressure remains minimal. In connection with also very deformation-resistant steel flex lines, the brake pressure reaches the brake disc from the Magura radial hand pump with almost no loss. Effect: a brake can hardly be better metered. Michelin Race 3 radial tires complete the sporty mix with safe driving characteristics and enormous liability reserves.

The overall result of the work: With astonishing ease, not comparable with the series, the BMW rushes through fast changing bends and steers with absolute precision. The mega-potent boxer hangs on the gas with pressure, the superb brakes are a pleasure. The chassis reacts to load changes in an unusual manner. The front rises far from the large negative spring travel, the hindquarters hardens when accelerating strongly. When braking, the opposite is true: the Telelever, which is sensitive in itself, hardens, and the motorcycle reacts with restlessness. Peculiarities that are rooted in the conceptual design of Tele- and Paralever. Driving fast with the racing boxer requires a radical adjustment from pilots who are used to conventional chassis with telescopic fork and chain drive. The lap times achieved, however, prove the great potential of the construction.

This boxer can wear the first name Sport without blushing. And it is an example of how large companies are sometimes too cautious in breaking new ground. Many solutions could be transferred to series production without functional restrictions, and that with an increase in performance and a decrease in weight. Why not like that, BMW? Wouldn’t that be the sports boxer the world had expected? Such a BMW would make a dazzling base for mass sport. Make yourself and the fans all over the world happy and let your technicians run wild. To the delight of all motorcyclists.

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