Saturday, August 3, 2013

Text of the June 1962 Cycle World BMW R69S Road Test
“Birth of a Legend”

Ask any motorcyclist what he considers to be the two-wheeled equivalent of the Rolls-Royce and you will almost certainly be told "BMW". That answer will not be too far wrong, either, except that the products coming from the Bayerische Motoren Werke incorporate a good deal more in advanced engineering features than the famous English car. Actually, the BMW motorcycle is more like the Mercedes than a Rolls-Royce: conservative in many respects, but quite advanced nonetheless. In any case, the BMW has attributes that make it unique, and it has acquired a reputation that makes it a "prestige" motorcycle — even among people who ordinarily don't give two wheelers a second glance.
One of the reasons for the BMW's reputation is its appearance, which is overwhelmingly massive in flavor. Even to the "layman's" eye it looks as though nothing in this world would be enough to break it, or even spring it just a trifle. The frame is a two-loop cradle of heavy, round-section tubes that extend from the steering head back almost to the rear axle. It is not triangulated, or gusseted, but somehow, in looking at it, one gets the idea that it isn't ever going to bend. "Unyielding" is a word that describes it very well. All of the miscellaneous hardware is just like the frame. The fenders, tank, and the headlight fairing are drawn from heavy gauge steel and are fixed in position with a vengeance. Every part is enameled, with a black that looks like polished obsidian, and a white pin-stripe following the fender-bead and the tank contour provides just the right amount of trim. Where chromium plating is used, as on the exhaust system, wheels, air-feed pipes and the spring/shock units, it is deep and we would bet that it's there to stay. The suspension system is interesting: at the front, a true "Earles fork" is used, which has long leading arms locating the wheel. This system gives a useful amount of anti-dive action, which keeps the bike's nose from dipping when it is braking hard, and which also permits quite long wheel movements — a feature that accounts for part of the BMW's phenomenal riding qualities. Here again, in the front suspension, there is that massive quality and in this instance, it lends a much appreciated stiffness to the fork and, consequently, precision to the steering. We noticed too, that an alternate mounting is provided for the suspension links; the purpose is to allow the fork geometry to be re-set for sidecar work. A final very nice touch was the telescoping hydraulic steering damper. This device looks exactly like a small shock absorber — which it is — and it stops any fluttering of the forks before it can begin. It acts in the same way as the adjustable, friction-disc type steering dampers more commonly used, but it is superior to the friction type in every way. The rear suspension is reasonably conventional, but with a couple of "different" touches. For example; the trailing links that locate the wheel serve a double function. The right link is also a torque-tube that houses the BMW's drive shaft. The springing is handled by spring/shock units that fit up into a pair of high steel housings that extend upward from the rearmost frame loop. The mounting looks odd, but it does the job and that is all that matters. Adjustments for the load can be made by hauling around on levers that are on the bottoms of the spring/shock units. The rear suspension, like the front, gives an unusually long wheel travel and quite soft — and ultra-comfortable — springing. The BMW's brakes are unusually large for a touring motorcycle. Of course, these machines are often used in hauling sidecars with a passenger and a mountain of luggage, so the company has shown a lot of foresight in providing the big brakes. The actual drum diameter is just under 8 inches (with shoes 1.4 inches wide) and the drums are cast from aluminum alloy and have cast-in iron liners. The front brake is of the double leading shoe type, with the brake cable pulling on one actuating-cam lever and the cable housing forcing the other lever forward with reaction pressure. The arrangement assures that both levers will be applied with equal force, and has the additional virtue of adding to the mechanical advantage. As a direct result, the brake action is light and smooth; you couldn't want anything better. The rear brake is more conventional, having only one leading and one trailing shoe. However, it is not worked as hard as the front brake and probably doesn't need the two-leading shoe feature. Besides, it is more effective when the bike is rolling back, and that is more important with a heavily loaded sidecar. In the midst of all this mechanical excellence stands the engine, which has the characteristics that account for at least half of the BMW's overall appeal. It is an opposed twin, mounted with the crank centerline parallel with that of the motorcycle's and the cylinders poking right out into the airstream. There are numerous advantages to this layout. Improved cooling is one; with the cylinders horizontal, and standing clear of the front wheel the air can blast can travel right over the cooling fins without any interference. Also, the wide separation of the cylinders assure that there will be no hot-spots between them and finally, when the bike is stopped, the heat from the cylinder will cause the air between the cooling fins to rise, creating a natural draft — just like a chimney — and drawing up cool air from underneath to remove heat from the engine. There are, obviously, some disadvantages. The first one that comes to mind is that if the rider "comes a cropper" the fall may damage the cylinder heads, which are of aluminum alloy and are somewhat exposed. Actually, the heads are strong enough to take a dreadful whacking without breaking. You may scar them a bit, but serious damage is very unlikely. For the rider who is nervous about this, BMW offers a sturdy set of crash bars that solve the problem neatly. A more real objection to the opposed twin layout is that the cylinders occupy a part of one's foot space. A BMW rider's feet actually fit under the cylinders and if the weather is cool the situation is very cozy — warmer weather will involve warmer feet. Whatever its merits as a foot-warmer, the BMW engine has few faults as a powerplant. Externally, it is distinguished by great cleanness, with cast enclosures surrounding all of the machinery that is usually "left hanging out like the vitals of an Elizabethan traitor's" as one British journalist once put it. Close attention has also been given to the seals and gaskets, and there are no oil leaks — not even the usual seepage. Inside, there is a great lot of roller and ball bearings — plain bushings are almost nonexistent. The crankshaft is made in three pieces and has the crankpins pressed into place, which permits the use of one-piece connecting rods. The crankpins are spaced at 180 degrees, so that the pistons move in opposite directions and each piston cancels the out-of-balance forces from the other, which makes the overall balance of the BMW engine nearly perfect. The offset between cylinders introduces a slight twisting vibration, around a vertical centerline, but not enough magnitude to be particularly noticeable. The only area in which the BMW could be improved is in its valve gear. With a centrally-mounted camshaft, the pushrods are entirely too long and heavy, and the BMW cannot be expected to "rev" with most of its contemporaries. The valve gear is simply too ponderous to allow very high engine speeds and while the R69S has been refined to permit much higher engine speed than any others in the BMW line, it has its limits. On the other hand, the BMW is a touring machine and for that kind of service its smoothness is the most important characteristic. BMW's transmission system is as different as their engine. A single-plate clutch, mounted on a flywheel, as in an automobile, takes the drive to a truly massive gear train. Shifting is done with sliding dog-clutches — as in any other bike — but the sheer strength of the unit is extraordinary. The bike actually makes three steps to the side: A pair of spur gears takes the drive from a spring-and-cam on the back of the clutch shaft to the transmission's "cluster gear". Then, the drive jumps over through another gear-set to the transmission's mainshaft and from the mainshaft it passes through a U-joint to the drive shaft and finally to the spiral-bevel gears that drive the rear wheel. The drive shaft is rather thin, like a torsion bar, and it is designed to "wind-up" a bit under shock loadings and thus cushion the drive. The BMW drive layout dispenses with all of the jangling chains we usually see in motorcycle , and it must be commended on that score. However, we would be less than fair if we failed to mention that in eliminating those bothersome chains, BMW has created a drive that passes through no less than five gears at all times and is, in fact, less efficient than the conventional chain drive. The road behavior of the BMW is intended to be, and is, the very thing for the long-distance, touring rider. The ride is extremely soft, the engine is unbelievably smooth and the saddle is deeply-padded, "form" fitting and comfortable in a way that beggars description. For extended touring, this really is THE bike to have. Starting is easy: much of the spark and carburetion machinery has been arranged to insure that there will be no fussiness on those cold mornings. We do have one complaint though: the kick pedal swings outward from the left side of the bike and the bike cannot be conveniently started from an "onboard" position. This has, no doubt, been done to facilitate starting with a sidehack attached, but it creates some difficulties when the BMW hasn't some kind of a prop to holding it up. Our acceleration and speed tests with the BMW revealed that, even in R69S form — as our test machine was — it was no world-beater for speed. The performance data could be improved by a bike with more miles behind it, our test BMW's odometer showed only 3500 miles, and it takes more than that to get everything in their closely fitted engines to bed-in. We are told, by people who know the BMW well that they do not reach their peak until approximately the 10,000 mile mark. Therefore, one might logically expect that our 16.0 second "standing quarter" would be slightly improved and that the top speed might go up to, perhaps, 108 or 110 miles per hour. For those who are interested: removing the BMW's mufflers showed that: A, they are extensively baffled inside; and B, they are enormously heavy. Indeed, we are not sure if the improved acceleration can be attributed to reduced backpressure, or reduced weight. Whatever the BMW's merits in a contest of speed, it is still the smoothest, best finished, quietest and cleanest motorcycle it has ever been our pleasure to ride. To be honest, we think that anyone who would worry much over its performance-potential is a bit of a booby. The R69S is fast enough to handle any encounter, and it has attributes that are, in touring, infinitely more valuable than mere speed. All things considered, if we were planning a two-wheel style vacation/tour, the BMW would have to be our choice of mount.