BMW Telelever made simple!

The dynamics of a motorbike has always fascinated me. When I was a little kid I loved my Lego Technic, I built everything with it, but mostly cars and motorbikes. Thanks to the fact that “back in the good old days” the Lego Technic range wasn’t that elaborate at all, in fact, it was quite bulky and cumbersome. This of course was the design obstacle, you could not build exactly what you wanted, simply because the materials weren’t flexible enough. But this was a good thing for me. You see, I had to overcome that problem and design my vehicles with what I had. Sure I cheated sometimes by drilling a hole or bending the plastic by heating it with a lighter, but that wasn’t really helping that much.

One of the biggest problems I had was actually designing a car with the combination of four wheel drive, front steering and suspension. One of them was not a problem, two became cumbersome, but all three was either a very ugly design decision or simply, not feasible. Motorbikes, on the other hand, were much easier to design. Sadly there were no such things as motorbike tyres, let alone in any size that I wanted. I remember it quite clearly when my dad took me to watch trials. Where we lived there was a creek-stage, and these bikes went in, out and around this little creek of an old mill. It was very fascinating for a small boy.

Of all the times we went to watch the races, I can clearly remember one thing, This huge trail bike, it really looked massive, but the thing I remember mostly about it, was it’s single sided swing arm. This piece of engineering was truly amazing, so amazing that I adopted it for my Lego-bikes. It wasn’t that stable, but it looked good. And remembering back, the Lego wheels looked a bit like the hub of, you guessed it, the BMW GS!

The BMW GS range is now a living classic range. When it was launched it did something that nobody really thought that would work – a huge and heavy off road bike – can’t be done..! Oh how wrong – the GS is now the best selling BMW model, simply amazing. I remember “riding” my Lego GS models over anything that I could find in the house; pillows, old chocolate boxes, thresholds, anything with some sort of surface. The surface could not be even, because what would the point of front and rear suspension be on a flat surface?! I used rubber bands to act as the shock; more rubber bands – stiffer suspension. Some of them even had brakes; I used a little lever to push onto a smaller wheel attached to the rear axle spindle, worked like a treat.

Unfortunately, for me, my mechanical engineering career never took off, there were simply no schools around for that sort of jobs, and I didn’t like crunching the numbers – “Anyone can do that”, so I ventured onto other areas, but I never forgot the simplicity of the Lego’s and what they could do.
Luckily this came in handy not to far ago. My beloved girlfriend had a job interview with a motorcycle manufacturer and to prepare for it we sat down and discussed the technical aspects of bikes. We spoke about engine layouts, we spoke about centre of gravity, brakes, handling, tyre sizes, you name it, we talked about it. At some point I picked up the latest BMW R1200GS brochure. One of the pictures is a stripped down GS, with no panels, no extras, just the frames, swinging arm, wheels, gearbox, engine and complete front suspension. We were talking about how the individual parts of the GS bike make no sense and that there are better compromises.

Shaft drive is, heavy and expensive, but it is maintenance free – “heavy” is bad on an off-road bike. The flat twin engine is self balancing, but the layout is wide and produces sideways engine inertia. And so forth – there are better individual parts, but if you bolt them together like BMW has done, it all starts to make sense. And on top of that all big “Beemers” have got the wonderful Telelever front suspension. When you see the naked GS you see that it really is an engineering masterpiece. To me it is more elegant than anything that has come out of the Ducati factory.

As a graduate engineer with limited hands on experience with spanners and, above all, Lego, my girlfriend struggled to see exactly how the Telelever suspension really worked without resorting to drawing on the diagram and jot on the beautiful picture. To me, this was completely absurd, nobody, never ever will be allowed to draw on this Mona Lisa of engineering. To me, the only solution was to show her that there are other ways of understanding this. Ways that don’t require powerful CAD programs, pens, paper and calculator! All that was needed was an adventurous mind, materials and a good laugh.

It was 11 o’clock in the evening when I pulled out my trusty hot-glue gun, and ran around the house looking for materials. I found old CDs, old pens, old drink bottles and cans and other such things. I also got some tools like knife and scissors out. I then started thinking, and I started out with gluing an empty can of pop onto an old CD-ROM, this was the base, this was the body of the Beemer. I then proceeded to cut out a bottle neck to use as the fixing point for the Telelever’s forward facing swinging arm and the front frame that holds the shock and the top triple clamps of the forks. I manufactured the forks out of two similar pens that I slaughtered – the ink-reservoir tube was used as the top and the outer “pen-part” as the bottom. These inner-outer tubes slide nicely – just like BMW’s construction. I then took the inner-ink-tubes out of two other pens and manufactured the swinging-arm. I used a pen and a part of a pen-cap to make the pivot point, the top sub frame was just an outer-piece of a pen. I used a bit of cardboard to create the point where the top frame pivots with the forks. I used needles as the pivot points. To finish it off I got a spring from a pen that can act as the WP-shock unit (note that the WP unit fitted to the real GS model is much more expensive than the one used on the model). End result is a model that works exactly like the BMW Telelever front suspension.

The beauty with the Telelever system is that it retains the looks and functionality of a normal fork-setup, but it gives the engineers much more precision when engineering the characteristics of the bikes handling.
A traditional fork-setup has got two big disadvantages – the first one is the length of the forks – they are very long, and aren’t braced in anyway. This means that they have to be very sturdy to take the longitudinal forces. The Telelever on the other hand has got the swinging arm fastened as close to the wheel as possible.
The biggest advance, though, is the Telelever system combines the advantages of both the forks and a swinging arm – well, it’s got both, doesn’t it. ? A normal front fork-setup has got fixed geometry, now this is very good, apart from the fact, that the bike changes its geometry. When you apply the brakes, the centre of gravity moves forward on the bike thus increasing the pressure on the front springs. This means that the forks compress (d’Oh!), all normal so far. However, the bad thing is that geometry changes when the forks compress (and the rear doesn’t), the rake of the front has suddenly decreased – you get the same effect as if you would drop your fork legs through the yokes. While this isn’t really a big problem, the big problem is the dive and the weight shift under braking.

If you have ever seen a pooch slide on a newly waxed floor, you’ll notice that he’ll extend his front legs, not bend them. He does that to get more pressure on the front legs to stop quicker and to stop him from tumbling over. Your traditionally-equipped-bike does exactly that – wants to tumble over.
Thanks to having a swinging arm, the lower pivoting point of the forks can be engineered to move. The swinging arm, after all, has got a radius just like any arm attached to a pivot point.
By adjusting the length of the arm, and the position relative to the lower pivoting point on the fork-legs the rake of the fork legs can be engineered to either increase, decrease, or, surprise, surprise stay the same. Technically the Telelever can be engineered to give zero dive under braking. Amazing. Der Engineeren have engineered in a bit of dive, for us mortal humans, so that we can feel that we are stopping.
You also get a lot of other advantages, such as only one shock-spring-unit. However, there are also disadvantages, mainly which are due to the swinging arm. The construction isn’t really suitable for all sorts of bikes, mainly depending on engine-layout. It would be very hard to engineer a bike with both an inline four and the Telelever suspension. I also suspect that it’s quite an expensive construction.

You also might wonder why other manufacturers don’t use the Telelever construction, well… it’s patented – Natürlich!

All in all, the new BMW GS is a piece of engineering art – to check it out, go down to your local BMW garage, and try one out – you’ll see what I mean.

The Telelever suspension is “über alles” when it comes to front suspension. In fact the whole BMW package, flat twin, Telelever, separate gearbox, Paralever shaft drive, is an incredible package. It’s well thought out, I might even go as far as saying that the BMW engineers have engineered out anything that’s not desired from the original flat-twin-shaft-drive construction.

Hats off to engineers!

Jocke Selin

Copyright © 2004. All rights reserved. Users may download and print extracts of content from this website for their own personal and non-commercial use only. Republication or redistribution of content, including by framing or similar means, is expressly prohibited without the prior written consent of Motorbikestoday.