The SkiBike Shop

Wayne Richards has already forgotten more about ski technique and bike technology than I will ever be able to learn in this lifetime, he now continues his essay on the nuances of skibike design from a DIY self-build perspective.

OK here’s where it all gets a bit tricky and probably there are far more experienced people out there who have tried and done many of the things I am about to discuss, please write into Mark and put your theories over as there is almost no information out there discussing these points. I’ll have a go but can only relate it to my MX, more latterly MTB cycling knowledge and from the other side of the sport, an in depth knowledge of skiing. Lets treat this as knowledge that will need refining as we go along and our experience builds up.

Head angle, well a thorny subject and something I think is not particularly understood in the ski bike world. It has an implicit effect on how the bike handles, probably more than suspension settings. Head angle in mountain biking terms is there to give a caster self steering effect i.e. let the handle bars go and the front wheel should self centre, the slacker head angle you have the greater the effect, the less manoeuvrable, the more dead the front steering will feel. Now as we steer very little on a ski bike that may at first sight seem to be a good thing and I think that is where most of the manufacturers have gone, a relatively lazy or in MTB terms, slack head angle.

Good handling is all about slack head angles

I would also suspect they have done so to resolve a fundamental perceived handling problem of ski bikes, that of the front ski ( and to a lesser degree the rear ) feeling really skittish along flat trails. Anybody who has been ski biking will have particularly noticed this on fresh packed down snow, green trails or very flat runs, where the front handlebars constantly want to make tiny turns in either direction at random ( MXers call it head shake ) without the riders input, it can be quite disturbing unless pre-warned about it. What causes it, well it’s relatively simple and nothing to do with the bike.

Remember back in the early eighties ( prior to snowboards ) a monoski was the “derigour” for anybody who was a little bit offbeat and wanted to look cool, the big problem with them was they were almost impossible to ski on flat trails because the ski constantly fretted about until, with both legs locked side by side, the rider was ejected onto their arse. They didn’t last long and with the advent of boards soon disappeared. So what is the cause ? Skis have curved edges designed to carve radii in the snow, which ever edge is digging into the snow, the ski will want to radius around on, simple, that’s what they are designed to do. Now flat runs are not flat and have lots and lots of little mini hills where other skiers have left lines and indentations and little ridges. Each time an edge feels a higher part of the piste, it will want to take over and turn toward that edge. Flat monoski on a flat piste with the ski not knowing which edge it wants to radius on, means that tell tale handlebar waggle is going to happen. Equally the rear ski can feel all waggly and horrible for those very same reasons.

You can build the skibike with a slack head angle

How do we resolve it, well you can build the bike with a slack head angle or if you are converting a MTB then you are really committed to what you have already built into the frame ( downhill frames will have the slackest but will also weigh the most ). Mechanically we can lower the rear of the bike a bit or use longer travel forks than what the frame was designed for, use different length ski adaptors with a longer one at the front perhaps, but you will never actually fully stop it until the front angle is so slack that the front steering will feel very sluggish and with very little feed back. There are other downsides, a slack angle, the longer the bike will become, longer forks or higher ski adapters and COG suddenly becomes very high, mechanically the forks are not working optimally ( stiction ) with higher loadings on the headstock, its all a trade off of one form or another.

There is an alternative - just plain simple better rider technique

There is an alternative that lets you keep that sharp turning, lots of feedback from the front ski, lively feel, that we have come to expect from a good MTB setup. Just plain simple better rider technique. Never ride straight and flat, always make graceful long radius turns along any flat areas. By doing this you dictate which ski edge the ski is on and you will totally eliminate the shimmy and head shake you can get. The benefits of a tighter head angle are more pronounced for the Peggers amongst us, where we tend to ride standing up, we are inherently more unstable and by being unstable we are more manoeuvrable. Come those little tight flat access tracks between pistes, we can turn on a dime, sitting down is bit more taxing, but slacken that head angle, and that turning on a dime just becomes a whole lot harder.

So what is the optimum angles, sorry at the moment ski biking in the modern form we are talking about, is so new that we are really just experimenting, sooner or later an optimum angle will be worked out. For those starting with a MTB frames, back into the equation.

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OK the next thing to think about is the skis themselves, that will be discussed in Part 4.