DIY Skibike Build - Modifying Alpine Skibikes Conversion Kit

Posted: Saturday, 10 January 2015 by Mark Kinnon in Labels: ,

When the Alpine Skibikes adapter kit system was first introduced, there had never been a similar product available that could so easily transform your much loved mountain bike into a skibike.
The emerging freestyle skibike scene was heavily focussed on all mountain riding in Colorado powder and freestyle stunts in the snow park. Controlled carving on European, rock hard, groomed snow just wasn't on the agenda.

Alpine Skibikes conversion kit - unique when first introduced

The Alpine Skibikes design uses a clever concentric spring design that allows a great deal of tilt of the skis, whilst still returning them to a neutral position should you find yourself airborne. It is a neat  engineering solution, that reflects inventor Matt Hanson's aviation background.
In my experience of using these adapters, for many weeks of riding, spread over quite a few seasons, I began to appreciate that there was quite a fine balance point beyond which the front ski would tuck under and you would find yourself abruptly thrown over the handlebars. This is something that a motor cyclist would call a "high sider" or I might call the "superman" ejection.

Alpine Skibikes conversion kit - a clever concentric spring design

I was eager to find a solution to this aspect of the design, eventually I saw another Alpine Skibikes user had created a solution. It was based on adding a bicycle crank to the front bracket, attached to the end of the crank was a rubber strap which was looped around the brake arch on the front forks. This is very much a simplified version of the system used on the Lenzsport skibikes, which are noted for their stability and ease of control.

I wanted to make something similar, so my first task was to hunt through my garage scrap pile for a suitable crank piece. I found some nice box section aluminium tubing, originally part of a now defunct photographic stand. In retrospect, it is hugely over engineered, but I would rather this than have parts fail on you half way down the mountain.

Scrap pile surprise - box section aluminium tubing

Finding the right type of rubber strapping proved to required a fair bit of searching which eventually lead to Matlock brand cargo straps. These are designed to secure the curtain sides of heavy goods vehicles; any item designed to withstand that level of vibration, across a gamut of temperatures, whilst under constant tension should be up to the task.
With all the parts gathered, I spent a couple of hours mocking up the arrangement I had in mind, playing around with locations and working out the correct length of the crank. I intentionally made the bar slightly longer than needed, then drilled a selection of mounting holes to allow for plenty of adjustment for bungee length and tension.

The "dry run" - mocking up the arrangement I had in mind

The trickiest part of the process, for me, is accurately marking out and drilling the pilot holes, after that you just have to go slow and steady enlarging them to the appropriate size. You can do this by working your way up through drill sizes or use a step drill which saves considerable time swapping drill bits.

The tricky bit - marking out and drilling of the pilot holes

I never had the opportunity to test the system on snow before the start of the 2013-14 season, but I was delighted to find that the whole system worked perfectly from the start and needed little modification. The straps create a very nice progressive increase in resistance, having little effect on the flat, but saving you from going past the point of no return mid-carve and having the front ski suddenly tuck under.

The straps create a very nice progressive increase in resistance

Carving ability was taken to a whole new level by allowing you ride with a much more aggressive riding position, weight well forwards, putting downward pressure on the handlebars. It is also easier to put the skibike beyond regular tail slide drifting and into a totally sideways slide, much more like the classic skier's hockey stop. The increase in confidence created, meant I was much more likely to stand up on the foot pegs, riding in the classic "pegger" stance, rather than seated, as had been my previous dominant riding style.

Fellow Blog writer, Wayne Richards suggested that the effect was purely psychological, a case of "Emperor's New Skibike" perhaps? Towards the end of the season and after quite a lot of riding, the curved hooks on the end of the strap began to suffer from metal fatigue and straightened out enough for them to pop out on a number of occasions. As soon as this occurred, the result was to return the skibike to it's old handling characteristics, which usually resulted in a fall. As this happened on the first couple of occasions "blind" without me realising what was going on, it proved that the effect is tangible and not just perceived.

Modified Alpine Skibikes conversion - carving ability improved

For this season I have reversed the position of the rubber straps with the mounting hooks on the outside and secured them permanently with a nut, bolt and washer combination. One downside is that this makes the mounting of skis less convenient than it used to be.
In the past I would transport two skibike frames in the boot of my car and keep the Alpine Skibikes brackets mounted to the skis permanently. This made for a quick and convenient method to setting up two skibikes, which could be transported within the confines of my sub-compact car's boot. With the adapters permanently mounted to the frame, I am either going to have to up-scale my vehicle or mount a bike rack to the rear.

I am going to have to up-scale my vehicle

Even though I have sacrificed the ability to quickly mount and dismount the ski adapters, I still feel it is worth the addition effort, as this; easy, cheap and quick modification makes such a difference to the skibike's handling.
Another future modification that would be a real game changer, would be some form of quick release plate, such as those used on professional camera tripods, so that you could pop on and off skis with a quick flick of a lever.

Interestingly within days of making my modifications, a second generation of Alpine Skibikes conversion kits were launched with a similar, but greatly finessed iteration of the same layout.

Looking for parts to build a skibike? Or perhaps one ready to ride away? See our Parts For Sale page here.