DIY Skibike Build - Forks & Geometry

Posted: Sunday, 14 December 2014 by Waynemarlow in Labels: ,
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A primer for skibike front ends

OK lets divide the bike into parts, let’s look at the front first, certainly if we can get the front right then the rear will follow. I have copied a paragraph from Wikipedia to get the “flavour” of what does what at the front. Do look up the whole article and do a bit of “bedtime reading “ as the next little nugget I am going to divulge is extremely important to us.
Trail, or caster, is the horizontal distance from where the steering axis intersects the ground to where the front wheel touches the ground. The measurement is considered positive if the front wheel ground contact point is behind (towards the rear of the bike) the steering axis intersection with the ground. Most bikes have positive trail.
Trail is often cited as an important determinant of bicycle handling characteristics and is sometimes listed in bicycle manufacturers' geometry data, although Wilson and Papodopoulos argue that mechanical trail may be a more important and informative variable, although they both describe very nearly the same thing.
Trail is a function of steering axis angle, fork offset, and wheel size

Trail - a function of steering axis angle, fork offset and wheel size

So if we look then at a classic ski bike installation, in its simplest form, as drawn above. If you have done your homework, you will realise that the red line is the head angle or rake ( steering axis ) and the green line is the effective centre of the wheel, or in our case the centre of the ski.

So now let’s introduce Wiki’s paragraph on “Mechanical Trail“
Mechanical trail is the perpendicular distance between the steering axis and the point of contact between the front wheel and the ground. It may also be referred to as normal trail.

Although the scientific understanding of bicycle steering remains incomplete, mechanical trail is certainly one of the most important variables in determining the handling characteristics of a bicycle. A higher mechanical trail is known to make a bicycle easier to ride "no hands" and thus more subjectively stable, but skilled and alert riders may have more path control if the mechanical trail is lower.

So if we now take the distance of a typical mountain bike set-up we would have about 30–50 mm of positive mechanical trail (again Wiki has a diagram to show this on varying wheel sizes). That positive mechanical trail is so important to how the bike feels and rides. If we look at the set-up above, which is exactly how most skibike conversions are, you can see that we have little or no mechanical trail. What does that mean? Yep you guessed it, that jittery feeling we so often feel in the handlebars over long flat areas and the almost instant turn when we weight the handlebars.
If you are unsure what I’m saying is correct, then as an experiment, simply turn your forks back to front and turn the handlebars 180 degrees. The fork offset is now to the rear. It does transform your bike into a cruiser with very steady steering, but that feedback you need through the steering has become so dulled as to make the skibike feel a little, well ordinary.

OK another familiar example here. Think of your average supermarket trolley, to make sure all the wheels steer and allow you to push it around the supermarket in an orderly and easy fashion, the wheels are “castered” i.e. the centre of the wheel is always behind the turning point (attachment point) of the frame, to give caster or mechanical trail. Many have the rear wheels with almost no caster or trail to avoid them clashing with your feet. Very often if you push them fast enough and then slightly turn the trolley, you will see the rear wheels “shimmy” and almost become out of control. Is this not dissimilar to many of our skibikes ?

I have long wondered why most manufacturers seem to opt for the long travel (and unnecessarily heavy and expensive) front forks and quite a high front ski attachment, coupled with a very slack head angle. Having ridden just such a skibike, the front feels really dead and not lively, almost like the ski is locked into the snow. Now that’s not a bad thing but, as budding racers we all want that instant turn and slide feeling that one gets on the likes of high powered quad bikes or when we start to throw our cars through turns with a little too much throttle, good fun and what we really should be aspiring to. So look at the drawing below.

Common skibike design - long travel forks and high front ski attachment

Here we have a very slack 68 degree head angle with a 300mm high adaptor. It may get the mechanical trail in the right place but this would not be a very nice feeling front end with a number of problems, principally the ski has moved to the rear and almost certainly would clash with the rear ski unless you move the rear ski back as well. Also the slack head angle would make the bike feel quite ponderous and slow to turn. It would work though but let’s see if we can do better.

Old fashioned trailing link suspension

A long time ago bikes had what were called trailing link suspension.They were the real first suspension units and we could take a lesson from that old design. So then what about...

Lightweight forks, very low ski adaptor, reduced trail

Looking at this, we now have our lightweight 100mm or so suspension, very low ski adaptor to prevent twist and overly weighty adaptors, about 20mm of mechanical trail and that really nice feeling 70 degree head angle. Nice.

Alternatively if you want to keep your existing ski adaptors, some and not all front forks are identical side to side, it’s just the internals which are sided. So simply turn the lower part of the fork 180 degrees so the mounting offset is to the rear. I have tried to do that on the Marzocchi forks I have and it does work well, it’s not for the faint hearted, but if you look on YouTube or some mountain bike forums, most forks are documented as how to over haul them. Do make sure you still have enough room though to prevent the front and rear ski touching each other.

Job done or food for thought? Please leave your comments in the box below or join on the Blog Facebook Group to join the discussion.

DIY SkiBike Build - The Right Frame

Posted: Sunday, 7 December 2014 by Waynemarlow in Labels: ,
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Looking at my previous articles and thinking about the nuances of converting a mountain bike frame to a ski bike and the time it takes to convert an existing frame, it’s sort of obvious that one can move things on a bit in a “clean sheet” design. So let’s think about a design that will encompass a bit of the learning curve so far.

Weight

Weight, well lack of it is everything to the day’s enjoyment. Just the lifting of the skibike to and from the car, to managing it on ski lifts, to getting it back to the car after a few too many bevies in the après ski bar; the lighter it is the more you will enjoy your day. Some of the builds we are doing are 7 kg all up, including skis, but if you can get below 10 kg then you will be alright. To put that small 3 kg difference of weight in perspective, pick something that is a bit bulky, say 6, ½ kg bags of sugar, put them in a rucksack and walk, carrying them at mid arm’s length for 15 minutes and you will understand what I mean.

If you can get below 10 kg then you will be alright

Oddly, the heavier skibikes do feel more leisurely once actually on the ski slopes. My first skibike, which is about 11 kg, seems to have a lovely mellow feel about things, it just seems to do everything in not so much of a hurry and I think that is just inertia slowing down all the movements of the skibike. A bit of a conundrum that one, I can equate it to comparing heavy American muscle cars to Euro sports hatches; they both get there equally as fast on the road in different ways, but once you turn into the parking lot that smaller, lighter car has a lot of benefits !

Chairlift Fit

Getting a skibike to fit the chairlifts and the lift system is fundamental to getting up the mountain for a day’s skibiking. Getting clearance over the rear of the skibike to allow the chairlift to pass over it without tangling the chairlift, is there a curve where the bike can sit on the chair with the ski below, if you intend to put the skibike alongside you? Will the seat still fit under the safety bar if you sit with the skibike between your legs as some riders do? Is the top frame low enough to allow the lifts with Perspex canopies, to fully close? Can you take off a ski easily to fit the skibike into one of the small cabin style lifts? So many things to think about here, but with a bit of good design it can be done.

Can you take off a ski easily to fit into one of the small cabin style lifts?

I could name another ten requirements, but for the moment we shall just consider a basic shape that will fit most situations. Unfortunately the standard bike frame, whether as a “hard-tail” or with full suspension, is so compromised by its basic unfriendly ski lift shape, that we need to think laterally a little, but somehow still retain that “bike” feel and look which we so love.


Retain that “bike” feel and look which we so love

So let’s talk about Y shaped ski bikes. Why Y shapes you may ask ? Well that old Trek classic shape of the early 90’s has real benefits as a ski bike. Look at the following shape and you can see the clearances for the ski lift over the rear, that clearance carries forward of the foot pegs to allow the skibike to sit on the seat beside you, the scalloped top tube allows the safety bar to come down into its correct place. This curved Y shape frame fits the lift system well and has enough rider ergonomics to make it a very useful shape to play with as a starting point.

 
Skibike design - why Y shapes, you may well ask?

Get Your Boots On! - Footwear for skibiking

Posted: Sunday, 30 November 2014 by Mark Kinnon in Labels: ,
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I had an interesting enquiry from Dee recently...
"Can I wear good hiking or snow boots with a skibike, instead of ski/snowboard boots? If so, what type would be best"

If you are going to ride a skibike using the freestyle/pegger method i.e. without using foot skis, then your boots need to fulfil the following requirements:
  • Be well insulated and warm
  • Be water and snow proof
  • Have good grip in slippery situations
  • Provide some ankle support
  • Allow normal articulation for walking or getting off a chairlift
As Snowboard boots fulfil many of the above skibiking needs, are relatively inexpensive and readily available, they are the number one choice for most freestyle skibikers.

Snowboard boots - the choice of most skibikers

However some skibikers still prefer normal hiking boots, I tried them but ended up with wet feet, which apart from the discomfort, could cause health issues after prolonged exposure, such as frost bite or trench foot.
Alternatively; snowmobile, quad or dirt bike boots have been used by other freestyle skibikers with great success. Lastly, from personal experience, I can confirm that both downhill and ski touring "randonee" ski boots are totally unsuitable for this application and should be avoided at all costs, even spray painted Doctor Martens boots woud be better, get your boots on!



Blog Tour 2014-15 Season Kick Off

Posted: Wednesday, 26 November 2014 by Mark Kinnon in Labels: , ,
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Many years ago a young work colleague, with wisdom beyond his years, told me "There's no point working this hard if it's not for something". Throughout the summer and autumn, during all those long afternoons doing boring jobs, I've been day dreaming about this moment of freedom.
The purpose of this trip was to test out a nice selection of new (to me) items and to get my stiff and flabby body into some resemblance of order before the season proper starts in a months time.

My first port of call was to be Bottrop, near Essen, home to the Alpincenter, claimed to be Europe's longest indoor snow slope. You can read more about the slope and its facilities from my earlier visit. The trip from London to Essen was nearly all plain sailing till the last 30 miles, Germany is clearly aiming to be more British when it comes to totally blocking up the infrastructure with road works, don't do it Germany, it's not worth it.

Alpincenter - Europe's longest indoor snow slope

Arriving just after the 10am opening, I set about with a warm up on skiboards. My tools were a pair of Line skiboards, picked up a month or so ago for the princely sum of £10 from eBay, they even came with the proper carry bag. These were complimented with a pair of Raichle Flexon boots that I picked up in the early summer for £20 also off eBay. In absolutely mint condition and by jingo they fitted a treat too, the only downside is that they are very, pink. In the early 90s, such acid colours were all the rage, no doubt a lime green and purple ski suit plus a Chris Waddle power mullet wig would fully complete the look. Let's just say that for a man to wear pink boots you have to be very confident about your sexuality, one way or the other, nuff said.

Pink boots - you have to be confident about your sexuality

These two thrift store bargains made a great combo and I had a couple of happy hours warming up my rusty body with them, I anticipate they will be a good upgrade for this season, in resorts that don't allow skibiking or where filming duties are required.

Feeling toasty I pulled out my skibike, I had just made another modification to the front ski mount and was keen to see if it would stand up to real world use. I slipped straight into the grove from the first run and just kept getting more confident and fluid as the day progressed.

Before dusk arrived, I nipped out to the car park and swapped over to the 90cm NISM skibike skiboards, what sheer bliss, I didn't change back. They are on special offer here on the blog at the moment, but if no-one gets them soon, I can see me taking the plunge. In the clinical environment of an indoor centre you can really focus on technique, they are remarkable devices once you work out how to really get them on an edge.

It was an amazing day, I started just after 10am in the morning and stayed till closing time at 10pm, almost 12 hours on the snow. How tired and stiff would I be for day two though?

One noticeable change on this visit was a radical change to the canned music played, gone are the garish 80s selection, to be replaced by modern pop music, the sort were the singer sounds like a malfunctioning robot. I believe it is a genre called EDM by the cognoscenti. Yo motherfudgers, get turned up to death.


 


It was a bit much to expect my body to cope with the onslaught of so much activity without some recoil; never the less, the following morning I still managed to drag myself out of the sack and get properly scrubbed up for the short drive to the nearby town of Neuss, just outside of Düsseldorf. It's an area of open flatlands, making the distinctive silhouette of Allrounder mountain resort easy to spot from miles away.

The distinctive silhouette of Allrounder mountain resort - easy to spot for miles

Allrounder mountain resort is very glitzy compared to Bottrop, all stainless steel and glass, shiny, shiny. Following protocol I scouted out the slope on skis incognito, on paper it is quite a short slope, just 300m long, which is half the length of Bottrop. In reality, the usable length is the same and the presence of a full scale chairlift system is an outstanding feature, making for hassle free and speedy uplift.

A full scale chairlift system - an outstanding feature

The snow on the slope at Allrounder mountain resort was in excellent condition, if I understood the German correctly, the marketing blurb refers to it a powder snow, which might be going a bit far, but it was definitely deep, crisp and even. The temperature was distinctly chilly, yesterday I was riding in just a polo shirt and fleece, today I had to add another layer to stay warm and should really have dug out thicker gloves from the suitcase too.

I had previously contacted the management at Allrounder mountain resort to see how they regarded skibikes and received a favourable response; this was confirmed when I spotted a well worn Brenter skibob next to the engineering station and a baby one on the juniors play slope getting a good work out.

At lunchtime I slipped into skibiker mode and made my way to the chairlift, an operator shot out pretty quickly, I showed him my leash as I had been instructed, he grinned and disappeared back inside and that was that. I spent a very pleasant afternoon going over jumps, making wide carves, following the fall line and generally wiggling around to my heart's content.

At lunchtime I slipped into skibiker mode

Around 6pm I had to quit, I was tired and had to be heading off to my overnight accommodation in Belgium. It was very much a case of mission accomplished; I had tested out my kit successfully, given myself a valuable pre season warm up refresher course and even learnt a couple of new tricks along the way.

Best of all was to have found another potential year round skibike training camp at Allrounder mountain resort.

Skibikes at Allrounder mountain resort - mission accomplished

November Knockout - 20% price reduction on ex-demo NISM skibike skiboards

Posted: Saturday, 1 November 2014 by Mark Kinnon in Labels: , ,
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On the Internet you can learn something new everyday:

November (Listeni/nˈvɛmbər/ noh-VEM-bər) is the eleventh month of the year in the Julian and Gregorian Calendars and one of four months with the length of 30 days. November was the ninth month of the ancient Roman calendar. November retained its name (from the Latin novem meaning "nine") when January and February were added to the Roman calendar.

For the whole of the month of November NISM have agreed to drop the price of our ex-demo NISM skibike skiboards to 20% of their original price.

The price for the NISM 100cm "All Mountain" skibike skiboards is now £188 delivered (were £235)

And the price for smaller NISM 90cm "Park" skibike skiboards is now £176 delivered (were £220)

Snow has been falling in the Alps and is even forecast for Scotland this week. so come on UK skibikers, what are you waiting for?


NISM skibike specific skiboards - 20% off in November

For Sale - New $100 Economy Skibike Conversion Kits

Posted: Sunday, 12 October 2014 by Mark Kinnon in Labels: , ,
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For many skibikers their first skibike is a mountain bike conversion, for some the lure of creating a skibike utilising a scrap mountain bike frame and some home DIY materials, such as; lumber, wood screws and skateboard trucks proves irresistible.
Whilst it no doubt gives great pleasure to build such low budget ghetto skibike creations and ride them at the local sledging hill, it is unwise to take them to a proper mountain resort where they are very likely to be a danger to both yourself and other snow users.

Fortunately there is now a greater choice of skibike conversion kits than ever before and Bike the Slopes from Calgary in Canada have broken a new price point with a conversion kit for just $125 Canadian Dollars, a mere £69 at the time of writing.

This special deal will only be available for the 2014-15 winter season, with a total cost to UK based buyers of $225 Canadian dollars (approximately £125) including shipping in 8-10 days by air post.

All mounting hardware is included to easily convert your mountain bike to a skibike engineered to provide maximum comfort, handling and affordability.


Bike the Slopes - skibike conversion kit, just $100 CAD (plus delivery)

Buyers in Canada and the Continental United States - click below



Buyers in the United Kingdom, Europe and South America - click below


For Sale - Lenz Sport Alpine Brawler Freestyle Skibike - £1499

Posted: Saturday, 11 October 2014 by Mark Kinnon in Labels: , ,
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This is something you won't get to see every day, the big daddy of skibikes, a gorgeous hand made Lenz Sport Alpine Brawler, on sale, right here in the UK and at a knock down price to boot. If you haven't heard of Lenz Sport, where have you been for the last decade?
Already a well-respected manufacturer of high-end mountain bikes, Lenz Sport entered the ski bike market in 2004 after Devin Lenz, the owner of the company, traded two of his old mountain bike frames for some commercially made ski bike conversion kits.

The brand has been continuously evolving since then, most of the parts are manufactured in house to very high standards and Lenz Sport has become the benchmark against which many other brands are judged.

For Sale - Lenz Sport Alpine Brawler in Kawasaki green

This particular one is a large framed model, finished in a classic Kawasaki Green colour. It was purchased new directly from Devin Lenz a few years ago and for the owner it is a reluctant sale, he has had a lot of fun on it in the Alps, but now mostly skis with his kids.


Condition:

It is still in very good condition with just a few light scratches on the frame. There is some light rust on the ski edges, which will come right off once tuned up for next season and there is also a small hole in the seat cover (thanks to a rogue bungee hook).

For Sale - Lenz Sport Alpine Brawler


Specifications:
  • 8 inches of front travel with a Rockshox BoXXer Fork
  • 6 inches of rear travel
  • Lenz SECUREST chairlift managing system
  • Lenz precision machined ski mounting system
  • Long padded seat for comfort and protection
  • Fitted with “Monster” foot pegs for superior control 

Rockshox BoXXer - 8 inches of front travel

Collection:
 
Available for pick-up only in Headley, East Hampshire, UK which is about an hour from London down the A3, between Guildford and Petersfield.


Summary:

This is a premium specification skibike which retails at $3274 (over £2000) in the USA. Sterling may be strong against the Dollar currently, but nothing like this is currently available in the UK. Even if you can find similar items in the USA, don't be fooled by the price shown in Dollars. Once you have paid the courier costs (£75+), import duty (2.7% of value), VAT (20% of value) and sundry other "incidental" costs, the real price could be nearly doubled.

This Lenz Sport Alpine Brawler is right here in the UK, all ready for pick up, oh and don't assume it will still be here in January, the owner is considering taking it with him to Switzerland, don't let this rare opportunity slip away.

Lenz Sport Alpine Brawler - Securest™ chairlift system for easy loading

Contact:

Drop me a line through the contact form and I will make arrangements for inspection and payment.

As if you need any further inducement, here's a video of two Alpine Brawler skibikes, riding in Flaine, France, to whet your appetite...



UPDATES:

None so far

Oktoberfest surprise - 10% price reduction on ex-demo NISM skibike skiboards

Posted: Saturday, 4 October 2014 by Mark Kinnon in Labels: , , , ,
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Oktoberfest is a word that might not be in everyone's lexicon, so here's what the Wikipedia has to say about it:
Oktoberfest is the world's largest funfair held annually in Munich, Bavaria, Germany. It is a 16-day festival running from late September to the first weekend in October with more than 6 million people from around the world attending the event every year. Locally, it is often simply called Wiesn, after the colloquial name of the fairgrounds (Theresienwiese) themselves. The Oktoberfest is an important part of Bavarian culture, having been held since 1810. Other cities across the world also hold Oktoberfest celebrations, modelled after the original Munich event.

To celebrate this year's Oktoberfest NISM have agreed to drop the price of our ex-demo NISM skibike skiboards by 10% for the whole of the month of October.

The price for the NISM 100cm "All Mountain" skibike skiboards is now £211.50 delivered (were £235)

And the price for smaller NISM 90cm "Park" skibike skiboards is now £198.00 delivered (were £220)

Come on UK skibikers, what are you waiting for?

NISM skibike specific skiboards - 10% off in October

For Sale - NISM 100cm Skibike Skiboards - Down to £188

Posted: Monday, 4 August 2014 by Mark Kinnon in Labels: , ,
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I am in the position of being able to offer a pair of ex demo NISM 100cm Snow Bike specific skis for sale. Marketed by NISM skibikes as an "all-mountain" ski, particularly suited to downhill mountain bike to skibike conversions. They will excite those riders who want to lock into a carve and achieve wheel like stability whilst on edge. They are a great to ride in all soft snow conditions, especially off-piste, those riders who want speed to be their top priority will not be disappointed with theis design of skibike specific skis.
In rigorous testing, right here on this site, they proved themselves to be a capable ski design for all mountain use.

For sale NISM 100cm snow bike skis - for those riders who want to carve

If you have only ever come across SnowBlade™ type skis then these will come as somewhat of a shock; they are considerably wider, giving the impression of being half way point between a normal ski and the snow board type commonly only seen on SnowScoots. I shouldn't have to tell you that these are skis specifically designed for use on a skibike and not as something that goes on your feet. Every aspect of the design is geared towards giving you the sort of riding experience that simply cannot be obtained with regular short skis.

They are fitted with both the standard 40 X 40mm skiboard binding mount pattern, as used on many popular skibike adapter systems and also one suitable for owners of LenzSport skibikes.

For sale NISM 100cm snow bike skis - perfect fo skibike conversions

For their size these NISM skis are amazingly light, we incorrectly assumed that they were foam cored. In reality they are constructed from vertically laminated poplar with a double layer of fibreglass for added strength and a white urethane fill between the wood core and the outside of the ski to protect and waterproof.

NISM 100cm snow bike skis - not skinny "SnowBlade™" style skis

As testament to the extensive nature of our testing process, some light damage has occurred to the top sheet where it caught between the skibike frame and ski. If you are overly concerned about appearances and given the matt nature of the NISM graphics, I would be very tempted to lay on a few coats of paint to match your skibike's colour scheme and be done with.

Please remember these are not skinny "SnowBlade™" style skis, they are wide skibike specific ski boards. I have checked on eBay and elsewhere, nothing like these are currently available in the UK. Even if you can find similar items in the USA, don't be fooled by low prices shown in Dollars. Once you have paid the courier costs (£25+), import duty (2.7% of value), VAT (20% of value) and sundry other "incidental" costs, the real price could be nearly doubled.


Skibike spares are not exactly plentiful in the UK, stocks are limited to just this one pair and it is highly unlikely that further items will be available, so don't tarry if this is what you need for your skibike project.

The cost is £188 for the pair, inclusive of delivery to any UK address.

For Sale - NISM 90cm Skibike Skiboards - Down to £176

Posted: Saturday, 2 August 2014 by Mark Kinnon in Labels: , ,
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Unusually, I am in the position of being able to offer a pair of ex demo NISM 90cm Snow Bike specific skis for sale. Although marketed by NISM skibikes as a "park" ski, particularly suited to BMX skibike conversions, in rigorous testing right here on this site, they proved to be both testers favourite NISM ski design for all mountain use.
Nimble, light and stable they are an absolute joy to ride in all soft snow conditions, whether on or off piste. They earned our top commendations off-piste, by turning any gully into a natural half-pipe to be joyfully exploited to its full potential.

NISM 90cm snow bike skis - a joy to ride in all soft snow conditions

If you have only ever come across SnowBlade™ type skis then these will come as somewhat of a shock; they are considerably wider, giving the impression of being half way point between a normal ski and the snow board type commonly only seen on SnowScoots. I shouldn't have to tell you that these are skis specifically designed for use on a skibike and not as something that goes on your feet. Every aspect of the design is geared towards giving you the sort of riding experience that simply cannot be obtained with regular short skis.

They are fitted with both the standard 40 X 40mm skiboard binding mount pattern, as used on many popular skibike adapter systems and also one suitable for owners of LenzSport skibikes.

NISM 90cm snow bike skis - fitted with both common mounting patterns

For their size these NISM skis are amazingly light, we incorrectly assumed that they were foam cored. In reality they are constructed from vertically laminated poplar with a double layer of fibreglass for added strength and a white urethane fill between the wood core and the outside of the ski to protect and waterproof.

NISM 90cm snow bike skis - some light damage has occurred

As testament to the extensive nature of our testing process, some light damage has occurred to the top sheet where it caught between the skibike frame and ski. If you are overly concerned about appearances and given the matt nature of the NISM graphics, I would be very tempted to lay on a few coats of paint to match your skibike's colour scheme and be done with.

NISM 90cm snow bike skis -  stocks are limited to just this one pair

Please remember these are not skinny "SnowBlade™" style skis, they are wide skibike specific ski boards. I have checked on eBay and elsewhere, nothing like these are currently available in the UK. Even if you can find similar items in the USA, don't be fooled by low prices shown in Dollars. Once you have paid the courier costs (£25+), import duty (2.7% of value), VAT (20% of value) and sundry other "incidental" costs, the real price could be nearly doubled.




Skibike spares are not exactly plentiful in the UK, stocks are limited to just this one pair and it is highly unlikely that further items will be available, so don't tarry if this is what you need for your skibike project.

The cost is £198 for the pair, inclusive of delivery to any UK address.