Kids DH Bike Part 3: XS Specialized Demo 8

This bike project started in early 2013 in order to get a proper Downhill (DH) bike ready for Ben's third trip to Whistler and his first racing season. At this point we had two years of experimenting trying to find and/or build bikes that would work. Our learning process started with attempts to ride our XC bikes (bad idea), then renting and testing other freeride bikes.  We bought a Kona Stinky 24 and rode that for a year, then built a custom Specialized SX Trail and rode that with 24” wheels for about a year. It became evident those bikes weren't the best choice for many of the trails we were riding. It was time to try out a legit DH bike. At this point, he needed a bike that could inspire confidence on steep, technical terrain and help him stay in control at high speeds and in the air.  

This 2013 Specialized Demo 8 XS has changed over the years to meet new demands from a growing rider. The first version had 24" wheels, custom tuned suspension, and carefully selected components to match the frame's color scheme.

Every component was carefully considered for both form and function, but the most critical decision was the frame choice. While it might be hard to believe that a 9 year old can leverage the advantages of an expensive DH frame, I have personally seen it done. The slack geometry and small cockpit accommodate body positions on steep terrain you just can't achieve on a trail bike. One of the most important things to consider when you are building a bike for a very small rider is this dimension I'm referring to as 'cockpit size'. This is a combination of the typical geometry measurements of Reach, Stack, Standover, and Seat Tube Length.  To use another perspective, consider the dimensions from the bottom bracket (BB) to the handlebar to the seat clamp.  This is where the rider moves around to find the right balance and manipulate the bike while riding.  We decided on the Specialized Demo frame because 1) It had proper DH geometry, 2) It has one of the lowest stand-over heights, 3) The cockpit was smaller than anything else we looked at.

Of similar importance for an 80 pound rider standing about 4.5 feet tall is the wheel size. It was a judgement call, but I wanted to keep the wheels at 24". There are pros and cons here and this subject of 24" wheels for little dh'ers is probably worthy of its own Blog. In hindsight I think I might lean towards starting out 26" wheels if I had it all to do over again. Some of that is about saving money, but the other main consideration is ground clearance. There is one exception: the 24" wheel offers more clearance for the rear suspension to move deep into travel without coming in to contact with the seat.  Remember, for a rider this size you will need to slam the seat as far down as you are able without disrupting rear wheel travel.

That's a good segue into the topic of suspension. With an 80 pound rider - we would need a new shock spring and air forks on the front for the suspension to properly function.  In the rear - we used Avalanche Suspension to tune Fox Van RC with a 200 lbs. spring.  In the front - we used a Rockshox Boxxer World Cup customized by ISOTuned and ran it at about 20psi.   Being able to use a spring rate that low yet still have some adjustability on rebound required some customization on the dampers.  I also needed an experienced tuner's input on damper settings since I wasn't expecting any from the Ben.   This suspension setup worked well for him and allowed for us to get some sag while still allowing good function.  The pictures below show good compression with Ben 'preloading' the bike on the face of a jump at relatively high speed. 

When 2014 rolled around we made some changes to accommodate his growth. We upgraded to 26" wheels, higher spring rates, and an interesting product we found from Canfield Brothers: a stem that would allow us to drop the bars below the upper crown. One of the challenges that exists for a small rider is finding ways to shift weight to the front wheel - and high bars make this difficult.  This is yet another opportunity where a proper DH bike with dual crown forks can come in handy for small riders. Lower Handlebars with more travel? Yes. The combination of a negative rise stem, flat bars, and an internal headset had his handle bars about 2" lower on the Demo 8 than the SX Trail with a 180mm travel single crown fork.  There's a lot that goes in to this, but one factor that raises bars are external cups on headset bearings that increase stack height.  Another factor that was a surprise is the axle to crown on 7" single crown forks is not much less than what it is on a dual crown 8" fork. The bottom line is you can probably get your riders hands lower on a DH bike with 8" of travel than you can on a 150mm trail bike - certainly a 180mm trail bike.

By the end of 2014, Ben was really getting in to stride on this bike.  He was blowing through travel on his Van RC that Avalanche Suspension tuned for his riding weight and ability in 2013. The difference between a 9 year old at 85 lbs. and a 10 year old at 93 lbs. was surprising. We changed the shock to a Cane Creek Double Barrel (coil) and were able to tune it just right for his weight and riding style.  At this point in time we also had to move him from single ply trail tires over to dual ply downhill tires.  Trail tires simply could not survive the beating anymore - even running tubeless.

In 2015, Ben was still under 5 feet tall. We felt like the bike was perfect with the exception of one thing:  he was riding the same size crank arms as I was - yet I was over a foot taller! This was the year we found the one missing piece to this build - 155mm cranks that fit an 83mm BB shell. The standard crank length for downhill bikes is 165mm - regardless of rider size. When we put together Version 1 of this bike in 2013, I thought about this, but I couldn't find a crankset with shorter arms that still fit the Demo.  That changed in 2015 when Canfield Brothers (once again) released a niche product that we needed.  We installed a set of their AM/DH cranks and gained the advantage of a more appropriate crank length for a small rider along with improved clearance for pedaling in the rough stuff.

We also experimented with a Double Barrel Air as a rear shock.  While Cane Creek does not officially support this shock in the Demo - it was interesting to test the advantages of lighter weight and air adjustability.  There are definitely advantages with an air shock, but in the end we stuck with a Double Barrel Coil and have been able to tune those shocks for a wide range of conditions and Ben's changing body weight.  We have used the CCDB with 200, 250, and 300 springs.

As of today, Ben is about 5'4'' and the current version of this Demo has 165mm cranks with a 36T chain ring and Gravity Light Direct Mount stem.  These parts accommodate his larger size and should give him a couple more months of riding.  Sure - this was an expensive bike to own and ride.  We put about $7,000 in to the bike for it's original build - with no help from any sponsors.  While this kind of investment doesn't make sense for all riders - this is the sport that Ben loves, and I've found a ton of enjoyment learning the aspects building bikes that work for unique riders.  We would absolutely recommend the Specialized Demo 8 XS to any small rider that's ready to hit the steep stuff.  This bike has been a blast to ride, reliable, and helped him get to many podiums over the years.