Spectre 29" MTB Prototype

The big-wheeled mountain bike trend hasn't caught on that much in Europe yet, but it does have quite a large cult
following in the States. The so called '29 inch' wheel is actually a 700C rim, which when fitted with a 2" knobbly tyre,
comes close to a 29" diameter. The idea is that a bigger wheel rolls over surface imperfections more easily, and is
thus faster. The downside is that the bigger wheel is heavier, and thus is going to take more effort to accelerate - so
the theory is that a 29er is faster on big open courses, but slower in the woods than a 26" bike. But for bikes along
the lines of the Spectres, which are fully rigid, the bigger wheel idea makes more sense, as passive smoothing of the
ride is the whole idea. Henrik and I talked about it last year, and I drew up the geometry for one to try. Now, on
most 29ers, the front end finishes up being massively high, as the big wheel, combined with a suspension fork, jacks
the headtube up in the air. Riders typically use a negative rise stem to overcome this. My plan, not having to
accomodate suspension travel, was to use an ultra short fork, combined with a small headtube, to allow the
handlebars to be at the right height with a regular stem. And with the rear wheel tucked up as close to the seattube as
possible, I could get the wheelbase very close to that of a 26" bike.

Taiwan produced the prototype frame for us, but didn't supply a fork. I'll get a proper one built soon, but in the
meantime I have adapted a 26" fork, which just fits - though the tyre clearance is so tiny that I wouldn't want to ride
it in the mud! Importantly for testing, the fork is within a few mm of the designed length and offset. I was able to find
a brake which I could modifiy to work on the brake bosses (which are obviously set for a smaller wheel), and then
stole the parts from my 26" Spectre to build the bike up for testing.

Initial rides have been very good - it does seem to romp along quite nicely. I will do some back-to-back rides with a
26" bike and a heart rate monitor soon to get a better idea of the differences.

I finally had the opportunity to build a new fork for the bike, with a low crown - but with decent mud clearance!
Turned out pretty well, but I may build a second one a bit stiffer - this one is pretty springy; which is nice for comfort
but perhaps a bit too much for tough terrain.... Haven't actually ridden it offroad yet, so we'll see. I also changed it
down to a single chainring - with the big wheels I found that there really wasn't much need for the big ring when riding
offroad. Just having nine gears keeps it nice and simple - and eliminates the front derailleur, which was tight for
clearance with the tyre anyway. I just have a small chain keeper instead.

May '08 Well the steel fork I built ended up a bit too springy for my liking, so when I disovered that White Brothers
were making a rigid fork in a length just slightly longer than I designed the frame for, I decided to just use that - in
theory the slightly longer fork will slacken the head angle a little, which should make the handling better for the bigger
terrain here than the tight woods riding it was designed for. I used Pace canti brake mounts on the fork. Now, before
I was diagnosed with mono last month, I had intended to use the 29er to defend my Cascade CreamPuff 100 mile
title from last year. Therefore I upgraded the parts a little - KCNC superlight brakes and levers, very fancy Tune
hubs with Stan's NoTubes rims and tyres and a custom built chain keeper. All this got the weight down to 17.5lbs,
so with my CCP entry defered to next year, I am ready early!



Frame: Spectre aluminium
Fork: White Brothers Rock Solid
Headset: Cane Creek hidden
Seatpost: USE carbon alien
Saddle: Selle Italia SLR titanium
Stem: Spectre aluminium, 120mm
Handlebars: Pazzaz carbon
Brake levers: KCNC
Shifters: SRAM X.7 gripshift
Front Brake: KCNC
Rear Brake: KCNC
Bottom Bracket: Token ISIS titanium
Chainset: Middleburn RS7 Duo with only 32T ring, 170mm
Pedals: Shimano XTR
Chain: KMC X-9SL
Front Derailleur: Custom chainkeeper
Rear Derailleur: SRAM X.9 Short cage
Cassette: Shimano XT 11-32 9spd
Front Wheel: NoTubes 355 29er rim, Tune Mig70 hub, 32 Dt revolution spokes, alu nipples
Rear Wheel: NoTubes 355 29er rim, Tune Mag160 hub, 32 Dt revolution spokes, alu nipples
Tyres: NoTubes The Crow 29er
Wheel skewers: Tune
Bottle cage: Spectre carbon

Weight: 17.5lbs