Project 650b Ti

CAD Photo - 27.5" / 650b Mountain Bike

This project, which is still under way, started during the spring of 2009. A long time customer came to me after a devastating fire took not only his house and car but also his two beloved custom Ti Alpine Designs Bikes in a blaze of glory. When he brought the old bikes in to show me it was pretty nuts! The frames were blackened, but not melted, and the components were toast... Especially the carbon fork on his roadie and the magnesium fork on his mountain. Needless to say the old bikes were worthless. Even though the frames were still ok looking I suspected that the intense fire temperatures effect on the unshielded Ti would probably have made the frames brittle, ride pretty noodley and possibly unsafe. So after making arrangements with the customers insurance agency we set out to design and build some sweet replacement bikes.

The bike profiled here is a custom titanium cross country hardtail. The really cool feature is the 650b wheel set. Yes that is 27.5", so bigger than your standard 26" mountain bike wheel and smaller than the behemoth 29" wheel. The customer also had me build a custom ti road bike as well (which is also profiled on these pages). That bike was relatively easy since I have done it a thousand times. This new wheel platform offered up plenty of challenge.

  There are always many factors to consider when designing the customers frame but the new 650b wheel platform included new fork axle to crown height and various dimensions as well as wheel diameters and tire widths. Those are two big pieces of any custom frame design and usually it is really straightforward mainly due to the fact that there are so many component choices. Not the case with the 650b platform. There are really only a small number of off road companies embracing the 27.5er. Luckily they are some of the best. We ended up choosing the White Brothers Fluid 650b fork and the Velocity Blunt rims paired with, the godfather of 650b himself, Pacenti tires. Both of these companies were able to provide the numbers I needed to design the frame around their essential products.

 Another challenge was the chain and seat stays for this frame. No tubing distributor had a set of stays designed with a bend for the 650b (especially in ti...) so we custom bent the chain and seat stays ourselves after a substantial amount of design time on the CAD program.

 Custom bent 3/2.5 Titaium chain & seat stays for 650b wheel ready to be trimed and tig'd

 The component specifiactions for the complete bike are as follows:

FRAME: Custom geometry, TIG welded 3/2.5 Ti w/ 6/4 Ti Paragon dropouts & fittings (Made in USA)

Tubing Specs: H/T 38.0, D/T 44.5mm, T/T 38.1mm, S/T 34.9mm, Stays 22.2 & 19mm, BB 1.625'' OD x 73.5 mm l

FORK: White Brothers Fluid 650b (Made in USA)

WHEELSET: Handbuilt, Velocity Blunt rims 32h, DT Swiss SS spokes, Dt Swiss Alloy nipples, Chris King ISO hubs, Salsa Ti wheel skewers

BRAKES: MAGURA MARTA SL

CRANKSET: SRAM

BB: SRAM GXP, CERAMIC BEARING

CHAIN: WIPPERMAN STAINLESS 10 SPD

CASSETTE: SRAM X-DOME 11-36T

R/D: SRAM, 10S, MED CAGE

F/D: SRAM, TOP PULL, 34.9MM

SHIFTERS: SRAM

HANDLEBAR: RITCHEY CARBON WCS RIZER

STEM: RITCHEY 4 AXIS, WCS

HEADSET: CHRIS KING (RASTA)

SEAT POST: RITCHEY WCS CARBON

SADDLE: WTB STEALTH TI

GRIPS: OURY LOCK ON

SEAT CLAMP: DKG FLIP LOCK

TIRES: PACENTI 650 X 2.1

RIM STRIPS: ROX USA

PEDALS: CRANKS BROS TRIPLE TI

This post will be updated until the complete bike has been photographed and delivered. RIght now the frame is in the fabrication stage. Please check back for alot more info and pics if you are interested in this wheel platform.

Ti tubes/fittings inspected, marked and checked against drawing

 

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