Readers’ Rides: Seb K’s heavily modified 11.1 lb / 5.08 kg mountain bike!

There are weight weenies, and then there are weight weenies. The emphasis added is what sets apart those that simply buy light weight parts to add to their ride, and those that are willing to potentially destroy high dollar parts just to try and remove a few extra grams. These tinkerers find great challenge and reward in the process of dropping every bit of weight possible, and it’s safe to say that Sebastian K. falls into that category.

These days, you can buy a production road bike that is sub 11 lbs (with enough $$$), but a mountain bike? That’s a bit more extreme. Obviously Sebastian’s mountain bike is fully rigid and single speed, but he still had to go to great lengths to modify it down to a hair more than 11 lbs. Just how do you get a mountain bike that light? Read on for more…

Starting with the frame (which is an unspecified carbon model), Seb ended up machining down the bottom bracket shell to allow for a crank with a shorter spindle. That also meant he had to make the driveside chainstay narrower to accommodate the chainring which involved machining down the surface of the stay and reinforcing it with carbon/kevlar fabric and carbon filler. Oh, there was also a section of the downtube removed which was reinforced with industrial epoxy resin, as well as new custom dropouts machined to replace the stock pieces. Finally, all hose and cable guides were removed and the remaining holes were widened for good measure then filled with silicone. Crazy? Seb’s just getting started.

To match the shortened BB shell, a set of RaceFace carbon cranks had their axle removed and replaced with a custom carbon fiber axle. This allowed Seb to get rid of all crank spacers while simultaneously removing the clear coat, decals, and granny ring tabs to remove every gram possible.

The DT Swiss carbon fork sees similar mods with bored out legs and the removal of all extraneous finish and hardware to make it lighter than the Niner rigid carbon fork.

How do you make the wheels even lighter? Fewer spokes, of course. Seb doesn’t specify the lacing pattern (the photo above is of an unfinished wheel), but from the photos it appears that he ended up using just 13 spokes with special nipples on the low tension side. He also took the opportunity to remove 3 of the 6 rotor bolt mounts and only uses three bolts to mount each rotor. Inside the rim, the spoke holes on the upper, non load bearing wall were widened to remove more weight.

Then there are the brakes. Starting with the already incredibly light Brake Force Ones, Seb rigged up a custom hose set up so that only one lever is needed to activate both brake calipers. Not content with just that mod, Seb added Schmolke carbon bolts that have been turned down in a lathe to make even lighter, used clear hoses, added titanium pad pins and custom bore caps.

For his perch, Seb used a custom Schmolke post with an MCFK pin, AX Lightness premium yoke clamps, and MCFK bolts that hold an Extralite Hypersaddle that has been cut down to create a new shape complete with center cutout. The sides were then painted with white enamel paint to create a 42g saddle.

Will this thing ride with the confidence of a heavier bike? Probably not, but it looks like Sebastian has had a great time putting it together and shaving every gram possible, which is it’s own reward. For more on the whole process, check out his Google+ page with step by step comments.

Thanks to Seb for sending this in!