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

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Seb K 11 pound mountain bike 5 kg modification readers rides (4)

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…

Seb K 11 pound mountain bike 5 kg modification readers rides (5)

Seb K 11 pound mountain bike 5 kg modification readers rides (1) Seb K 11 pound mountain bike 5 kg modification readers rides (2)

Seb K 11 pound mountain bike 5 kg modification readers rides (15) Seb K 11 pound mountain bike 5 kg modification readers rides (3)

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.

DSCN1077[1]

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.

Seb K 11 pound mountain bike 5 kg modification readers rides (8) Seb K 11 pound mountain bike 5 kg modification readers rides (7)

Seb K 11 pound mountain bike 5 kg modification readers rides (9) Seb K 11 pound mountain bike 5 kg modification readers rides (13)

Seb K 11 pound mountain bike 5 kg modification readers rides (10) Seb K 11 pound mountain bike 5 kg modification readers rides (12)

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.

Seb K 11 pound mountain bike 5 kg modification readers rides (6)

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!

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73 Comments
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Kristina Koscova
6 years ago

That´s not a mountainbike. That´s a city commuter …

Von Kruiser
Von Kruiser
6 years ago

How much does the guy weight who made this? He should go on a hunger strike to denounce the wastefulness of over-built bikes, then he could loose even more lbs! Would be cool to see this bike on PNW trails or anything in BC Canada. Also riding naked would be only appropriate to save weight. A a guy like this would not need a helmet either.

AS
AS
6 years ago
Reply to  Von Kruiser

That bike might survive the journey on my bike rack across town. Might.

GV (@gvelayo)
6 years ago
Reply to  AS

That bike is so fragile

3j0hn
6 years ago

Among all the insanity here, those “non-traditional” pedals are the deal breaker for me.

me
me
6 years ago

yeah…not to be ridden in this world…in the moon?…yes probably safer over there.

Frank
Frank
6 years ago
Reply to  me

That saddle nose would put a whole in your spacesuit as soon as you tried to mount it, then where would you be?

me
me
6 years ago
Reply to  Frank

on Nirvana stage!

RobJ
RobJ
6 years ago

Cute road bike.

chase
chase
6 years ago

I could sit n the seat and the wheels would collapse. I think bamboo(sarc) is starting to look practical next to this thing.

wookie
wookie
6 years ago

all that and he used powder coated white hubs and spokes??

Jon
Jon
6 years ago

Disqualified for being a single speed and unrealistic brakes – would love to see him ‘try’ to ride it off road.

Peter
Peter
6 years ago

There is a reason why all the pics are from a basement… That bike wouldn’t even make it around the block.

Da Reverend
Da Reverend
6 years ago

Thank you Sebastian and Zach for sharing this story – in particular as you probably envisaged you’d attract some commentary that is … well, telling us something about people rather than bikes.

JH Aberschmidt
JH Aberschmidt
6 years ago

wonder what he uses those grips for in teh basement?

yard dog
yard dog
6 years ago

not the most practical bike but always fun reading how some people push the envelope. cool!

AlanM
AlanM
6 years ago

Could we get a test ride review of this bike? I know there are a lot of negative comments on this post, but for good reason. What’s the point of a light bike if it isn’t functional. I could do all sorts of crazy stuff to my bike and make it weigh almost nothing, but it wouldn’t be functional.

Burton
Burton
6 years ago

Clever guy. Rigid forks rock — I’ll die before riding suspension.

Collin
Collin
6 years ago

Why stop at 11 spokes. HED’s been using 3 forever. Do that with some acid dipped 3x butted spokes, makes for a real light wheel. They won’t be too stiff but for hanging from the basement, it will work fine.

CowtownCyclist
CowtownCyclist
6 years ago

As someone who loves tinkering and DIY bike stuff, those brake hoses scare the bejesus out of me.

adam
6 years ago

bikes are for riding.

Mike
Mike
6 years ago

This must be a joke. I have a Cannondale F29 hardtail with pretty normal parts that weighs under 20lbs. And I can hammer the crap out of it. The weight this guy’s saving is all coming out of his teeth. There’s no way that thing’s remotely safe.

Mike
Mike
6 years ago

Oh, and…

13 spokes. 13 spokes? THIRTEEN SPOKES!!! Nope. Nope nope nope nope nope nope nope.

We’re being trolled.

Luiggi
6 years ago

There is a thin line between geniality and stupidity, and I think we all know in which side this contraption resides.

Jim E.
Jim E.
6 years ago

How far does a “bicycle” have to roll with a rider on it to qualify as a legitimate bicycle? This looks like an experiment in self destruction vs. time ridden. That CF crank spindle literally looks like black swiss cheese. These thought experiments are cool and all but this just seems stupid.

David Grabulosa Puigdemont
David Grabulosa Puigdemont
6 years ago

For me there are a lot of work and thinking, it is a extreme exercise of weigt loss, I can apreciate these work.

Craig
Craig
6 years ago

Cool to see the mods done. I’m sure the project has been a fun one to create and I imagine the bike is quite fragile, but as long as he rides it sensibly and only occasionally then it will be fine.

Peter
Peter
6 years ago
Reply to  Craig

Isn’t the point of weight reduction to go faster or use less effort or a combination of both? If you need to ride it “sensibly”, you will definitely be slower than a 20 lbs bike, probably even a 30 lbs enduro bike. This bike, sorry, freak build, couldn’t make less sense.

Heffe
Heffe
6 years ago

weird

Allan
Allan
6 years ago

seems unsafe

AlanM
AlanM
6 years ago
Reply to  Allan

Understatement.

Erik
Erik
6 years ago

Should drill some holes in the down tube to make it more aero and save some weight.

hllclmbr
hllclmbr
6 years ago

Being a weight weenie is such an odd hobby, but if it bring one happiness and doesn’t harm others, by all means, do your thing.

satisFACTORYrider
satisFACTORYrider
6 years ago

building it with no confidence to ride it? i have other word than rewarding..

gibbon
gibbon
6 years ago

(deleted)

Flatbiller
Flatbiller
6 years ago

Should we now rename this site to wwBR?!

joenomad
joenomad
6 years ago

It is his money, time and life. let him do what makes him happy.

AlanM
AlanM
6 years ago
Reply to  joenomad

He can absolutely do what makes him happy. But if you’re going to post it up on a place like BR, you better believe you’re going to get feedback.

MTB4ME
MTB4ME
6 years ago

Begins with “frame is an unspecified carbon model”….and that’s where my suspended belief and I ended….

bob
bob
6 years ago

My cross bike is several times stronger and probably about as good offroad lol.

Its fun to mod a bike to be lighter but if it’s absolutely unuseable as a bike, whats the point really? Theres several compromises are that just dont work.

Kevin Roberts
Kevin Roberts
6 years ago

I know for a fact that he never rides this bike! I did follow him on Google+ but had to drop him after finding that out

Jamie not so fast Mann

Nice going seb

hawgietonight
hawgietonight
6 years ago

Nowhere in the article it says this bike is supposed to be ridden, so most rants above are invalid. Anyway I would leave out the “Mountain” part in the title.

Peter
Peter
6 years ago
Reply to  hawgietonight

Is it still a bike if it can’t be ridden? Maybe it should be called a piece of modern art. Not a very nice one, but still. That would make more sense.

Frank
Frank
6 years ago

@3j0hn, those “non-traditional pedals” are US-made Aerolites. They require time and effort to set up properly because the clips have no float, but once set up they are awesome: long-lasting, dependable, strong and the lightest you can find. I have them on all my road bikes.

Todd
Todd
6 years ago
Reply to  Frank

Exactly. Your road bike. Putting those on a “Mountain Bike” is a joke. I still would never ride those.

Lumpa Lumpa
Lumpa Lumpa
6 years ago

Please stop the jokes…..

Johan
Johan
6 years ago

SS rigid is a mountain bike, you just need to HTFU.
The pedals seem odd, but otherwise seems perfectly useable.
What brake rotors are those? If they are over 55gr per rotor there is more weight to shed. Quasar?

Ryan S.
Ryan S.
6 years ago
Reply to  Johan

SS rigid is the only way.

Todd
Todd
6 years ago

Simply stupid, unsafe, and not trail or road worthy. This “mountain bike” is good for hanging on the wall. What a waste.

satisFACTORYrider
satisFACTORYrider
6 years ago

^your logic works for the rest of us and how we choose to comment

satisFACTORYrider
satisFACTORYrider
6 years ago

^@joenomad

Dustin
Dustin
6 years ago

I suppose being an extreme weight weenie is healthier than having an eating disorder

shafty
shafty
6 years ago

Why not go fixed and remove all remnant of brakes? Since it won’t be ridden, just find the smallest gears you can possibly mount, while achieving reasonable chain tension, and be done with it. Then he could use non-disc hubs, and also remove all brake mounting from frame and fork. Ditch the grips in favor of a glued on texture.

Single digits(lbs) or stay in your basement Seb!

Mike
Mike
6 years ago
Reply to  shafty

I commute every day with a fixie with only a front brake, and in (totally not weight weenie) form it weighs like 15 lbs. I think you’re onto something with the fixie. Use a 9-tooth rear cog from a bmx bike and like a 26 tooth front… there’s all sorts of dumb to be had here.

ed
ed
6 years ago

Further mods: bond seat to seatpost, remove rear brake and front disc should be all carbon. Use Gates belt instead of chain.

Ol'shel'
Ol'shel'
6 years ago

I’d totally live in a scrap-wood-and-tarp shelter if it allowed me to afford an unrideable 11lb mountain bike.

Seb K
6 years ago

Just to say a big thankyou you for Bikerumor to feature my bike .

Usually with WeightWeenie stuff you tend to get a lot of hate and especially on the extreme side of things as people do not understand how something so light can still be used .

The bike is fully rideable and can cope with off road trails but no big stuff like freeriding, DH and certainly no jumping . This was an experiment (and there is more to come as the bike isn’t finished yet and I have other bikes too ) and has increased my knowledge of the WW world and has allowed me to look more in depth into bike design and building .

I see a lot of WW bikes and like a lot of the older players have stated ( like a guy named Jonus who I regularly look at his blog) that the newer guys are simply buying light parts and assembling the bike together which pretty much any random biker can do . To learn how to modify, build and machine parts takes things to the next level and in the WW this is slowly getting lost .

The comment about the crank axle looking like ‘swiss cheese’ . The axle is as strong as hell but I didn’t bother sanding it or making it look pretty as it is inside the frame and is more function over looks . It is made from 4 tubes of prepreg carbon, industrial strength epoxy resin and finished with carbon filler and then layered again with more resin .

The reduced number of spokes also isn’t a problem . The wheels are still stiff and strong but they are no freeride wheelset (obviously ) . The wheelset is less than 1kg so my work paid off (again) .

Am I mad to have done this – of course but being a WW is being crazy and having wild ideas It’s what allows industries to look at what people like my self do and get ideas of their own t make parts lighter .

All I can say really is just by looking at the pictures doesn’t do the bike any justice . It isn’t a piece of hanging wall art or anything alike . It is a fully functional MTB . You just cannot use it like a heavy DH.freeride/bmx/trials bike .

The frame is by Planet X and is a custom matt black medium carbon frame . I should have mentioned that earlier (oops) .

Oh and this is not my basement 🙂 !!!

nightfend
6 years ago
Reply to  Seb K

I just want to know how you can ever get back into those pedals after stepping on the slightest bit of mud. That pedal system is super sensitive to any dirt…and requires road shoes.

Peter
Peter
6 years ago
Reply to  Seb K

If only there was some sort of proof that this bike has been ridden, I would be inclined to give you the benefit of doubt with regards to the bikes structural integrity. But as all pictures are from this shed or whatever, I might as well draw my own conclusions as you have ridden it as little as I have.

adps
adps
6 years ago
Reply to  Seb K

i suspect by rideable and no jump, no freeriding what you mean is no “trail riding” which is what is being criticized. what MTB call trail riding involves rocky, rooty terrains, small jumps, etc.
What you seem to call trail riding is what we’d call gravel riding (zero jumps, terrain that is more like a fireroad, etc)

I’ll not that I can do the trail small jumps with my CX road bike just fine without any fear of breaking things (CX bike which is heavier than your MTB at 15lbs).

Hope that helps understand.

Joe Hohmann
Joe Hohmann
6 years ago

Might as well drill some holes in the cranks and seat post

Red Headed Woodpecker
Red Headed Woodpecker
6 years ago

Would be surprised if the brakes had any power w/ a clear non braided brake line. The plastic line by no means will keep intended volume for the brake design from growing when pressure is increased. Would like to see what any brake manufacture has to say about linelines like this (Magura, Shimano, TRP, Hope, SRAM, FSA, etc…). Brakes are key for control and safety and this does not look safe. I love innovation but at what expense are people willing to pay for making a bike this unsafe and unable to blast down a hill w/ confidence?

Johan
Johan
6 years ago

The guys dismissing this type of bike have surely not tried them in knarly environments.
I rode my rigid carbon SS in very rough terrain. you actually need to look where you are going and move more on the bike, this actually means you seldom put the components through the kind of abuse that a full sus long travel mtb would be exposed to.
The mtb tyres also mean you kind ride terrain ( rocky and sandy) which are pretty near impossible on a CX bike.
Also it climbs like a homesick squirrel .
Try it before you dis it.

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