My latest 650b low trail fredmobile for the peanut gallery

[blasdelf]

You may recall the knowledge dropping (and/or shit stirring) that I did in SignatureJustin's threads a few months back when he was looking for information on this sort of bike: http://www.velocipedesalon.com/forum...ead-30742.html | http://www.velocipedesalon.com/forum...ere-30790.html | http://www.velocipedesalon.com/forum...ack-31233.html — or the thread about that 650b Firefly — or my 6 post info bomb on wtf the deal is with porteur racks. If you can get past the butthurt those threads make for great background on what makes this more than a homercar.

Well I recently did the initial build on my latest one and have put 500 miles on it: New Elephant - a set on Flickr



Frame and fork built by Glen Copus of Elephant Bikes, see the BikeCAD Model for dimensions.


Versus my Rawland rSogn the chainstays and front-center are 1cm shorter each, the BB is 5mm lower, and the seat tube angle is nearly a degree slacker.

I designed around disc brakes so I could use cheap 650b carbon rims that are 20x stiffer and stronger than the light alloy ones I was using at the same weight (I 'm on my third rear rim on my Rawland!). The extra 4mm of inside width vs. a normal 23mm rim doesn't make the tires any wider, but it does make them significantly rounder which took a bit of getting used to.

The Extra Léger Hetres are set up tubeless, and the low rolling resistance of that combo is definitely noticeable, but I find myself inflating them to 30-35psi instead of 25-30 because of the lack of compression damping in the casing. The sidewalls even wrinkle visibly under load! I find normal Hetres at 20psi to still be perfectly rideable, but these sag a lot when that low and squeal obscenely just turning the bars on asphalt.






The bike is 23.3lbs as shown without fenders or bottlecages: frame is 4lbs even, fork is 2.2lbs, and the rack is 1.2lbs. I could shave at least a third of a pound off the rack by making it in 5/16" x 0.028" instead of 3/8" x 0.035", and might do that next time, I just didn't want to change to many variables in the design at once.

The TT & DT are single oversize OX Platinum in 7/4/7 with the longest center butts, the seattube is 28.5 6/4/5 S3, the seatstays are also S3 in .5mm 16/11 taper, and the chainstays are from the Dedacciai 29er tubeset. The fork uses a Nova crown with matching oversize 29/21 blades and a superlight steerer (normal steel 9/8" steerers are thick enough to thread for some fucking reason).

By the numbers the front end should be marginally stiffer than my 9/6/9 standard-diameter bikes (like Columbus SL). I was pleasantly surprised that it's definitely a bit more flexible under pedaling, but also doesn't get bounced off its line as much plowing through a rock garden. Perhaps the superlight seat tube has something to do with that, but it's hard to tell. See the porteur rack thread for details, but the main charm of this sort of geometry is that you can build the frame to be super responsive/sprightly without affecting the load-carrying ability.


Here it is dirty on my way home from an overnight bike camping trip on the North Fork Snoqualmie:



Obviously it still needs to be painted, that'll get done in a few couple months with a rather ridiculous design, the vintage splash tape should serve as a clue.

I still need to add some bosses and wire anchor points to the front rack, make a custom mini rear rack for it to hold a stuffsack when camping and serve as a taillight mount, make some weigle-style mounting hardware for the Honjo fenders I have for it, do a custom wiring harness with lapel-mic cable, and machine accessory clamps for the paired triple seat tube bosses to hold a pump and/or folding saw.

When the rain starts letting up again I'll put 2.3" knobbies on it and take it out for some real mountain biking.

[christian]

Cool.


I believe I was promised peanuts?

[pdxmech13]

My mind has been officially blown.

[Saab2000]

What's the advantage of carrying all the weight over the front wheel instead of behind the rider? Curious because I don't know. Not an expert on touring/utility bikes.

BTW, that thing rocks. What's the tail light?

[blasdelf]

What's the advantage of carrying all the weight over the front wheel instead of behind the rider? Curious because I don't know. Not an expert on touring/utility bikes.

basically you can make the frame as if it didn't have to carry a load at all, no extra stiffness to resist the torque of rear racks, the tail wagging the dog, or any of that jazz

it can respond to your pedaling like a race bike instead of a turdly surly

with the proper fork geometry, you don't feel the weight even riding out of the saddle (unlike a saddlebag) and the bike still corners awesome

it's also *more* aerodynamic than a pair of rear panniers — think about how airfoils work, it makes the bag a fairing instead of a pair of air-brakes

there's a bunch more info in http://www.velocipedesalon.com/forum...ack-31233.html and http://www.velocipedesalon.com/forum...why-30681.html

What's the tail light?

Philips - SafeRide LightRing Dynamo SRRDLGBLX1 - Rear lights - LED bicycle lights - Lighting

It fell off later that week because I left the QR functionality intact but then couldn't get the tiny retainer screw in with the fender in the way.


I mounted the battery version of the same light for a 400k Brevet

I'll probably end up mounting a rack style light like the B&M Toplight Linetec once I make the custom mini rear rack to put it on.

[Jonathan]

Thank you, it was getting to the point where I had confused 650b with having the bars higher than the saddle. Who would've known it was a wheel size?

[jitahs]

Sweet, like the quadra-plated dual fork setup.


Is this thing:

a) more racy than the Rawland
b) about the same
c) can't tell the tires are chubbed-out.

[blasdelf]

the tires are somewhat chubbed out

but there's a distinct difference between rolling resistance and how fast the frame wants you to pedal it

and the frame is absolutely racier than my Rawland in terms of pedaling response (what Jan calls 'planing')


it is kinda hard to isolate what difference the carbon rims make not having ridden it with other wheels

and it'd be interesting to build another otherwise-identical fork with the tandem chainstays for blades to see what difference that would make (other than the extra half pound)

[Matthew J]

Really like it. All purpose, no bullshit.

[Matthew J]

What's the advantage of carrying all the weight over the front wheel instead of behind the rider? Curious because I don't know. Not an expert on touring/utility bikes.

BTW, that thing rocks. What's the tail light?

Adding to Fred's comments, I find it Porteur much more practical for city commuting and errand runs. One big bag right at your hands is easier to get and bring in to the many different places I may stop at on a ride. Almost the convenience of a messenger bag, none of the discomfort.

[thollandpe]

Will you share the front end geometry?

[blasdelf]

Will you share the front end geometry?

It's all in BikeCAD — but that's probably a bit obtuse to poke around in if you haven't used it before

HTA is 73° with 65mm of fork offset, that means 35mm of trail on Hetres.

My Rawland was supposed to be 73°/63mm but the actual HTA was closer to 73.5° (among other things that were off)


I intentionally had the fork made 10-15mm taller than necessary to make the rack design simpler

As a side-effect that also makes it possible to convert it to traditional 72°/47mm cyclocross geometry with an off-the-shelf carbon disk fork.


Other notable measurements: the chainstays are 435mm, front-center is 633mm, and the STA is around 71.5° (I eat setback for breakfast)

[sonny]

glen is cool
lack of panniers is cool
your bike is cool (cable routing ftw)

we should be friends

[PJN]

I don't know shit about lowtrail/650b-nerdyness but this tread is fucking awesome.

Sounds like you're STOKED on your new rig and know what you wanted geometry wise.

Couldn't ask for more!

[Brian Smith]

It looks like you're having some fun on that machine. One question: why is your FD cable housing run along the top location instead of on the bottom where it would free up your other two housing runs? The mechanic in me might choose that option, which seems available to you.

[gjuffer]

Really like it. All purpose, no bullshit.

Let's not get carried away . . .

[blasdelf]

why is your FD cable housing run along the top location instead of on the bottom where it would free up your other two housing runs? The mechanic in me might choose that option, which seems available to you.

It really does work best this way for all three housing runs, I tried out every permutation.

Using the upper stops for the rear loops makes them stick up significantly more, and they don't arc around the seat tube as nicely without the FD loop lying underneath them.

The FD loop also gets a better radius using the upper loop, and moving its adjuster stop down the seat tube wouldn't help that much. Moving the TT stops forward would help relax it more but also put them where my knee might hit them.


The one thing that's suboptimal about the arrangement is the need to have assembled the stops out of individual ones. AFAICT nobody's made an integrated triple-stop for a 28.6 tube in a long time, and machining a pair would have been really annoying. If anyone has a stockpile of such bosses or knows where to get them, I'm all ears.

[nate2351]

No matter what's bolted to them, it's not a rando bike without a 110bcd Ritchey Logic square taper crank, ya heard!

[SteveP]

beauty of the bicycle.
you can do a lot of different things.

[MisterDangerPants]

Wicked.