Saturday, June 25, 2016

24" MTB Build: "Kona Queso"

It all started with a free bike, a 24" Kona Hula (12" frame) that my friend's son had outgrown.  The frame is really on the large side for my son, who is only a year into his Isla Bein 20" Small.  While the bike as it was was a perfectly ridable bike, I decided that we would turn this into a bike-building project.  My son loved this idea.  And we set right to collecting parts for this too-large bicycle, because to do anything else would have required patience and deliberation.

The project goals were pretty simple:
  1. To have fun personalizing and customizing the bike.
  2. To work on it together (hopefully he'd learn a bit about the mechanics of it)
  3. And to drop 10lbs from the finished product (original weighed in at 30lbs; goal was 20lbs). 10lbs is pretty significant to a 50lb rider.
The constraint was to try to stay within budget of what his next (24" bike) would have been.  Luckily my wife and I have separate allowance funds; this way the discretionary expenses (the majority of the costs here) wouldn't cause marital discord :)

The plan for the bike was:

  • Convert to disc brakes.  This was bold, but research suggested there were some options that didn't involve welding mounting tabs to the [aluminum] frame.
  • Convert to rigid fork.  The affordable kids suspension forks don't actually compress for little 50lb children.  The high-end forks would exceed the budget (and how!).
  • Convert to 1x10 drivetrain for simplicity (and weight savings) but with enough range to ride any terrain around here.

The Frame

Here's the original frame.  It's a Kona Hula, a 12" frame size according to the sticker.  Made of 7005 aluminum alloy.  Thankfully, very standard specs: 27.2mm seatpost, 1 1/8" headtube, 68mm BSA (threaded) bottom bracket. 

"We" (I) decided early on that we'd convert this to disc brakes, so we ensured we couldn't change our mind by sawing off the brake bosses.

I removed the material with a dremel.  Luckily my friend Kurt has a pro-grade workshop and helped grind this down to finish this like a pro:

I drilled out the cable stops so we could run full-length housing for the brakes and derailleur.

I let my son choose the color.  We used Nova Powder Coat which uses (among others) Prismatic Powders; my son chose Hot Yellow.  Good choice, kid.  (I encouraged a high-viz color choice.)

Part of the fun was getting to bike down to Chantilly to pick it up.

The finished product really looked fantastic:

We got some Kona stickers off eBay.  They're not the same as the original ones, but they look good.

The Brakes

Before starting this project, I had no idea that people actually converted rim-brake frames to disc-brakes.  (Often the preference is to run a "mullet" with disc front and rim-brake rear.)  I decided to investigate, though, since I had a set of cable brakes from my commuter (before switching to hydro) that I wanted to use. I learned that there are several ways to convert a rim-brake bike to disc-brakes; the one I opted for was the A2Z DM-UNI adapter.  Found one for $20 from the UK, which was a lot cheaper than the domestic options (mostly ebay).
Before we sawed off the brake bosses, needed to make sure that this idea would actually work.  After spending some time with a file flattening out the dropout lip on the inside of the dropout, the adapter sits flat against the dropout and fits quite well. However, you can see that there's some space at the bottom (between the lower left bolt and the frame):

While this wouldn't be a problem for regular braking from forward motion, it would be a problem if applying the brake while rolling backwards.  That didn't seem like a great state of affairs.

Without any fancy tools, my solution was to hunt down some big aluminum washers in just the right diameter that would eat up the extra space.  This actually looked like it would work fine, if a little ugly:

Kurt rescued me again here with a much better idea, involving drilling through the frame and tapping out the thick aluminum backplate to the adapter for an M6 bolt.  This is a much swankier solution.  You can see the extra M6 bolt right above the QR skewer:

(A little preview of the finished product there.)  You can see in the photo above that I'm using TRP Spyre disc brake calipers.  This is worth mentioning, because these are road brakes, not mountain bike.  This actually is perfect for a build for a little person, though, since BMX brake levers are (typically) short-throw, just like road levers.

The Fork

I spent awhile investigating the options for forks.  There are a few suspension forks that are decent for this size wheel, but they're pricey.  The off-the-shelf suspension forks don't compress under the weight of tiny people, so they're really just good for weighing down the bike.  Many people also use 26" forks.  I measured the axle-to-crown distance on the suspension fork that was on the bike; it was around 425mm.  After scouring the various carbon fiber forks on ebay, I found a 26" fork with a 415mm axle-to-crown measurement, so while this might be a little taller than perfect for the 24" wheelsize, it was going to be 1cm lower than the RST fork it was replacing.

Critically, this fork was available in tapered or straight steerer.  We chose the green logo, which locked in our color scheme.


I am really impressed with this fork, actually.  The finish is top-notch and the weight is pretty incredible at 421g.

I would consider using this on a CX build (only slightly taller than the standard 400mm axle-to-crown measurement of a CX fork).  If only it came with thru-axle.

The Drivetrain

After doing a bit of research, I settled on a Shimano Deore SL-M591 (10-speed).  My son has SRAM (X4) grip shift on his current bike, which works fine, but folks on the interweb suggested that Shimano trigger shifters were easy for little hands -- and I found someone selling a take-off shifter and derailleur combo for $60.  Done!


I perplexed for a long time over the crankset.  I wanted one with short arms.  Ideally something like 145mm, which is what he has on his Isla 20" bike now.  Most cranksets with arms that short are BMX cranksets.  While a BMX crankset would work, it is hard to find BMX cranksets with 4-bolt 104mm BCD, since typically BMX chainrings are much bigger than the 30-32t I was hoping to fit.  Also BMX chainline is different from MTB; BMX bikes have narrower rear spacing.

In the end, I decided to splurge and buy the Trailcraft 1x crankset which includes a 30t ring.  The arms are a little longer, at 152mm, but this seemed fine.  Of course, we went with a green chainring to keep our color theme going!

Now this is a crankset that needs a square-taper bottom bracket.  The standard Shimano square taper bottom brackets are really heavy (300+grams), so I was really fortunate to find someone selling a used Race Face Taperlock BB on eBay for $25.  This has a titanium spindle and weighs in at a paltry 165g.

For the cassette, I really went overboard and picked up a (used) XTR 11-36t cassette.  While I would never buy myself a titanium wear-and-tear part like that, I figured that as lightly as he rides it'll probably last through both kids and while [the used one] cost me twice the price as a [new] standard cassette, the weight savings are huge (230g for the XTR vs ~400g for a standard SRAM PG1030).

The Wheels

I should really have led out with a discussion of the wheels, because this was really the keystone of the build: or at least the reason we were converting to disc-brakes.  I really wanted to build a wheelset using Stans Crest 24" rims and the leftover 28-hole Novatec D712SB / D771 hubset I had (the rear couldn't be converted to 11sp). 

We used Laser spokes and alloy nipples.  This is a very light wheelset.

This was one of the more fun parts of the build for me too -- and I think for my son; he did the bulk of the wheel lacing (with help & instruction).

We ordered Schwalbe Rocket Ron tires from Germany (it was cheaper than domestic prices, even paying 20EUR for shipping).  There aren't many tires options for 24" wheels; the Rocket Rons are generally agreed to be the best.  Mounting them tubeless was super easy, thanks to the excellent Stans rims.

Cockpit & Other Bits

Not too much to say here.  I traded a Ritchey WCS alloy road bar from my parts bin for a Easton EA90 SL carbon flat bar.  Another example of something I'd never buy myself.  My son helped cut them down a little narrower.

Found some lower profile ODI grips with green endcaps.  Probably could have gotten something even narrower for his hands, but these seem to fit fine.  Picked up some green BMX levers. 

For the seatpost, I was gonna use my old carbon Bontrager XXX seatpost, but it doesn't slam down far enough for him right now (yeah, the bike is a bit large), so we're using an Easton EA70 seatpost I had in the bin.

For saddle, I floundered around a bit.  Originally I found a great deal on a Bontrager Kovee Elite (ti rails), but this proved to be way too long a saddle to work.  Eventually I found the Selle SMP Junior Lite saddle for 50% off in the UK and ordered it. A bit pricey, but I think it'll be moving between bikes (and between kids) for many years.  It's probably more tailored to road riding, but my son says he likes it (we haven't been on any long rides yet, to be fair).

Finished Product

My son named his bike "Kona Queso", since the yellow/green/red color scheme was like District Taco and apparently my son can't get enough of DT queso :)

The weight came out better than expected at 17lbs 12oz (8.05kg).

Osiris (co-owner of District Taco) hooked us up with a DT sticker, which we cut out and placed on the toptube:

We haven't done any long rides yet, but it's been ridden a whole bunch since we finished.  Including some light mountain biking (with little brother who has just started riding the little Isla CNOC 14).

Friday, June 27, 2014

Disc-Brake Road Bike (Part 3: The Build)

In a continuation of parts one, two, and the related wheel-build post, I've now finished assembling my Yishun FM145 disc-brake road bike and been using it for a few months -- it doesn't get ridden as much as the daily commuter, but I've put a little over a thousand miles on it and I am loving it.

Here's a photo I took a few months back; I've tweaked a few of the normal things since then (stem, bar height) as I've ridden  it more.  In short, though, I am really happy with how it came together.

A few things changed from my original plan.

  • Originally, I was planning to buy the Whisky No 9 fork and use that  instead of the fork that came with the frameset.  The Whisky fork is 15mm thru-axle and would save a little weight, but at ~$600 it's pretty pricey and I discovered that using a DT Swiss 9mm thru-bolt does an excellent job of preventing any brake rub.  So I'm gonna leave this -- unless my fitting tells me that I cut the steerer too short, then I'll have to reevaluate :)
  • I was also going to move over my Sram Rival group from my previous bike, but in the end I decided to sell that bike complete (instead of frameset) and found a good deal on a Sram Force group (without the cranks, which I already had) for this bike.  I love the zero-loss shifting, though now that I am used to it -- it shifts before I expect it to, so I had been over-shifting in the beginning.
The build in the end came out at 17lbs 4oz (7.82 kg) (weighed with cages, pedals, garmin mount, etc.)  So not a weight-weenie build, but a reasonable road bike weight.

Build Highlights

Obviously the highlight of the build is the disc brakes.  I opted for the TRP Spyre brakes, since the dual piston design seems superior (to Avid/Hayes), the weight is better (than Avid/Hayes), and the calipers are narrow to avoid any heel-clearance issues.  And I decided to get the regular version -- not the carbon-armed SLC.  This was mainly driven by stock availability; I had to wait until the post-recall brakes were released and the non-SLC was available first.  But also price and to a lesser extent aesthetics.  I also had read a couple of reports -- granted, from tandem users -- about failure of the carbon arms on descents and I decided that I would be a little more comfortable with the alloy model.  Same reason I opted for 28 instead of 24 spokes in the wheels: I don't want to be  feeling like I need to be careful with this equipment.

The Yokozuna Reaction cable housing is pretty impressive.  That stuff ain't cheap, so I guess one would hope to be impressed.  I'm also a big fan of the Avid HSX rotors.  I have used the TRP Spyre brakes with the stock rotors (and same cables/housing) on my commuter bike and the stopping performance of the Spyre calipers with the HSX rotors is markedly better than the performance with the TRP rotors.

A few people ask about the stickers.  I just went to and ordered some text ("hozn", a nickname) scaled to fit on the downtube.  I think it looks great and it's held up just perfectly for the past thousand miles.  The skull and crossbones on the headtube was just a sticker from an ebay seller -- that has held up great too.  While I would probably get it painted by the factory next time around, I think it looks great in raw black with the gloss black decals.


It's hard to compare bikes since there are so  many variables.  I came to this bike from a Motobecane Le Champion CF frame with an Enve 2.0 (straight-steerer) fork that I had built up with SRAM Rival and 50mm Farsports carbon clincher wheels.  Compared to that bike:

  • This frame is lighter.  The overall build is around the same weight (maybe slightly heavier), but the frame itself is at least 200g lighter than the Motobecane.
  • The frame feels more forgiving (aka a little less stiff).  This may be in my mind (especially given the next point), but it feels both a little more comfortable over bumps (which makes sense given how thin the seatstays are and that this is a 27.2 mm seatpost instead of 31.6) and also perhaps very slightly less stiff in the bottom bracket when climbing (though still much stiffer than any of the ti or steel bikes I have owned).
  • The frontend, though, feels very significantly stiffer.  I didn't think my frontend on my other bike was flexy until I rode this new one.  It might be the tapered steerer.  It might be the beefy fork.  It might be the 9mm thru-bolt -- or some combination of these factors.  I do appreciate the stiff frontend when climbing, though.
  • These 45mm light-bicycle wheels also seem a little more susceptible to crosswinds (than the 50mm Farsports wheels).  I'm not sure if that's due to differences in geometry (I think I had placed myself too far behind the pedals on previous frame), differences in build (e.g. 28 spokes vs 20), or the actual aerodynamics of the rims themselves.  It's not really a problem, just a subtle difference.  Of course, the hugest difference with the wheels is that these actually stop spinning when I apply the brakes :)

I don't have any real regrets with the build; every time I ride the bike I think that it's just fantastic.  I guess there are a couple of things I would consider doing differently, though, next time around:

  • I would probably have the frame painted / decals done at factory.  Not that there's anything wrong with how they turned out, but I kinda took the easy black-on-black path, whereas something a little original might be nice next time.  (Of course deciding on color scheme could take weeks!)
  • I would build the rear wheel with an 11-speed compatible hub.  Saving $20 for the 10-speed hub was a dumb choice.  I'll have to rebuild the rear if I want to upgrade to 11 speed in the coming years.  I am happy with the Novatec hubs, though; granted they are still very young, but they seem to be working great and have a nice sound (not too loud,  but loud enough to be heard which is nice).
  • I  might have gone down a size.  Right now this works great, but if I wanted to drop the bars much more I'd need a -17 stem.  Probably a 58cm frame size would have been a better choice given that the seat tube angle is steeper (73 vs 72.5) so the effective reach wouldn't be that different and the it would provide more bar height and length adjustment.
Here are a few more photos of the build!

Tuesday, January 21, 2014

Road Disc-Brake Wheel Build

As part of my series on building up a road disc bike (part 1 and part 2), I figured I would devote a post to the wheels.  Like all things road-disc-brake, disc wheels are still pretty niche. At least the standard seems to have settled down on 135mm rear hub spacing.   But there aren't a ton of factory options out there.  And I will admit that I love deep & wide carbon clinchers -- not so much for the speed (I'm sure there are a few mph tenths there) as much as the stiff road feel, the lack of any side-to-side flex, the cornering (wide rims), the sound, and the aesthetics.  I know that there are disc-brake clinchers made by the big brands: Zipp, Reynolds, Enve, Roval (Specialized), Vision (Cannondale), etc.  But the cheapest of these retail for $1800 and that's about $1000 more than I'm willing to spend on wheels.  (And most are 24-spoke,  which makes me a little nervous with disc brakes.)  November makes a disc verison of their Rail available, but it's still somewhere north of $1400.  I bought a Saab 900 for that price.  Yeah, I really couldn't justify spending more than $800 on these.  Even that feels pretty extravagant.  But this isn't exactly a project born of necessity.

I've some experience with Chinese carbon clinchers from Farsports (50mm deep x 24mm wide); I bought those as wheels (not just rims) and the lesson I took away was that I should have built these myself. The main issue you read about with carbon clinchers -- and the main reason I would go with a reputable brand -- is braking surface.  Not only is the braking performance inferior to alloy rims,  but you also run the risk of delamination under heavy braking -- e.g. down a hill -- and you might die.  (The Farsports rims had a high-temperature braking surface which mitigated this concern, though I probably still would have reconsidered riding them down mountains.)

But for this project braking surface is irrelevant and I saw little reason to spend 3-4x the price for a set of wheels that have superior thermal properties.  So, in short, I decided to build my own wheels using carbon hoops from China and budget hubs.  

The Rims

For this project I decided upon the 45mm U-shaped rims from Light-Bicycle.  These get good forum reviews; there was apparently a production run that had issues with clearcoat over the braking surface, but it sounds like customer service was good and the problem was resolved -- and, again, I could care less about braking surface.  I worked with Nancy on the order, which went extremely smoothly.  I ordered 28h rims with 3k matte finish and no braking surface.  I received the rims within a couple weeks and the quality of the finish was fantastic -- almost flawless.

I wasn't sure about the 3k, but I like the result.

The beads are very straight/smooth with a good bead hook.

The only flaw I could find was this wrinkle/seam in the superficial layup.
I measured the rims; the ERD I measured matched exactly the 554mm manufacturer-claimed ERD.  The weights were also very close to claimed weights, with one rim weighing 449g and  the other weighing 454g (claimed weight 450g).  This may be a placebo, but the tight tolerances leave one with a good feeling about the manufacturing process and quality control.

The Hubs

I have used BHS hubs for many of my recent wheel builds, but for this project, I decided to try out Novatec hubs w/ Japanese EZO bearings.  The hub geometry looked attractive; the prices and weights were reasonably good; there is a front hub (the XD711SB) that has interchangeable hub/axle options; and the freehub bodies include an "anti-bite guard" technology (looks like a steel reinforcement on one of the splines) to keep cassettes from gouging up the freehub.   I went with the D712SB-10 rear hub, figuring that I didn't need 11-speed yet on this bike.  In retrospect, I should have paid the extra $20 and used a spacer, since the hub geometry is the same.

Originally my intent was to run these with 15mm thru-axle, planning to replace the fork that came with my frame with a Whisky No 9 road (disc) fork.  Upon further consideration, I decided to save some (a lot) of money and just use the fork I already had :)  So I decided to run a 9mm thru-bolt instead; the XD711SB hubs also support this option, so I ordered these end caps and had them from Taiwan in jjust a few business days.  My goal was to prevent side-to-side flex that I do experience with my QR front disc hubs on my commuter.  Well, the 9mm thru-bolt appears to have done just fine; I cannot make the rotors rub in out-of-saddle climbs or hard sprints with this wheelset.  Success.

Actual weight for rear hub was 279g (published weight was 269g).  Actual weight for front hub and the 15mm end caps was 142g (published weight was 139g w/o end caps).

XD712SB-10 with "anti-bite guard" freehub body.

XD711SB with 15mm end caps.

The Build

I built these with 28 spokes front & rear.  The idea of under-building the front wheel doesn't make sense to me with disc brakes, given that is where the bulk of the braking force is applied (especially with larger 160mm rotors up front).  I have been  running 28-hole front wheels on my commuter for the past year; I did break a front spoke after ~6k miles, but I attribute that to my build technique rather than something inherent in spoke/rim/hub configuration.  I retensioned the wheel and the last ~4k have been smooth sailing.

I chose Sapim CX Ray spokes since they are light, are disc-approved (unlike Lasers), and seem appropriate for deep carbon wheels.  I used 2x front and rear.  I could have gone 3x, I suppose, but I like the way 2x looks -- and it should be relatively inconsequential.  I did the Shimano (etc.) recommended lacing with outer spokes setup leading on the NDS to resist rotor torque.  This probably doesn't matter a whole lot, but it's what I've always done.

And 14mm alloy nipples because I wanted something  that was deep enough to protrude through the 4mm-thick rim bed and I see no reason not to use alloy nipples.  I've had alloy nipples fail me during builds in the past, breaking in half when spoke threads were insufficiently lubricated or rim bed was rough.  I use Sapim Polyax nipple washers now to provide consistent interface (and help spread the load a little)  -- tensioning has been noticeably easier with washers.  I also used regular motor oil this time, instead of boiled linseed oil, as per suggestion of Roger Musson in his wheel building book.  This was my first time  building with carbon rims; it worked out just fine.  It is a credit to these rims that they built up true with very even tensions.

Final build weight was 727g/869g front/rear for a 1596g wheelset.  Not bad!
Front wheel in 15mm thru-axle configuration

XD711SB front hub

D712SB-10 rear hub

Rear wheel

The Ride

I have only had these out on one 15-mile ride at this point.  It's very hard to compare these to other wheels since it's also a new bike, but the ride had many of the familiar characteristics of my other carbon clinchers -- confident cornering, the wind-tunnel noise at speed, and on the gusty day I took them out they got blown around a bit more than my alloy rims.  So I enjoyed building these and it looks like I'll enjoy riding them even more.

Update: a few months later

I have ridden the wheels a little over 1,000 miles now and I've been extremely happy with them.  Recently I rode them on the Diabolical Double (mountainous double metric) ride and loved that I could ride carbon rims without worrying about the braking (down the mountains in the rain).  I haven't had any issues with trueness or tension, which is what I'd expect when I'm building with bladed spokes and able to avoid any windup issues.  I've smacked them pretty hard into a few potholes without any problems.  I did notice that I've managed to add a few superficial scratches in the carbon, but the scratches are hard to see; the finish still looks great.  So, very happy with these so far.  Looking forward to many thousands of miles more.

Saturday, November 2, 2013

Disc-Brake Road Bike (Part 2: Frame Received)

As I outlined in part one of this series, I'm building up a disc-brake road bike -- the FM145 from Yishun Bike specifically.

The frame shipped out within a day or so of my "two week" estimate (wasn't built yet) and I received it exactly one week after it shipped (EMS).

The Frame

In short, the frame looks great (as I was expecting it to)!
The weight for the 60cm frame (with hardware) turns out to be 1080g (a little under the claimed 1100g).
This is a raw UD matte carbon finish.  As such, when you get closer you can see the layup seams for the UD layer (I assume this is just a superficial layer).  This is also true for my UD carbon wheels and perusing other raw carbon finishes from bigger names (e.g. Canyon is notorious) this seems to be normal.  It definitely gives it some "character", though.

I'm not sure I love this carbon aesthetic, but some people do; I'm sure it'll grow on me or I won't care.  (I realize now that my Motobecane Le Champion CF frame must actually be painted a matte black, as it has a completely uniform -- no seams -- finish.)  You can see the additional port there under bottle mounts; I assume that's for Di2 wiring, so won't be applying to me in the near future.

Looking down into the head tube you can see some artifacts from the construction process.  Inside the seat tube and BB junction the tubes look very clean, but this shot reveals a little about how the sausage is made.

The caliper post mounts look clean.  I have read of issues with lining up the calipers on some frames; obviously I haven't gotten that far yet.  These is configured for a 140mm rotor (and I would guess that a larger rotor would not clear chainstay).
The derailleur hanger arrived without incident and looks to be well-secured (I have left the rubber guard on it).  Quite an sharp angle there from the chainstay to the dropouts.  I know some comments on the FM166 frame (which seems very similar if not identical) suggest needing to take out the skewer to remove wheel.  Even if that proves to be the case, I don't anticipate that being a problem.
You can see the guide for the derailleur cable sticking out there.  I imagine it's standard practice, but I'm glad these are included! :)  I don't know much about internal routing, but it seems that some frames want you to route solid housing and others, such as this frame, want just cables in the frame; there are stops for the housing and only room for cables in the guides under the BB.

I received this frame with some expectation that there would be some imperfections. The first one (and only one so far) that I have had to deal with is the right-side grommet for the derailleur cable inner routing.  At first it appeared it just wasn't all the way screwed in:
Some more careful study revealed that the hole in the grommet wasn't lining up with the hold for the screw in the frame.  There was more material on one side of the port, so I took a file and evened it out.
After evening out the port, the grommet snaps in and the screw lined up perfectly..

While I had it on my work bench, I went ahead and measured the rear dropout spacing.  I wanted to confirm that it was 135mm, since the schematic had listed 130mm (definitely *not* what I want for a disc-brake hub).  The sales rep had assured me it was 135 and that the drawings were wrong, but I still wanted to confirm.
Well that looks to be just about exactly 135mm, so that's great.

The Fork

This appears to be the same fork that is sold with the Hongfu/Dengfu FM166/FM079 frames.  Including the somewhat tacky sheet metal cable guide.  While the fork seems very solid, I'm planning to buy the Whisky 15mm thru-axle fork instead.  I'll just sell this later to perhaps offset the rather hefty price tag of the Whisky No 9.
Weight came in at 448 grams (claimed weight 440g) -- not super light, but not bad for a disc-brake fork.  (For comparison, the Enve road disc fork has a claimed weight of 435g.  The Whisky No 9 is 375g.)

I think the finish on the fork is excellent.  Unlike the frame, the seams are not obvious.

Of course that sheet-metal cable guide is a little tacky.  Painting it black would be a good first step.  (If I were keeping the fork, I would give this more thought.)
Here are the UD seams inside the fork legs.
And the disc caliper post mounts.  (This is for a 140mm rotor; 160mm will need an adapter.)

So, on the whole I'm very pleased with the frame.  Next step in this process is likely going to be building the wheels.  More to come on that topic once I've received all the parts.

(Update: continue on to part 3 for overall build & impressions.)