Sunday, March 26, 2017

Garmin Varia mount for Topeak racks

Last year I finally upgraded from the traditional style bike speedometer (with wires and magnets) I had been using for over a decade to a GPS-based computer, the Garmin Edge 25. Compared to the larger and more expensive ones, it's pretty basic, but it does the things I need, and it also supports external sensors. Over the winter I acquired my first external sensor: the Garmin Varia rearview radar. It allows a rider to monitor the location of vehicles approaching from behind within about 300 feet, and also functions as a tail light that gets brighter and blinks faster as cars approach. I really like it, and I think it's especially useful here in west Texas, where there are a lot of narrow roads with high speed limits, and enough wind to make it sometimes difficult to hear vehicles approaching from behind.

The Varia uses a Garmin quarter-turn mount, and comes with a seatpost version of the mount. Two of my bikes have Topeak rear luggage racks that seem to me better mount points for the Varia than the seatpost. The Topea racks have a bracket on the rear for attaching a reflector (included with the rack) that looks like this:


This seems like an ideal mount point for the Varia, but of course nobody makes a Garmin mount that is designed to attach to something like that, so I designed one. The starting point for the design was the Garmin mount insert used by K-Edge:


K-Edge makes a number of different after-market mounts, all of which use the same plastic insert. I could have tried to replicate this myself, but as I've discovered from buying a less expensive after-market mount, a secure attachment requires getting the dimensions of the interface points right, and K-Edge have clearly already done so, so for $5 I can leverage their design and just focus on the interface with the Topeak rack. As shown in the picture, the insert comes with 2 M3 angle-head screws which are designed to screw into the metal mount. In this case, I needed a bracket that was thick enough to accommodate the screws and hold corresponding M3 nuts on the back side.

The design I came up with is this T-shaped bracket, which I had 3D printed by Shapeways.


It is 4 mm thick. The angled rack attachment holes are for angle-head M5 screws. To attach this to the rack requires 3 angle-head M5 screws and corresponding nuts. I used 12 mm screws and nylon-insert lock nuts, but plain nuts will probably work fine. Two M3 nuts are needed because they are not included with the K-Edge mount insert.


Bracket installation begins with inserting the M3 nuts into their corresponding recessed holes on the back of the bracket.


The bracket is then attached to the rack with the 3 bolts.


The K-Edge insert is attached to the bracket using the M3 screws. This is done after the bracket is already attached to the rack because the K-Edge insert slightly overlaps the top M5 screw.


At this point, the Varia can be attached.


Wednesday, September 21, 2016

3D printed cable guide for X-Peria tandem fork

In my original entry about the X-Peria tandem, I noted that the fork did not have an obvious method for routing the cable to the disc brake, but that there was a screw hole on the inside of the left fork blade. My solution was a 3D-printed bracket designed to attach to the screw hole and reach around behind the fork blade where the cable would pass through it.

I used OpenSCAD, a free CAD software to create the design. This is an OpenSCAD rendering:


Note that the hole for the screw mount has a flared shape to accommodate an angle-head screw, so as to minimize the amount the screw protrudes into the space inside the fork. The OpenSCAD source code for this design is below:

guidelength = 20;
width = 15;
cablesize = 5;
thickness = 1.5;
screwhole = 5;
len1 = 5;
len2 = 5;
th2 = 2.5;
angle = 70;
bendradius = 10;

$fs=0.01;
$fa=3;

r2 = screwhole/2+4;
cr = cablesize/2;
ofs = width/2-r2;
d = (guidelength-width)/2;

rotate(angle) {
difference () {
    union () {
        // cable guide outer
        translate([0, 0, -d]) cylinder(guidelength, r=cr+thickness);

        // connector section 1
        translate([0, -th2/2, 0]) cube([len1, th2, width]);

        // connector bend
        translate([len1, -th2/2-bendradius, 0]) rotate([0, 0, 90])
        rotate_extrude(angle=-angle) {
            translate([bendradius, 0, 0]) square([th2, width]);
        }
    }

    // cable guide hole
    translate([0, 0, -d-0.01]) cylinder(guidelength+0.02, r=cr);
}


// connector section 2
translate([len1, -bendradius-th2/2, 0]) rotate([0, 0, -angle])
translate([len2, bendradius+th2/2, width/2]) rotate([90, 0, 0])
translate([0, 0, -th2/2])
    difference() {
        hull() {
            cylinder(th2, r=r2);
            translate([-len2/2, -ofs, 0]) cylinder(th2, r=r2);
            translate([-len2/2, ofs, 0]) cylinder(th2, r=r2);
            translate([-len2-1, -width/2, 0]) cube([1, width, th2]);
        }
        translate([-len2-r2, -width/2-0.05, -0.05]) cube([r2, width+0.1, th2+0.1]);

        // Screw hole
        translate([0, 0, -0.05]) cylinder(th2+0.1, r=screwhole/2);

        // flared hold for angle head screw
        translate([0, 0, -1]) cylinder(screwhole/2, screwhole, screwhole/2);
    }
} 

The part was printed in white ABS plastic by Shapeways. I have produced other parts using Shapeways before and have found the results to be very high quality. A couple of weeks after placing my order, the cable guide arrived.


The hole for the cable was actually just a little too tight for the cable to fit, so I widened it slightly with a drill. This is actually the second version of the design, the result of some changes I made to my first design after I had a chance to test it on the bike. Here is the final product, installed on the bike.




Monday, September 19, 2016

Custom mounts for Topeak Explorer rack

I have the Topeak Explorer rack on two of my bikes, the Raleigh Olympian and the X-Peria tandem. This rack comes with adjustable steel rails that attach to the upper part of the rack.


These rails are designed to be bent to fit the particular frame on which they are mounted, and can fit nearly any frame, provided there is a set of mount points to attach to. In the case of both the Raleigh and X-Peria tandem, there are no upper eyelets, so in both cases I made my own mounts to attach to other available mount points.

In the case of the Raleigh frame, I used the rear brake mount. The custom mount was made from 1/8" (3.175 mm) aluminum sheet. Because I intended for the mount to be specific to this bike and therefore not adjustable, I cut out the shape I had in mind in paper first to ensure that all of the holes were in the right place. I cut the aluminum to the shape I wanted with a circular saw (a fairly crude tool for this sort of job, but it's what I had available and it cuts the aluminum of that thickness relatively easily). I drilled the holes, and used a sander to smooth all of the edges. Bending the aluminum sheet to the desired shape takes a lot of leverage, so I used the holes to attach the ends of the cut out piece to some long pieces of scrap wood. I was eventually able to get the mount into the shape I wanted, but the aluminum got pretty scratched up in the process, so I did some more sanding on the finished product to remove all of the scratches, leaving it with a brushed look.


Here's the whole rack, held perfectly level by the custom mount.


The X-Peria tandem does not have dedicated upper rack mounts, nor does it have a caliper brake mount in the rear, since it is a disc brake frame. As I noted in my original blog about the tandem, there is a seatstay bridge where one would expect a caliper brake mount, which has a threaded hole underneath, possibly for mounting a fender. I used the same method and gauge of sheet aluminum to create the fender mount for the X-Peria. Since I happened to have some white paint close to the color of the bike, I painted this one.


The threaded hole on the frame is for an M4 screw (similar to what is used on water bottle mounts), but there is not a lot of clearance, so instead of a standard water bottle bolt (below left), I used an angle head screw (right).


Combined with a hole to match the shape, the screw protrudes only a minimal amount, leaving more tire clearance.


This is what the finished product looks like, installed.



Wednesday, August 24, 2016

MC286 with SRAM 1x

SRAM has been pushing their 1x groups for road use lately, and has taken it a step further with the recent release of the SRAM Apex 1x group. One important aspect of the new group for anyone trying to build a cyclocross bike on a budget was the release of a new version of the PG-1130 cassette: a 11-42 cassette that is compatible with the 10-speed freehub standard that is found on older road wheels and is still in use on MTB wheels.

At the time I was buying the frames and parts for these bikes, I noted in my post about components that my choice to buy Mavic's budget-oriented Crossride MTB wheels forced me to use only 10 of the 11 cogs in the Shimano 105 cassette because MTB wheels are still using the 10-speed freehub standard. Building a cyclocross bike with the Crossride wheels and SRAM 1x at the time would have required using an XD cassette and buying the XD driver that is available for this particular Mavic hub (which retails for $100). The ability to use a wide range cassette that is compatible with the built-in freehub on stock MTB wheels reduces the cost of a SRAM 1x build significantly.

Since Heather likes the SRAM shifters on her road bike better than Shimano, this summer I decided to convert her cyclocross bike to SRAM 1x so I could use the Shimano 105 group on another bike. For the conversion, I used SRAM Rival brake levers and right shifter, Rival crankset with 42t chainring, Apex derailleur, and the aforementioned PG-1130 cassette.

The original setup consisted of a 50-34 crankset and 11-32 cassette. The new setup results in a lowest gear (42/42 for a 1:1 gear ratio) that is slightly lower than the original 34/32. The highest gear, a 42/11, is approximately equivalent to a 50/13, meaning that the new setup replicates the original setup minus the highest gear of 50/12 (since the 11 tooth cog was never installed). Having ridden my cyclocross bike for over a year, I don't believe I've ever used the 50/12, so I don't believe this is particularly important for the type of riding we do (or most riders do) on this kind of bike.


Gearing range is clearly not a problem, but the other possible caveat to a 1x conversion is gear spacing. I did some spreadsheet analysis of the gear ratios on the original 2x10 setup compared to the 1x11 setup and found that the difference is not that large. The 12-32 cassette has a maximum jump in gear ratios of nearly 16%, between the 19 and 22 tooth cogs. The 11-42 has a maximum jump of 18%, between the 13 and 15 tooth cogs. Perhaps more importantly, that larger jump is closer to the edge of the range in less used gears, where the largest jump was previously in the middle. The difference should not be particularly noticeable to most riders.

Based on our experience so far, I think the SRAM 1x groups are an excellent choice for cyclocross and gravel bikes. It's not surprising to see so many bikes coming out with this setup from the bike bike brands.

Sunday, December 20, 2015

X-Peria 5200 Tandem


It's now been over 5 years since I bought the Bike Friday Family Tandem. I have no regrets about it, but I'm ready for something new. I eventually gave up on the conversion to drop handlebars, because even with the various tweaks I made, shifting never worked quite as well as the original shifters did, so I put the original flat handlebars back earlier this year. The telescoping seatpost was important when my kids were shorter, but now the kids are tall enough to fit some full size tandem frames. I also found the Bike Friday to be fairly heavy (around 50 pounds) and I felt that the frame lacked stiffness, a feature that can be partly attributed to its geometry.

My requirements for a new tandem were:
  • Full size frame that's a reasonable weight.
  • $1500 or less. I don't know how long my kids are going to be interested in riding with me on the tandem, so I want to avoid putting too much money into something that might not be used much.
  • Fit a tall rider (me) in front and a shorter rider in the rear.
The Cannondale Road Tandem 2 comes in over $3000, and newer used ones routinely sell on eBay for nearly 70-80% of that. One other option is the KHS Milano, which has a list price of $2000 for an aluminum road tandem with disc brakes and Shimano Tiagra. The only way to get a good road tandem for less than that is to buy used. The problem with most older used tandems (with the notable exception of Cannondales) is that most 1990s and early 2000s tandems had level top tubes that work great for two riders of similar size but would be much to tall in the back for me. Sloping top tubes that can accommodate a larger height differential have become much more common on tandems in the last 10 years, but many of those newer tandems are usually out of my price range. There is a steady stream of used tandems on eBay, but the number of older used road tandems of the appropriate size and price range turns out to be relatively small, and the number of those sellers willing to ship a tandem (a necessity when you live in west Texas) is smaller still.

After searching eBay for some time, I eventually stumbled onto a listing for the X-Peria 5200 tandem frame, which was being offered new for somewhere around $500 by the French online bike shop CR2V. The frame is offered in two sizes, the larger of which is pretty close to the correct measurements for me. At this price I decided I could build my own for something close to my target price. CR2V has a number of eBay listings for frames that they offer to ship internationally, but there are more options available directly on their web site, which is how I eventually ordered my frame. The site is completely in French, so I had to navigate it with the help of Google translate at times. It turns out the $500 price tag included the eccentric bottom bracket but did not include a fork, however they do offer a package with BB, fork and headset for about $90 more. Shipping to the USA is not available as part of the normal checkout process on their site, but after some emails back and forth with them, they offered to ship to the USA for an additional 100 EUR. Total cost was just over 700 USD including shipping. When I placed the order, they had just run out of stock, so there was some delay while a new frame was ordered from the manufacturer, which took nearly 3 weeks. After the frame was finally shipped, it was only a little more than a week until the frame arrived.

At first glance, the frame has a lot in common with a Cannondale, but a closer inspection shows that the welds don't look nearly as clean as can be expected on a Cannondale. I would compare it to the quality of frame one typically sees on lower end aluminum road bikes in a local bike shop. While X-Peria is clearly a French company, it's not clear to me whether the frames are made in France or somewhere in Asia. Regardless, as long as the frame holds up, it suits my purposes just fine. The combined weight of frame, fork, headset and eccentric bottom bracket is about 9 pounds.


The specifications on X-Peria's web site do not specify whether the fork is aluminum or steel, but I believe it is steel because the fork blades look too small to be aluminum, and the junction of the steerer tube (which is clearly aluminum) and fork crown suggests an interface between two different metals rather than a single continuous piece of metal.

The frame has post mounts for 180 mm brake discs front and rear. I used 203 mm brake discs with 180-203 Shimano adapters and Shimano BR-R317 cable-actuated brakes.


The rear dropout spacing is 135 mm, so it's compatible with 29er MTB wheels. Nearly all higher end 29ers now use through axles, so most quick-release 29er disc brake wheels are targeted at less expensive bikes, which gave me a number of good options at a reasonable price, particularly since cost and durability were higher priorities for me than weight. I ended up with these 32-spoke WTB SX19 wheels. 36 and 40 spoke wheels are common on tandems, but it's difficult to find pre-built wheels with more than 32, and I think these will be sufficient for me. The tires shown here are 37 mm Continental Contact, though their actual width appears to be a bit less than 37 mm. Both wheels fit in the frame easily. The fork could easily fit 40 mm tires or bigger, but the rear doesn't have much extra space.


For the drivetrain, I bought used Shimano Ultegra 6603 shifters (3x10 speed) and a 9-speed Shimano Deore XT rear derailleur. (Shimano 10-speed road shifters will work with 9-speed MTB derailleurs but not 10-speed MTB derailleurs). I set it up with single-side drive, which means I'm only using 2 of the front shift positions, but I have the option to use a triple in the future. The reasons for single side drive were keeping cost down (I already had one of the cranks I needed) and size options. I am using a 180 mm front crank and 165 mm rear. When the kids get a bit taller, I will probably eventually go to 170 rear and 175 front with regular tandem cranks.

The rear crank is made by Origin8. It's inexpensive and also comes in even shorter lengths, an ideal option for someone setting up a single-side drive tandem for a short stoker. I used 39 tooth chainrings for the timing chain because I already had one in that size. The inner two rings pictured here are 48 and 32 tooth rings, which have been paired with a 11-32 10 speed cassette. This gives a gearing range just slightly lower than a 50/34 compact road crankset with similar cassette. The 1:1 ratio of the low gear should be enough for moderate climbs and the high end is more than enough for how I anticipate using the bike.

The finished bike comes in at 38 pounds as pictured, a full 12 pounds lighter than the Bike Friday. I don't have an exact cost total, but it came in somewhere between $1600 and $1700. It is probably possible to build one of these in a similar way with true tandem cranks (such as Sugino XD) for under $1800.


The frame has a few quirks that I didn't expect. None of them are serious flaws, but things that might have been helpful to know about in advance:
  • shift cables are routed for a top-pull front derailleur. As far as I know, this means most road derailleurs won't work.
  • only 2 water bottle cage mounts.
  • no guide for brake cables on the fork, as would be expected on a disc brake fork.
  • There are double threaded eyelets on the rear dropouts, but no rack eyelets at the top of the seatstays. There is, however, a threaded hole underneath the seatstay bridge and chainstay bridge, which is presumably for mounting a fender. I'm working on a custom bracket for attching a rack I have that uses this hole.

Sunday, May 31, 2015

The completed MT-MC286 bikes

I have finally completed assembly of both bikes, so here they are. First, the 58 cm bike that I will be riding.


I will eventually put SPD pedals on this before doing any serious riding. The flat pedals are for purposes of riding around the neighborhood while I get the shifting and brakes adjusted. This bike has the narrower than expected Continental Contact tires that I wrote about previously. They will probably be a good tire for riding on roads, but that's not the primary purpose of this bike, so I will probably eventually get something wider. For those who are interested in such things, I weighed the bike and it came in a little under 22 pounds as pictured. The handlebars were wrapped with Bike Nashbar's handlebar tape. I used two rolls of it (white and "nuclear green") to get the striped pattern, spacing them fairly close together so that I used about 2/3 of each roll. That has the effect of making the padding about 50% thicker than normal. The green color turned out to be remarkably close to the green color we used in the frames.

Here is the 48 cm bike that Heather will be riding:


The two notable differences on this bike are the fatter tires and a big set back on the seatpost and saddle. I wanted to go with carbon seatposts because they are supposed to be more comfortable (I don't have personal experience--I'm still using an aluminum seatpost on my carbon road bike), and I knew this frame was going to require significant set back because of the steep seat tube angle. The geometry chart for this frame can be seen at Miracle Bikes web site. The 58 cm frame has a 73 degree seat angle (the same as my road bike), but the 48 cm frame has a much steeper 75.5 degree angle. That has the effect of moving the seat forward about 2.5 cm. So, for the 58 cm frame I bought a zero set back seat post and for the 48 cm frame I bought a post with about 2 cm of set back. I originally got a different saddle for this bike, but I was not able to get it back far enough, so I eventually swapped it out for this one that came stock on a Giant road bike and has longer rails. I understand these kinds of compromises are necessary on shorter frames, but in this case I don't think the seat tube angle needed to be this extreme.

This bike has a pair of 700x40C WTB Nano tires. They were tried with some success by someone on the forum discussing this frame at mtbr.com, so I thought I would get a pair and try them out on one of the bikes. So far I've only bought one pair, but if we like them after using them a bit, I'll probably get a pair for the other bike. Miracle Bikes specifies the maximum tire width as 38 mm, so this is technically exceeding that by 2 mm. The fork is clearly not the limiting factor here, as it appears to have more clearance than in the rear.


In the rear, things are a bit tight behind the bottom bracket, but I think it will work.


The seat stays also offer barely enough clearance, which I find strange because there is no particular reason not to make the clearance in this part of the frame more generous.


So, I think this frame will work with a 40 mm tire in dry conditions. Mud might be another story. The frustrating thing about the clearance in the rear is that there is plenty of clearance between the seat tube and rear tire, implying that the unusually steep seat angle on the 48 cm frame was not actually necessary. I think it could have been 1/2 to 1 degree less steep without making the gap between seat tube and rear tire the limiting factor in clearance, which would offer much more flexibility in choosing saddles and seatposts.

Based on my experience assembling the bikes, here are some things that I would change about the frame design:

  • Reduce the seat tube angle by 1/2 to 1 degree in the smaller frame sizes.
  • Make more tire clearance between seat stays. This is easy and doesn't compromise anything else in the frame.
  • Make a little more clearance between chain stays. This may not actually be possible without some very creative engineering such as that being done by Open Cycle, but I'd love to put an even fatter tire on this bike if it were possible.
  • Move the exit hole in the left chain stay for the brake cable forward a bit. Right now the cable has to make a bit of an awkward bend to get to the rear disc brake (Avid BB7 on these bikes).
  • Taller head tubes. Nearly everyone on the mtbr forum thread discussing this frame that has posted pictures of their completed bikes has had 3-5 cm (or more) of spacers between the top of the headset and stem. I think this is a sign that the head tubes on this frame are probably shorter than they need to be. However, this frame is designed for cyclocross, and I don't really have experience with cyclocross frames, so it's possible that this is normal geometry for cyclocross racing, and that I and many others who are buying this for dirt road riding just have higher handlebar preferences than your average cyclocross racer. 
Having said that, none of these are serious problems, and I fully anticipate that we'll have a lot of fun riding the bikes.

Monday, May 4, 2015

MC286 component considerations

The logical choice for components for the MC286 is to install a road drivetrain and a set of mountain bike wheels because 142x12 rear wheels for mountain bikes are readily available for reasonable prices. It turns out one of the great challenges of making this frame work on a reasonable budget is the incompatibility between 11-speed road cassettes and mountain bike hubs.

When 11 speed was introduced to road components a couple of years ago, it required a slightly longer freehub body. (Note that this is all just from reading rather than experience; my road bike is still at 9 speed.) Mountain bike components didn't introduce 11 speed until more recently, and so far they have stuck with the old freehub body dimensions. This means that using a standard mountain bike wheel won't work with an 11 speed road group. There are very few road-specific wheels available with a 142x12 rear axle at this time, though I'm sure that's likely to change soon enough. The 142x12 standard is relatively new to cyclocross bikes and to my knowledge is not used anywhere (yet) on regular road frames. I suspect most cyclocross bikes being sold by the major brands that include 142x12 rear axles are using proprietary wheels. Because this standard is being introduced on higher end bikes, there aren't likely to be many budget-oriented options right now.

I did a lot of research and considered several options for wheels:
  • Use a mountain bike wheel with the new Shimano XTR 11 speed cassette and a road group. Aside from the high cost of XTR, this may not be workable because it's only available with a 40 tooth large cog, which likely exceeds the capacity of the road derailleurs. This could become viable in the future if Shimano were to offer more options (in price and gearing ranges).
  • Use a Campagnolo 11 speed cassette. According to this article by Lennard Zinn, the Campagnolo 11 speed freehub bodies can fit on most 10 speed road hubs. However, this requires finding a hub that has both 142x12 and a Campagnolo freehub body available as options. I don't know whether this exists, and if it did, it would be very expensive and also quite restrictive in the available gearing ranges.
  • Find a wheel specifically built for cyclocross and through axle wheels. Right now the only thing I can find off the shelf is the Stan's Iron Cross wheelset. The new DT Swiss 240S DB hub is also designed exactly for this purpose, but I don't know what the cost is, and haven't yet found any wheels for sale based on this hub. In both cases, however, I think the cost is higher than what I was hoping to spend.
  • Use a standard mountain bike wheel and install only 10 of 11 cogs from the road cassette.
As far as I can tell, only the last two options are even likely to work, but the last option has many more price options available because there are so many wheels available for 142x12 29er mountain bikes. I ultimately chose the Mavic Crossride wheelset because it looks like a good reliable set of wheels and is half the price of the Stan's wheels.

For components, I considered Shimano 105 and SRAM Rival and eventually settled on Shimano 105 because in part because I was able to get a great price on the complete group without brakes from Starbike.com in Germany. They were one of the few retailers I could find anywhere that offered their road groups with brakes optional, and they also had a great price on the Mavic wheelset I wanted. Starbike's prices are such that I'm sure they would have been competitive even a year ago with shipping from Germany to the US, but the strong US dollar vs. the Euro right now made the price even better. For two wheelsets, two component groups and several other miscellaneous parts, shipping was only an extra 10 Euro for what turned out to be two very large boxes. The parts arrived in less than two weeks.

This is the drive side of the Mavic rear wheel. The freehub came with the sticker on the right wrapped around it, warning against using cassettes that use individual cogs as opposed to a carrier. I got a 11-32 cassette with my Shimano 105 group, which uses individual cogs for the first 8 cogs and a carrier for the last 3 cogs. The reason for this warning is the aluminum construction of the freehub body. Individual cogs will eventually dig into the splines of the aluminum feehub body, where the carrier spreads out the load and avoids this. Using the cassette that I have chosen will therefore have a risk of damage to the freehub body over time, particularly in the middle cogs, which will be subjected to more torque than the smaller cogs. For now I'm going to accept the risk and try it for a while.

This is the complete 11 speed cassette set in place on the freehub without the lock ring. The last cog spins freely in place because the splines are not tall enough to engage it. In addition, the threads do not extend far enough to properly engage the lock ring. It's possible to get it on, but it will only catch about 1/4 turn worth of the thread. So, it's clear this won't quite work.

The excessive stack height of the 11 speed cassette is made clearer by attempting to install the wheel with the whole cassette on it in the frame. The picture on the left shows all 11 cogs in place, and the picture on the right shows only 10 cogs. With 11 cogs, the lock ring rubs against the dropout so that it would not be able to spin with the cassette, and the smallest cog is so close to the dropout that even without the lock ring problem, the chain would likely rub against the frame. On the right, there is enough space for everything to work properly, just with one fewer speeds. Because the first two positions each require special cogs, doing this properly requires buying both a 12 tooth first position cog and 13 tooth second position cog, and using them to replace cogs 11, 12 and 13. However, someone wishing to not buy the cogs could theoretically just remove the 13, leaving a 11, 12, 14 ... combination, which would leave an unusually big jump in gearing between the 12 and 14. The picture above shows the 12, 13, 14 combination, which added an extra $20 or so in costs, but made it possible to keep the total cost of the bike down by quite a bit.

The last important consideration for this bike is tires. The Miracle Bikes web page for this frame specified that the frame could handle a 38 mm tire. I went ahead and bought some 37 mm tires and installed them on the rims. I looked at a lot of tires trying to find a balance between smooth center for riding on pavement and some kind of tread on the sides for riding off pavement. I decided to try the Continental Contact, which is really more of an urban/commuting tire. Here it is installed in the frame.


My first reaction is that I wanted something wider than this and there appears to be a lot of room. By my measurement the tire is closer to 32 or 33 mm. I measure about 50mm between the stays, and similar clearance at the bottom bracket and top of the fork. This made me wonder if I could have gone wider and knobbier, so I'm going to try a set of 40 mm tires instead.

Sunday, May 3, 2015

Arrival of the MC286 frames from Miracle Bikes

The MC286 frames arrived earlier this week.


The total time from placing the order to arrival at my doorstep was a little over 7 weeks. Most of that time was the custom paint job. I was warned it would take a while, but it took a little longer than I was planning. After about 5 weeks, I emailed my contact at Miracle Bikes asking about the status. She sent me a photo of one of the completed frames, and a couple of days later sent me a shipping number. The shipping numbers can be tracked by the US postal service, but often there is a lag (in this case close to a week) between receiving the number and the USPS tracking system recognizing it. The time from receiving the shipping number to arrival was just over two weeks, so I imagine a buyer not wanting custom paint could receive a frame in less than three weeks.

The bikes look great, a nearly perfect rendering of the artwork I sent them, and the quality of the paint looks really good. The through axles I had added to the order were already installed in the dropouts. They seem to be specific to this frame design (which is also the consensus on this thread at mtbr.com), any prospective buyer is advised to order them with the frame. I didn't think to ask about it during the process of purchasing the frame, but headsets were included. I'm waiting for a few more parts and then will be ready to start assembling them.

Tuesday, March 17, 2015

MT-MC286 from Miracle Bikes

Last summer, I moved from central Illinois to west Texas. I've done some riding since then, but not as much as I'd like to because I just haven't found the riding very enjoyable here, the primary reasons being narrow roads with fast traffic and a surprising number of loose dogs. Like central Illinois, the area is crisscrossed with small farm roads, but the farm roads here are mostly unpaved. The dirt roads are readily accessible from where I live, and I've found them to be much more traffic and dog free, so I've concluded that riding the dirt roads is my future, and that I want a bike designed for such riding. That is the origin of my next project, a cyclocross bike, or rather two cyclocross bikes so Heather and I can ride together.

My first plan was to find some kind of inexpensive cyclocross bike from someone like bikesdirect.com, where aluminum frame cyclocross bikes with disc brakes start at about $900. We both like our carbon road bikes a lot, and since my last experience ordering a frame with custom paint job direct from China last year was relatively painless, we eventually decided to spend a bit more and go in the direction of carbon again.

I had three requirements for the frames: the size range needed to go as far as 48 cm and 58 cm (60 would be preferable, but I can make 58 work), disc brake compatibility, and through axle dropouts. Because I haven't owned a mountain bike made more recently than the mid 1990's, I really don't have much prior experience with disc brakes and through axles, but based on all of my research, this is the direction cyclocross bikes are going, with road bikes likely to follow soon. Some major brands, such as Giant, are already selling cyclocross bikes with through axles. My primary motivation for doing this is forward compatibility: through axles and disc brakes make it more likely that the wheels and frame will be interchangeable with future wheels and frames.

It took some time to find someone selling a frame that met all three criteria. Nearly everyone has a disc frame, and several manufacturers appear to have recently introduced through-axle compatible frames, but I could only find one that offered all of the sizes I wanted: the MT-MC286 from Miracle Bikes. The frame is also listed on Alibaba.com, which is how I contacted them. I got a reply pretty quickly, and I went back and forth for a few days with the person about what I wanted. The base price of the frame was quoted to be $480. I don't know whether this represents any kind of a discount over the price of only buying one frame. A custom two-color paint job was quoted at $70. Shipping is effectively two for the price of one because the frames will ship in a single box. (The frame I bought last year was in a box probably big enough for two.) They requested payment via PayPal, and add 4% to the cost to cover the fee that PayPal deducts. Total for the two frames came to $1300. I was told that they have a bit of a backlog of up to 20 days on their painting (apparently due in part to Chinese New Year). All of this is pretty consistent with my previous experience, so I wasn't too worried.

Before sending money, I thought I should read some more about them. I didn't know anything previously about Miracle Bikes, but after doing some research I did find at least one blog that discusses importing frames directly from Chinese manufacturers, and he lists Miracle Bikes as one of the ones he considers to be reputable. Given that and the built-in protections that come from using PayPal, I decided I was ready to give it a go.

We've decided to get matching frames, so we came up with a design, and sent the following image to Miracle Bikes:



I placed the order a little over a week ago, and I'm hoping that it will ship within about 2 weeks.

I'm in the process of finding components to go on the frames, but one persistent question in my mind has been what kind of through axle to use. It's my understanding that there are different types of through axle designs, and they need to match the dropouts of the frame, but there's very little information online about what is compatible with this frame. I eventually found this very helpful thread on the forums at mtbr.com. A number of commenters on that thread have already bought this frame from Miracle Bikes, and some of them bought through axles from Miracle Bikes with the frame. I contacted Miracle Bikes and was quoted a price of $29 for a set of axles, so I have added that to my order. Now, I just wait...

Thursday, February 19, 2015

Tire clearance on the VB-R-027

I've become a believer in riding on the widest possible tire for the application. After many years riding very skinny tires, I decided to try 25 mm road tires a few years ago after fixing one too many flat tires at the side of the road. The reduction in pinch flats since the change was quite dramatic, so when I bought my new frame from Velobuild, I hoped it would allow me to go one step further to 28 mm tires, given that their model VB-R-027 was a bit more relaxed in its geometry than some of their other frames.

I can now report that 28 mm tires work fine, as long as they aren't really 28 mm. I got a new pair of Continental Grand Prix 4 Season tires this winter in the 700x28C size.


The problem is, I don't think they are actually 28 mm wide. They seem to be about the same size as the old tires I removed, a less expensive pair of tires that were marked 700x26C. A relatively rough measurement using a ruler and eyeballs seems to confirm that they are about 26 mm wide. (This also appears to be confirmed on various forums I've read).

Here is what the Continental tires look like in the fork:



There are maybe 2-3 mm to spare all the way around. Clearance is similar behind the bottom bracket:


The worst clearance on the frame is the rear brake bridge, which in my opinion should have been 1-2 mm higher.


I forgot to photograph the seat tube clearance, but it's about 2-3 mm. The 28 mm tires that are really 26 wide work just fine on this frame. A true 28 mm tire might work, but it would be very, very close. For this reason, I'm perfectly OK with the tires being slightly smaller than advertised.

I have occasionally had problems getting the rear wheel in and out of the frame. The angle of the dropout combined with the size of the nut on the very old quick release skewer I'm using forces the wheel forward enough that the tire rubs a bit on the seat tube and chainstay bridge. I compared it to another carbon frame made by Giant and discovered that its dropout is angled differently and avoids this problem. This isn't a very big deal for me, but if someone were worried about quick wheel changes in a race, it could be a problem.