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, 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 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, 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.