Where I've been

In case anyone's been wondering why there hasn't been a post in 15 months, here's what happened. I got real busy working on this:

Woo hoo!

Then we went to Mexico to celebrate.

Then I got real busy being a post-doc, still at UT.

Back when I used to blog regularly, it seems I generated most interest on this blog by posting about my Dynamic Crosstown and about bike commuting in Austin, so here's an update:

I still commute almost every day on a bike. My back-and-forths take me about 80-100 km each week. After three years on my Crosstown 7, I've racked up almost 13,000 km (8000 mi). It's still holding together nicely, although I think I'm going to need to replace the shifter and cables and give the rear axle a good cleaning to make the shifting a little more precise. Shifting has been finicky lately. Also, the cranks are a little creaky. They probably need to be greased and tightened. Overall, though, no major complaints.

During the summer, I used the new Capitol Metro Red Line commuter train, because sometimes, it's just too hot to go both ways.

If you're still reading, post a comment to say hi.

Cheers!

Commuter Tires

By request (I'd say popular demand, but that's a bit pretentious, and there was only one request) I'd like to say a few words about tires for commuter bikes.

I used to work for the research and development branch of Michelin North America, and now I have a  fondness for tires. I cannot help but notice them on cars (my wife used to laugh about this, now she just rolls her eyes and nods politely), and I am a firm believer in paying for quality.

If you've read this blog before, you probably know that I devote many of my posts to describing my experiences with my Dynamic drive-shaft bicycle. If you've read my reviews of that bike, you may know that I was disappointed with the quality of the tires that they supplied with it. In particular, because I have fenders and because removing the rear tire is less than convenient, the puncture resistance of those tires was unacceptable. I was having to repair a flat on at least a weekly basis.

That led me to one of the best $30 purchases I've made for my bike. I visited my LBS (Clown Dog Bikes) and requested Kevlar commuter tires, and the guy there handed me a pair of CST Selecta Kevlar tires. These tires have a steel bead, a Kevlar carcass (forgive the tire-nerd lingo, that's the weave inside the rubber that provides the strength and shape for the tire), and a reflective strip in the sidewall. There is a very light, directional tread pattern, which for a road bike doesn't serve a whole lot of purpose. The tread pattern is designed in such a way that it does not induce a vibration or noise during rolling (as a mountain bike tread would do, for instance) and may provide some help with water evacuation (although in my experience with tire design, the swoopy directional patterns tend to be more marketing hooplah than functional features).

What's to say about a bike tire? Well, in 6000km, I have had to patch my inner tube precisely two times: once because of bad rim tape, and the other time because of a nasty sharp nail that could have pierced plate armor. Note that when I ride my wife's bike (to which I retired the original tires provided by Dynamic), flats occur on about a weekly basis, more or less, over the same route. The Kevlar works.

What else? The reflective strip, after two winters' worth of riding through dirty sandy black road water, is still visible in my car's headlights (and this camera's flash). There is at present no sign of that strip separating or coming out of the sidewall.

Last of all, the tread. I see only modest signs of chunking. There is still plenty of tread depth left. The photo above is of the front tire, which spent 5000km at the more aggressive rear axle. I'm guessing these are only about halfway through their life on this bike. I ride moderately aggressively and with a heavy backpack.

6000 km

Today the odometer on my Crosstown 7 flipped 6000 km. My average speed over the life of the bike (342 hrs) is 17.5 km/hr, or 11 mi/hr. I'm the first to admit that I'm not the next Lance Armstrong, but remember that number includes all the time I walk the bike or go slowly accompanying a daughter on a ride up the street and back. I started riding it in August of 2007, so that's an average of 315 km/month over 19 months. Since my commute is about 20 km/day, that means I've been able to ride almost 4/5 days. (Some days are partial commutes when I pick up Ian at Tae Kwon Do and ride the bus home with him.)

Now that I'm back on the bike after the recent repairs, it's nice to be riding consistently every day. This morning was rainy and wet, but I was still able to pull my daughters to school in their bike trailer without rooster tails or chain cleanup. Fenders are a must on a commuter, and have I mentioned before that the drive shaft is nice for not requiring a lot of messy maintenance? This was the first rain in a long time, so the water on the road was really dirty and oily. Yuck! There's more on tap over the next few days, but I don't really mind. It's nice to be out in the weather, whatever it is.

Back in the Saddle

I promised to upload some photos of my restored Dynamic Crosstown 7. (Shhh, I'm using a lab camera to take and post these while our own camera goes in for warranty repair.) So here they are. Note: I saw a little video blurb called BrightBike about putting reflective tape on your bike and decided to get visible. In addition to adding to the cheese factor and increasing visibility, the white tape on the top tube covers up and inappropriate "Tempo" logo. This bike is not the Tempo model but uses the Tempo frame, apparently.

When I went to go buy the reflective tape, I brought Caroline with me, and she got into her head that she needed a new bike helmet and that I was going to get her one at the hardware store. I did some fast thinking and convinced her to accept her own $2.50 package of reflective tape instead. Of course she chose the read and white candy stripe pattern, some of which ended up as decoration on her helmet and some of which ended up adorning the drive shaft cover on my bike. (And yes, that's a spare pair of socks I keep at my desk that you see. I didn't notice it in the photo before.)

Eliza came out with me while I was working on the bike. She, my Little Helper, wanted to participate, so I set her to cleaning the spokes and hub. Everything's nice and shiny now and it looks more or less brand new.

I had mentioned previously that I was having trouble with the shifting. A new cable and sheath and a good clean-out of the rear hub fixed that problem. I had a little bit of worry when I noticed that the gears were grinding during my first commute on the new frame. That turned out to be a simple error on my part of not sufficiently tightening the right-side axle nut on the rear hub. It was allowing the bevel gears to get out of alignment and grind. It was very easily fixed.
I'm happy to be back in the saddle again.

Framed!

The frame arrived this evening. Unfortunately (arghhhh!) my camera has a "lens error" and won't focus now. We have lost more cameras to lens errors. Bummer, because I wanted to document the rebuild with photos. Oh well... Maybe I'll just nab a stock photo:

I'm surprised by how light the frame is. Total shipping weight including the box and packaging was 6 lbs. It's nice and shiny and new and looks just like the old one with two small exceptions. First is a "Tempo" decal which tells me that the frame is common with the Tempo model. OK. The second is another small lug of some sort on the seat stay just above where the brake mounts are.

Dynamic, per my request, sent the frame with the steer-tube bearings pressed into place already, so the only other tricky thing I have to do is press out the left-side bottom bracket fitting. I'm looking forward to getting going on it tomorrow when I get home. It will be nice to be back on my regular commuter.

Driveshaft Disassembly

Today I finished stripping my Crosstown 7 in order to replace the broken frame. That involved removing the driveshaft assembly, cleaning it out, and re-greasing it. The bottom bracket came out by loosening the three screws on the left-hand side. Here's what the inside looks like. Somehow, dirt managed to get in there, but I don't think that had any consequence on performance, since the whole front crank case is sealed.

Here's what the front crank-case assembly looks like fresh from the bottom bracket.

Loosening the three screws on the other side allowed me to open the case and remove the gears for cleaning. Initially, the inside of the crank-case was full of grease, which I removed with clean rags.

I noticed that the gear ratio was 11:27. Because 27 and 11 are both prime, each tooth on the shaft eventually interacts with each tooth on the bevel gear, and no wear pattern develops. After cleaning everything up, I closed it up again and shot it full of fresh Teflon grease.

Here's what the rear end of the drive shaft looks like. This is where the 7-speed internal hub connects. The hub is similar to the chain driven version except for the bevel gear in place of the chain cog.

The next step is to receive the new frame and reassemble. I'm expecting the frame on Wednesday, so I'll post photos of the reassembly process then.

Stripping the Frame

As I said I would, I started to take apart my Crosstown 7 in preparation for replacing my broken frame. So far, this job has been about what I expected, with no surprises. I started by removing the bike rack, seat post clamp, and rear fender, which all came apart as an assembly. Then I removed the brakes.

Then I removed the front brakes and unhooked the shifter cable, which allowed me to remove the handlebar, with everything still attached. At this point, my neighbor Emily saw me over the fence and offered me the use of her husband Jeff's work stand. I accepted, and boy what a difference that made. That enabled me to remove the kickstand and take off the cranks. Fortunately, I had a crank extraction tool from a previous project. Without a crank extractor, that task is near impossible and guaranteed to mess up your bike.


One interesting thing to note here is that when you add grease to the crank, it eventually comes out through the bearing on the right side near the crank arm seal, which makes it kind of messy since this spot is tough to clean with a rag with the crank arm still installed. In the photo below you see a year and a half worth of grease accumulation. The color of this grease when clean is light brown, almost white. A couple of times I had added shots of the green marine grease that I use for my water-brake dynamometer at school. I plan to open this up and clean it out thoroughly and re-grease with the white teflon grease supplied by Dynamic.

In a way I'm glad for the opportunity to get inside my bike and see how it all goes together, although this process is time consuming and no so convenient. I'll take the challenge to learn a little about bike repair rather than complain. Here's how I left things when it got too cold and dark to keep going tonight. (My workspace is the back patio. I miss my garage workshop.)

Frame Update

Micro-post here: as promised, Dynamic shipped my frame yesterday. This morning I got the shipping notification from UPS. It should arrive next Wednesday. I hope to start posting disassembly photos this weekend.

The downside of aluminum frames

It's time for an update on my Crosstown 7 (see all the articles here). This is a shaft-driven bike from Dynamic Bicycles, most similar to the currently available Crossroad 8. A couple of weeks ago, I noticed that the bottom bracket was starting to move side to side more than usual, and I thought that was probably not a good sign and that it would suffer a fatigue failure. Well, today, as I was riding home, I noticed the frame get loose and start to creak. When I stopped to look it over, I noticed a nice big ugly crack where the seat tube meets the bottom bracket. That's not supposed to happen. Unfortunately it's an inevitable consequence of aluminum butt-welded frames, and I think that the design of the bottom bracket on this shaft driven bike may have amplified the stress or strain in that area. Since purchasing the bike in August 2007, I have put 5900 km (3670 miles) on the bike. It's the 22" frame, and I'm a heavy guy (~215 lbs) and carry a heavy (~15 lb) back pack on the book rack, and I tend to have more of a stoking rather than a spinning pedal style, so it's safe to say that I'm a heavy user, but not unusually so.

When I got home today, the first thing I did was to locate my warranty and confirm that there is a lifetime guarantee on the frame. I called up Dynamic and told them what happened, and I was very pleased to hear and immediate "Man, I'm so sorry that happened to you. We'll get a new frame shipped out to you right away." We went over the details of what I need, including agreeing to how much I would need to put together, and was I able to do the things, and did I have the right tools, etc. The attitude I got was 'what can we do to make this right for you as quickly as possible?' and I have to say that I appreciated that. I've had some very poor customer service experiences before, but not with Dynamic. Others have complained about them, but it's just not been my experience, I've always found them to be friendly and helpful.

I'll post again when the new frame arrives, and maybe I'll document the repairs that are necessary.

In the mean time, keep on biking, and click on over to support my friend Margo in her New Year's resolution to start biking to work again. Leave supportive comments, and ask her to blog about the very funny story of when we rode home together one time...

How is a Man Like a Peach Tree?

I recently read about peach trees that they need a certain amount of cooling in order to be productive. That is, if they don't spend a minimum number of days below a certain temperature, then their fruiting is limited. I wonder whether there could be a hormonal or other chemical basis for a similar response in humans...

This morning, for example, I awoke to a dreary drizzly day, with temps in the 40's F. I experienced a brief struggle between the desire to ride in on my bike and to ride to the bus stop and enjoy reading a book on a nice warm dry ride. I was starting to express this to my wife and had got as far as saying that I was thinking of riding to the bus stop when she interrupted (innocently, I'm sure) to say what a great idea that was. I had, after all, mentioned more than one how drizzly and cold it was outside.

Then the oddest thing happened, at the top of my street, where I turn left for the bus stop and right to ride all the way in, the whole struggle came back to life and the desire to ride through the invigorating weather bubbled up inside, and before I knew any better, I was accelerating down Daugherty, to the right. I arrived at school slightly damp, but quite recharged. It's as if I need to be cold in the winter. If I don't get chilled down enough days, then the endless heat of summer becomes oppressive and unbearable.

Does that make any sense? Am I completely crazy? Is there possibly any physiological basis for this?

And just in case anyone's paying attention, I've put about 5700km on the Dynamic Crosstown 7 now. It's still doing well with no major problems. The shifter has lost a little precision, and I have a little trouble downshifting into 1st. I don't know whether the indexes in the shifter are wearing out a little or maybe the shifter cable is dirty. I just can't get it quite right with the adjuster barrel. At some point it will become irritating enough for me to take it all apart and clean it out, but for now it's not that big a deal.

Also, I think it's always done this, but the other day I noticed that the bottom bracket does deflect quite a bit to the left on a right-side down stroke. Not so with the left-side. Hmmm. No problems yet, but I wonder whether this will turn into a fatigue failure at some point.

Pedal Therapy

I wish I could convey the kind of day it was today: sunny, cool, and quiet with an out-of-place rising current of nonsensical irritation that made me realize I needed to get out and exercise. I realized that I'm addicted to my bike. I found myself looking for an excuse to get out and ride somewhere, so I convinced my son (with whom I had recently snapped out of an unpleasant downward dance of mutual aggravation) to hook up the tagalong trailer and come with me to get a part to repair my chainsaw. On the way, I remember that I had something on hold at the library, so we zipped in to pick it up. Then we spent some time wandering around trying to find the repair shop. While we were finishing up there, I realized there was an archery store nearby that I had always wanted to visit since Ian has expressed some interest in getting a bow. (He's actually made several that work pretty well but have subsequently broken.) Well, it didn't take too long to realize that it was a very high-end store and the least expensive option for a beginner youth bow was far above what I wanted to pay. We went on, and I decided to make a small detour to see the new library branch that's going in, and we happened to be by a friends house, so we stopped in for a visit and a fudgesicle. Then it was home. The trip was about 10 km all together and took something like 2 hours.

I'm sure I wouldn't have wandered around like that in a car. I'd have been worried about gas and taking too long and getting home and probably wouldn't have been paying attention to my surroundings enough. The bike is kind of a refuge for me: I pray, sing, think, listen. It provides a comfortable solitude that is not lonely and that the car does not provide, so I find myself seeking out opportunities to go out and bike.

Plus, there's my odometer obsession, and I was looking for a way to flip 52oo km before the end of the week. I bought the bike (my Crosstown 7) in August of 2007, so that's 5200 km in 16 months, or an average of 325 km per month, or about 83 km per week. Most weeks that I bike I go about 100 km or a little bit more, and there are weeks that we are gone that I don't bike at all, so that seems about right.

Today as we were in the final stretch coming home, the bike felt good, the wind was the perfect temperature, and there was a certain freedom to being out and about with no expense and no stress.  It was therapy.

It's Hot!!!

We are about to break an 83 year old record for the most days over 100°F here in Austin, according to the Statesman. In my own particular corner of the world, the implication is that it's like biking home through an oven. My water bottle is about 1.5 L, and I usually finish it about 3/4th of the way home, and I usually have to cool off a little bit before going inside, where the air-conditioning (set to 81°F) is too cold for me and give me chills if I transition too quickly. Yeesh!

The high temperatures tend to introduce a few new creaks and squeaks on my bike, too. For a while, I started experiencing rim-flats, when the cheap rubber rim tape that came with my bike got too soft in the heat and allowed the inner tube to expand through the spoke holes and touch the spokes nuts. Whoever thought that would happen? Easy to fix with some better quality cloth rim tape, but annoying nonetheless. In addition, the grease in my drive line has thinned out noticeably in the hot weather and I have to re-grease more frequently and notice a bit more friction, which doesn't really help the body heat issue. Finally, there's a new creaky noise in the cranks (not the one I blogged about earlier) that got a little better when when I tightened the cranks but never really went away. It's not there in the morning, when it's cooler, but appears faithfully in the afternoon when when the heat's on and I'm baking my way home.

This is the time of year also brings out the perverse phenomenon of what I call "summer frost bite." I noticed it recently when my advisor walked into the lab wearing a sweatshirt. Many of the area secretaries also bring sweaters during the summer months. Apparently, Texans feel the need to show off how well our air conditioners work, so in many of the offices and labs, the thermostat is set below 70°F. Try walking in from outside, with your skin at 102°F and adjusting 30° down. The worst eve case of this was when I lived in an all-bills-paid apartment with roommates who kept the air at 66°F. I think I actually got sick one time after a bike ride. Fortunately, I'm alone in my office much of the time, and I've found the thermostat control...

A Little Update on the Bike

I recently received a comment from Jeff on my review of the Dynamic Crosstown 7 bicycle. (Amazingly, SiteMeter tells me that page is consistently my best draw, followed by my visit to Mellow Johnny's. Go figure...) Jeff was influenced in part by my review to take the plunge on a shaft driven bike, and he has outclassed me entirely by setting up a whole website to detail his experiences. His complete honesty has shamed me somewhat and caused me to realize that I'm a little guilty of something we might call "wishing away buyer's regret." That is, having plunked down a fair chunk of change for the bike, I'm determined to like it, facts supporting or no. Jeff has been undeterred by the size of his investment and freely given vent to both frustration and praise for his bike. Why would I not learn a little from him and share the good, the bad, and the ugly? Besides, I'm approaching 4000km (2400 mi) on the bike, and it's been almost a year since I bought it, and that's far enough for a pretty good assessment of long-term issues. 

First of all, the drive-line. Now that I have the gear greasing figured out, it's pretty much transparent. I just don't notice it. I can ride 500-600 km between shots of grease, and this is not an issue for me. In fact, it's a big advantage. I really don't miss chain maintenance. At all. (If you read Jeff's site, you'll find he's greasing every 75 mi or so, which to me seems way too often.)

My main drive-line complaint comes intermittently on hot days when I get a "tunk" sound once per pedal revolution when my left crank is straight up and down. Faster cadences make it louder than slow. Light pressure and very hard pressure make it go away, and if the temperature is below 90°F, I don't hear it.  It's always over 90°F in the summer in Austin, and I only get about half the time. Although it's only a minor annoyance, I wish I knew what it was.

Build quality. It's a little late for me to talk about build quality since I already mentioned the state of the wheels on receipt, but I did purchase a Park TM-1 spoke tension meter and tuned up the wheels. This is a necessary item of maintenance anyway, and I probably should have done it 2000km ago, but it feels like a new ride now, and I'll make this a regular date with the bike in the future. Regarding build quality, everything else is holding up well, and no other defects have come to light.

One last unspoken complaint relates to getting the driveline. This may seem a little obscure to all but the few Dynamic-owner readers that I have here, so feel free to skip on by if you want. Early in my setup, I was having trouble with grinding gears that turned out to be a problem of sorting out the proper kind of grease to use. During the process, though, I found I could make a big improvement to the feel of the drive line by adjusting the number of spacers on the rear axle. These are thin shim-stock washers that go between the hub and the drop-out to properly align the bevel gear with the drive shaft. The bike came with three fitted, and I improved the feel of the drive line noticeably by removing two of them. Later, the teflon-based grease solved the rest of the grinding problem, but I recently put them back in, just for kicks, to see what would happen, and I had to pull over and take them back off because the drive train became rough and the friction increased. I'm guessing that my gear set has probably worn in to its current arrangement and that putting them back in a long time ago wouldn't have had the same effect. Again, this is minor, and probably only of note to anyone else searching the net for information on shaft drives.

So I set out to try to complain a little bit about my bike, but I've ended up dismissing all of my complaints as minor. The fact remains, I like the bike, and I don't (honestly now) regret choosing it over a more conventional one, even after 4000km through Texas heat.

My Crosstown 7 Reaches 3000 km

Just in case anybody cares, I flipped 3000km (1860 miles) on my odometer yesterday on my ride in. Lifetime average speed for the bike is 18.1 km/hr, or about 11.2 mph, including all of the stops and walks, etc. I've had the bike since the end of last Juy, so it's been almost a year.
No major problems have come up, and it continues to perform well.

A Great Day with my Boy

Yesterday, I rode with Ian down to the Austin Energy Regional Science Fair, where he had was judged on a poster he put together at his home school coop on water molecules. It was fun to be there with him, but we actually only spent about 20min at the fair. We arrived there at 11:00 ad he was finished being judged by 11:20, and awards were not announced until 3:00. We decided to take a nano-risk of missing anything significant at the awards ceremony and go get cheeseburgers instead.
The real fun, for both of us, probably, was that we traveled to and from the site on bikes, about 30 km round trip. You can see the route profile plotted below courtesy of my new friends at Veloroutes.org. Click here for the route map.
Ian was on the tag-along trailer pulled by me on the Crosstown 7, and at one point on the way home nearly fell asleep. Needless to say, we were both wiped out pretty thoroughly by the ride. I call that just about as perfect a day as you could get.

Dynamic Crosstown 7: A Review at 1200 miles

Last summer, I had to retire my old faithful commuter with something like 12k miles because it need about $400 worth of new drive train, wheel, hub, etc. Having paid about $400 for it 12 years ago, it was time to check out the market and replace it with a new bike.
I looked around at several options, and I ended up choosing the Dynamic Crosstown 7 over the Bianchi Milano, Bianchi Bergamo and the Breezer Uptown. This time around, I wanted reliability, low maintenance, and a good balance of cruising speed and comfort. Having had enough of cleaning dirty derailers, I was sure I wanted to get an internally geared hub. I ended choosing the Crosstown 7, a shaft-drive bike with the Shimano Nexus 7 internal hub.
I made my choice based on rides of the Bianchis at Ozone Bikes and reading the reviews of the Dynamic online. BikeCommuters.com gave a good review on their site. Many of the people who write in to the Dynamic website are hard core year-rounders in the sticks of Maine who ride through snow and summer rain alike. I took that to be a pretty good endorsement. The shaft drive had strong appeal to me since I have long ago tired of sprocket tattoos, greasy fingers, chewed up pants legs, and expensive drive train replacements. The shaft drive has no exposed moving parts, does not need to be cleaned, and is an $89 part when and if I have to replace it. (Dynamic estimates its lifetime at about 10k miles.) How many chains, gearsets, and derailleurs have I been through on my previous bike in 12k miles? At least $300 worth... :-\ Daring to be a little different, I took the plunge.

The buying experience was good overall with minor hiccups. Since they are fairly small volume, there are not local dealers, and my order was over the phone but the sales rep was helpful, knowledgeable, and willing to customize the order. They swapped the cheapo pedals and seat for a good cycle computer, and I added fenders, too. With the added delivery charge, the total came to about $750, delivered to the door. Their website estimates 3-5 days delivery to Austin. I ordered late on Friday, and it took them until the following Wednesday to put it in the mail, and five business days later (Monday) it arrived. From order to arrival was actually 10 days.
Assembly was straightforward: the shaft drive poses no special difficulty, and I was eager to take it for a spin. I noticed right away that the shaft drive was not silent but growled a little bit, especially right before shifts. Otherwise everything felt good.
I did quickly develop two beefs, though, that are pretty much inexcusable for a bike of this cost. First, out of the box, the front wheel had a wobble large enough to brush the front brakes. >:( I cured this with a spoke wrench and wheel alignment rig, discovering in the process that three spokes were way loose. How this got past quality control, I have no idea, but this was a disappointment. ??? The other beef is that the crank was a little loose and creaks embarrassingly when I stand on the pedals. :-[ This has been largely resolved by using clipped pedals and shoes (no switching torque direction) and a quick tightening of the crank arms, but I would expect the cranks to be appropriately seated and tightened to avoid the noises. Again, this is minor and relatively easily fixed, but with no local dealer offering a free first tuneup, and for the price I paid, I would expect it to be ready to go straight out of the box. :(
In any case, that was 1200miles ago, and quickly forgotten. I have five months riding it, in cold weather and hot. I've changed flats, and spent a lot of time in the saddle (The trip computer estimates about 100hrs.) So here are my well-worn impressions now:
In Re: the growling, a shot of grease to the front crank case completely solved the problem. I would have expected it to be done more thoroughly out of the box, but this was not a big deal. Properly done, it is totally silent. The bevel gears and drive shaft add a very small amount of friction relative to a brand new chain, but I think this would reverse for an older chain, and as I expected, the drive has gotten smoother with after a short break-in. On average, I've been adding grease to the front crank on a more or two less monthly basis. I ride a lot and more vigorously than some, so my greasing interval is slightly shorter than the recommended by Dynamic. I can tell it's time to add grease when the drivetrain gets a little growly. It's really very easy to do and takes me all of 15 seconds to do, so this is a HUGE improvement over the messy chain cleaning process I used to dread.
I definitely enjoy the lack of worry about pant cuffs, grease marks, and having been through the rain a few times this week and have not at all missed needing to clean the chain and derailleurs, etc.
I love the Nexus 7 hub, and highly recommend it: the shifts are precise and instantaneous. The gearing is well suited to my commute, which is moderately hilly (mostly along Shoal Creek from Anderson to campus). Anything hillier, and I'd recommend the 8-speed, whose extra gear is at the bottom of the range, for climbing. It took a little bit of time to reprogram my muscle memory since its grip shift is setup in the opposite sense from a derailleur's. I.E. twist forward to shift down and backward to shift up. At first I had to think about; now it comes naturally. Regardless, I love the ability to shift without pedaling, a huge help for hill starts.
The geometry is, for me, the right compromise between being far enough forward for speed and power but upright enough not to stress my wrists and lower back (especially with a backpack: I prefer not to use a bike rack). I saw a complaint online about the aluminum frame being too stiff, but I find it very comfortable and not too jarring, and I appreciate the lighter weight. In addition, the aluminum frame displays some beautifully well done TIG-welds, for those who appreciate that sort of thing.
Regarding flats, it's not a big deal to remove the rear wheel, although it is certainly more of a process than on a bike with a chain and quick release skewers. I keep two extra tools that I would not otherwise: a stubby flat-head screwdriver, and a thin wrench to fit the bolts on the rear axle. The main problem with getting the rear wheel off is actually the fenders. With the rear-open axle drops, you really have to remove the fender to get the wheel off. That makes it more involved than a conventional setup, so in order to minimize that problem, I replaced the Kendra tires it came with with some Maxxis urban tires with a Kevlar lining (and a reflective sidewall). Since putting on those tires, I've not had a single flat, and removing the rear wheel hasn't been an issue. Better tires are an option that Dynamic offers, and I would recommend paying the extra money for them.
Overall, I'm pleased with the purchase and would characterize it with one word: smooth. I look forward to putting lots more miles on the bike. In general, the build quality and components are good (with the above noted exceptions), and the Nexus 7 really shines. The shaft drive is pretty transparent and noticeable only because of the annoyances it doesn't give. I think I'll appreciate it more and more as I don't have to tune it, oil it, clean it, replace it, or hide my greasy pants legs. I hope that shaft drives become more accepted in the mainstream in the future. I think that would be well justified, especially among the bike-as-transportation community.