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Dynamic Crosstown 7
The good folks at Dynamic Bicycles offered their “Crosstown 7″ commuter bike to us for testing. In many respects, it is like so many other commuter-oriented bicycles on the market — TIG-welded aluminum frame, mounting points for fenders and rear rack, upright riding position. Where this bike differs, however, is how power gets from the pedals to the rear hub. This bike uses a very clever and deceptively simple shaft-drive. Yeah, that’s right — no greasy chain, no chainrings to chew up your pants. In fact, Dynamic takes things a step further by mounting the shaft-drive to a Shimano Nexus Inter-7 internal hub. So, no derailleurs either!

The heart of the Dynamic drivetrain — the shaft-drive assembly:
The shaft-drive assembly

Here’s some of the specs, straight from the manufacturer’s website:

    -7005 Aluminum Frame, butted for light weight
    -Aluminum front fork
    -Alex DA-16 High Profile Alloy Rims (28-38C tires)
    -Kenda EuroTour Tires, 700×35C, 50-85psi
    -Dynamic Street Shaft Drive
    -Shimano Nexus Inter-7 Gearing, All-internal (17-gear range)
    -Shimano Nexus 7-speed Twist Grip Shift
    -Tektro Quartz alloy brakes; front disc brake optional
    -Tektro 2-finger Alloy brake levers
    -Base price: $679.00

The frame for this bike is unique: a narrower-width bottom bracket (BB) shell that is also larger in diameter from a traditional BB and elevated chainstays that are welded to the base of the seat tube rather than to the back of the BB shell. The elevated chainstays give room to mount the shaft-drive assembly. The rear-facing “track style? forkends position the rear wheel in the frame and align the rear hub’s spiral bevel gear with the rest of the shaft-drive assembly. Obviously, retrofitting this shaft-drive assembly to a traditional bicycle frame is out of the question.

Details of the unique frame:
Elevated chainstays and big, narrow BB

Bottom bracket clearance to the ground with 700x35C tires is a whopping 10 inches! And this is pure clearance, too – there is no chainring to catch on obstacles if a rider should happen to find him- or herself hopping over a steep curb.

Did I mention the paint job on this bike? In low light, it appears to be a dull charcoal grey. In sunlight, however, it shines with pink and blue iridescence…every bit as flashy and sexy as a Japanese keirin bike! For folks who like to keep their bikes on the down-low, the frame decals are applied OVER the clearcoat and are easily removable.
Here’s a picture of the headtube and the glossy paintjob…the photo doesn’t do this color justice!
Paintjob

The frame feels stiff…jarringly so. To be fair, this is the first aluminum-framed bike I’ve ridden more than a couple miles – I don’t know if aluminum bikes always transmit this amount of shock. The Dynamic frame appears utterly flex-free, and with the beefy, ovalized down tube, aluminum forks and 36-spoked deep profile rims, the ride felt harsh. Over two miles of my round-trip commute is over cobblestones, and it was pretty punishing! Perhaps a carbon fork and a suspension seatpost would have improved the “seat feel? of this bike and taken some of the edge off?

The parts specifications for this bike have high and low points. Tektro Quartz linear pull brakes are about the best “off-brand? V brakes money can buy; easy to adjust and tremendous stopping power. The Nexus hub is superlative – smooth and easy to shift and virtually maintenance-free. The front hub is a sealed bearing model made by Access. I am unfamiliar with the brand, but the hub is beefy and smooth, and comes disc-ready (Dynamic offers a front-disc brake upgrade for an additional $60). The Alex DA-16 rims are tough – real pothole killers! The handlebars and stem are workmanlike…nothing fancy. The saddle and pedals? Well, they suck. Saddles are such a personal choice that I wholly expected this “Velo Plush? saddle to be a pain in the ass, and I was right! Also, the pedals that come with the bike should immediately be scrapped in favor of something a little bigger and with more traction. Even with lugged running shoes, my feet slipped off the pedals a couple times in the dampness that is summertime Florida. Since this bike is meant for urban commuting and getting around town, BMX-style platforms would be ideal – and wouldn’t require dedicated cycling shoes.

Over the past month, I have ridden this bike over 100 miles to and from work and on a number of recreational rides. While I don’t have any way to quantify (with cold, hard numbers – this ain’t a physics lab) just how much more efficient a shaft-drive is as compared to a traditional chain-driven bicycle, I can say with confidence that this shaft-drive feels s-m-o-o-t-h. In fact, it is so smooth that it feels oddly boneless; chain-driven bikes give the rider a lot of feedback in terms of friction as the chain wraps around cogs, chainrings and derailleur pulleys. When I rode the Dynamic, the only sensation was that I could very faintly feel the bevel gears meshing against each other – in fact, the more I rode it the more I noticed it. It is DEFINITELY different-feeling than a chain-driven bike! Another perceived benefit of this shaft-drive is there is no “gear lash? or lag when pedaling – pedaling force is instantly and seamlessly converted to forward motion. On a chain-drive bike, there is always a bit of lag as chain slack is taken up by the derailleur springs and as the freewheel/cassette pawls engage. Not so with the Crosstown 7 – you pedal and GO!!!

The rear spiral bevel gear of the shaft-drive system as attached to the Nexus hub:
Rear bevel gear attached to Nexus hub

Standing on the pedals to grunt up hills was when this system felt weirdest – and when the nearly frictionless drivetrain was most noticeable (and appreciated!). The system is silent – the only noise it makes is some occasional faint ticking in certain gears, and that can be attributed to the Nexus hub, not the shaft-drive. This bike is STEALTH all the way! Shifting is a breeze – the Nexus hub is spectacular. I found myself shifting more often because it was so easy and smooth, and I found the range of seven speeds to be more than adequate for my relatively flat commute. For people living in more hilly areas, an 8-speed Crosstown model is available from Dynamic.

How much does the shaft-drive system add in weight to a bicycle? The manufacturer claims that the system adds less than one pound as compared to a geared bicycle, and this makes sense…after all, the entire assembly consists of four chromoly spiral bevel gears, a shaft and an aluminum housing. I think most people can live with an extra pound…and for the real weight-weenies out there, a few judicious parts swaps could help lose some of that extra weight.

Maintenance is, for the most part, a non-issue with this bike. I rode this bike in two heavy Florida summer downpours with deep puddles almost up to the hubs, and I never had to worry about a rusty chain. Dynamic recommends adding a shot of grease to the drive every 600-1000 miles. The shaft-drive comes complete with a zerk-type grease gun fitting…just attach your grease gun and squirt a bit in there. The manufacturer recommends Finish Line’s Teflon grease. I couldn’t find my grease gun, so I used a 12cc syringe with a plastic “gastric tube lavage? tip to inject 4-6cc of grease into the shaft-drive after removing the zerk fitting with a 7mm box wrench. The Nexus hub needs occasional cable adjusting, which takes all of two minutes, and the brakes could use some occasional tweaking. Is it ever that simple on a gearie?

No grease gun? No problem, especially if you know a medical professional with access to syringes:
Syringe replaces the grease gun

Are there additional steps when changing a flat rear tire? Yes, but the process only takes an extra 30 seconds from a traditional bolted-on or QR wheel. With a screwdriver, remove the two screws that hold the black plastic rear hub cover on. Slide the cover off. Pull the shifter cable sharply downwards to release it from the hub’s cable guide and detach the leaded end from the hook on the hub. Unscrew the axle nuts with a 15mm wrench, taking care to keep the unique washers on each side of the hub in proper order. Change the flat and reverse the disassembly process. Those special washers realign the hub with the tail end of the shaft-drive, so no fiddling is required to get things running smoothly again. Hell, it takes longer to write it out than to actually do it!

The “track-style” rear forkends and plastic hub cover:
The back of the bike -- hub cover

Does the shaft-drive wear out? Well, yes…eventually. Patrick Perugini, the president of Dynamic, indicated that the shaft-drive is rated for 6000 to 10000 miles (depending on frequency of greasing) before it requires replacement. And, a replacement assembly with all bearings is only $89.00, available directly from Dynamic. Now, compare that to a traditional geared bike – can you get 10000 miles out of one set of chainrings, cassette cogs and a chain? I didn’t think so! Can you replace two (or three) chainrings, 8/9/10 cogs and a chain for less than $89.00? Only if you really, really shop around!

Two gripes stand out in my mind: the first is the riding position, which is VERY upright. While this position gives the rider a commanding view of the streets, there is no place to hide once stiff headwinds come into play. As configured, the Crosstown 7 is really not suitable for long-distance fast commuting. I would love to see a drop-bar option for this bike (or would consider one of the road-bike models Dynamic makes if a more aerodynamic position is desired).

The other gripe is that while Dynamic inexpensively offers accessories such as a rear rack and fenders, at this price point I expect to see both of those included as standard features. Most similarly-equipped bikes from other manufacturers (and here I mean geared commuter bikes) come standard with rack and full-coverage fenders.

Overall, I think Dynamic has a winner with their Crosstown 7. It appears (and rides) in every way like the around-town errand, commuting and recreation bike it was meant to be, and you just can’t beat its low-maintenance features. No more greasy chain tattoos, tattered pants cuffs or dirty hands from a mid-ride tire change!

Hits:

    -low maintenance
    -smooth, effortless drivetrain and shifting system
    -sexy paintjob
    -lifetime frame warranty
    -perfectly suited for around-town cruising and medium-distance (5-12 miles) commuting
    -Dynamic’s sterling customer service – questions promptly answered and great website documentation for maintenance and service of these bikes.

Misses:

    -Stiff and unforgiving ride
    -Saddle and pedals must be swapped out immediately!
    -Upright stance gives some aerodynamic issues in headwinds

Visit Dynamic’s website to learn more about the shaft-drive – there is a great “FAQ? on the site – and to see other models Dynamic manufactures.