VIVA WALTER!!

If you have been in the shop this week you may have noticed a new employee helping out. If not here's your chance to come on in and meet the newest addition to the BBC, Walter. He adopted us late last week and seems pretty cool with hanging around the shop and greeting customers. Walter is very laid back and playful, so stop by and say hello. Thanks

Dish = bad, off-center rim = good

On a typical multispeed bike, the width of the gear cluster causes rear wheel offset, or “dish”.

The above diagram is from Jobst Brandt's book The Bicycle Wheel, and shows that a much higher spoke tension is required for drive-side spokes to balance the lateral (side-to-side) forces on the rim. [Ignore the red lines for now.] The weight of the bike and rider are therefore supported almost entirely by the drive-side spokes, which effectively halves the number of spokes in the rear wheel. The diagram shows an old six-speed hub; the offset is even greater for current ten-speed hubs. This results in a wheel that is less sturdy and more prone to go out of true than a comparable front wheel.

In order to compensate for dish, some wheel designs move the non-drive hub flange closer to the center; this helps even out spoke tension but does not add lateral strength to the wheel. Other designs use twice as many drive-side spokes as non-drive-side, which requires a rim that can support the tension of three closely spaced spokes.

One clever solution to rear wheel dish is the off-center (or asymmetric) rim. The idea is simple: move the spoke holes to the left side of the rim. This allows for a rear wheel with both wide spacing between the hub flanges and equal spoke tension. In the diagram above, the red lines show what the spoke angles would look like if the rim had off-center spoke holes.

Mavic’s top-of-line, carbon-spoked R-Sys wheelset is built with an asymmetric rear rim. The shop has several of these wheelsets in the store and you ought to check them out, if only to marvel at their light weight (1355g the pair) and multiple high-tech features. A cross-section of the front and rear rim shows the asymmetric shape of the rear:

[One quick note: The voluntary recall of Mavic R-Sys wheels has nothing to do with its asymmetric rear rim. In fact, they're not even recalling the rear wheels. Whether carbon spokes are a good idea...well, that's an entirely different topic. 12jan2009]

In a slightly more traditional vein, Velocity USA offers two excellent off-center alloy rims. The Aerohead OC is a light (418g) semi-aerodynamic rim that is built for speed, while the Synergy OC is a burlier (490g), wider rim, perfect for the tourer, the clydesdale, or mountain biker.

Both rims come in a variety of sizes and spoke hole drillings, and can be purchased individually or in pre-built wheelsets. The guys at the shop can help you decide which options would best fit your needs.

Birmingham Bicycle League Mystery Ride, Saturday December 20th...

Once again we are hosting the Birmingham Bicycle League ride from the shop this Saturday, December 20th. The ride will roll at 9:00am and we will be on the road for approx. 3 hours and there will be one sprint zone this week. Please go to http://www.bhamvelo.com/blog/?page_id=32 for a detailed description of the ride and the rules/regulations that we ask all participants to abide by.

The shop has multiple changing rooms for those folks coming in from out of town that need a place to change into the riding gear and the shop will open at 8:00am. There will be water, Powerade and air available at shop prior to the start of the ride. After the ride we will have food and drink that has been graciously donated by Milos Hamburgers and Tracy's available to all ride participants.

Scott Bicycle & Zipp Wheel Demo & the B.B.L...

Scott Bicycle has brought their demo van to Birmingham and it is full of road and mountain bikes for you to test out. The three featured Scott bikes are the Addict, the Spark and the Genius. In addition we also have seven (7) pairs of Zipp Wheels to demo. The featured Zipp Wheels are the 404 clincher, 303 clincher, 202 tubular and the Flash Point 60 clincher. All the wheels come with Zipp tires and all we need is your cassette and you will be ready to ride.
The demo road bikes, mountain bikes and road wheels will be available starting Tuesday December 2nd. Please call or stop by the shop for more details including the models and bikes sizes currently available. The demo bikes and wheels are available to ride for up to six (6) hours and reservations will be handled on first come first serve basis.
For the riders that are going to participate in Birmingham Bicycle League (B.B.L.) ride on Saturday, December 6th the Scott Addict's and the Zipp wheels are available to demo on the ride. The bikes and wheels will need to reserved by Friday, December 5th by the close of business (6:00pm) and can be picked up Saturday morning starting at 8:00am. The B.B.L. ride will leave from the bike shop at 9:00am and will return around 12:00pm (noon). Lunch will be provided for all the B.B.L. riders by Smiths Oysters and Steaks and is sponsored by Scott Bicycles and Birmingham Bicycle Company! Please call or stop by the the shop for more information and to place your reservation today.