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What Does "Geometry" Refer To?
Written by Sport Chalet Administrator on Tuesday, 29 March 2011 20:15
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What does “geometry” refer to?

When dealing with bicycle frames, and specifically size and fit, the term “geometry” is commonly used. But what exactly is a bike’s geometry? Geometry refers to the length of the frame tubing and the angles they create.

Each type of bicycle has a different geometry that best suits the style of riding. A road racing bike, for example, tends to position the rider closer to the front of the bike in a low position to provide aerodynamics and responsiveness. A “cruising” or hybrid style bike, on the other hand, positions the rider more upright to provide comfort and accommodates variable body types.

While many factors go into designing a bike frame, the four primary components of a bike’s geometry are: the effective top tube length, effective seat tube length, seat tube angle, and head tube angle.

EFFECTIVE TOP TUBE LENGTH (A): The horizontal distance between the center of the top tube/head tube junction and the center of the seat tube. With new frame designs utilizing a sloped top tube, the “effective” length has become more and more important to compare a bikes actual fit from model to model. It’s important to find the right size top tub for you. If its too long, you’ll be over stretched reaching for the handlebars. If too short, you run the risk of toe and knee overlap with the front wheel and bars.

EFFECTIVE SEAT TUBE LENGTH (B): The distance of the tube running from the bottom bracket to a virtual intersection point with a horizontal top tube. This measurement often dictates a bike’s size (in inches or cms). Here you want a size that allows you to set your seat height to a level where you are comfortably reaching the pedals, without having too much excess seat post pulled outside of seat tube itself.

SEAT TUBE ANGLE (C): The angle of the seat tube relative to the top tube – assuming a level top tube. This angle dictates where the seat is positioned relative to the crank axis and is generally in the range of 70° to 80° degrees depending on the bike’s use. The steeper the seat tube angle, the more aerodynamic the positioning you can create; however, typically at the expense of maximizing the power of your pedal stroke.

HEAD TUBE ANGLE (D): The angle of the head tube relative to the ground, most commonly somewhere between 69° and 75° (where 90° is perpendicular to the ground). The steeper the head tube (more vertical), the closer the rider’s weight is to the front of the bike, creating more responsive steering.

A PHD understanding of frame geometry certainly isn’t necessary when buying a new bike, but having basic knowledge will help you guide your shop’s sales associate set you up with the perfect ride.

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Night Rider - Sport Chalet CFO Howard Kaminsky
Written by Sport Chalet Administrator on Tuesday, 16 November 2010 18:24
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On November 10th Sport Chalet honored me with a great gift for my 25th anniversary with the Company.  Rather than something traditional like a watch, I got a Santa Cruz Blur LT Carbon!  Robert, Paul and I tested it out with a night ride to Cherry Canyon, a great place for a first ride and intermediate single tracks with enough terrain to test the new bike’s abilities.  The bike climbs smoother than anything I have ever ridden. I need to work on tuning a few things to get more comfortable downhill, not that I couldn’t keep up with Robert and Paul, but I was a bit tense.

Thanks to everyone for the gift and special thanks to those who helped pick it out, not an easy decision, but the right one, and thanks to Santa Cruz for opening up Sport Chalet.  

Over the weekend I rode again, a secret place, after reducing the air in the tires, moving the seat back and adjusting the rebound, I’m going fast downhill again!  I weighed the bike, 26 pounds, my old Marin Attack Trail for comparison purposes weighs 28 pounds.  

Anyone wanting to go for a ride let me know. Be sure to check out SportChalet.com for everything Cycling!



Sport Chalet CFO - Howard Kaminsky

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Bike U 2010
Written by Sport Chalet Administrator on Tuesday, 12 October 2010 16:27
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BIKE U 2010 - SAN DIMAS, CA
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Sport Chalet's Bike University was held Wednesday and Thursday, October 6th and 7th.  It was at the Frank G. Bonelli Regional Park in San Dimas, Ca.  I was able to attend the event on Wednesday.  It was cloudy and rainy but the clinic was awesome.  

Most cycling and gear vendors were in attendance, like:

They all brought 2010 and 2011 gear to talk about.  Although it was pouring, Bike U was very entertaining and I learned a lot of about bikes.  I haven't been on a bike since I was 12 but after the event I really want to get the Diamondback Lux for women.  Check out the image below (in the middle):


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I checked out the Electra beach cruisers and fell in love as well - so I am torn at the moment.  What to do? 

 

I took a few pictures throughout the day - check them out below:

 

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BIKE U 2010 - CRAIG LEVRA & AARON DUNN  

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BIKE U 2010

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THULE & SPORT CHALET

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DIAMONDBACK DEMO

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MAKING MY WAY DOWN TO CANARI

 

More to come later.

Shop Cycling @ SportChalet.com


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SE Bikes
Written by Sport Chalet Administrator on Tuesday, 28 April 2009 20:39
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Holdin it down for LaHood
Written by Graham Baden on Friday, 24 April 2009 07:08
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When I told the League of American Bicyclists National Bike Summit that "Cyclists are important users of America's transportation systems," I meant it.

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