It’s always been our honor to have Grant Petersen of Rivendell Bicycle Works on our Board of Advisors. His contributions to our bicycle design have been the very reason we’re able to offer such a unique ride to anyone who’s up for the lifestyle cycling experience.
“Bike frame geometry” is an all-out mystery to a lot of urban cyclists. It’s just too easy to check out the curves, lines, angles, colors... Imagine how they’ll complement your own vibe... how they’ll look chained outside the local watering hole... Before you know it, you’ve completely missed the architecture behind the eye-candy. Thing is, it matters."
With a new fair-weather season upon us, Grant offered to walk us through the ever-elusive (and all-important) aspects of frame geometry in a way we can all understand. Of course, “yes, please!” was our answer, and here's what he had to say...
“Frame geometry” refers to the design of the frame, specifically the tube’s lengths and angles. It’s a term that pops up often among the spandex set, but even so, it’s good to know something about it. If you read and understand this, you’ll know more than they do. It’s easy…
Seat Tube Angle
The seat tube angle affects your seated pedaling position. Most seat tubes are between 71 and 75 degrees (from horizontal). If the seat tube is 74-degrees or more, it’s considered “steep,” and if it’s 71 to 72-degrees, it’s “shallow.” I prefer shallow seat tube angles, so that’s what the BKC bikes have. It helps you sit further behind the pedals and, to me, feels more natural and relaxing. There are zero drawbacks, unless you’re a triathlete.
Head Tube Angle & Fork Rake
Head Tube Angle refers to the steepness of the head tube. All else equal, shallower head tubes (70 to 71 degrees) make the steering less reactive; steeper ones (74-75 degrees) make it more reactive.
And Fork Rake is the amount of forward bend in the fork — how much it curves or angles forward. It’s usually 1 ½ to 2 ¼ inches.
A combination of Head Tube Angle, Fork Rake, and the front wheel size influence a bike’s steering feel and stability. Think about it like… Sports car or truck? On city bikes like the BKCs, you want something normal-feeling and not so reactive that if you hit a pothole while steering with one hand, the bike topples over.
I consider all of those things in the steering of Brooklyn Bicycle Co. bikes, so that the end result feels instantly familiar and unremarkable, which is how it should be.
Top Tube Length
The length affects how far you have to reach to grab the bars, but it’s just one of many factors that do (along with the seat tube angle, stem, and handlebar shape and height).
On Brooklyn Bicycle Co. bikes, I designed a top tube that “reads” long to somebody accustomed to starting at bike frame geometry spreadsheets, but it doesn’t feel long; and it doesn’t feel long because the bars are high and sweep back toward you. Meanwhile, the longer wheelbase (which comes of a longer top tube) makes the bike ride better over rough ground.
Chainstays are the tubes that run from the crank to the middle of the rear wheel, and the range (from short to long) is 16 to 17.5 inches, typically. Personally, I like chainstays that push 19 inches. It contributes to a longer wheelbase, a smoother and more comfortable ride, and a better ride over rough pavement better. There are no negatives, only positives.
The BKC chainstays are just under 19 inches, longer than those on most (maybe all) other city bikes.
Drop and Bottom Bracket Height
Drop is how far the crank sits below the wheel centerline, and along with the wheel diameter and the seat tube angle. It affects how high your saddle is above the ground, which in turn affects how easy it is to touch the ground with your tow when you’re half-sitting on the saddle at a stoplight. It also affects how likely you are to hit a pedal on the ground when you lean your bike and pedal around a corner. Drop is always a compromise that favors one thing (touching the ground easily?) over another (pedal clearance?).
When I specify the drop on a BKC bike, I look at all of these things and where the bike will be ridden (on pavement, for the most part). There is a little more drop on a Brooklyn Bicycle Co. bike than there is on most urban bikes. I think it is the best balance of toe-ability and pedal clearance, but it is also the most easily overlooked contribution to a really great frame geometry.
Want more Grant Petersen? Check out his "Blug"
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|COLOR-MATCHED FENDERS & CHAINGUARD||SADDLE|
|3-SPEED INTERNAL GEARING||GRIPS|
|KICKSTAND INCLUDED||TIRE COLOR|
This is probably the most notable difference between our step-through models. With the Willow featuring our Swept-Back Handlebars. This means a much more upright (European-style) riding position (think sitting in a chair) that is well suited for leisurely riding.
The Franklin models feature our Relaxed Ride Handlebars, which are slightly more aggressive and ideal for both commuting and leisurely weekend rides.
The Willow comes with cream tires, whereas the Franklin sports black tires. Do note that regardless of color, all our tires offer an added layer of puncture resistance.
The Willow is our premium model and includes a rear carrier, as well as an upgraded sprung saddle and grip set from Selle Royal’s Royalgel™ line.
The Franklin features Selle Royal Vegan Leather saddle and grips. Please note that this bike does not come with a rear carrier. If you would like to purchase a rear carrier for this model, you will need a 26” carrier for the S/M Franklin and a 700C carrier for the Large Franklin model.
Both models come with color matched fenders and chainguard, as well as a kickstand.
4. RUST-PROHIBITIVE COATING & GEARING
As our signature model, the Willow has a few additional premium features including a rust-prohibitive coating on the chain and internal gearing resulting in less maintenance and more riding.
5. FRAME MATERIALS
On a more technical note – the geometry on both frames is identical, however the Franklin and Willow models are made from different materials. Are you currently thinking “WHAT DOES THIS MEAN?! I KNOW NOTHING ABOUT BIKES!!”? Do not fret – we totally get it! Take a breath and read on…
The Willow frame is made with double-butted 4130 Chromoly Steel. We use a stronger grade of steel, which allows us to use thinner tubing resulting in a lighter frame.
The Franklin frame is crafted with specially engineered high-tensile steel. What does this mean? We are able to offer a similar bike of a more moderate price point. Our Franklin model is the most economical step-through model in our portfolio of bikes (as well as a team favorite)!
Don’t forget: All of our bikes include Free Shipping & Professional Assembly.