Design and Specifications
of Kirk Frames
The goal of Kirk Frameworks is to build bicycle frames with unsurpassed craftsmanship and attention to detail. I aim to make the process of designing and building your dream bicycle a rewarding experience for you, with customer service and attentiveness that can only be found in a small operation.
I build simple, functional, durable and beautiful machines. I believe that a frame that is properly designed and built is likely to please the body and the eye, as well as the spirit. A truly good frame can create an experience like nothing else.
This page describes some of the details and options that comprise a Kirk frame. See the models page for a description of different types of Kirk frames.
Jump down to: materials : lugs : fillets : dropouts : paint : decals
The Terraplane Seat Stays
One of the hallmarks of Kirk frames are the curved Terraplane seat stays. These are available as an option on most frames.
The curved seatstays of the Terraplane allow a small amount of vertical movement and are designed to keep the rear tire in firm and constant contact with the surface. Each set of stays is bent by hand to a given radius determined by the size and weight of the rider and the intended use of the bike. The feel and stiffness of the frame is regulated by the amount of bend in the stays. Heavy riders generally would have less bend to allow less movement. Lighter riders would have more bend and more travel.
With the Terraplane option you'll feel more confident cornering and descending, and you'll enjoy true all day comfort. Terraplane stays work with most any type of brake system; they are available with all Kirk frames with the exception of cyclocross frames.
Traditional straight stays are available on every Kirk frame.
The Terraplane seat stays add $300 to the cost of a frame. For complete details, see the pricing page.
What's the deal with frame flex?
I'd like to share my thoughts about frame flex with you, as I believe this is a widely misunderstood topic. These are thoughts and conclusions that I have come to after 15 years of being a professional builder and 25 years as a serious cyclist. Read the article.
Kirk frames are made exclusively of brazed steel.
I use steel because it offers many advantages, including:
- Ride quality
- Fatigue resistance
- Availability of tubes with a wide variety of specs
Steel's combination of stiffness and fatigue resistance allows smaller diameter tubing compared to titanium or aluminum. Tubing diameter is one of the main factors that influences ride quality. For example, aluminum tubing needs to be large in diameter due to its poor fatigue resistance. Titanium, on the other hand, is much more flexible than steel so it needs to be large in diameter to be stiff enough to handle properly and transfer energy. Steel tubing offers a balance of a supple ride and durability that make it a choice building material.
Having worked with nearly every type of steel bicycle tubing available, I have learned that several brands of tubing have specific benefits and applications. The selection of tubing for each frame is based on you and your needs.
Traditional brazed joints are the choice for Kirk frames. Some advantages of brazed joints are:
- Lower heat compared to welded joints
- Smaller heat-affected zone
- Allows for the use of thinner tubing
- Aesthetic qualities
Brazing heats the steel to about 1,800 degrees F - just hot enough to allow the brass or silver to melt and flow into the joint. Welding, by contrast, heats the tubing to its melting point (around 3,500 degrees F). At this temperature annealing occurs in most tubing, causing a weakened area adjacent to the joint. Brazing allows for a much smaller heat-affected zone than welding. The use of lugs or fillets spreads the load over a larger area than a welded joint. This can allow the builder to use thinner tubing for a given size rider, without risking failure.
Moreover, I believe a properly built lugged or filleted frame is the most beautiful way a bicycle can be constructed.