Butting titanium tubes: What is it, and why is it important?

At the core of any titanium frame is a balance between stiffness and comfort, and titanium's ability to offer both in great measure is one of its best attributes. One of the key ways that we tune that balance in our frames is by changing the wall thickness of key tubes along their length, or "butting": a technique that No. 22 has mastered to deliver performance and comfort in appropriate amounts across our lineup.

What is Butting, and What Are Its Advantages?

Butting refers to the process of varying the wall thickness of a tube along its length. The primary goal is to reduce weight without compromising strength, especially in areas of the frame that experience less stress. By strategically thinning the tube's middle section—where forces are lower—and maintaining thicker ends for joint strength, butting achieves a balance that enhances overall ride quality.

The key advantages of butting are:

• Weight Reduction: lighter frames translate to faster acceleration and easier climbing.
• Increased Strength: thicker ends of main tubes bolster the frame at critical stress points.
• Enhanced Comfort: vibration damping is improved due to the tailored tube flexibility in thinner central sections.
• Optimized Performance: specific butting profiles allow for fine-tuning the bike's characteristics to the needs of a particular model.

How is Butting Done, and Why is No. 22's Approach Special?

There are three primary approaches to butting tubes in titanium framebuilding: manual grinding, buying pre-butted tubes, or butting by CNC.

For cost reasons, most titanium frames do not use butted tubes at all, and instead off-the-shelf tubing in a constant wall thickness for all tubes. This does keep manufacturing costs down, but also leaves a critical resource to refine ride quality and trim weight untapped.

Among framebuilders that use butted tubing, the most common approach is to manually grind away the center section of the tubes. This is done using a centerless polishing machine, and each tube is passed through the machine several times, each pass grinding away parts of the wall thickness. This approach is economical, but also doesn't give a high level of precision to the location of the butting in the tube, or to its final wall thickness.

Less common is the approach of buying pre-butted tubing from a titanium mill. This approach allows a framebuilder to choose their tubing from several pre-butted tube diameters from a very small number of industry suppliers. This tubing is typically of very good quality, but the range of available butting profiles is limited to what the supplier has on offer: typically only a single butting profile for any given tube diameter.

Finally, the approach that we take at No. 22 is to perform all of our tube butting in-house on a state-of-the-art CNC lathe. A tube is loaded onto a mandrel and placed in the CNC, and then a computer program cuts the tube walls to machine them to precisely the wall thicknesses we need. This not only grants us greater control over the butting process compared to other methods, but also empowers us to create proprietary butting profiles. These profiles are developed to complement each unique frame model and size, ensuring that every No. 22 bicycle is delivering the absolute best balance of ride and handling possible in a titanium frame.