A version of this article was originally
published in Triathlete Magazine

Dear Tech Support,

I am looking for some advice on what my next bike purchase should be. I am 6′ 5″ (inseam 34″) and weigh 205lbs. I am currently riding a 63cm Cannondale Multisport 800 with 650 wheels. According to CompuTrainer, I can ride comfortably at about a 230 Watt average. If I really push myself I can average about 255 Watts over a 20 mile ride. I often wonder if a material other than aluminum would be a better bike for me. However, in my research, I do not see a lot of manufacturers offering bikes big enough for me. Can you talk a little bit, in Clydesdale terms, about frame materials, wheel size, frame size and suggest some manufacturers that carry bigger bikes? Thanks for your time.

Robert
St. Clairsville, OH

Robert,

I can only scratch the surface of your questions here. This should give you a good starting point though.

Frame Size: Don’t make the mistake of choosing a frame first and then trying to make it fit. Get fit first. The frame geometry information gained from a fitting session with a technician skilled at triathlon specific fitting will be the most helpful information you have when determining your best options.

The two biggest limiting factors with stock frames and taller riders are top tube length (a main variable in your reach) and head tube length (a main variable in your handlebar height). The following guidelines can help you determine if a frame’s top tube and head tube are going to be long enough:

1) Cockpit length is a combination of top tube length and stem extension. If you have a 62cm top tube and a 10cm stem, your cockpit length is 72cm. This same length could be formed from a number of combinations – for example, a 59cm top tube with a 13cm stem would also have a 72cm cockpit. However, the aero position places a lot of weight on the front of the bike, which can compromise handling. Long stems only contribute to this concern and I do not recommend a frame that requires you to use a stem longer than 11cm in the aero position.

2) By measuring the stack spacers between your stem and headset, you can determine if your frame’s head tube is long enough. Fork manufacturers recommend no more than 3-4cm of stack spacers for fork strength and proper handling characteristics. A hi-rise stem can sometimes be used to lower your stack height. If you already have a hi-rise stem and you still must use over 3-4cm of stack spacers, a frame with a longer head tube is needed.

The largest readily available triathlon frames have about a 60cm top tube and 18cm head tube. At 6’5”, you most likely need something larger than this and a custom frame should be at the top of your “must have” list. A few manufacturers skilled at building custom frames for larger riders are mentioned below.

Frame Materials: A frame’s ride characteristics are not determined by the material used as much as how that material is applied through the shape, diameter, and wall thickness of its tubing and the frame’s design. Depending upon the tubing and design, a titanium frame can be built unbearably stiff and an aluminum frame can be made “wet noodle” soft. Most stock frames are designed to be closer to the middle as economies of scale dictate that the same tubing be used in all frame sizes and manufacturers usually choose a tube designed for the “average rider” (usually 150-170lbs.). Bigger or smaller than average riders should pay close attention to the tubing used in a frame to avoid ending up on a bike that rides softer or stiffer than optimal for them.

Two good ways to address this concern are:

1) Custom tubing. Some custom frame builders not only offer geometry options that address individual needs, but they also offer rider specific tubing. Serotta offers flex-fighting custom “XL” and “XXL” diameter titanium tubing in their TT model and Calfee Design offers a stiffer carbon fiber tube option in their triathlon models too. While custom frames are not available at entry level price points, they are still a good value because they work so well for the individual and are a long term investment that lasts for many seasons.

2) Beam suspension. Because beam suspension bikes address the opposing characteristics of torsional (side-to-side) frame stiffness and vertical compliance (comfort) independently, they can be made very stiff and very comfortable. If you are over 200lbs. and considering a Softride beam bike, look at the Classic beam frames as Softride does not recommend their Rocket frames for riders over 200lbs. For rider’s larger than stock beam bike geometries allow, custom builders like Elite Bicycles can build a custom beam frame for you.

Wheel Size: For riders over 5’10”, 700c wheels usually make the most sense. 700c wheels offer more consistent surface contact with the road which lowers rolling resistance and absorbs more shock than a 650c wheel – both items that become more important as the weight on the wheels increases. On larger bikes, 700c wheels also create a more balanced and proportional overall package in regards to rider weight distribution and frame geometry. The components you choose (especially the wheels) really affect the way your bike rides; be sure to choose parts that compliment your frame’s ride characteristics and your needs well.

Best of luck.

Ian

Originally published May 2002/Copyright © 2002