How to choose a rim

by John Neugent

Tech articles | Commentary articles

John Neugent probably knows more about bicycle wheels than anyone else alive. Maybe more about bikes as well. He's spent his life in the bike business, at every level. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price. If you are in the market for a set of wheels, please, check out John's site. He really knows his stuff. —Chairman Bill

John Neugent

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John Neugent writes:

Most people buy wheels and not rims but it’s good to know how the shapes, material, and composition affect performance.

For alloy rims, there are three types of joins. Pinned, sleeved, and welded. Pinned rims are the least expensive and heaviest, so you won’t see them on higher end wheels. The channel used to pin the rim together run the entire circumference of the rim on both sides so even though you are pinning a small section at the join, the channel gives it a big weight disadvantage. Sleeved rims have an internal sleeve at the join and are glued. Welded rims have no sleeve but are welded at the join which gives them a very slight weight advantage over the sleeved but they suffer from the distortion caused by the welding. I prefer sleeved over welded because of that but they are pretty much equal.

The width, height, and shape of rims affect performance, aerodynamics, and weight; but not so much stiffness, which is more affected by the number of spokes. Please notice I said number of spokes but not spoke tension (which also does not affect stiffness). The deeper the rim the more aerodynamic it is. Also when you get into carbon rims, it’s much better to have a bullet shaped rim rather than a sharp V shape because it is much less affected by side winds. I often get asked how much faster do deep aero rims make you go. My general rule of thumb is that, if you average 17 mph on the flats without wind you will probably get about 1 mph advantage and the faster you go the more of an advantage you will get. If you average 14-15 mph you most likely will not notice any difference.

It wasn't very long ago that even the top pros time-trialed using square-sectioned aluminum rims. Here Laurent Fignon rides the prologue of the 1984 Tour de France.

Within the last few years, more and more road riders have been switching to wider rims. The old standard was 19 mm external width, now it’s 23-25 mm or even higher. The reason: making the base wider increases air volume, which results in better handling and comfort.

Both alloy and carbon materials have come a long way in the last 20 years resulting in much stronger and rounder rims. Carbon rims of 15 years ago would crack if you looked at them wrong and you had to keep a very low spoke tension or the spoke nipple holes would crack. The newer layups and glues now make them much stronger and new glues are now available that make them much more heat resistant for braking.

Tadej Pogacar rides the final stage of the 2020 Tour de France with carbon aero rims. Sirotti photo

Finally, one should consider spoke count. Spoke count is important because it can add weight (5 grams for a spoke and alloy nipple for Sapim CX Ray spokes) and they are a major factor in aerodynamics. On a road race bike, or something similar, you need fewer spokes on the front wheel because there is much less weight on it compared to the rear. Something like 40% versus 60% on the rear. Plus, the rear wheel is the drive wheel which adds stress to it. In the old days bikes were made with 36 or 32 spoke wheels, front and rear. Now, most higher end wheels use 20—or down to 16—in front and 24 or more in the rear wheel. Most of the top pros stopped using 20-hole carbon rear wheels because they were not stiff enough and would rub on the brake pads.

How you ride is probably as important as how much you weigh when it comes to wheel durability. I have 250 pound plus riders who can ride very light wheels with no issues and very light riders who trash wheels after a relatively few miles. Things that affect wheel durability are using very high pressures, not “unloading” the bike when you go over bumps and holes, not avoiding bumps and holes as much as possible, and using a low rpm/high torque riding style. Get on your pedals and finger tips when you hit a rough area, you wheels will love you for it.

John Neugent was was one of the first to establish quality hand building in Taiwan around the turn of the century. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price.