from Rookie’s keyboard
Hello,
It’s weird how little some people in the bike industry know. It’s understandable to be ignorant if you are just a rookie starting out, but when you are part of the system, you gotta know bikes at least to some degree.
Yesterday, I called to order new rims for a client who was converting from 23mm to 28mm tires.
I asked the seller about the width of the rims they were offering me, and they said “23mm”. When I asked if that was the inner or outer width, they thought I was from another planet.
Why does that matter?
It comes down to compatibility.
If the external width of the rim is 23mm, then the rim is very likely to support 28mm tires.
But if the number 23 refers to the internal width of the rim, then the rim is too wide for a 28mm tire.
Internal and External Rim Width
The external width of a rim is the perpendicular distance between the outer sides of the rim walls. Or in simpler words, the external width is the total width of the rim.
The internal rim width is the perpendicular distance between the closest points on the inside of the rim.
The inner rim width is the most commonly used data point when referring to a rim’s width as it provides information about the tire sizes that the rim is compatible with.
Below you will find a table serving as a guideline for rim and tire compatibility:
| INNER RIM WIDTH | COMPATIBLE TIRE SIZES (MM) | COMPATIBLE TIRE SIZES (IN) |
| 13-14.9mm | 18-25mm | 0.7-1in. |
| 15-16.9mm | 23-33mm | 0.9-1.3in |
| 17-18.9mm | 25-50mm | 1-1.95in |
| 19-20.9mm | 28-62mm | 1.1-2.5in |
| 21-22.9mm | 35-62mm | 1.35-2.5in |
| 23-24.9mm | 37-68mm | 1.45-2.7in |
| 25-26.9mm | 44-76mm | 1.7-3in |
The data in the table shows that a rim with a 23mm inner width should be combined with 37-68mm/1.45-2.7in tires.
Meanwhile, a 28mm tire requires a rim with 15-20.9mm inner width.
Note: The numbers in the table are estimations. Slight deviations are possible without repercussions.
If a narrow tire is combined with an excessively wide rim, the user can face:
- Excessive pinch flats (punctures that take place when the wheel hits a non-sharp but hard object).
- Rim damage (the narrower tire does not provide as much protection for the rim)
- Less-than-ideal tire to rim connection
Why Did I Advise My Client to Go From 23mm to 29mm Tires?
It’s a massive jump. I know. But it’s worth it. Personally, I hate 23mm tires for anything but racing and even then they still suck.
Below are the advantages of the switch.
- Comfort
Wider tires can operate at lower air pressure without risking pinch flats. The lower air pressure allows the tire to deform upon meeting a road irregularity. The final outcome is a smoother ride easier on the rider’s joints.
- Greater Roll-over Ability
The wider the tire, the easier it is to roll over obstacles. Hence why you don’t see mountain bikes with skinny tires. This quality makes 28mm tires better for riding on imperfect roads. A new rider may be surprised how much off-road one can go on 28mm tires.
- Lower Chances of Trapped Wheels
A slim 23mm tire can fall into a road crack or a water drain. When that happens, the rider goes over the handlebars instantaneously. Technically, the same can happen with a 28mm tire too, but the chances are notably slimmer. Hence why 28mm tires are superior for commuting purposes.
- Better Traction
If two tires have the same tread pattern, but one is wider, the wider one offers more traction and thus stability thanks to the larger contact patch.
Downsides?
You know me by now (hopefully) and that I like my posts to be as honest as possible. Hence I am listing the downsides of switching to larger tires, in this case 28mm.
- Extra Weight
Wider tires require more material and weigh more. If one wants the lightest possible bicycle, thinner tires will help with that goal. That said, recreational riders are unlikely to experience a degraded performance from the extra grams.
- More Drag
Wider tires come with additional drag. Тhe penalty isn’t severe and will be a topic of analysis only when competing on the highest level.
- Reduced Clearance
One of the major downsides of this switch is the reduced fork and frame clearance. Truth be told, if the bike is an aggressive road or track model, it may be unable to accept 28mm tires due to their size regardless of the rim.
Also, the wider tires could make the installation of accessories such as full fenders difficult if not impossible. If one is using the bike for intensive commuting, this could be a major issue.
Until next time,
Rookie
Leave a Reply