Condensed Answer: In most cases, a 700×35 inner tube can be successfully coupled with a 700×32 tire. That said, there are some downsides to using an inner tube wider than the recommended size.
Tire Sizes Are Rarely Accurate
Truth be told, the nominal size of a tire rarely corresponds to its real size one installed on a rim. For example, a 35mm tire might end up measuring 32mm or 37mm upon putting it on a wheel. One of the reasons for that is that it’s incredibly difficult to produce a tire that’s precise to the last millimeter.
Also, the width of the rim affects the final measurement. The wider the rim is, the wider the tire can be. Conversely, a narrower rim results in a pointy and thus slimmer tire.
And since tires themselves aren’t as accurate as possible, inner tubes have to be flexible and fit a greater variety of tire models. This is easily achieved because inner tubes are made of very stretchy rubber knowns as butyl. Hence why inner tubes can expand to incredible proportions. (This can be demonstrated by inflating an inner tube outside of a tire).
At the end of the day, the nominal difference between a 700×35 and a 700×32 tire is only 2mm. Since the discrepancy is small and inner tubes are designed to serve a wide range of tires, one is unlikely to experience major issues with this setup. Nonetheless, it’s necessary to know that some problems can occur, especially if the 700×35 tube is on the wider side and designed to serve even 700x40c tires.
The Downsides of Using a 700×35 Tube In a 700×32 Tire
- Less Space For The Tire
Inner tubes designed for 700×35 tires are wider and will therefore take up more space when mounted on the wheel.
Since the tire bead (the part of the tire connecting to the rim) and the inner tube are fighting for space within the inner rim, the wider tube reduces the real estate available for the tire.
The inner tube is incredibly flexible, and the tire will successfully squish it and create space for itself. However, the valve stem area is an exception because it’s inflexible and can shrink only so much.
For that reason, there’s a slim chance that the wider inner tube will stop the tire bead around the valve stem from fully seating into the rim. In that case, the tire is compromised because it’s not maximally secure. In extreme scenarios, the tire may pop off the rim.
Thus, it’s recommended to carefully examine the valve area upon mounting the tire. If the tire bead isn’t fully seated, the wheel is not safe to use.
- Pinch Flats During Installation
The larger profile of a 700x35mm inner tube increases the chance of pinching the inner tube between the tire bead and the rim wall during installation. Of course, this outcome can be avoided if the user is experienced and performs the procedure with great care.
The downfall of using wider inner tubes than originally prescribed is the reason why some cyclists intentionally “downsize” and choose to rely on inner tubes that are one size smaller than what the tire is rated for.
- Lost Storage Space
The larger inner tube takes up a bit more space when stored in a saddlebag or a tool bottle.
- Extra Weight
Technically, wider inner tubes are heavier. However, in this case, the extra weight is inconsequential.
The Advantages of Combining a 700×35 Tube With a 700×32 Tire
- Thicker Outer Layer
Extra stretching of the inner tube results in a thinner and thus weaker outer layer more susceptible to punctures. Since 700x35tubes do not have to be inflated as much as narrower models, one can argue that inner tubes would have a greater resistance to punctures.
However, in practice, the difference is slim to non-existent. If a puncture is going to take place, it will most likely do so regardless of the extra thickness.
- Additional Options
If you experience a puncture, and the only tube available at your location is a 700×35 one, it will save the day and allow you to return home.
Summary: What You Need To Know
- A 700×35 tube can be coupled with a 700×32 tire. However, since the size isn’t accurate, one can expect to face some issues.
- If the tube is on the wider side for 700×35 tires, and the rim is narrow, there’s a chance that the tire bead around the valve area won’t fully hook onto the rim. If the tire bead refuses to seat properly even with a little help, then the inner tube is too large for the rim and tire combination. In that case, the user will have to buy a tube of the appropriate size. This is a safety issue and should not be neglected.
- A wider inner tube is more difficult to install.
- A wider tube is more likely to get pinched between the tire bead and the rim.