How much can we change our bike wheel diameters before needing another bike fit?
If we change the size of our bike tires, it raises or lowers the front or rear of the bike. That means it can affect the reach, handlebar height, setback, saddle angle, and handlebar angle. That means even after tilting the seat up or down to make it flat, we need the setback readjusted, and we likely need a new stem to readjust the reach and handlebar height. Adjusting the setback affects the reach.
It seems like even a mm of adjustment can be significant in terms of optimizing our bike fit. If we extend our knees, our hamstrings are engaged when extending our hips like on the downstroke but if our knees are bent, they don't get activated so we get less power. Most of us notice the stretch in our hamstrings when when trying to reach our toes with our knees extended. There's a reason why a bike fit can take at least 2 hours. Some bike fitters recommend another bike fit when we get new shoes as they can have different sole heights in addition to needing the cleats adjusted.
Sometimes we need or want to change the diameters of the wheels.
- Tire clearances are different for both the front and rear wheels while the rider desires fitting the widest tires possible. Adding a fender also decrease tire clearances.
- Even replacement tires with the same width markings can have slightly different actual widths when installed onto the rim.
- Rim replacement since changing the rim inner widths can affect the tire widths.
- Spare wheels since some cyclists have multiple wheels for different conditions, race days and training, different gear ratios, etc.
- Upgrading the hub to a hub dynamo, internal hub gearing, coaster brake, power meter, etc. The new hub may have different hole counts so a new rim, which may have a slightly different inner width may be needed.
How much can we increase the difference in the two wheel diameters before we need another bike fit?