/A Short Bike Theory Lesson By The Brainy Bike Master (a.k.a. Me)/
BMX tires can be installed on an MTB when they are of the right size for the MTB’s rim.
Standard BMXs use 20″ tires which won’t fit on an adult size MTB. However, there are also 24″ and 26″ BMX tires that can be mounted on older and children’s MTBs.
If you want to install an entire BMX wheel on an MTB, you can do so only when it’s the same size as the original MTB wheel. Otherwise, the switch will cause dramatic changes to the bike’s geometry.
Rear BMX wheels are designed for 110mm dropout spacing and are therefore too slim for an MTB without serious adjustment which will be described later down the article.
Front BMX wheels have hubs with 100mm O.L.D. and are therefore more straightforward to install on an MTB.
Requirements For Installing a BMX Tire On an MTB
A BMX tire can be installed on an MTB when the following criteria are met:
- Proper Size
Standard BMX tires are designed for 20″ rims. Meanwhile, modern MTBs use 27.5″ and 29″ wheels. For that reason, it’s impossible to mount a standard BMX tire on a standard MTB rim.
However, there are also 24″ and 26″ BMXs and MTBs. Thus, if you have a 24″ or 26″ MTB, you will be able to install some BMX tires on it.
- Rim Width
The rim on which you’re installing the tire should be wide enough. In most cases, this won’t be a problem because average MTBs use tires as wide or wider than what we see on BMX bikes.
But if the bike in question is an MTB that has been converted to a hybrid/commuter, it may use thinner rims.
Requirements For Installing a BMX Wheel On an MTB
Installing a BMX wheel on an MTB is a tricky, ungrateful procedure due to numerous differences between the two bike models. Nonetheless, it can technically be done in certain highly conditional situations.
Rear Wheel
The distance between the rear dropouts of MTB frames is greater than that of BMX frames.
The main reason for that is that MTBs use multi-gear cassettes requiring a wider rear hub whereas BMX bikes are single-speed and thus rely on a narrower wheel.
To fully understand this dependence, one has to be familiar with the term Over Locknut Dimension (O.L.D.)
The O.L.D. is the usable part of the hub between the two locknuts.
The rear O.L.D. of geared MTB bikes is 135mm whereas that of BMXs is 110mm.
Consequently, installing a rear BMX hub on an MTB frame creates a gap on the non-drive side requiring the use of spacers.
Simultaneously, the drive side of the hub gets much closer to the drive-side chainstay and thus the wheel gets off-center. To fix this problem, the user or a mechanic will have to re-dish/re-center the rear wheel.
(For more information on this part, consider reading the dedicated post.)
Note: Another option would be to cold set (bend) the frame so that the dropouts get closer to one another. This procedure is viable only when the frame is made of steel. All other materials lose significant strength when they’re cold set.
That said, even if the frame is made of steel, the procedure may be unsuccessful because it hurts the bike’s chain line.
Another problem that you will face when installing a rear BMX wheel on an MTB is the extra thickness of the BMX axle.
MTBs have a 10mm rear axle whereas that of BMX bikes is 14mm. Consequently, it will be necessary to file the dropouts for the BMX axle to fit in. This procedure is viable only when the frame is made out of metal. (Note: The frame will lose its warranty.)
FAQ: What about single-speed MTB frames?
If the frame is originally designed for a single-speed drivetrain, the user will have a much easier time fitting the wheel. That said, single-speed MTBs are closer to dirt jumpers than MTBs.
In conclusion
Installing a rear BMX wheel on an MTB is a difficult procedure with many conditions. In most cases, it’s wiser to avoid it.
Front Wheel
The O.L.D. of front MTB hubs with quick-release skewers is 100mm and matches that of BMX wheels.
Consequently, it’s possible to install a front BMX wheel right away. That said, if the MTB has a front thru-axle, the conversion won’t be possible due to the structure of the hub.
Summary: What You Need To Know
- BMX tires can be installed on an MTB only when they match the wheel size of the bike. This leaves only two options – 24″ and 26″ models.
- Rear BMX hubs are 110mm wide whereas rear MTB hubs are 135mm. Therefore, the user has to do some serious modifications to make a rear BMX hub compatible with an MTB frame. For that reason, it’s recommended to avoid installing a rear BMX wheel on an MTB.
- BMX front hubs are 100mm and match the spacing of front MTB hubs with quick-release skewers. This makes the installation of a front BMX wheel on an MTB easier.
