Do 27.5" wheels fit a 29" mtb? The 29er is with disc brakes. If they fit, is there any other problem
They fit, in the sense that you can install them in the frame (if the axles are correct, hub width is correct, etc). The problems are:
- The bike stands a few centimeters closer to ground. Which means less ground clearance for obstacles and cornering. Frames designed for smaller wheels take this into account
- Less trail at front, which affects steering
- Lower gearing because of smaller wheel radius
- You still have the long rear fork of frame designed for 29" wheels and the associated weight distribution and clumsiness.
Yes and no. Installing them with normal sized (2-2.3") tires will result in that much less ground and pedal clearance as well as tweak the geometry of the bike. So that's not likely to work out well.
However, 27.5+ tires (2.8-3") get the tire outside diameter into the ballpark of normal 29", so the bike's geometry and clearances still work as intended. For example, there are now bikes intended to be swappable between the two, and conversions have become common on older bikes. Many 29er frames and forks have the clearance to take a 27.5+, although it's something you'd have to experiment with yourself.
You can install almost any smaller wheels so long as the axles aren't too wide, I rode this 29'er bike around for a few days while trying to get my front rim fixed. But brakes would be misaligned if they're rim brakes, and since the bike is not designed for other sizes it's not ideal. But it will work.