The dimensions indicated in the abbreviations MTB 27.5 and 29 refer to the size of the wheels of mountain bikes.
A MTB 27.5, also called 27.5 inch or 650b, has wheels with a diameter of 27.5 inches, corresponding to about 69.9 cm. These wheels are larger than traditional 26 inch wheels and offer some advantages over the latter. The 27.5 wheels offer greater stability and traction than smaller wheels, allowing you to overcome obstacles more effectively. They are also more maneuverable than 29 inch wheels, which may be preferable on technical and winding routes.
On the other hand, a MTB 29, also called 29 inches, has wheels with a diameter of 29 inches, corresponding to about 73.7 centimeters. The 29 inch wheels offer greater stability and a better ability to overcome obstacles than smaller wheels. This makes them particularly suitable for faster routes and smoother terrain. Larger wheels also maintain better traction on slippery terrain.
The choice between a MTB 27.5 and a 29 depends on the personal preferences, the type of terrain on which you want to use the bike and the desired riding style.
The MTB 27.5 are often preferred by cyclists looking for greater handling and agility, while the MTB 29 are more suitable for cyclists who want more speed and stability on smoother terrain.
It is important to test both options and consider your own riding style and characteristics of the terrain where you intend to use the bike before making a decision.