I bought a 27.5 in Dec 2015 and use it to get to & from work daily (40 km / 24 miles each day), so have done 5,000 km (3,100 miles) in 8 months (I'm 53 years old). I had road tires fitted as none of my riding is off-road. When the bike had done about 2,500 km (1500 miles) the problems started...