Originally Posted by
Mother_of_birds
I think I may have found something. A Trek Marlin 6. Its an XS frame which is perfect for me and hard to come by second hand apparently. I guess since the typical mountain bike owner is a taller bloke, 80% of bikes for sale are large or XL. It looks in good condition from pics and it's in my budget. 27.5x2.2" tyres, 2x8 speed, hydraulic disk brakes and front suspension with lock out. It might be overkill for what I'm planning to do with it but hopefully it will help me trust the bike and give me a bit more confidence.
Sounds good. 27.5 is a bit of an outlier in sizing, only 25mm larger diameter than typical 26" mountain bike tires and wheels, I think a stupid reason for creating a whole new standard. The big leap up in mountain bike tires to "29er", just fatter tires on 700c rims, made more sense, but you don't want that, it would be totally out of proportion to the frame. In my opinion, typical 26" wheels would be best, just for enormous selection of tires. But as long as 27.5 tires and tubes are available and comparably priced, not an issue.
Usually, 8 speed mountain, not as much gear range as the new cassettes, would come with a triple crank to get mountain low gears. As long as the 2X crank gives you the gear range you need, it's fine, especially if it has a wider step between the two rings, 16 teeth, like most current 2X cranks.
A Marlin 6 has a sharply sloping top tube in your size, good for fit, but it means a tall seatpost with more bending moment under rider weight (not necessarily you, but the previous rider might have been taller); Make sure you inspect particularly closely at the top front weld between the seat tube and the top tube, this has been a place for cracks on other bikes with long seatposts. And the entire frame, looking for any cracks, it doesn't take long. Nearly anything else can be fixed.