10 speed to a 12 speed
 

What is the best way to convert a 2018 Trek Stache 5 to a 12 speed.

The cheapest way is to keep it 10 speed. Don't fall for the marketing hype.

My kid wants to upgrade his 12-speed to a 9-speed.

After wrecking two SRAM Eagle rear derailleurs, one XT 12-speed rear derailleur, and an SLX 12-speed derailleur, he has had enough.

But if you really want to do it, SLX is arguably the best option. SRAM was the worst for us.

Thanks for the advice. I will probably re-consider keep it at a 10 speed.

We just got a 10-speed Microshift drive-train to make the switch to 10-speed. (11-48T Cassette, 10-speed shifter, derailleur and free-hub shell and chain.)