Stems

neon said:

How often should you replace your MTB stem. The idea of it bracking when riding a 25 kpm on a down hill single track is little scary.

It will depend on a number of variables:
1) what kind of riding do you do? - if it is 'general' XC riding I wouldn't see the need to replace the stem at all. If you're doing big jump/DH/freeride stuff, then maybe every 1-2 years
2) how hard are you on your equipment? - if you are a 'smooth' rider, then you can keep your stem for longer. if you land hard on jumps, then it would be better to replace it sooner than later
3) how often do you crash? - obviously the more you crash, the higher the chance that you're doing damage
4) what kind of stem is it? - if it is on designed for XC use, and you're doing jumps on it, then my advice would be to get one designed for that specific use.

Personally, I race and ride XC and have never had to, nor seen the need to replace a stem, except for bike positioning purposes (in which they were exchanged literally brand new).

Also, if you need to replace the stem because you feel it is 'fatigued' or damaged, then I'd suggest replacing the bar too at the same time, if not sooner 😉

HTH

the more u throw at ur stem the more you'll hav to replace my stock norco stem lasted me about 2.5 years, without me doin 2 much extreme stuff.