I'd like any advice on changing the setup to minimize the chances of this happening again. I'm a pretty big guy, 330lbs, and it was a 170mm crank from bontrager (stock for this fx2) im looking into changing the crank to something sturdier and was hoping for any and all advice on what to consider in the process.
by JJTortilla
4 Comments
You’re going to want to go with MTB cranks, I’ve heard good things about the Race Face Atlas cranks.
If you run into issues with your wheels, I would apply the same logic to it. Also in the future I’d go with steel over aluminum, if its a good frame it won’t be meaningfully heavier if at all. Lastly, I’d up the size of your tires when these wear out.
The issue here is that the cranks that come on this bike are cheap junk that clearly are not strong enough (or there’s a manufacturing issue).
While you are over the weight limit for the bike by 30lbs, I don’t think that has much to do with the issue. The cranks on any bike should be able to hold up to much more pedal force than you, or any other human, can put out.
I’d go directly to Trek with this issue via email. Tell them you’ve snapped two cranks so far and that there is potentially a manufacturing issue with these cranksets. Ask them for a replacement crankset of much better quality. Don’t mention your weight. See if you get anywhere.
Were you hurt? Naturally cranks fail at peak stress, i.e. often when standing. Which is a little unfortunate, since it’s hard to stay upright in those circumstances. Make sure you break your next one away from traffic!
The dark areas of the crack face – barely visible in the photo and concentrated on the trailing edge that is under tension on the downstroke – prove that there was old damage to this crank before the event that finished it off. Those dark areas are corrosion and dirt washed into the fissure by water.
This observation is important, because it shows that these crank failures don’t occur out of the blue. In other words, if you carefully inspect your cranks regularly, you can hope to spot fatigue cracks before they critically weaken the crank. Periodically examine the clean cranks under a hard light source. Direct sunlight is ideal. Concentrate your search on the areas under tension: trailing edge and outer face. Dark cracks are easier to spot on silver cranks than black ones – something to consider for your next cranks.
I am not familiar enough with MTB/trekking cranks to recommend a specific model. As a general rule, Shimano products are well engineered – but of course that has to exclude all those bonded Hollowtech cranks that are failing in droves. So who knows. Low-end solid (not hollow) Shimano cranks are probably one of your safest bets.
Looks cheap.. I’d try a MTB crank from a reputable brand. Shimano Deore would probably be good and strong.
How many chainrings, two or three? How many teeth per chainring?