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Discussion Starter · #1 ·
Recently i stuffed my front wheel into what was approximately an 18” rock step up at about a 45 degree angle. Stopped me short, almost went otb but didn’t, i messed up a tight tech section of trail. My stem rotated (guessing/ ballpark) 15 degrees with the impact. I had it properly torqued with a park torque wrench to 5nm per instructions from raceface. This was probably the first stem rotation in a crash i have had in 20+ years. It makes me wonder if 5 nm is tight enough for all events that i could conceivably ride out of. I get the idea of leaving brake levers loose enough to rotate and not snap on a hard impact but skeptical about this concept with a stem. For the record, i followed torque printed on the stem, used a park torque wrench, followed standard bolt tightening sequence I learned in as a shop rat and have been implementing for 20ish years. Currently i have the stem to steerer bolts past 5 nm, i set the wrench to 5 then pushed a little past that mark for (hopefully) good measure due to past experience. Thoughts/ experience with this?
 

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I had an issue with my headset coming loose every couple of weeks. Replaced the headset and to be sure I replaced the stock stem for a Truvativ Hussefelt stem which had bigger 5mm bolts, torqued them to spec at between 7-8Nm and that thing never twisted or moved again.
 

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Your stem was tight enough. Sometimes, bars will just spin a little during an impact. Not a bad thing considering the next point of give could be your front wheel. Or worse, your forks crown. Better to simply adjust your bars than to true or replace a front wheel.
 

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I think the bike industry mostly sets torque values based off of a range between tight enough to not move most of the time and loose enough to not snap bolts. I have doubts that they are actually specifying torques based on an engineering analysis of the component, as evidenced by the nearly blanket statement of 5Nm on so many parts. I mean geez, very few parts come with actual high strength bolts, instead using chintzy, decorative, or even rubbish stainless steel fasteners.
 

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It quite common to twist the forks on a dirtbike during a crash, and I'm referring to a 250# machine with double triple clamps, with multiple bolts on each clamp. It's common practice to knock the front wheel against a tree to straighten them back out after going down.
That said, if I'm comfortable going 85mph on that setup, having a bicycle stem twist during a crash doesn't alarm me either. All it needs to do is be dependable during the roughest riding conditions, once you're on the ground it's a moot point to me.
 

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FWIW, I always check my stem bolts and wheel skewers on any road trip requiring 2hrs+ drive time to the trail head. AND more importantly, I check the fasteners any time I have my bike serviced at the LBS. I really shouldn't have to check the fasteners after its been serviced but mistakes happen and I learned the hard way.

Also, blue Loctite the threads.
 
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Discussion Starter · #9 ·
Great replies. Thanks everyone. The stem spin in the crash seemed like it was supposed to happen but i have seen so little of this in 25 years of mtb i wanted to ask. I’ve probably just been over tightening my stem all these years. Guess ill back to the recommended 5nm.
 

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I've been running .5 to 1 Nm higher torque values on stem at both steerer and handlebar clamp. Also using Motorex carbon assembly paste on both handlebar and steerer. That has kept everything nice and tight with no slippage and no damage 👍
 

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FWIW, I always check my stem bolts and wheel skewers on any road trip requiring 2hrs+ drive time to the trail head. AND more importantly, I check the fasteners any time I have my bike serviced at the LBS. I really shouldn't have to check the fasteners after its been serviced but mistakes happen and I learned the hard way.

Also, blue Loctite the threads.
I hate to say it but yeah, you should do a quick safety check after your LBS has worked on your bike. No way of knowing if the mechanic was interrupted with a phone call mid-job or they let the teenage intern work on your bike. It's not okay, but I've seen it happen. Just grabbing the bars and seeing if you can twist them in any axis is adequate.
When we assemble a new bike we leave the stem bolts loose on purpose till we put it on the ground and set the proper angles, then there's no chance of leaving them un-torqued but falsely appearing to be safe to ride.
I've gotten in the habit of using my pre-set torque tool on every bolt on the stem to double check before every bike goes out the door, in front of the customer. Both for their safety and in case they let their cousin 'who knows bikes' try to adjust their handlebars later and blames us when they crash.
 

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Torque specs are to either protect the hardware or the part itself. Stems will twist in a crash. I think you'd want that. I'd rather have the stem move than to have potential damage to another bike part or even myself. I do not recommend the over tightening of any bike part. I've seen parts damaged by over tightening. Carry a small multitool with a torque bit...problem solved. I carry a Topeak Nano Torqbar. It's got a 5nm bit.
 

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I hate to say it but yeah, you should do a quick safety check after your LBS has worked on your bike. No way of knowing if the mechanic was interrupted with a phone call mid-job or they let the teenage intern work on your bike. It's not okay, but I've seen it happen. Just grabbing the bars and seeing if you can twist them in any axis is adequate.
When we assemble a new bike we leave the stem bolts loose on purpose till we put it on the ground and set the proper angles, then there's no chance of leaving them un-torqued but falsely appearing to be safe to ride.
I've gotten in the habit of using my pre-set torque tool on every bolt on the stem to double check before every bike goes out the door, in front of the customer. Both for their safety and in case they let their cousin 'who knows bikes' try to adjust their handlebars later and blames us when they crash.
Do you think people should safety check their bikes after you service them? Do you think most of them do that?
 

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Do you think people should safety check their bikes after you service them? Do you think most of them do that?
Well of course I don't think people need to double check my work, but in general, yes. Mistakes happen, and some bike shops employ a person or two who have no idea what they're doing. I've seen the worst in college towns where they hire some kid to help with basic labor and he gets in over his head. Not all shops are a boutique run by a couple guys that have been in the business for decades.
 

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Well of course I don't think people need to double check my work, but in general, yes. Mistakes happen, and some bike shops employ a person or two who have no idea what they're doing. I've seen the worst in college towns where they hire some kid to help with basic labor and he gets in over his head. Not all shops are a boutique run by a couple guys that have been in the business for decades.
Well the first sentence of your previous post said that they should check your work, after all they have no way of knowing if you were daydreaming or maybe had a few beers during lunch.

I guess my point is the vast majority of customers don't do that and for many reasons they really shouldn't. If I torque a fastener holding a delicate carbon component to 5.2nm I definitely don't want someone going at it with a 4mm hex to make sure it's tight. I know what your saying and for sure there are plenty of shoddy shops and that's a shame, imo the industry in general somehow needs to be held to higher standards because peoples safety and even their lives are literally on the line.
 

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Well the first sentence of your previous post said that they should check your work, after all they have no way of knowing if you were daydreaming or maybe had a few beers during lunch.

I guess my point is the vast majority of customers don't do that and for many reasons they really shouldn't. If I torque a fastener holding a delicate carbon component to 5.2nm I definitely don't want someone going at it with a 4mm hex to make sure it's tight. I know what your saying and for sure there are plenty of shoddy shops and that's a shame, imo the industry in general somehow needs to be held to higher standards because peoples safety and even their lives are literally on the line.
Not sure what your point is, I never said anyone needs to check my work. I said after your LBS works on your bike, and unless you're my customer I'm not included in that. ;) I've never had a shop work on any of my bicycles but in the years of visiting various bike shops I've definitely seen a few that would worry me. I've worked with several different guys that should have never touched a bicycle. The former owner of the shop I manage now was letting some hipster dude learn to wrench in the back, and he was using shifter cables and housing for brakes too... I almost had a heart attack seeing that.
 
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