# can you overtighten stem bolts



## davemsc (Mar 4, 2014)

Hey all, 
Just wondering if you can overtighten the 2 stem bolts? I made them relatively snug.. I don't have a torque wrench.
Id told not to tighten the top head bolt much at all... And then to tighten the stem bolts tight.

Sound right?

There is no play and everything turns fine

Thanks


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## Erock503 (Oct 20, 2014)

The top cap bolt just snugs up the crown/headset assembly, the stem bolts do the actual job of holding the fork steerer tube. You can absolutely over tighten the bolts, it is after all most likely lightweight aluminum you're working with. This is precisely why almost all stems have torque values printed on the actual part. A decent torque wrench was the first thing I got when I decided to work on my own bikes. Everything has a recommended range for torque, so you don't strip parts or cause a safety concern.


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## davemsc (Mar 4, 2014)

Erock503 said:


> The top cap bolt just snugs up the crown/headset assembly, the stem bolts do the actual job of holding the fork steerer tube. You can absolutely over tighten the bolts, it is after all most likely lightweight aluminum you're working with. This is precisely why almost all stems have torque values printed on the actual part. A decent torque wrench was the first thing I got when I decided to work on my own bikes. Everything has a recommended range for torque, so you don't strip parts or cause a safety concern.


Yeah, that's the next thing I need to get.. A torque wrench. But I just want to make sure if I'm not stripping the stem bolts and hauling on them, that it's OK if I might have gone over the specs on the stem bolts....

With a normal sized Allen key, it's snug. Hard to describe how snug


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## Erock503 (Oct 20, 2014)

It's most likely fine man, just don't crank down too hard, but make sure it's tight enough where the stem isn't going to move on you. Just keep in mind the material you're working with.


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## mack_turtle (Jan 6, 2009)

Most stems require a mere 5 Newton meters of torque on each bolt. You can get a pre-set 5Nm torque key from a bike shop for about $20. Cheaper than a new stem!


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## gtbeast (Mar 5, 2015)

mack_turtle said:


> Most stems require a mere 5 Newton meters of torque on each bolt. You can get a pre-set 5Nm torque key from a bike shop for about $20. Cheaper than a new stem!


I agree with this wholeheartedly. I have worked on BMX bikes for over 15 years, and you should see some of the stems I've seen that have been over torqued and stripped. If you've ever had to remove stripped
bolts from a stem you know what I mean. I've had some
stripped so severely I had to take a hack saw to the bolts through the spacing in the stem to get them out.....not fun. Torque wrench is a sound investment. Even though I'm relatively new to MTB, I'm not new to bikes. Great tool for the tool kit.


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## DennisF (Nov 4, 2011)

Erock503 said:


> The top cap bolt just snugs up the crown/headset assembly, the stem bolts do the actual job of holding the fork steerer tube.


Exactly. The cap bolt doesn't do anything once the stem bolts are tightened. After I tighten my stem bolts, I tighten the cap bolt a little tighter so it doesn't rattle off.

I use a 5nm torque key for the stem. It's tight enough to stay put, but will still slip if you crash IME.


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## big_papa_nuts (Mar 29, 2010)

gtbeast said:


> I agree with this wholeheartedly. I have worked on BMX bikes for over 15 years, and you should see some of the stems I've seen that have been over torqued and stripped. If you've ever had to remove stripped
> bolts from a stem you know what I mean. I've had some
> stripped so severely I had to take a hack saw to the bolts through the spacing in the stem to get them out.....not fun. Torque wrench is a sound investment. Even though I'm relatively new to MTB, I'm not new to bikes. Great tool for the tool kit.


With BMX my experience is that most people don't know the difference between 6mm and 1/4", or they don't care, and they round the bolts out. I'm actually really impressed/depressed at what lengths people, usually kids/teens, will go to ruin the parts they didn't have the money to afford in the first place only to blame it on the part. Important life lessons I guess, and BMX is a bit of a different animal anyways.

Anyways, torque wrenches can be had cheap and will save you money, be it on medical expenses or bikes parts, in the long run.


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## gtbeast (Mar 5, 2015)

big_papa_nuts said:


> With BMX my experience is that most people don't know the difference between 6mm and 1/4", or they don't care, and they round the bolts out. I'm actually really impressed/depressed at what lengths people, usually kids/teens, will go to ruin the parts they didn't have the money to afford in the first place only to blame it on the part. Important life lessons I guess, and BMX is a bit of a different animal anyways.
> 
> Anyways, torque wrenches can be had cheap and will save you money, be it on medical expenses or bikes parts, in the long run.


Exactly!


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## davemsc (Mar 4, 2014)

gtbeast said:


> Exactly!


Just order one that ranges from 2-8Nm for $50. Should be good to go!

Thanks!


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## RS VR6 (Mar 29, 2007)

The torque number are for the _bolts_. So you don't snap the heads off. It will have a max number printed on the part.

My Race Face and Syntace stems say 8nm max. I got a Easton Havoc that says 12nm max. Most of the 5nm numbers are for the 4mm bolts. If you use some kind of friction paste like the Ritchey Liquid Torque...you can actually use less tightening torque.

As mentioned in other posts grab a torque wrench or key.

Ritchey 6-Bit Toqkey Wrench - 5Nm


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## Spindelatron (Aug 15, 2006)

Stand infront of your bike facing the saddle, clench the wheel between your knees and ankles, then try to wrench the bars around. If it slips you didn't go tight enough.

...or get a torque wrench.


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## Erock503 (Oct 20, 2014)

RS VR6 said:


> The torque number are for the _bolts_. So you don't snap the heads off. It will have a max number printed on the part.


Are you sure that's true for stem bolts? Most I've seen are steel, and I would think the aluminum threads would strip before shearing the steel bolt.


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## RS VR6 (Mar 29, 2007)

It can't be for the item its clamping. How would the manufacturer know what type of material it would be clamping? I have three stems that use three different sized bolts...the larger the bolt...the higher the torque number.

You have to make sure whether the number is the _max_ or the _recommended_ torque numbers.


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## zebrahum (Jun 29, 2005)

RS VR6 said:


> The torque number are for the _bolts_.


This part is not true.



RS VR6 said:


> So you don't snap the heads off.


This part is not true.



RS VR6 said:


> It will have a max number printed on the part.


This part is true for some stems but not all.

Bolts are (usually) steel and stems are aluminum or carbon in most cases. Steel is much stronger than soft aluminum or brittle carbon. The torque rating is so you don't pull the threads out of the stem or crush the bars. Torque ratings are especially important when you are using carbon in the bars or stem.

I would argue that tightening down the bolts evenly between the top and bottom screws on a 2/4 bolt stem is more important than nailing the torque rating on the bolts. If you tighten them unevenly you might pinch or unevenly load the handlebar.


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## gsa103 (Sep 1, 2014)

RS VR6 said:


> The torque number are for the _bolts_. So you don't snap the heads off. It will have a max number printed on the part.


If you have a carbon steerer or carbon bars (or seatpost), the torque value is usually to keep from crushing the carbon. The correct torque value is the minimum for the parts involved. A 12 Nm value written on a stem is fine, but you can crush a carbon steerer at 6+ Nm.

And yes, you will usually strip Al threads, assuming you have quality steel bolts. Cheap bolts is a your mileage may vary situation.


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## RS VR6 (Mar 29, 2007)

gsa103 said:


> If you have a carbon steerer or carbon bars (or seatpost), the torque value is usually to keep from crushing the carbon. The correct torque value is the minimum for the parts involved. A 12 Nm value written on a stem is fine, but you can crush a carbon steerer at 6+ Nm.


Then how come the manufacturer of the carbon part tells you to refer to the manual of the stem or clamp for torque numbers? 

When was the last time you saw a carbon bar or seatpost have max torque numbers?

Bolts are elastic by nature. They will stretch as load is applied to them. The bolt will be fine as long as you are in the "elastic range"...once you go beyond that...there is a good chance for failure. There is a good chance that the hardware will snap before the item being clamped gets crushed.


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## zebrahum (Jun 29, 2005)

RS VR6 said:


> Then how come the manufacturer of the carbon part tells you to refer to the manual of the stem or clamp for torque numbers?
> 
> When was the last time you saw a carbon bar or seatpost have max torque numbers?
> 
> Bolts are elastic by nature. They will stretch as load is applied to them. The bolt will be fine as long as you are in the "elastic range"...once you go beyond that...there is a good chance for failure. There is a good chance that the hardware will snap before the item being clamped gets crushed.


Yeah... but you're wrong. Here are some max torque numbers for carbon bars. If you look around, you'll find more of those and you can find them for seatposts too. They usually ship with installation manuals and those should be followed closely.

deity ::: T-Mo Enduro Carbon Handlebar - deity components
Manuals - Components | ENVE

You don't really get to make things up and pretend to call people out over it. This is a beginner forum and therefore you should really be careful about what you say because people will take the crap you're spewing as fact when, in fact, it's nonsense.

Almost every stem I've seen has a torque rating and when you get to a carbon bar every one of those I've seen has a torque rating as well. The torque rating on carbon bars is typically between 4 and 6 Nm and it should very much be paid attention to.

A quick calculation says that the proof strength of a 4mm bolt is around 500 lbs force. Proof strength is the force which can be applied without permanent deformation. That means roughly 1000 lbsf for a 2 bolt stem can be applied before you start to enter the point where you deform the bolts. Actual numbers are hard to find (if you have a stem and carbon bars to donate, I'll be happy to test them and report the results) but I suspect that 1000 lbsf is more than enough to pull 4 mm threads out of aluminum or to crush thin wall carbon. I'll say that in my experience (ample) you're going to strip threads and crush bars well before you snap a bolt; to say otherwise speaks highly to one's level of expertise.


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## RS VR6 (Mar 29, 2007)

Some parts have a max torque...yes I know that. Not every part comes with a torque disclaimer. 

I'm talking about the bolt...not the part its clamped to. How does the bolt manufacturer know what you are clamping? That is what I'm talking about. When you go to a site to buy a bolt...how do they know what you are putting it into? All they can do is to give you a max rating for the bolt.

Its not like these bolts are some custom made part. There is a good chance that they are bought in bulk from a fastener manufacturer.


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## zebrahum (Jun 29, 2005)

RS VR6 said:


> Some parts have a max torque...yes I know that. Not every part comes with a torque disclaimer.
> 
> I'm talking about the bolt...not the part its clamped to. How does the bolt manufacturer know what you are clamping? That is what I'm talking about. When you go to a site to buy a bolt...how do they know what you are putting it into? All they can do is to give you a max rating for the bolt.
> 
> Its not like these bolts are some custom made part. There is a good chance that they are bought in bulk from a fastener manufacturer.


Just because you haven't looked at the data sheet for your parts doesn't meant that they don't have a torque spec.

You're actually astoundingly thick; the bolt's ultimate tensile strength is much higher than the pullout strength of the threads they are interfacing with. You're misunderstanding the problem. Every part of the handlebar-stem interface will fail before the bolt does. The bolt is vastly stronger than the interfacing parts and the fact you keep coming back to bolt strength underscores your fundamental misunderstanding of why bike parts have torque specs.


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## RS VR6 (Mar 29, 2007)

Look man...I'm not trying to get into a pissing contest with you. I probably am misunderstanding the numbers.

So help me understand what the numbers mean on a stem. Easton has 8nm printed on the body of the stem. So that is the "pullout" limit of the stem? So if I go above that...I risk stripping the threads inside the stem? Some stems have different numbers for the bar clamp and steerer clamp...but the stem is made of the same material.

On Whisky's carbon bar installation guide...its says to _"Using a properly calibrated torque wrench, torque clamp bolts to
recommended specifications provided by the stem manufacturer"_. What do I do now?

http://whiskyparts.co/files/tech/whiskyparts_handlebar_instructions.pdf

So poking around the web...I found this on FSA's site,

FSA's FAQ: _"Going above the maximum torque written on the stem may cause the bolt to break."_

FSA Stems FAQs - FSA


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## Erock503 (Oct 20, 2014)

Stems are made of different grades of al, different sizes, different clamping angles, thickness, etc. The manufacturer will have specific torque values based on their design.


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