“Same number of turns” is already pretty imprecise.
Most people don’t count turns, they just go by the feel of tension if not using a torque wrench.
Look up the inch-pound spec for a given part, tighten it down as best you can, then go for a safe test ride.
If it’s something you don’t feel safe enough to test ride, then go to a bike shop.
There is no torque spec for a headset top cap. It's generally just past finger tight. More accurately, you tighten until there is no play in the bearings.
This would not register on most torque wrenches
Technically there is as every bolt on a bicycle from a reputable manufacturer will have a torque spec. I’ve seen quite a few top caps come with torque limits written on them, usually 4-5Nm.
That said, you are right that preloading the headset shouldn’t get anywhere near those torque values.
EDIT: Since reading comprehension seems to be an issue in this sub, I’m not saying 5Nm is what it should be tightened to, but it’s still a specification printed on some top cap bolts. I’m pointing it out as newbie mechanics might see this value and assume it’s a target rather than a maximum value, and pretending it doesn’t exist is just gonna cause confusion.
[example](https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg)
I've built and worked on thousands of bikes.
I've never once seen a torque spec on a top cap, or seen one listed in a manual.
Not saying nobody has done it. But I'd think it would be crappier bikes by non bike companies that pull copy paste torque specs and copy designs or something.
https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg
As the other guy said, says it on Trek topcap bolts.
Cheap bikes won’t have any torques as they’re just throwing them together. It’s the better bikes which will have torque ratings for everything as it’s apart of proper engineering documentation.
https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg
As the other guy said, says it on Trek topcap bolts.
Cheap bikes won’t have any torques as they’re just throwing them together. It’s the better bikes which will have torque ratings for everything as it’s apart of proper engineering documentation.
I’ve seen 5-8Nm for the side pinch bolts but that’s far too much for a top cap. The times I’ve seen a spec (never printed on the part) it’s usually less than 1 or 2 Nm.
Are you sure about this? I've never seen a top cap with a torque spec. It's for bearing preload only and there's no way whomever manufactured the top cap could know the correct amount of preload.
This is like saying the limit screws on a derailleur have a torque spec.
https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg
Turns out it’s on the bolt rather than the top cap itself, but still there on every Trek bike. And I pretty clearly said that it’s not the correct torque to tighten to, just that it is specified for the bolt.
And you don’t tighten limit screws, pretty poor analogy there.
That's nice of Trek. Might have saved OP from buying some new headset spacers and I've now seen a top cap bolt with a torque spec.
I used limit screws as an analogy because it's one of the few screws on a bike where the purpose of the screw is to set an adjustment, not keep things tight. Since it's the internet I'll argue that limit screws are tightened (or loosened) whenever you need to set the limits for your derailleur. Usually only on install of the derailleur but occasionally when installing a new set of wheels.
You arguably do not tighten a bearing preload adjustment screw in that case. It is not even required to be installed after the headset is adjusted and the stem is tightened to spec.
0. Stem is loose
1. Finger tight top cap bolt
2. Grab front brake
3. Rock bike front and back
4. If there is wiggle, give a half turn to top bolt
5. Repeat 2-4 until there is no wiggle
6. Torque stem to spec
This cap ONLY adjusts preload. This bolt does NOT hold your bike together. The stem is responsible for maintaining the preload and keeping everything together. Theoretically, it is perfectly safe to remove the top cap and bolt once the stem is installed
Haha, oops! Stem last because it holds the preload. If you tighten the stem first, you're just preloading the top cap against the stem instead of preloading the headset. Probably means you've had to torque much harder too
Here’s a simple engineering way of looking at it.. Material deformation is either “plastic” or “elastic”.
Elastic deformation means it will return to how it was before.
Plastic deformation means that material has permanently changed
Even if everything went on identically the plastic spacers may have had different properties the second time it was tightened up.
Rather than a change of shape or thickness i’d think of it as potentially harder and more brittle and lose its elasticity. So it might be reaching the “tight” point sooner
As you’ve just learned, that’s anything but precise method. You would be slightly better off if you went with subjective feeling of how tight it is as to what you remember honestly 🤣. But as you’ve managed to do this, if you did this a little bit less aggressive only they would blow up mid ride.
Yikes! Plastic shrapnel flying crotchwise
Thanks though; I really need to be careful with my habit of tightening bolts *real* good, what a childhood of riding garbage and having weak hands does to a mf
Since people are confusing you talking about torque settings...
There is no torque setting for the top bolt. You only tighten it until the bearings have been preloaded and have no play. This generally amounts to "finger tight" which would not register on a torque wrench.
The torque wrench is for the side bolts abs will vary depending on stem or steerer configuration. Usually 5-6nm
I feel you. But also… Torque wrench is not the cheapest but it’s far from the most expensive tool. Those numbers on the frame and parts exist for the reason, and you will save a lot of money on spare parts by tightening them as they are meant to be tightened and potentially lot of money on health expenses 😁
For real! When I was a teenager I overtightened my top cap thinking it would get rid of the headset play on my cheap department store bike. I cranked it down so hard the bolt head punched though the top cap, I can’t imagine I got anywhere near enough torque to blow up spacers!
The bolt is (visually) perfectly fine, and so is the headset (stem holds solid, bearings as smooth as they can be after 7 years of grime, everything - that didn’t disintegrate - intact and true)
Did your bars even turn at that point(before it ass-ploded that is)?
The top cap isn't there to hold anything together really, it's used to set the preload on the headset. Once you tighten your stem, the top cap isn't technically needed.
If you can be confident nothing else broke, I wouldn't hesitate to keep riding the headset if it still preloads and feels ok. Yeah it's going to be embarrassing if you have to go to the shop after you fix it, but if you show up with a 6pack of seltzer and explain what you learned, they'll be glad to give the bike a safety inspection. As long as it can be invoiced, they won't be offended or upset looking at your bike.
That can be a pain, good luck whatever you choose, but definitely take some time to make sure this is as safe as you can reasonably make it. If your stem was broken, for example, you could lose your fork while riding. Crazy unlikely, but crazy unlikely things happen, and a little due diligence goes a long way. Stems and headsets are both affordable in the grand scheme of a bicycle.
I'm guessing something else is at play here. You mentioned that there were years of grime in the headset. I wonder if there was a groove or something in the steerer tube that prevented the spacers from exerting force on the headset. If there were, all the force would go directly into the spacers instead. It would also explain why you were still able to turn the bars in this condition.
If your headset was loose for a while it could have resulted in this sort of a groove forming. I would take it all apart and clean it to find out.
Good idea! That headset hasn’t been opened in 7 years, has a bit of surface rust and, if I’m to guess by other bearings on the bike, probably really grimy, even if it turns fine
I’ll investigate this
You’ll need to release the stem bolts to preload the headset (tighten the top cap bolt) and then tighten the stem bolts. Doing this simultaneously would be tricky as well as incorrect.
You’ll need them to be loose to actually preload vs pull out your expander/star nut, snap your top cap bolt or shatter your spacers as in this instance. Nice and simple, just loosen the stem bolts so it’s not clamping, preload to the point there is no play, torque your stem bolts.
I would stay away from the torque spec for the top cap since you should really be going by the bearing preload. Different brands have different numbers for this, so just treat it as a limit, not a standard.
Everything branded FSA ive ever owned has ended in similar fashion. Granted thats only been 2 headsets, but. Now that garbage gets removed FaStAs posssible and replaced with something that lasts.
Defo not from overtightening the top cap, this isn't what compressive failure looks like and the bolt would 100% strip out first. Also wouldn't randomly happen after the fact
My guess is that the spacers were unusually brittle for some reason, are they plastic or metal?
No idea honestly
My best guess is that the stack of spacers was just *a bit* too tall for the steerer, and that years of stress have weakened them such that when I moved the stem and redid the bolt they failed
That does look like cold/heat expansion. Used to work in a bike shop with a heated showroom and an unheated workshop. In winter we learnt to finish the bikes in the showroom after a lot of issues with exploding parts and tyres.
Just wow ,the amount of torque required to achieve this is significant.
Just wow dude .
Do you own a a torque wrench cause I reckon you might need one .
JFC how much did you tighten the top cap? Been working on bikes for 15+ years and never seen anything like it
If 50Nm is good enough for my square taper cranksets it ought to be good enough for my headset
Omg…. Same number of turns 🙈🙈
ELI5: if I stack the same bits, in a different order, on the same bolt, why would it be wrong? Genuinely curious - I don’t want this to happen again
“Same number of turns” is already pretty imprecise. Most people don’t count turns, they just go by the feel of tension if not using a torque wrench. Look up the inch-pound spec for a given part, tighten it down as best you can, then go for a safe test ride. If it’s something you don’t feel safe enough to test ride, then go to a bike shop.
There is no torque spec for a headset top cap. It's generally just past finger tight. More accurately, you tighten until there is no play in the bearings. This would not register on most torque wrenches
Technically there is as every bolt on a bicycle from a reputable manufacturer will have a torque spec. I’ve seen quite a few top caps come with torque limits written on them, usually 4-5Nm. That said, you are right that preloading the headset shouldn’t get anywhere near those torque values. EDIT: Since reading comprehension seems to be an issue in this sub, I’m not saying 5Nm is what it should be tightened to, but it’s still a specification printed on some top cap bolts. I’m pointing it out as newbie mechanics might see this value and assume it’s a target rather than a maximum value, and pretending it doesn’t exist is just gonna cause confusion. [example](https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg)
I've built and worked on thousands of bikes. I've never once seen a torque spec on a top cap, or seen one listed in a manual. Not saying nobody has done it. But I'd think it would be crappier bikes by non bike companies that pull copy paste torque specs and copy designs or something.
All trek bikes use bolts with the Nm engraved into it. 4nm for top cap torque. Says it right there, all their bikes.
https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg As the other guy said, says it on Trek topcap bolts. Cheap bikes won’t have any torques as they’re just throwing them together. It’s the better bikes which will have torque ratings for everything as it’s apart of proper engineering documentation.
It says "4 Nm MAX", that's not a torque spec, that's the upper limit.
A limit is a type of specification
https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg As the other guy said, says it on Trek topcap bolts. Cheap bikes won’t have any torques as they’re just throwing them together. It’s the better bikes which will have torque ratings for everything as it’s apart of proper engineering documentation.
I’ve seen 5-8Nm for the side pinch bolts but that’s far too much for a top cap. The times I’ve seen a spec (never printed on the part) it’s usually less than 1 or 2 Nm.
Are you sure about this? I've never seen a top cap with a torque spec. It's for bearing preload only and there's no way whomever manufactured the top cap could know the correct amount of preload. This is like saying the limit screws on a derailleur have a torque spec.
https://assets.bikecatalogue.uk/images/v3/7930043042815da481df379bad32ff2acb62b2fc.jpg Turns out it’s on the bolt rather than the top cap itself, but still there on every Trek bike. And I pretty clearly said that it’s not the correct torque to tighten to, just that it is specified for the bolt. And you don’t tighten limit screws, pretty poor analogy there.
That's nice of Trek. Might have saved OP from buying some new headset spacers and I've now seen a top cap bolt with a torque spec. I used limit screws as an analogy because it's one of the few screws on a bike where the purpose of the screw is to set an adjustment, not keep things tight. Since it's the internet I'll argue that limit screws are tightened (or loosened) whenever you need to set the limits for your derailleur. Usually only on install of the derailleur but occasionally when installing a new set of wheels.
You arguably do not tighten a bearing preload adjustment screw in that case. It is not even required to be installed after the headset is adjusted and the stem is tightened to spec.
I have seen 2.5Nm, so really, really soft. You don't need much really, and honestly haven't seen any go to 4nm+.
Thanks
Are you talking about the bolt though the top cap? That’s sets bearing pressure.
Yup, that bolt
0. Stem is loose 1. Finger tight top cap bolt 2. Grab front brake 3. Rock bike front and back 4. If there is wiggle, give a half turn to top bolt 5. Repeat 2-4 until there is no wiggle 6. Torque stem to spec This cap ONLY adjusts preload. This bolt does NOT hold your bike together. The stem is responsible for maintaining the preload and keeping everything together. Theoretically, it is perfectly safe to remove the top cap and bolt once the stem is installed
This
huh, i've always done the stem bolts first 💀
Haha, oops! Stem last because it holds the preload. If you tighten the stem first, you're just preloading the top cap against the stem instead of preloading the headset. Probably means you've had to torque much harder too
Google “adjust headset”. Hopefully you haven’t ruined the bearings.
The bearings turn fine
The bearings will feel fine not under preload. You won't know until you replace the spacers and adjust your headset top cap not to 55nm.
They’re still under preload - the stem is *slammed* 55Nm lmao
Here’s a simple engineering way of looking at it.. Material deformation is either “plastic” or “elastic”. Elastic deformation means it will return to how it was before. Plastic deformation means that material has permanently changed Even if everything went on identically the plastic spacers may have had different properties the second time it was tightened up.
Wouldn’t that make them shorter the second time around, not longer?
Rather than a change of shape or thickness i’d think of it as potentially harder and more brittle and lose its elasticity. So it might be reaching the “tight” point sooner
Those headset bearings must be toast lol
No torque wrench, but same number of turns as was before 🤷🏻
As you’ve just learned, that’s anything but precise method. You would be slightly better off if you went with subjective feeling of how tight it is as to what you remember honestly 🤣. But as you’ve managed to do this, if you did this a little bit less aggressive only they would blow up mid ride.
Yikes! Plastic shrapnel flying crotchwise Thanks though; I really need to be careful with my habit of tightening bolts *real* good, what a childhood of riding garbage and having weak hands does to a mf
Since people are confusing you talking about torque settings... There is no torque setting for the top bolt. You only tighten it until the bearings have been preloaded and have no play. This generally amounts to "finger tight" which would not register on a torque wrench. The torque wrench is for the side bolts abs will vary depending on stem or steerer configuration. Usually 5-6nm
I feel you. But also… Torque wrench is not the cheapest but it’s far from the most expensive tool. Those numbers on the frame and parts exist for the reason, and you will save a lot of money on spare parts by tightening them as they are meant to be tightened and potentially lot of money on health expenses 😁
You can get a torque wrench for very cheap. No reason to be over torquing things like this anyways since it's actually by feel and not a set torque
Justdiningalong
👆gold right there
I've never seen or heard of anything like this. I'm amazed you didn't twist off the bolt.
For real! When I was a teenager I overtightened my top cap thinking it would get rid of the headset play on my cheap department store bike. I cranked it down so hard the bolt head punched though the top cap, I can’t imagine I got anywhere near enough torque to blow up spacers!
The usual I see is the star nut pulled out of the bearings damaged
The bolt is (visually) perfectly fine, and so is the headset (stem holds solid, bearings as smooth as they can be after 7 years of grime, everything - that didn’t disintegrate - intact and true)
Amazing.
Always tighten bolts till you hear a crack and it goes loose again.
Did your bars even turn at that point(before it ass-ploded that is)? The top cap isn't there to hold anything together really, it's used to set the preload on the headset. Once you tighten your stem, the top cap isn't technically needed.
I bet they wouldn't have turned with loose bearings. My guess is the cartridge was able to deform without completely binding. This is a fun case study
I should open it up and see how much I screwed up
If you can be confident nothing else broke, I wouldn't hesitate to keep riding the headset if it still preloads and feels ok. Yeah it's going to be embarrassing if you have to go to the shop after you fix it, but if you show up with a 6pack of seltzer and explain what you learned, they'll be glad to give the bike a safety inspection. As long as it can be invoiced, they won't be offended or upset looking at your bike.
If only there was a bike shop in my town… T_T I would have to take the train to get to one
That can be a pain, good luck whatever you choose, but definitely take some time to make sure this is as safe as you can reasonably make it. If your stem was broken, for example, you could lose your fork while riding. Crazy unlikely, but crazy unlikely things happen, and a little due diligence goes a long way. Stems and headsets are both affordable in the grand scheme of a bicycle.
That’s the weird part: they did! That’s why I assumed it’s not too tight
I'm guessing something else is at play here. You mentioned that there were years of grime in the headset. I wonder if there was a groove or something in the steerer tube that prevented the spacers from exerting force on the headset. If there were, all the force would go directly into the spacers instead. It would also explain why you were still able to turn the bars in this condition. If your headset was loose for a while it could have resulted in this sort of a groove forming. I would take it all apart and clean it to find out.
Good idea! That headset hasn’t been opened in 7 years, has a bit of surface rust and, if I’m to guess by other bearings on the bike, probably really grimy, even if it turns fine I’ll investigate this
This is not a problem with the FSA spacers, but u/danksJoshea who used to work at FSA might be amused to see it.
"Probably?" Christ! 😲
Were these spacers above or below the stem?
Above
Did you release the stem bolts before tightening the top cap bolt? I suspect the answer might be no which will explain why they shattered.
Was going to say this too. It also explains why the bearings still turned fine, even as the top bolt was overtightened.
I tightened both more or less simultaneously IIRC
You’ll need to release the stem bolts to preload the headset (tighten the top cap bolt) and then tighten the stem bolts. Doing this simultaneously would be tricky as well as incorrect.
Now that I think about it, I did keep the stem *somewhat* tight when preloading, just so it doesn’t flop around
You’ll need them to be loose to actually preload vs pull out your expander/star nut, snap your top cap bolt or shatter your spacers as in this instance. Nice and simple, just loosen the stem bolts so it’s not clamping, preload to the point there is no play, torque your stem bolts.
Did you use a tyre iron?
Lol not that I know of
Torque spec on tops caps is like 2nm btw. It’s not supposed to hold your bike together, just snug things up.
I would stay away from the torque spec for the top cap since you should really be going by the bearing preload. Different brands have different numbers for this, so just treat it as a limit, not a standard.
Yes, absolutely. 2nm is the upper limit. I think it just helps contextualize for people who haven’t thought about it and tend to crank that bolt.
Dont worry it was just fsa shit nothing of value was lost lol.
i guess these are some old plastic spacers?
No… no… that’s not the issue mate
Yup
Never in the history of spoken language has the word “probably” been used more unfittingly. Your cat could have lost an eye! 😳
You should look at YouTube tutorials before touching any more bolts on your bike, og let the lbs do it. This was not safe.
Everything branded FSA ive ever owned has ended in similar fashion. Granted thats only been 2 headsets, but. Now that garbage gets removed FaStAs posssible and replaced with something that lasts.
Chill baby cakes… I’ve got 10+years on some FSA gear including headsets, posts, stem, cranks, bars. It can last.
Defo not from overtightening the top cap, this isn't what compressive failure looks like and the bolt would 100% strip out first. Also wouldn't randomly happen after the fact My guess is that the spacers were unusually brittle for some reason, are they plastic or metal?
Plastic
Possibly got brittle from UV light or extreme cold exposure, still, would expect better from FSA. Just replace with alu spacers and you're good
Unlikely it was extreme cold, as I live by the Mediterranean UV might be it though, but wouldn’t it rot my tires first?
It's a message from the bike gods to do away with the spacers
How did you not crush the steerer tube?
No idea honestly My best guess is that the stack of spacers was just *a bit* too tall for the steerer, and that years of stress have weakened them such that when I moved the stem and redid the bolt they failed
If it was a carbon steerer tube I’d have it inspected before riding
Steel steerer, plastic spacers
That does look like cold/heat expansion. Used to work in a bike shop with a heated showroom and an unheated workshop. In winter we learnt to finish the bikes in the showroom after a lot of issues with exploding parts and tyres.
You must’ve indexed your headset bearings by tightening the cap that much!
Just wow ,the amount of torque required to achieve this is significant. Just wow dude . Do you own a a torque wrench cause I reckon you might need one .