I have a CNC machined aluminum stem. Without knowing the required Nm, would you revert back to the bar’s recommended torque spec? So the usual 5Nm. Also, would you use grease for what I’m assuming are steel bolts on the stem. Whoever had the stem before me, used some sort of lubrication on the bolts, which I’ve heard conflicting info about. So would it be better to go dry or lubricated? giggity.
I’m no pro mechanic and I didn’t stay at some hotel last night, but I’d probably do 5 Nm. I’m not sure if the bolt size makes a difference, but I would think that the smaller the bolts, the smaller the torque amount should be. I’d also use some grease if it were me. I’m not sure the bolts would seize without it, but I don’t think it would hurt to use some grease.
And if the bar becomes loose during the ride, just re-tighten down to 6 Nm and so on and so forth…
Yah, I’ll be sticking to 5Nm. Hopefully that with the carbon paste should do the job.
Upon closer inspection, the “grease” on the bolts is something copper-ish. So I’m assuming it’s a copper anti-seize. Follow up question. Grease (polylube 1000) or anti-seize (park tool or a similar copper lubrication)? Oh lubrications…
I’d think either would work fine. The lubrication is just to help prevent the metals from grinding one another when being threaded. I’d probably use polylube 1000. If it were something with a higher torque spec, I’d go with anti-seize, but I think polylube 1000 would be just fine.
You’d really have to take each into account. My rule has generally been that with an aluminum stem, torque to the specs on the bars and steerer. Overtorquing can crack either if they’re carbon whereas you’re pretty unlikely to strip out or crack the stem with a little extra twist due to the clamping design. Still, don’t overdo it.
Also, I never grease bolts that hold critical pieces in place. Whether or not that’s right, I don’t know, but I’d rather throw a stem away because I had to cut the front plate off than deal with a loose clamp.
The 5nm is a good value. I strongly prefer having some form of lubrication, grease, triflow, antiseize etc on all interfaces. Steel into aluminum is a good place to lubricate. I grease the threads and also the face of the bolt against the washer. Grease can be a dirt attractor on the outside so carefully remove any excess. No need to glob it on either. The actual thickness of the grease between the surfaces is very small.
Despite having worked on bikes for 30 years, I did damage a faceplate on a Deda stem a few years ago. Use of a torque wrench is highly recommended. The simple version is the Ritchey Torqkey with a preset 5nm for 4mm bolts. Works for most stem and seat post clamps.
First thing I’d do would be to try to figure out that make and model of both the stem and fork/steerer. Then I’d go online to the mfrs sites looking for the manuals of both (or at least manuals of similar models). They almost always have a torque spec. Choose the lower of the two.
The 5 nm number that you see on most stems is the maximum torque. Not necessarily the recommended torque
Definitely use something to keep it from seizing. Grease or loctite works. Grease is what many manufacturers use to determine the proper torque specs and its what many shops use.
Hah, I knew I’d get the differing opinions on lubrication. It’s a custom piece, so I’m going off of what would be best if you had to guess. I’m not quite entirely sure of the bar clamp torque either (new TriRig Alphas). I’m assuming 4ish Nm is the way to go with carbon paste then I’ll use some polylube on the stem bolts.
I have a CNC machined aluminum stem. Without knowing the required Nm, would you revert back to the bar’s recommended torque spec? So the usual 5Nm. Also, would you use grease for what I’m assuming are steel bolts on the stem. Whoever had the stem before me, used some sort of lubrication on the bolts, which I’ve heard conflicting info about. So would it be better to go dry or lubricated? giggity.
I’m guessing you got one of the old flat stems for your DA?
The bolts are where the early prototypes had problems.
Find grade 12.9 bolts, do not use stainless or the later versions with the 8.8. Replace them often. Do not exceed 7Nm. Lubricate the lower head surface and threads.
Is the stem surface smooth or does it appear to have machining marks? does it have a laser etched Felt logo on the faceplate?
-SD
I’d think either would work fine. The lubrication is just to help prevent the metals from grinding one another when being threaded. I’d probably use polylube 1000. If it were something with a higher torque spec, I’d go with anti-seize, but I think polylube 1000 would be just fine.
Yeah. It would never occur to me to not grease threads when tightening as arluke does.
Yah, I’ll be sticking to 5Nm. Hopefully that with the carbon paste should do the job.
Upon closer inspection, the “grease” on the bolts is something copper-ish. So I’m assuming it’s a copper anti-seize. Follow up question. Grease (polylube 1000) or anti-seize (park tool or a similar copper lubrication)? Oh lubrications…
The copper anti-seize to to prevent dissimilar metal corrosion, which is what happens with a steel bolt in an Al alloy stem. Any similar anti-seize will work
In my experience the best anti-dissimilar corrosion compound out there is Boeshield T-9, it’s a wax that physically separates the metals.
5 N-M is the right torque
I have a CNC machined aluminum stem. Without knowing the required Nm, would you revert back to the bar’s recommended torque spec? So the usual 5Nm. Also, would you use grease for what I’m assuming are steel bolts on the stem. Whoever had the stem before me, used some sort of lubrication on the bolts, which I’ve heard conflicting info about. So would it be better to go dry or lubricated? giggity.
I’m guessing you got one of the old flat stems for your DA?
The bolts are where the early prototypes had problems.
Find grade 12.9 bolts, do not use stainless or the later versions with the 8.8. Replace them often. Do not exceed 7Nm. Lubricate the lower head surface and threads.
Is the stem surface smooth or does it appear to have machining marks? does it have a laser etched Felt logo on the faceplate?
-SD
Haha…Uh oh, I’ve been marked down as that “guy always complaining about the DA brake and flat stem”. What kind of bolt issues?
I have the flat stem with machining marks and etched Felt logo. I put some pictures below. The only bolts I received were for the stem’s face plate. They are (if I got this correctly)…M4, 14mm, A4-70. Originally, I was going to use the stem bolts and pinch bolt from the stem I have now, but I guess they aren’t strong enough (8.8). The A4-70 bolts don’t have as high of a tensile strength as the 8.8s. Since they are only for the face plate will they still work? I wasn’t exactly specific with which stem bolts, so after seeing the 7Nm I figured you may be talking about the stem/pinch bolts.
Talk about a wild goose chase. Now I have to find stronger bolts and thanks to my location…that’s freakin hard. I’ll PM you this response, since you may not see this thread later in the day.
I have a CNC machined aluminum stem. Without knowing the required Nm, would you revert back to the bar’s recommended torque spec? So the usual 5Nm. Also, would you use grease for what I’m assuming are steel bolts on the stem. Whoever had the stem before me, used some sort of lubrication on the bolts, which I’ve heard conflicting info about. So would it be better to go dry or lubricated? giggity.
I’m guessing you got one of the old flat stems for your DA?
The bolts are where the early prototypes had problems.
Find grade 12.9 bolts, do not use stainless or the later versions with the 8.8. Replace them often. Do not exceed 7Nm. Lubricate the lower head surface and threads.
Is the stem surface smooth or does it appear to have machining marks? does it have a laser etched Felt logo on the faceplate?
-SD
Haha…Uh oh, I’ve been marked down as that “guy always complaining about the DA brake and flat stem”. What kind of bolt issues?
I have the flat stem with machining marks and etched Felt logo. I put some pictures below. The only bolts I received were for the stem’s face plate. They are (if I got this correctly)…M4, 14mm, A4-70. Originally, I was going to use the stem bolts and pinch bolt from the stem I have now, but I guess they aren’t strong enough (8.8). The A4-70 bolts don’t have as high of a tensile strength as the 8.8s. Since they are only for the face plate will they still work? I wasn’t exactly specific with which stem bolts, so after seeing the 7Nm I figured you may be talking about the stem/pinch bolts.
Talk about a wild goose chase. Now I have to find stronger bolts and thanks to my location…that’s freakin hard. I’ll PM you this response, since you may not see this thread later in the day.
Ok, those are some 6061 CNC stems, using a non-forged face plate and a very tight tolerance on the axis shaft adjuster. Use plenty of anti-sieze on the adjuster pinch clamp surface.
The two M6 mounting bolts from the stem that came with your DA are likely the correct length but triple check. The engagement into the co-molded aluminum inserts must be precise. If the bolts are too short, you’ll run the risk of pulling the aluminum threads out of the fork. If they are too long, they’ll bottom out on the insert and drive it out of the fork or split the carbon structure. I don’t have both drawings in front of me to compare, you may need new M6 bolts.
8.8 could be ok for short term, you need to replace the bolts often. In the end, no M5 bolts of any strength or grade were able to survive our fatigue testing** of that particular stem design. I’ve found dozens of sources for bolts online if you don’t have a local hardware store. The bar clamp width also doesn’t fit our new Bayonet3 handlebars. The stem also doesn’t house the new 5-port Junction A Di2 connector as it was originally intended. It will fit the previous 7970 and 6770 non TT junction boxes.
If you use a different bar and replace the bolts often, you may not have a failure. Unfortunately we cannot use that stem design in mass production as “may not have a failure” doesn’t fly in the litigious consumer world.
-SD
I have a CNC machined aluminum stem. Without knowing the required Nm, would you revert back to the bar’s recommended torque spec? So the usual 5Nm. Also, would you use grease for what I’m assuming are steel bolts on the stem. Whoever had the stem before me, used some sort of lubrication on the bolts, which I’ve heard conflicting info about. So would it be better to go dry or lubricated? giggity.
I’m guessing you got one of the old flat stems for your DA?
The bolts are where the early prototypes had problems.
Find grade 12.9 bolts, do not use stainless or the later versions with the 8.8. Replace them often. Do not exceed 7Nm. Lubricate the lower head surface and threads.
Is the stem surface smooth or does it appear to have machining marks? does it have a laser etched Felt logo on the faceplate?
-SD
Haha…Uh oh, I’ve been marked down as that “guy always complaining about the DA brake and flat stem”. What kind of bolt issues?
I have the flat stem with machining marks and etched Felt logo. I put some pictures below. The only bolts I received were for the stem’s face plate. They are (if I got this correctly)…M4, 14mm, A4-70. Originally, I was going to use the stem bolts and pinch bolt from the stem I have now, but I guess they aren’t strong enough (8.8). The A4-70 bolts don’t have as high of a tensile strength as the 8.8s. Since they are only for the face plate will they still work? I wasn’t exactly specific with which stem bolts, so after seeing the 7Nm I figured you may be talking about the stem/pinch bolts.
Talk about a wild goose chase. Now I have to find stronger bolts and thanks to my location…that’s freakin hard. I’ll PM you this response, since you may not see this thread later in the day.
Ok, those are some 6061 CNC stems, using a non-forged face plate and a very tight tolerance on the axis shaft adjuster. Use plenty of anti-sieze on the adjuster pinch clamp surface.
The two M6 mounting bolts from the stem that came with your DA are likely the correct length but triple check. The engagement into the co-molded aluminum inserts must be precise. If the bolts are too short, you’ll run the risk of pulling the aluminum threads out of the fork. If they are too long, they’ll bottom out on the insert and drive it out of the fork or split the carbon structure. I don’t have both drawings in front of me to compare, you may need new M6 bolts.
8.8 could be ok for short term, you need to replace the bolts often. In the end, no M5 bolts of any strength or grade were able to survive our fatigue testing** of that particular stem design. I’ve found dozens of sources for bolts online if you don’t have a local hardware store. The bar clamp width also doesn’t fit our new Bayonet3 handlebars. The stem also doesn’t house the new 5-port Junction A Di2 connector as it was originally intended. It will fit the previous 7970 and 6770 non TT junction boxes.
If you use a different bar and replace the bolts often, you may not have a failure. Unfortunately we cannot use that stem design in mass production as “may not have a failure” doesn’t fly in the litigious consumer world.
-SD
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For the adjuster pinch clamp and face plate bolts, is there an issue with using longer screws? Other than aesthetics? I’ve been able to find M5/12.9/14mm for the face plate, but not the same length (16mm) for the pinch bolt. Instead I found 20mm.
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What type of issues did you encounter with the fatigue testing? What did your fatigue testing consist of? Was the failure due to higher torques/going above 7Nm?
I have a CNC machined aluminum stem. Without knowing the required Nm, would you revert back to the bar’s recommended torque spec? So the usual 5Nm. Also, would you use grease for what I’m assuming are steel bolts on the stem. Whoever had the stem before me, used some sort of lubrication on the bolts, which I’ve heard conflicting info about. So would it be better to go dry or lubricated? giggity.
I’m guessing you got one of the old flat stems for your DA?
The bolts are where the early prototypes had problems.
Find grade 12.9 bolts, do not use stainless or the later versions with the 8.8. Replace them often. Do not exceed 7Nm. Lubricate the lower head surface and threads.
Is the stem surface smooth or does it appear to have machining marks? does it have a laser etched Felt logo on the faceplate?
-SD
-
For the adjuster pinch clamp and face plate bolts, is there an issue with using longer screws? Other than aesthetics? I’ve been able to find M5/12.9/14mm for the face plate, but not the same length (16mm) for the pinch bolt. Instead I found 20mm.
-
What type of issues did you encounter with the fatigue testing? What did your fatigue testing consist of? Was the failure due to higher torques/going above 7Nm?
-
I don’t recall if the version you have has blind holes in the stem body or if they are punched all the way through and tapped. If the bolts you sourced are too long, just cut them down. Problem solved.
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The bolts break under fatigue testing. The attachment of the stem is so solid there is more load on the stem’s face plate bolts. The aerodynamically oriented face plate (more aero than the older 26.0mm version) does not support the bar in left/right oscillations such as standing on the pedals and climbing on the base bar. If I recall correctly it was the out-of-phase EN1471 testing of the stem caused the bolts to break. I’ve explained a few times the stems do not pass testing yet, so they are not available for sale. I would not use that stem design nor is that early version compatible with the Bayonet3 bars. If you choose to use it despite the risks, change the bolts frequently as they failed in fatigue, not in impact, tensile or ultimate strength testing.
-SD
Generally curious and just thinking. Once I thought about it everything made sense.
I’m not an engineer and by no means was I great physics student…but wouldn’t the problem be fixed by simply having the face plate on the front like every other bike stem? Most of the stress on a stem is from vertical movement, so it would make sense that the bolts would take all of that energy. Which leads me to question as to why Felt would continue to keep the face plate on the top for all of the new fixed stems (90x30, 100x30, so on)? I have the newer fixed stem as well, and honestly there isn’t much of a difference between that and the machined stem when it comes to the bolts.
8.8 could be ok for short term, you need to replace the bolts often. In the end, no M5 bolts of any strength or grade were able to survive our fatigue testing** of that particular stem design. I’ve found dozens of sources for bolts online if you don’t have a local hardware store. The bar clamp width also doesn’t fit our new Bayonet3 handlebars. The stem also doesn’t house the new 5-port Junction A Di2 connector as it was originally intended. It will fit the previous 7970 and 6770 non TT junction boxes.
Bolts aren’t equal. Did you have issues with aerospace grade bolts or just the junk you’d find at the hardware stores? BTW, you may want to take a look at NASA-STD-5020 and in particular the fatigue related info. I worked on that standard and we did a fair amount of analytical and test work do develop criteria for fatigue.
Bolts aren’t equal. Did you have issues with aerospace grade bolts or just the junk you’d find at the hardware stores? BTW, you may want to take a look at NASA-STD-5020 and in particular the fatigue related info. I worked on that standard and we did a fair amount of analytical and test work do develop criteria for fatigue.
Where would one find aerospace grade bolts? I’m currently home in an aerospace capital, so…if I can find something stronger than 12.9 grade alloy that’d be awesome.
Generally curious and just thinking. Once I thought about it everything made sense.
I’m not an engineer and by no means was I great physics student…but wouldn’t the problem be fixed by simply having the face plate on the front like every other bike stem? Most of the stress on a stem is from vertical movement, so it would make sense that the bolts would take all of that energy. Which leads me to question as to why Felt would continue to keep the face plate on the top for all of the new fixed stems (90x30, 100x30, so on)? I have the newer fixed stem as well, and honestly there isn’t much of a difference between that and the machined stem when it comes to the bolts.
We’ve reconfigured the face plate to the top of the stem instead of the front to reduce frontal area and reshape the stem to be more aerodynamic. Many BMX stems (read high stress & clamping force requirement) attach this way as well.
All other fixed stem sizes have overcome the bolt breaking issue and work perfectly fine long past our required fatigue cycle.
Flat (0mm rise) stems have been redesigned to withstand fatigue and will be produced eventually.
-SD