Hi CMR, I just wrote a rather long, detailed response before accidently powering off my computer and losing it. But maybe its for the best and I can keep this short :)
I'm also not an engineer, but a theoretical physicist, so everything I said was "in theory" :) I stand by my original statement that the clamping force for a stem with an M8 bolt should be much higher than one with an M5. But, at the end of the day, its a frictional force that is actually preventing your bars from rotating. And frictional forces are notoriously difficult to model properly. The devil is in all the details there, and likely design and manufacturing play a large role (My guess in that the thinness of the clamp material and the larger surface area of flat plate style stems are better at transferring that clamping force into frictional force. Maybe Technomic's stiff "open" style that the bolt has to overcome leads to momentary drops in clamping force due to impacts? Dunno, we'd have to ask an engineer!). So, I'm definitely not going to argue stem A with Bars B will or will not slip. Was only trying to gently point out "more bolts" not necessarily "more better" :) And, in full disclosure, I ride 26 mm clamp bars offroad with both Technomic and Faceplace style stems. They're all drop bar style bars. I've never had an issue with my bars rotating (well, as long as I've properly installed them! :) I've always assumed the warning from Nitto wasn't about the bar rotating in the Technomic style, but full stem failure. It's a long thin bit of aluminum going through a lot of dynamic loads with high max peak stress. Just look at Nitto's (and Rivendell's) recommended alternative: the Nitto Dirt Drop stem. It uses the same single bolt clamping design, but with a beefier aluminum bit after the bend and a bend angle that keeps things a bit more vertical, putting less stress on the stem. If you're out there rocking a 120 mm Technomic and hitting jumps, well maybe you shouldn't? But if you due, check for cracks in the stem! Wow, that was still long! :) On Thursday, March 6, 2025 at 12:09:49 PM UTC-8 CMR wrote: > Hi Ben, I wonder if the design of the stems has more of a factor than the > number and size of the bolts. The technomic is a wrap around design that > bends the metal to grasp around the stem, while an open face plate stem is > more of a clamp. I am not an engineer (obviously)! > > In my experience the technomics are the most beautiful design possible but > will slip with albatross/boscos/billies, and are not a great fit for > offroad riding with these long leveraged bars. They are also very flexible > which is again not a great fit for offroad riding. For city bikes I'd > happily ride them, but I think there is much less slipping with any open > face plate design. > > > > On Wednesday, March 5, 2025 at 5:50:09 PM UTC-8 Ben Miller wrote: > >> Hey all, just thought I'd mention that more bolts doesn't necessarily >> equal more clamping force. Clamping force is generally proportional to the >> lowest preloaded bolt in the system. More bolts really only help to even >> spread the force, not magnify the clamping force (The main reason to use >> multiple bolts is to spread the shear/tensional load across multiple bolts). >> >> That said, the Technomic/Tallux actually uses a much larger bolt than the >> UI-2: I believe M8 vs M5. The yield strength on the M8 is ~x2.5 greater >> than an M5. So, a properly preloaded Technomic *should* actually be >> providing about two and a half times greater clamping force. Of course, it >> will actually be less than that, mostly because of the inherent stiffness >> of the Tech/Tallux clamp itself that the bolt has to overcome and likely >> some other loses due to the single bolt design. But I'm guessing it's still >> a whole lot higher for the Tech/Tallux vs UI-2. (It'd be interesting if >> someone had a thin film pressure transducer to measure it, but I doubt TF >> pressure transducers in the ~2000 PSI range are hard to come by. It's >> probably be easier to just measure the torque requires to get the bars to >> slip...) >> >> Other than bolt diameter on your stem, the main other thing resisting >> turning is the diameter of the clamp itself. That is why modern MTB have >> gone to 31.8 or 35 mm clamp diameters. You can also help things out by >> doctoring your coefficient of friction by adding some anti-slip >> grease/carbon assembly paste. >> >> *TL;DR More bolts are used to lessen chance of bolts breaking, not >> increasing force. Clamping force is roughly proportion to the stem bolt >> size. Bigger bolts can provide significantly more force. * >> On Wednesday, March 5, 2025 at 3:32:22 PM UTC-8 der_amerikanische_freund >> wrote: >> >>> Hi Mike, thanks for the recommendation, I've looked it up and looks like >>> a good compromise between a Tallux and full-on 4-bolt stem. >>> >>> El miércoles, 5 de marzo de 2025 a las 0:22:09 UTC, mwill...@gmail.com >>> escribió: >>> >>>> Just in case you’re interested, Blue Lug has the Nitto UI-2 stem (26.0 >>>> clamp) in stock in all sizes from 60 to 120. Great stem for Ortho bars. >>>> Nitto 90-190’s in stock as well. >>>> >>>> Mike >>>> >>>> On Mar 4, 2025, at 2:29 PM, jaredwilson <duh...@gmail.com> wrote: >>>> >>>> Personally it sounds like you'll be fine given you know what to look >>>> out for and how to handle a bike appropriately given the terrain, but I >>>> will say the *fillet* Nitto Faceplater stems are well worth the coin >>>> and peace of mind if you can find one in your size. >>>> >>>> >>>> Best of luck and be sure to report back with your findings and pictures >>>> whenever possible. >>>> >>>> jared in SC, CA >>>> >>>> On Tuesday, March 4, 2025 at 11:23:50 AM UTC-8 der_amerikanische_freund >>>> wrote: >>>> >>>>> Thank you for all your answers. >>>>> >>>>> I was pretty confident on using the Technomic/Tallux based on all the >>>>> answer-s before Bill's. However, considering I will be using Ortho's or >>>>> similar bars, I may have to reconsider my position. I'm 170 pounds and >>>>> know >>>>> how to ride light (the only riding I know in fact!), but will be using >>>>> swept-back bars. >>>>> >>>>> Regards >>>>> >>>>> El martes, 4 de marzo de 2025 a las 18:10:02 UTC, davids...@gmail.com >>>>> escribió: >>>>> >>>>>> I ride a tallux through single track with no issues. However, to echo >>>>>> Bill's statements, always on drop bars and "riding light." >>>>>> >>>>>> On Tuesday, March 4, 2025 at 8:24:07 AM UTC-8 Bill Lindsay wrote: >>>>>> >>>>>>> It depends on lots of things. Top 5 in my mind are: >>>>>>> >>>>>>> Are you 140 pounds? That's a big plus in favor of using a Technomic >>>>>>> Deluxe wherever you feel like it. Are you 280 pounds? Not so much >>>>>>> What bars are you using? normal drop bars? That's a big plus. >>>>>>> Boscos or other very very long lever arm swept-back bars? Not so much >>>>>>> What does off road riding mean to you? Smooth roads that happen to >>>>>>> be unpaved? That's a big plus. Absolutely anything that the >>>>>>> adrenaline >>>>>>> junkies take bicycles on? Not so much >>>>>>> Do you know how to "ride light"? If so, that's a big plus. If you >>>>>>> don't know what that even means, maybe not so much >>>>>>> When your handlebar moves in the stem, do you just re-position it >>>>>>> and keep riding? That's a big plus. Do you fret and worry and rush to >>>>>>> replace your cockpit? Not so much >>>>>>> >>>>>>> Applying those five criteria to myself, I would have zero qualms >>>>>>> running a Technomic Deluxe for off road touring, and have done a ton of >>>>>>> off >>>>>>> road riding with a Technomic Deluxe or Nitto Pearl stem. I'm closer to >>>>>>> 140 >>>>>>> than 280, I use normal drop bars, off road touring to me means dirt >>>>>>> roads, >>>>>>> I know how to ride light, and if my bar shifts, I reposition it and >>>>>>> ride on. >>>>>>> >>>>>>> Bill Lindsay >>>>>>> El Cerrito, CA >>>>>>> >>>>>>> >>>>>>> On Monday, March 3, 2025 at 12:00:34 PM UTC-8 >>>>>>> der_amerikanische_freund wrote: >>>>>>> >>>>>>>> Hi all, just a quick question to users of the above stems. >>>>>>>> >>>>>>>> Nitto claims it's not intended for off-road riding, however I see a >>>>>>>> lot of builds (who look very off-road to me) with said stems. >>>>>>>> >>>>>>>> Has anyone used them in rough-ish terrain? I don't ride technical >>>>>>>> trails but I don't ride on pavement either, so just that middle ground >>>>>>>> of >>>>>>>> mild to rough gravel >>>>>>>> >>>>>>>> Thanks >>>>>>>> >>>>>>>> >>>>>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "RBW Owners Bunch" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to rbw-owners-bun...@googlegroups.com. >>>> >>>> To view this discussion visit >>>> https://groups.google.com/d/msgid/rbw-owners-bunch/b1892e71-c299-43bf-8270-d93b7c7d117en%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/rbw-owners-bunch/b1892e71-c299-43bf-8270-d93b7c7d117en%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. 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