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How strong is the "integrated" thread mount on a carbon drop bar?

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How strong is the "integrated" thread mount on a carbon drop bar?

Old 11-02-21, 07:30 PM
  #26  
mschwett 
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Originally Posted by bahula03
Come for the computer mount discussion, stay for the work/life nightmare Working wherever you are is the apparent necessity, in this case while cycling, and cycling computers aren't office equipment unless you're getting paid to ride. Pretty straightforward.

As for the actual question- Specialized are the only ones I'd trust for an answer unless they printed the mount's weight limit in the paperwork that came with the cockpit. Anecdotally, the Specialized mount seems to be the same one they use everywhere else, is listed as being compatible with the Alpinist cockpit, and includes bits to attach lights, GoPro, etc., so I wouldn't worry too much about the additional weight. The forces/load acting on the mount in your setup should be ballpark the same as having the weight out front.

https://www.lordgun.com/specialized-...r-bike-mount-1

Having already crossed the rubicon of common sense setups, you might be best served using that double-sided tape directly under the phone mount as the "primary" attachment, and then use a rubber grommet where your mount attaches to the cockpit insert so that a) you aren't preloading the insert b) mitigate load on the tape c) retain the capacity of the insert, which I'd spitball is higher than the tape.
thanks! that has the benefit of being cleaner looking than the rubber strap. i can probably design the mount with a sticking surface on top of the stem that would be pretty invisible, if relatively small. the more i think about it, i assume the way it’s designed the tight fit between the curved bar and the mount is what reduces the rotational torque on the insert. the thin but still compressible layer of tape i added between there on mine might be cross purposes …
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Old 11-03-21, 07:27 AM
  #27  
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Originally Posted by mschwett
the more i think about it, i assume the way it’s designed the tight fit between the curved bar and the mount is what reduces the rotational torque on the insert. the thin but still compressible layer of tape i added between there on mine might be cross purposes …
Yup .... max strength and minimized damage require zero movement. Flex is what you do Not want. If there is flex in the system the screw threads are constantly pulling on the insert threads, constantly trying to pull the insert out of the bike. A rigid mount (zero mount movement relative the the bars) is the safest.

You might look into something like Rivnuts ... you could possibly drill a couple small holes in the stem, epoxy in a couple of inserts of your own, and screw the mount down in three places (on the existing insert, plus two on the stem.) Not sure how that would affect stem integrity but possibly not at all if the inserts were loaded down with epoxy.
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Old 11-03-21, 07:59 AM
  #28  
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Drilling holes in the stem is likely not a very good idea. Do your research before drilling into CF tubing as you can easily create weak spots.

Here's one take: Technical FAQ: Drilling holes in carbon frames and more - VeloNews.com
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Old 11-03-21, 07:31 PM
  #29  
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don't worry guys, not drilling any holes into my bar/stem! the whole exercise was to use the anchor already provided
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Old 11-04-21, 01:36 AM
  #30  
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Bah! I have no fear of stress risers ..... in somebody else's stem.
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Old 11-04-21, 12:38 PM
  #31  
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Don't the bars have mount holes underneath for an out-front mount? If I were to actually use a phone I'd get an adhesive Garmin or Wahoo adapter for it and use a plain K-Edge out-front combo mount. I'd probably have a case specific for cycling with the adapter attached to it. An out-front position allows me to glance at the computer, without any need to turn my head or otherwise take my eyes off the road. I actually DO have exactly such a setup, but only use it on the indoor trainer (for things like the Zwift companion app). Indoors: phone. Outdoors: bike computer. Same mount. On two bikes no less.
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Old 11-06-21, 05:54 PM
  #32  
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Originally Posted by sfrider
Don't the bars have mount holes underneath for an out-front mount? If I were to actually use a phone I'd get an adhesive Garmin or Wahoo adapter for it and use a plain K-Edge out-front combo mount. I'd probably have a case specific for cycling with the adapter attached to it. An out-front position allows me to glance at the computer, without any need to turn my head or otherwise take my eyes off the road. I actually DO have exactly such a setup, but only use it on the indoor trainer (for things like the Zwift companion app). Indoors: phone. Outdoors: bike computer. Same mount. On two bikes no less.
they have an out front mount, using the one screw hole i've been using, but it doesn't appear to stick nearly far enough "out front" for a phone. i also prefer the phone over the stem, where i can use the screen with a hand on the bars. it's still a quick glance, just a little lower. i get the aero benefit of it being "in line" with the front of the bar, but we're probably talking a pretty miniscule effect.

i use the quad lock system as you've described, with multiple bikes and cars. there's no way i'd attach a phone to a moving vehicle with an adhesive mount, but of course there are cases with the integrated quad lock socket. it's similar to the garmin adapter but with much larger engagement surfaces, and to me at least way easier to snap in and out while riding compared to the garmin mount.
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Old 11-06-21, 06:01 PM
  #33  
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here's where i ended up with this for now. i ended up eliminating the space between the "end" of the mount and the stem, and added a layer of thick VHB tape there. i removed the thick tape between the mounting surface and the front of the bar in lieu of a thin layer of noncompressible tape just to minimize and rotation that might get transferred to the screw. i also decided to use a smaller phone while on the bike - 105g less and the "smaller" screen (still more than double the screen of a fancy garmin) is just fine. not sure i'll love the less advanced camera for rides where i don't bring a real camera, but we'll see.

it's now totally rock solid, even out of 3d printed nylon. more solid even than the quad lock out front mount used in the similar position. i'm going to thin it up quite a bit and have one printed in aluminum. the other thing i'm wondering about, with the smaller phone, is shortening it further and trying to move it down so that it sits in front of and slightly below the future shock adjustment knob. it would be nice if it was lower, and was previously constrained by the big phone. i think i'd probably like to be able to attach any iphone with a quad lock case, so i'm going to leave it for now and forgo whatever additional sleekness would come from it being a whole 1/4" lower.






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Old 11-24-21, 12:56 PM
  #34  
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i’ve now ridden the above setup around three hundred miles, including maybe 50 miles of gravel/rocks and a 120 mile ride yesterday. still seems rock solid. no signs of any stress anywhere, so i think i’ll now have an aluminum one made.

my main ride logging / dashboard app drained the iphone mini battery from 100% to approx 20% over the course of 8 hours and 120 miles, so i’d say that’s close to the limit without taking great care to conserve battery. i ran screen on maybe half or two thirds the time, didn’t use many other apps but answered a few dozen slacks and looked at some maps, exchanged a few texts etc.
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Old 11-24-21, 11:14 PM
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Computer will always be the best choice, but virtually anything would be better than this halfassed bodge.
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Old 03-26-22, 11:55 AM
  #36  
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made a smaller, lighter version of this that sits a little farther forward on the bars. weighs 8g in abs plastic (excluding the quad lock parts). still uses the screw mount, with a thin layer of conformal VHB tape between it and the bars so there's no scratching, a teeny bit of cushion, but minimal "flex." the bolt now isn't threaded through the plastic, so vibration shouldn't transfer into the mount as torque at angles. total weight of phone, case, quad lock lever, 3d printed arm is <200g, with 135g being the phone of course.

the build lines on one side of my home printed version are pretty crude, although it's so small that in person you don't see them nearly as much as the pic. i'll probably order a couple professionally printed ones.









i do wish it could sit a tiny bit lower, but that's basically the minimum stack with the quad lock hardware and a standard profile nut. a low profile nut could get it down a few mm.



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