reducing 15mm thru axle fork to 12mm

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visse89
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by visse89

not sure if this helps or make sense but mine looks like this.

Image

by Weenie


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joejack951
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by joejack951

visse89 wrote:
Sun Sep 23, 2018 8:18 am
not sure if this helps or make sense but mine looks like this.

Image
If I am seeing things correctly, that looks like a 'Syntace' style front axle. I didn't know such a thing existed. Do you have pictures of the axle and dropouts?

joejack951
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by joejack951

spud wrote:
Fri Sep 21, 2018 10:34 pm
possibly another, easier solution is a piece that threads into the 15mm side and takes it down to 12 mm, plus a slip sleeve locktited into place. Use as a straight 12mm axle, with allen head cap screw on the end, then you can accommodate a little bit of dropout thickness variance. Not ideal, but it will allow you to swap wheels between bikes easily.
I'm not sure what you are describing here. Can you sketch it out?

Whatever I do, I don't want the modification to be permanent for several reasons. What I'll likely do is add an o-ring groove on the slip-fitted piece that reduces the NDS to 12mm. This will hold it, and any spacers, in place during wheel changes. Using a separate slip fitted piece allows for using off-the-shelf axles rather than producing my own, with all the costs and headaches that incurs. I just need to be sure there are standard axles that will work with my proposed design.

babgvant
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Joined: Mon Dec 17, 2018 11:09 pm

by babgvant

I just picked up a 2016 Trek Domane frameset and it comes with 15mm (shown) and QR inserts for the fork. Would love to have a 12mm insert so I can swap wheels between bikes easier.

Anyone know where I can find one, or have one made? Trek's only "solution" was to buy a new fork...
Attachments
trek 15mm fork adapter.png

maximvanwijk
Posts: 5
Joined: Tue Jul 30, 2013 1:49 pm

by maximvanwijk

joejack951 wrote:
Sun Dec 31, 2017 3:37 pm
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Weight should be about 30 grams.
@joejack951, did you manage to make and test your design? I am actually looking to make a similar solution, trying to adapt my 15mm thru axle fork to accept a 12mm thru axle. What I am going to try is take a 15mm oil drain plug (which uses the same thread) and then tap a 12mm thread in it to accept the thru axle. This adpater should screw in on the outside of the fork. For the other side I'm going to use a sleeve to fill the space.
It will probably be a bit heavier than 30 grams, since it will be steel (can't find the proper plugs in alloy).

joejack951
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by joejack951

maximvanwijk wrote:
Sun Jun 02, 2019 12:41 pm
@joejack951, did you manage to make and test your design? I am actually looking to make a similar solution, trying to adapt my 15mm thru axle fork to accept a 12mm thru axle. What I am going to try is take a 15mm oil drain plug (which uses the same thread) and then tap a 12mm thread in it to accept the thru axle. This adpater should screw in on the outside of the fork. For the other side I'm going to use a sleeve to fill the space.
It will probably be a bit heavier than 30 grams, since it will be steel (can't find the proper plugs in alloy).
I have yet to try and produce these, mainly due to lack of interest. I'll eventually make parts for my own bike just so I have the option of running a 12mm thru axle front wheel. The key to make the adapter work is 'timing' the threads. You want the crests of the internal thread aligned with those of the external thread otherwise you'll have a very weak insert. Perhaps in steel you may get away with no timing the threads, though. You also need to keep everything concentric otherwise you'll load your wheel bearing unnecessarily as the thru axle tries to align everything. It won't be easy if you are doing this by hand. I planned on having them done on a CNC lathe.

spud
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by spud

if you do a run, I am definitely interested in it. Still running a 15mm axle, though I'd love to be able to use my 12mm wheelsets.

maximvanwijk
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Joined: Tue Jul 30, 2013 1:49 pm

by maximvanwijk

joejack951 wrote:
Tue Jun 04, 2019 2:13 pm
You want the crests of the internal thread aligned with those of the external thread otherwise you'll have a very weak insert.
Good point, I'll keep that in mind. Once I have the M15 plugs I'll find a professional metal workshop to tap the m12 thread in. I will also investigate 3D printing in metal. If that is strong enough, it will probably be the most accurate. Just need to brush up my (non existing) 3d software skills :)

joejack951
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by joejack951

maximvanwijk wrote:
Mon Jun 10, 2019 12:36 pm
joejack951 wrote:
Tue Jun 04, 2019 2:13 pm
You want the crests of the internal thread aligned with those of the external thread otherwise you'll have a very weak insert.
Good point, I'll keep that in mind. Once I have the M15 plugs I'll find a professional metal workshop to tap the m12 thread in. I will also investigate 3D printing in metal. If that is strong enough, it will probably be the most accurate. Just need to brush up my (non existing) 3d software skills :)
3D printing in metal will be quite expensive. I have the part modeled already but it will be $150-200 for a printed metal part. I can have a small batch CNC'd with far better precision and anodizing for not much more money. I just don't want to produce a bunch of parts that won't fit anyone's bike but my own. Collecting good info on how to design a universal adapter is proving quite difficult.

spud
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by spud

I think the insert to convert from m15 to m12 is the crux. if you make the insert long enough, the user can file the insert down so that it is flush with the inside of the dropout. I'm guessing that an off the shelf solution can be found for the axle, if one is willing to use a standard bolt, and perhaps fit a washer under the head to achieve tension in the bolt.

maximvanwijk
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by maximvanwijk

joejack951 wrote:
Mon Jun 10, 2019 2:04 pm
I can have a small batch CNC'd with far better precision and anodizing for not much more money. I just don't want to produce a bunch of parts that won't fit anyone's bike but my own. Collecting good info on how to design a universal adapter is proving quite difficult.
I understand your dilemma. How small a batch are you talking about? Variation in dropout width is something that can probably be solved with washers/shims. But finding enough people willing to chip in for a part that only a few people need is probably more difficult.

joejack951
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by joejack951

maximvanwijk wrote:
Tue Jun 11, 2019 3:47 pm
joejack951 wrote:
Mon Jun 10, 2019 2:04 pm
I can have a small batch CNC'd with far better precision and anodizing for not much more money. I just don't want to produce a bunch of parts that won't fit anyone's bike but my own. Collecting good info on how to design a universal adapter is proving quite difficult.
I understand your dilemma. How small a batch are you talking about? Variation in dropout width is something that can probably be solved with washers/shims. But finding enough people willing to chip in for a part that only a few people need is probably more difficult.
As with most things I get into, I fully expect to foot the bill for the initial parts and then find people who need them. I'm not a charity and not looking for crowd-funding :) I'm just struggling with how to make a robust universal design that will let me sleep at night knowing people's front wheels won't be falling out due to their or my fault(s). If I had everyone's forks and hubs in my hands to take my own measurements it would be a lot easier, too. Without that, I'm left guessing and/or expecting others to modify my parts to fit in a very critical area, and that scares that crap out of me.

I do have a design in mind that could be near-universal in fitment but there is a big compromise: the adapters would install from the inside of the fork legs and narrow the internal width of the fork by ~1mm. Doing this eliminates a lot of potential fitment problems with the adapters but now anyone using this kit would need to shim their rotors to allow them to fit the adapted-15mm fork and a 12mm fork. They'd also need to get over the 0.5mm fork leg flex (per side) that this design needs.

spud
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by spud

interesting idea, but one big drawback - I assume most people are looking at this so they can move wheels between bikes. That's certainly the case for me. Shimming the rotor for one bike ultimately means shimming all your wheels and readjusting your other bikes. Which then means a wheel from outside your collection will work poorly.

Could I commission you to make an insert that threads from the outside, and I'll take the responsibility to file it to fit then threadlock into place? If you only make that single piece and put the responsibility on the user to procure an axle, you've taken the liability out of the equation.

joejack951
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by joejack951

spud wrote:
Tue Jun 11, 2019 6:45 pm
interesting idea, but one big drawback - I assume most people are looking at this so they can move wheels between bikes. That's certainly the case for me. Shimming the rotor for one bike ultimately means shimming all your wheels and readjusting your other bikes. Which then means a wheel from outside your collection will work poorly.

Could I commission you to make an insert that threads from the outside, and I'll take the responsibility to file it to fit then threadlock into place? If you only make that single piece and put the responsibility on the user to procure an axle, you've taken the liability out of the equation.
Alright, I've given this enough thought and this seems a reasonable approach to get started.

Which axle do you plan to use? I'd like to confirm how much threading is available as ideally there'd be some unthreaded axle engaged in the dropout, which necessitates an unthreaded portion of the insert. You listed your fork specs earlier in the thread but confirming those again would also be helpful.

by Weenie


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joejack951
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by joejack951

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Needs to be road tested but here it is in the flesh. Currently designed to fit my Hong Fu fork (10mm thru hole drop out thickness, 15mm threaded dropout thickness) and to use a standard 12mm x 125mm long thru axle with 12mm of threads (https://www.jensonusa.com/Rockshox-Maxle-Stealth)

Note that the threaded adapter is slightly backed off from being fully threaded into the dropout. I expect that there will be some variation in dropout thickness so the plan will be to use shims under the outside flange to get the inner portion just flush with the dropout. I plan to include a few shims with each set for this purpose.

Price? Probably $30 shipped for the pair of parts.

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