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Flat mount versus standard tab mounts for disc?

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Flat mount versus standard tab mounts for disc?

Old 10-11-20, 01:52 AM
  #26  
guy153
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Originally Posted by unterhausen View Post
I certainly agree about TA being expected nowadays. Bad news is I finally gave in and ordered a set of 12mm TA front dummy axles, so sometime in the next month the industry is going to announce they are going to 13.5mm TA.
When I finally gave in and got 15mm TA front dummy axles, it was the same month the industry announced 12mm TA front.
What thread pitch did you get?
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Old 10-11-20, 05:43 AM
  #27  
dsaul
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Originally Posted by guy153 View Post
What thread pitch did you get?
Dummy axles should not have threads that go into the dropout. TA dummy axles only go a couple millimeters into the dropout, so you can flex the frame/fork apart to remove the axle.
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Old 10-11-20, 06:55 AM
  #28  
unterhausen
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That's right, no threads. I'm really happy that paragon now engraves the size on the axle, it's a real pain looking for the right dummy axle. They aren't as pretty though

Fortunately, everything I have bought so far is 1.5mm threads. It's really annoying that there was no standard.
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Old 10-11-20, 04:14 PM
  #29  
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It's not just the thread pitch that's not standard. The Paragon dropouts all have an unthreaded recess on the threaded side, to allow for the dummy axle to fit, but some of the other manufacturers don't do this. This means you have to spend some time modifying the dropout or modifying your dummy axle to fit the minor diameter of the thread. I make my own dummy axles and I have 3 different ones for 12mm x 142. One with both ends at 12mm, one with a 12mm end and a smaller end to match the minor diameter of the M12 thread and one to fit Syntace dropouts.
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Old 10-11-20, 06:39 PM
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Not to mention that nobody can agree how big to make the recess so the paragon dummy axles don't fit anyone else's dropouts. Production bikes basically don't use the dropouts to register the axle in place, from the examples I have seen recently
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Old 01-15-21, 04:48 PM
  #31  
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Thanks for all the input everyone! I finally had a little time to build the frame and fork.

The flat disk mounts on the fork were surprisingly easy to do without a fixture. However, am a little concerned about the stiffness of the fork with the .9mm blades being able to handle the twisting force of the disk brakes. The braze on ISO tabs I am used to seem to add some notable stiffness to the fork blade. I guess I will know if this is a problem soon enough.

A couple pics of the first and probably last frame of Sausalito Frame Co, showing my weak photography skills, imperfect frame cleanup work and imperfect paint.



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Old 01-15-21, 09:12 PM
  #32  
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Did you just line it up with a brake caliper and wheel?

I am somewhat concerned about the lack of reinforcement with flat mount on a fork. Let us know if it works
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Old 01-16-21, 12:42 AM
  #33  
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I put the brake/adapter on the rotor in the right spot, squeezed lever, marked and drilled holes. Then attached bottle bosses to the adaptors and repeated the above mounting so the bosses were in place. Then some aluminum foil over spokes, brakes etc, and a quick tack in each boss with LFB. Disassembled and brazed with 56, careful not to melt my tack.

I fed in lots of material on them, and even built up a little fillet on the outside. So I donít think they will fail. Iím more concerned about the overall stiffness. But maybe they do fail, and maybe things are also not stiff enough. Or maybe neither. Will update when I have the bike assembled
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Old 01-16-21, 08:42 AM
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I'm not worried about the bosses failing, I worry about the fork buckling.

If I make one, I'm going to ask Harry at the bike shop to do some stoppies for me.

I always thought that it would be really clean install and I like it a lot better than any other brake mount. Perfect for a steel fork. Then I started worrying about the long term reliability.
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Old 01-17-21, 10:21 AM
  #35  
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I have built a couple flat mount steel forks now, the oldest being about 2 years old. I personally haven't used standard road fork blades because of their wall thickness, though I really want to try it as disc blades don't have the same ride quality. I used Reynolds disc blades, 631 and a stainless set of 921. I too used H20 bosses but only on the lower mount, for the upper I made a flat mount post out of 3/8" stainless bar stock. The upper boss has a rounded end that butts up against the inside of the fork leg, probably not needed but I thought it couldn't hurt to have some further buttressing. Anyhow, after 2 years and intentional hard front braking and yes even stoppies I can't see any signs for concern. I hope this work out for you TIm.
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Old 01-31-21, 10:19 PM
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Just a little update in case anyone else plans to do a flat mount on a regular road fork blade...

Iíve put a few hundred miles of trail and road riding on this thing and have had no issues at all. I thought there might be some stiffness issues, but itís plenty stiff. I wouldnít dare do this with a curved blade, but it seems to work great with a straight blade.
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