Does the XT disc need a spacer using post mounts?

[Rich Beaudoin]

Hey v-salon collective wisdom,
Setting up a newly-built frame to weld the rear post mount, the caliper seems to sit too low to clear the rotor.
I am using Paragon BK2016 post mount, DR2091 dropouts and a 160 rotor.
In pics, I generally see XT & XTR calipers set-up directly to the post mount, but it seems like I would need to use those little 'CPS' spacers/washer/bolts to make this work.
Please educate me

[Todd Mosley]

I'm not clear from your post - are you about to weld the mount on? If you are using an Anvil Post Punk, set it on 160 and weld on. You probably won't need an adapter. If you aren't using a Post Punk or some other post mount jig, it will be hard to line up just perfect and you'll probably need some spacers to get it just right. That post mount is made for 160mm but it will usually need some grinding to fit just right unless your seat stays are lined up perfectly.

If this is a frame you bought, the BK2016 post mount is made so that the frame builder will only need to do minimal fitment to weld it in place so that it lines up for a 160mm rotor. But, if you grind on it enough, it could work for 140mm

[EricKeller]

mine doesn't have any spacers. Do you have a post-specific fixture?

[Rich Beaudoin]

image.jpg
Sorry, yes I am building it. I've built 8-10 disc frames, but all were IS mounts. This is my1st post mount.
My understanding from Paragon is that this mount is specific to these dropouts and specific to 160 rotors.
I don't have a Post-punk (and my Feng shui won't work for post mount) so I will rig something to tack it in place.
The pic shows how the mount doesn't touch the D/O with the caliper bottoming out on the rotor.
Rich

[Moustache]

I have never seen an XT disc caliper use spacers for a 160 post mount. I don't think that would be a viable solution for what you have pictured either.

[Too Tall]

This thread should be in Path.
#moved

[Jonathan]

Small frame, no? Tight rear triangle? You need a minimum seat stay angle to get Those parts play nice. There is more fab in you future.

[Rich Beaudoin]

Small frame, no? Tight rear triangle? You need a minimum seat stay angle to get Those parts play nice. There is more fab in you future.

With a more open triangle, wouldn't the mount just rotate around the D/O at the same distance from the axle?
This is actually a pretty 'normal' size frame. I definitely have more fab to make this work

[Jonathan]

With a more open triangle, wouldn't the mount just rotate around the D/O at the same distance from the axle?
This is actually a pretty 'normal' size frame. I definitely have more fab to make this work

Go check the paragon website, your answer is right on the product page.

"Note: if using this mount with our Syntace dropouts, the lower edge of the mount may need to be extended by the builder to get the correct position for the mount."

[steve garro]

Every frame shop needs a good chunk of 1/4" plate laying around


- Garro.

[Rich Beaudoin]

Thanks everyone, I did not notice that info on the Paragon site.
I have some material that will work.
Rich

[Rich Beaudoin]

image.jpg
I was able to get this welded perfectly.
I filed a small piece of metal to fit the dropout on bottom and flat on top, then I cut off the pre-mitered area of the brake mount so it would sit flat against the top of the other piece I had made. Additionally I used a small wedge-shaped piece to give the two pieces support and so I wouldn't worry about the strength.