Flat mount caliper, IS frame solutions?

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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by morganb

Has anyone made an adapter to use a flat mount caliper on an IS frame yet? I'm considering building a Ti All-Road and would prefer to use current gen Shimano but it is only available in flat mount. I understand that flat caliper/post frame is likely not possible, but IS seems like it might be. Strangely competitive cyclist is selling an adapter that says it works post frame/flat caliper but it seems to just be the opposite.

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by joejack951

Competitive Cyclist does not sell a flat caliper to post frame adapter even though the description on the page claims they do. There is nothing of the sort in the drop down menu, only the reverse as you've noted.

I would need to sketch it out to fully show the interference but I don't see how IS tabs make the issue of adapting a flat mount caliper any easier. You still need to create a mounting surface very close to the axle while keeping the caliper centered on the rotor. The IS tab will nearly certainly interfere with this effort by either forcing the caliper too far toward the centerline of the hub or pushing it too far out like a post mount adapter would.

Maybe if you planned to run a 180mm rotor. Maybe.

by Weenie

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maddog 2
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by maddog 2

I've not seen one. I've seen post caliper/flat frame (looks bad but I've seen it...) but all the IS adaptors I've seen mate to a post caliper, not a flat one.

You can mix post calipers with the latest hydro STI. You just need to make sure the caliper uses a 2.3mm bore hose, rather than the latest 2.1mm bore. Which is any 'older' Shimano caliper basically.

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