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Old October 13th 17, 04:50 PM posted to rec.bicycles.tech
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Default Disc brakes, adaptors to increase rotor diameter

On Friday, October 13, 2017 at 8:15:57 AM UTC-7, Joerg wrote:
On 2017-10-12 09:26, jbeattie wrote:
On Thursday, October 12, 2017 at 7:36:15 AM UTC-7, Joerg wrote:
On 2017-10-11 18:16, jbeattie wrote:
On Wednesday, October 11, 2017 at 2:36:03 PM UTC-7, Joerg wrote:
The adapters to increase rotor size in a post-post situation
(which I have front and back) look like this:

http://i.ebayimg.com/images/g/oK8AAO...Au/s-l1600.jpg

My MTB has a factory one from 160 to 180mm up front but I am
considering 203mm. That would make the thing even more
extreme, like this where the screws would look more cattywompus
or out of line than they already do:

https://i.ebayimg.com/images/g/w4MAA...bTa/s-l500.jpg

Why are the spacings so different on both sides while for
160mm their are not?

The angle of the caliper changes as you get into the larger
rotor sizes and thus the disparity.


Understood. This is also what Ralph wrote. However, many calipers
such as mine have round pads where it doesn't matter if the angle
is slighlty different.


I don't know your brakes, but the rotor might hit the internals if
the caliper is not angled correctly. You want the mechanism following
the arc of the rotor, which is what you will get with your spacer.



It should also work with this spacer which avoids long screws:

https://erpimgs.idealhere.com/ImageF...963c864243.jpg

It moves the rotor out plus up so the angle should remain roughly
similar. Shimano has these as well but I just got an answer from Jenson
USA which carries them. They are flat and only 10mm (looks less though)
and my calipers need more "dive room" than that.

http://www.jensonusa.com/Shimano-F20...Z47&l=BR407Z47

So I'd need the bellied ones like in the link.


You also want to engage as much of the rotor as possible. I don't
think any of this is optional, is it? You just put in the spacer, and
you're done.


Just have to make sure it's the correct adapter. Adding a washer here or
there for fine tuning isn't a problem.


I'm still having this problem with why you would want disk brakes on a road bike in California. Extra weight, extra rolling resistance, extra cost, far too much power the way it was and there is little rain in California to worry about the slight delay in action between a rim and disk brake.
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