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Disc brakes, adaptors to increase rotor diameter



 
 
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  #1  
Old October 11th 17, 10:36 PM posted to rec.bicycles.tech
Joerg[_2_]
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Posts: 4,453
Default Disc brakes, adaptors to increase rotor diameter

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?

--
Regards, Joerg

http://www.analogconsultants.com/
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  #2  
Old October 12th 17, 12:34 AM posted to rec.bicycles.tech
Joerg[_2_]
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Posts: 4,453
Default Disc brakes, adaptors to increase rotor diameter

On 2017-10-11 14:36, 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?


P.S.: Does anyone know whether these go from native 160mm to 203mm?

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

F/R probably means for front and rear. There are also F203 versions but
they look the same. Ideally I'd want 203mm rotors on both wheels because
the rack on my MTB is often heavily loaded.

--
Regards, Joerg

http://www.analogconsultants.com/
  #3  
Old October 12th 17, 02:10 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 77
Default Disc brakes, adaptors to increase rotor diameter

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?


Probably because the axis along which the brake gets extended is not
perpendicular to the outer surface of the disk, so as you slide the caliber
outwards, you have to rotate it a bit to keep it tangential to the outer
surface of the disk.

  #4  
Old October 12th 17, 02:16 AM posted to rec.bicycles.tech
JBeattie
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Posts: 2,696
Default Disc brakes, adaptors to increase rotor diameter

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. http://www.bikehugger.com/posts/road...vs-post-mount/

The deal with adapters is that they usually assume the resident posts are sized for 160mm rotors. That is a correct assumption for your bike. My CAADX was, amazingly, sized for a 140mm front rotor, so my 180mm adapter was actually a 160mm adapter.

-- Jay Beattie.
  #5  
Old October 12th 17, 04:04 AM posted to rec.bicycles.tech
Tim McNamara
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Posts: 6,681
Default Disc brakes, adaptors to increase rotor diameter

On Wed, 11 Oct 2017 18:16:20 -0700 (PDT), 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:


If you keep following that logic, you'll have a disc diameter of 622 mm.

Oh, wait....
  #6  
Old October 12th 17, 05:31 AM posted to rec.bicycles.tech
James[_8_]
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Posts: 5,643
Default Disc brakes, adaptors to increase rotor diameter

On 12/10/17 14:04, Tim McNamara wrote:
On Wed, 11 Oct 2017 18:16:20 -0700 (PDT), 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:


If you keep following that logic, you'll have a disc diameter of 622 mm.

Oh, wait....



Haha. I thought that, but couldn't be bothered typing it.

--
JS
  #7  
Old October 12th 17, 03:15 PM posted to rec.bicycles.tech
[email protected]
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Posts: 3,183
Default Disc brakes, adaptors to increase rotor diameter

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?


Your first adapter is the normal one used on all rear brakes for cross bikes as far as I know. Putting larger disks on road bikes is sort of counter-productive since the problem with them already is excessive power.
  #8  
Old October 12th 17, 03:36 PM posted to rec.bicycles.tech
Joerg[_2_]
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Posts: 4,453
Default Disc brakes, adaptors to increase rotor diameter

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.


http://www.bikehugger.com/posts/road...vs-post-mount/

The deal with adapters is that they usually assume the resident
posts are sized for 160mm rotors. That is a correct assumption for
your bike. My CAADX was, amazingly, sized for a 140mm front rotor, so
my 180mm adapter was actually a 160mm adapter.


My mounts are both native 160mm so ideally I'd like to go from there to
203mm without stacking two adapters. The front currently has a 160-180mm
adapter and for whatever reason that one also adds angle.

--
Regards, Joerg

http://www.analogconsultants.com/
  #9  
Old October 12th 17, 03:38 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,453
Default Disc brakes, adaptors to increase rotor diameter

On 2017-10-11 18:10, Ralph Barone wrote:
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?


Probably because the axis along which the brake gets extended is not
perpendicular to the outer surface of the disk, so as you slide the caliber
outwards, you have to rotate it a bit to keep it tangential to the outer
surface of the disk.


I wonder if that's critical for round pads. The 160-180mm that was
factory installed up front is angled but the calipers look like it
wouldn't have mattered.

--
Regards, Joerg

http://www.analogconsultants.com/
  #10  
Old October 12th 17, 03:45 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,453
Default Disc brakes, adaptors to increase rotor diameter

On 2017-10-12 07:15, 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?


Your first adapter is the normal one used on all rear brakes for
cross bikes as far as I know.



My bike has that kind on the front. I'd much prefer the type below
because it would avoid the extremely long screws that are otherwise
needed for a 160mm-native to 203mm-rotor conversion:

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

If they work for 160-203, which the sites that sell them don't really say.


... Putting larger disks on road bikes is
sort of counter-productive since the problem with them already is
excessive power.


It is for a often heavily loaded MTB where I sometimes get to the limits
of the current 180mm & 160mm setup. Where water contacting the front
rotor lets off some hissing.

--
Regards, Joerg

http://www.analogconsultants.com/
 




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