So I have a cube stereo 160, the back end comes with a post mount direct to 180mm brake set up, I am trying to put a 203mm rotor on there and can’t seem to get an answer from my cube dealer as to which adaptor I need to use, I have tried a shimano post to post 180mm adaptor both ways, and a 203mm post to post both ways and neither works?

or does no such adaptor exist?

The 180 one ought to do it I would have thought. That should be a 20mm increase on the standard 160. Is the caliper too close or too far away?

thats what my cube dealer said, and it does make sense in theory, but when you try it, one end of the calliper sits on the disk, and if you flip the adaptor the other end of the calliper sits on the disk

….and the 200mm one moves the calliper too far out does it?

How about introducing some washers as spacers between the adaptor and the post mounts on the frame? Sounds like you might need only a few mm on one of the posts to get the calliper to sit at the right height to ensure the pads are making full contact with the new larger disc.

Hope do a series of washers from 0.5mm to 2mm in 0.5mm steps that I used to use on IS mounts to centralise the calipers and probably still do.

not so much too far out, just not in the correct position, its almost as if it needs the same as on the 180mm adaptor where the spacer is on the actual bolt, so 20mm spaced directly on both bolt holes if you get me

Pictures please. Are you sure its not a 160 180 (EDIT!) spacer that you’re using?

ok so this is it standard with 180mm rotor:

and yes I have tried it with the 180mm adaptor that came off the front brake, checked the part number and everything

It doesn’t sound to me like the frame mounts can be 180. It shouldn’t be possible to come up too short with any adapter as they all add at least 20mm.

2 secs and ill take some pics of it with both the 180 and 203 adaptor

There are rear specific adaptors and Ive sometimes wondered why. Did you say you’ve been trying it with the adaptor off the front?

Avid brakes per chance?

yes a standard shimano 180 post to post adaptor from the front, my cube dealer also sent me the exact same one for this purpose, here it is tried both ways:

as you can see it makes the calliper rest on the disk on one side

here it is tried with the 203mm adaptor, both ways:

Doesn’t sit on the disk far enough

Then can’t get the calliper to even touch the adaptor

Washers under the shorter adaptor post looking at those pics. Or try and get a rear specific adaptor and see if it’s different.

EDIT: from the 180 adaptor pics. The 203 adaptor looks like an increase in 15mm to me.

thats it see i was trying to avoid bodging it on, was hoping there was a specific adaptor for this but looks like cube has made their frame 180 specific, been looking everywhere for adaptors but cant seem to find anything

Conical washers such as those used on avid brakes would probably make it perfect.

I understand where you’re coming from OP, however the washer approach is not really a bodge, I see it as fine tuning 😀

Paint them black and no one will know… Until you point them out of course 😉

Well waiting to hear from cube directly and the main uk cube dealer.. but will try the conical washers in the meantime

If the standard post mount rear size is 160, might a hope mount for a 183 disc do the trick?

no the standard post mount rear size on this frame is 180, thats why this is turning out to be such a problem

I realise that, but what you’re trying to do is accommodate and extra 23mm of rotor diameter. Hope have the same difference between 160 and 183 so might have a mount that would take 180 to 203 is what I meant.

ah i see what your saying, will have a look into it

I tried a bodge on my last FS bike…

IMAG0493 by pten2106, on Flickr

Solved with an Avid adapter.

IMAG1080 by pten2106, on Flickr

Notice the subtle difference in height with the upper mount.
Adapter was this one.

IMAG1082 by pten2106, on Flickr

Ah I see, thankyou