Post to Post rotor adaptor

slc123

Hi All,

I've encountered a slight issue on the latest bike build. my RS Yaris have 180mm direct mount for the rotors, but the rotors I bought secondhand turned up and the front one was 200mm. Assuming I need to get an adapter and can see on CRC that hope do one for about £13 which is the 160mm - 180mm. Effectively a 20mm+ adapter.

Does anyone know if this is correct and if there are any cheaper alternatives?

Thanks

cooldad

Yes and yes. Look around. Probably a fiver on EBay without the Hope name.

The Rookie

https://rover.ebay.com/rover/0/0/0?mpre ... 2780936293

slc123

Thanks Chaps.

Ordered one now!

slc123

So, I ordered the 180 adaptor, but I still can't get it to fit! The Centreline Rotor is definitely 200mm and the post direct mount is 180, so slightly confused as to why it still won't fit. I would say it probably needs another 5mm maybe.

Assuming a couple of washers might be the way forward?

Any ideas other ideas?

slc123

Got a solution, going to ditch the 200 front rotor and go with 180, seems more than enough!

cobba

What brakes are you using?

slc123

Guide R brakes

JGTR

Surely you need a 200mm adaptor for a 200mm disc?

I think because the calipers don’t sit inline with the centre of the disc it’s not as simple as just adding a few mm, the adapter needs to be the specific one for the job otherwise they would just be sold as 5mm,10mm adaptors etc.

Could be wrong though

cooldad

Nope, 20mm is 20mm.

Could be a 203mm rotor though?

Or adaptor is upside down.

slc123

cooldad wrote:

Nope, 20mm is 20mm.

Could be a 203mm rotor though?

Or adaptor is upside down.

Rotor says 200 and as far as I know sram don’t do 203 but 3mm looks about right so could be. Will investigate further. Pretty sure the adapter had an arrow showing the direction but will double check that too.
I’m doubting whether I’ve put it on the right way though now as it was a bit of a rushed job!

JGTR

cooldad wrote:

Nope, 20mm is 20mm.

Could be a 203mm rotor though?

Or adaptor is upside down.

Can’t see it myself, especially as Hope have fitted radially mounted calipers to overcome the specific issue of needing adaptors for different disc sizes. Hope mount their calipers centrally on the disc so you just fit spacers to change disc size, just move calipers in and out basically. Current standard is to fit calipers off centre so they need soecific adaptors depending on the size.

Personally I think the issue is that you have the wrong adaptor, you need the 180 to 200mm adaptor. If you look at the link below it seems pretty obvious that the difference between the 180 & 200 adaptor is not just an extra 20mm on the posts? Because the calipers are not mounted radially it’s not just a case of adding 20mm as the calipers need to move up and out.

PS Evans and CRC say to use the 203mm for a 200 disc?

slc123

Ok I’ve checked it and it’s definitely the right way round and just doesn’t fit. Where was the link you mentioned? Thanks

slc123

I’ve found this https://sram-cdn-pull-zone-gsdesign.net ... unting.pdf

Which to me suggests I may well need some spacers to get the configuration right.

This would presumably do the trick? https://www.merlincycles.com/avid-post- ... gKTkPD_BwE

JGTR

slc123 wrote:

Ok I’ve checked it and it’s definitely the right way round and just doesn’t fit. Where was the link you mentioned? Thanks

http://www.chainreactioncycles.com/mobi ... 119f9f49bd

JGTR

slc123 wrote:

I’ve found this https://sram-cdn-pull-zone-gsdesign.net ... unting.pdf

Which to me suggests I may well need some spacers to get the configuration right.

This would presumably do the trick? https://www.merlincycles.com/avid-post- ... gKTkPD_BwE

Problem is that the Avid guide does not list 180 post as an option for the forks, it only lists up to 160 so no way of knowing if that kit will fit.....are your forks definitely 180 Direct Mount??

cooldad

Apologies, I thought the new Sram brakes didn't need the stupid CPS washers/cups like the old Avids. Looks like some they might based on this.

https://www.worldwidecyclery.com/blogs/ ... ake-review

If so just make up the 5mm with those - if you have an old V brake lying around, they are the same bits used for the pad adjustment.

JGTR

http://forums.mtbr.com/brake-time/post- ... 21446.html

cobba

An extra 5mm of spacing under the caliper is equivalent to a 10mm increase in rotor size.

Are you sure that your Yari has 180mm post mounts?

Yari with 160mm post mounts, Guide brake, 200mm rotor and 40mm post adapter.
https://ep1.pinkbike.org/p5pb15427072/p5pb15427072.jpg

Yari with 180mm post mounts, Guide brake, 200mm rotor and 20mm post adapter.
https://ep1.pinkbike.org/p5pb15008985/p5pb15008985.jpg

With 160mm post mounts, the top post mount sticks out further then the bottom post mount.
With 180mm post mounts, the two post mounts are about the same size and are parallel to the fork leg.

Some more photos showing different post mounts on some Yari forks.

https://static.bike-components.de/cache/p/z1/4/4/RockShox-Yari-RC-Solo-Air-Boost-51-Off-Set-27-5-29-Federgabel-Auslaufmodell-diffusion-black-160-mm-1-5-tapered-PM-QR15-44739-131425-1481268022.jpeg

https://static.bike-components.de/cache/p/z1/5/6/RockShox-Yari-RC-DebonAir-Boost-51-Off-Set-29-Federgabel-Modell-2018-diffusion-black-160-mm-1-5-tapered-15-x-110-56880-178515-1492004413.jpeg

slc123

cobba wrote:

An extra 5mm of spacing under the caliper is equivalent to a 10mm increase in rotor size.

Are you sure that your Yari has 180mm post mounts?

Yari with 160mm post mounts, Guide brake, 200mm rotor and 40mm post adapter.
https://ep1.pinkbike.org/p5pb15427072/p5pb15427072.jpg

Yari with 180mm post mounts, Guide brake, 200mm rotor and 20mm post adapter.
https://ep1.pinkbike.org/p5pb15008985/p5pb15008985.jpg

Hugely helpful, I think they must have changed the post mounts on the newer Yaris, mine definitely looks more like the 160 post mounts as they are different sizes, I’ve decided to purchase a 180mm disc and the 40mm adapter so I’ve then got the options for both and see which works better. I’ve heard the 200 rotors can often be a bit much and not engage the brake properly. I always intended on 180, but when I bought the rotors secondhand one turned up as 200.

Thanks for all your help on this topic guys. Certainly not as straight forward as I thought!