# post to post adaptor for 180 post to 203 rotor



## Monster Truck (Sep 17, 2009)

The new Fox 36 has post mounts for a 180 mm rotor. Meaning you can run a 180 mm rotor without an adaptor. I am looking to run a 203 rotor. I am having trouble finding the correct adaptor. It has been suggested to get a 160 to 180 adaptor, but I am not convinced. Anyhow, anyone with specific knowledge on what adaptor to get and where to get one is appreciated.


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## cobba (Apr 5, 2007)

A 160mm to 180mm PM to PM adapter is basically a +20mm adapter, Avid now calls their 180mm PM to PM adapter the '20mm Post' adapter because there's different size post mounts and it can be used on them all.

140mm post mounts + '20mm Post' adapter = 160mm rotor
160mm post mounts + '20mm Post' adapter = 180mm rotor
180mm post mounts + '20mm Post' adapter = 200mm rotor
200mm post mounts + '20mm Post' adapter = 220mm rotor

With a '20mm Post' adapter or a 160mm to 180mm PM to PM adapter on 180mm post mounts you'd need about 1.5mm of extra packing under the caliper to place it in the correct position for a 203mm rotor.

A 160mm to 183mm post mount to post mount adapter is basically a +23mm post mount adapter, on 180mm post mounts it should place the brake caliper in the correct positionfor a 203mm rotor.

www.chainreactioncycles.com/hope-post-to-post-disc-brake-adaptor/rp-prod13728
http://northshorebillet.com/shop/post-mount-disk-brake-adapter/


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## Monster Truck (Sep 17, 2009)

Thanks, that should be easy enough


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## Monster Truck (Sep 17, 2009)

Follow up. To recap I am running a 203 front rotor on the new Fox 36. It comes with 180 post mounts. I need an adaptor to go 180-203, which is an item that does not exist by that name. So I purchased a Hope 160-183 Post to Post adaptor. It works perfectly with my Shimano XT brake. The rotor is in proper alignment with the pads and all is well in the universe. The key is that it is a +23mm adaptor. Good pics on Northshore Billet for install orientation.


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## cobba (Apr 5, 2007)

:thumbsup:


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## benhack (Oct 22, 2013)

Monster Truck said:


> The new Fox 36 has post mounts for a 180 mm rotor. Meaning you can run a 180 mm rotor without an adaptor. I am looking to run a 203 rotor. I am having trouble finding the correct adaptor. It has been suggested to get a 160 to 180 adaptor, but I am not convinced. Anyhow, anyone with specific knowledge on what adaptor to get and where to get one is appreciated.


I work at a shop and just talked to fox today about this -- i was trying to mount a 200 icetech to my 36 and thought all i would have to do is use the 160-180 adaptor (20mm increase). Fox doesn't suggest this, though. They make a specific unit for a 200mm post mount for the 36. It's $20 and you can order it directly from them -- which i would say is worth it. I've stripped post mounts out on a fork before and that sucks. 20 bucks to insure your $1200 purchase is worth it.

I also checked to see if Shimano was making anything specific for the 36 and couldn't find anything.

Cheers -

Ben


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## cobba (Apr 5, 2007)

benhack said:


> I work at a shop and just talked to fox today about this -- i was trying to mount a 200 icetech to my 36 and thought all i would have to do is use the 160-180 adaptor (20mm increase). Fox doesn't suggest this, though. They make a specific unit for a 200mm post mount for the 36. It's $20 and you can order it directly from them -- which i would say is worth it. I've stripped post mounts out on a fork before and that sucks. 20 bucks to insure your $1200 purchase is worth it.
> 
> I also checked to see if Shimano was making anything specific for the 36 and couldn't find anything.


* The two 183mm (+23mm) post mount adapters I linked above will do the same job as the Fox adapter.
* Ice-Tech rotors are 203mm not 200mm
* You could of used a +20mm adapter (160 to 180mm adapter) but you would of needed an extra 1.5mm of packing under each side of the the caliper to space it properly for a 203mm rotor.
* Fox wouldn't suggest you do that as they have their own adapter they want you to buy
* The Fox adapter won't stop you from stripping threads, you can strip threads with it just like you can strip threads with any other adapter if you tighten the bolts too much.

When this thread started the Fox adapter wasn't available, now that it is there's another adapter that will do the same job as the Hope & NSB 183mm (+23mm) post mount adapters.

Hope 183mm (+23mm) post mount adapter + Shimano brake + Shimano 203mm Ice-Tech rotor


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## cobba (Apr 5, 2007)

Shimano now makes a couple of 23mm adapters for fitting 203mm rotors onto 180mm post mounts.

Standard version: SM-MA-F203P/PM 
XTR version: SM-MA90-F203P/PM

The 180 to 203 adapters are basically the same as the 160 to 180 adapters, they're just a little bit bigger.

XTR & Standard 180 to 203 adapters: http://si.shimano.com/php/download.php?file=pdf/um/SI-0146A-000-00-ENG.pdf
Standard 160 to 180 adapter: http://si.shimano.com/php/download.php?file=pdf/um/SI-8170A-001-ENG.pdf
XTR 160 to 180 adapter: http://si.shimano.com/php/download.php?file=pdf/um/SI-8JB0A-001-ENG.pdf


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## 3names (Feb 7, 2015)

Hey guys i need some help. So bought a used bike and it has this combo for the front brake. Ihave fox 36 180 mm and i have a 203 mm disc on it with avid elixir 5. I went for a short ride and the brake works fine, but i am wondering isnt there supposed to be an adapter a 203 mm post mount? As you can see all i have is some washers betwen the caliper and fork mount.

You can also see that the brake pads fit the rotor nicely and there is no unused rotor surface. But still shouldnt there be an adapter? Or do some fox 36s have brake mount straight for 203 mm brakes?


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## love_that_flow (Nov 23, 2015)

Hope is the only brand i know that makes one. Chain reaction is the only place i have seen it.

Sent from my GT-I9505 using Tapatalk


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## cobba (Apr 5, 2007)

3names said:


> Hey guys i need some help. So bought a used bike and it has this combo for the front brake. Ihave fox 36 180 mm and i have a 203 mm disc on it with avid elixir 5. I went for a short ride and the brake works fine, but i am wondering isnt there supposed to be an adapter a 203 mm post mount? As you can see all i have is some washers betwen the caliper and fork mount.
> 
> You can also see that the brake pads fit the rotor nicely and there is no unused rotor surface. But still shouldnt there be an adapter? Or do some fox 36s have brake mount straight for 203 mm brakes?


Some Fox 36's did came with 203mm post mounts, I think they might all have 180mm post mounts now.

Re. the washers under the caliper, some but not all Avid calipers need those washers to place the caliper in the correct position over the rotor, your caliper is a model that needs those washers.

All looks good with your setup, if you ever change to a different brand of brake, you will have to remove those washers.



love_that_flow said:


> Hope is the only brand i know that makes one. Chain reaction is the only place i have seen it.


Shimano, Formula & Fox also make 23mm adapters (180mm post mount to 203mm rotor).


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## Jetta2010 (Jan 15, 2012)

I agree with cobba, all looks good. consider yourself fortunate that you get a little weight savings


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## jeffj (Jan 13, 2004)

Has anyone used the SM-MA-F203P/PM on a rear brake (I am using XT M785 brakes)?

I keep destroying 180 rear rotors on long downhill runs while my 203 front stays quiet and doesn't turn black/blue, even when I use the rear sparingly, and I'm hard on the front. . . . . Still squeals like an undead banshee. 

Ice Tech rotors don't seem to be any help either. Maybe worse than lower end non-sandwich'd rotors. Nothing new for me. I have always had to resort to 203 mm rotors front and back eventually. 

I'll probably also go back to resin pads from the metallic ones I am currently using, but I want to have braking to spare out back like I have up front.


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## cobba (Apr 5, 2007)

jeffj said:


> Has anyone used the SM-MA-F203P/PM on a rear brake (I am using XT M785 brakes)?


Do you have 180mm post mounts on the rear?


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## jeffj (Jan 13, 2004)

cobba said:


> Do you have 180mm post mounts on the rear?


Doh!!! A Homer Simpson moment. . . . . :madman: Not sure what I was thinking ut:

No, it has 160 post mount. Couldn't I just add a 180 to 203 adapter to the top of the 160 to 180 adapter?

LOL, just kidding! Certainly would not go that lo-tech even if it were possible.

Thanks for pulling my head out of a bad place


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## Fullblitz (Nov 23, 2016)

cobba said:


> Shimano now makes a couple of 23mm adapters for fitting 203mm rotors onto 180mm post mounts.
> 
> Standard version: SM-MA-F203P/PM
> XTR version: SM-MA90-F203P/PM
> ...


Can you use Shimano adaptors with Sram guide brakes?


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## cobba (Apr 5, 2007)

Fullblitz said:


> Can you use Shimano adaptors with Sram guide brakes?


Yes, but the adapter that you will need will have to be the right one for the rotor that you are going to use.


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## MarkMass (Sep 10, 2006)

Magura QM26

$10 online at Jenson, Universal, Art's, etc.


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## ka81ua (Oct 14, 2014)

RockShox pike soloair 27.5 . Right now there is a 200 mm rotor. 

I'l install saint br-820 with rt86 203 mm rotor.
Which adapter do i need?
I-SMMA90F203PPM
I-SMMAF203PPA
E-SMMAF203PPM


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## cobba (Apr 5, 2007)

ka81ua said:


> RockShox pike soloair 27.5 . Right now there is a 200 mm rotor.
> 
> I'l install saint br-820 with rt86 203 mm rotor.
> Which adapter do i need?
> ...


If you have 160mm post mounts and are currently using a 40mm Post adapter you would need a SM-MA-F203P/P

If you have 180mm post mounts and are currently using a 20mm Post adapter you would need a SM-MA-F203P/PM or a SM-MA90-F203P/PM


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## ka81ua (Oct 14, 2014)

cobba said:


> SM-MA-F203P/PM or a SM-MA90-F203P/PM


what's the difference?


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## cobba (Apr 5, 2007)

The latter is the lighter XTR version, they both do exactly the same thing.

Pikes have 160mm post mounts don't they?


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## ka81ua (Oct 14, 2014)

cobba said:


> Pikes have 160mm post mounts don't they?


Right now I don't have that fork next to me so unfortunately I can't answer that. Maybe someone else knows...


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## spikebike (Apr 26, 2007)

benhack said:


> I work at a shop and just talked to fox today about this -- i was trying to mount a 200 icetech to my 36 and thought all i would have to do is use the 160-180 adaptor (20mm increase). Fox doesn't suggest this, though. They make a specific unit for a 200mm post mount for the 36. It's $20 and you can order it directly from them -- which i would say is worth it. I've stripped post mounts out on a fork before and that sucks. 20 bucks to insure your $1200 purchase is worth it.
> 
> I also checked to see if Shimano was making anything specific for the 36 and couldn't find anything.
> 
> ...


Part number for the 200mm post mount for the fox 36? I find plenty of adapters for the 203mm, but not the 200mm.


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## cobba (Apr 5, 2007)

spikebike said:


> Part number for the 200mm post mount for the fox 36? I find plenty of adapters for the 203mm, but not the 200mm.


Ice-tech rotors are 203mm not 200mm, there's a mistake in that post you quoted.

If you want to use a 200mm rotor on a fork with 180mm post mounts, use a Shimano SM-MA-F180P/P2 adapter, it's basically an adapter that increases the rotor size by 20mm, on 160mm post mounts you would use a 180mm rotor with it, on 180mm post mounts you would use a 200mm rotor with it.


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## ka81ua (Oct 14, 2014)

spikebike said:


> Part number for the 200mm post mount


00.5318.007.003
https://www.bike-components.de/en/Avid/Disc-Brake-Adapter-40P-for-PM-to-PM-p29820/


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## cobba (Apr 5, 2007)

ka81ua said:


> 00.5318.007.003
> https://www.bike-components.de/en/Avid/Disc-Brake-Adapter-40P-for-PM-to-PM-p29820/


That's for a 200mm rotor on 160mm post mounts, it's not for a 200mm rotor on 180mm post mounts.

For a 200mm rotor on 180mm post mounts you would use any of the following adapters which increase the rotor size by 20mm......
https://www.bike-discount.de/en/buy/shimano-adapter-sm-ma-f180p-p2-for-front-180mm-37435
https://www.bike-components.de/en/Magura/QM40-Adapter-for-PM-to-PM-180-mm-160-mm-p42967/
https://www.bike-components.de/en/Avid/Disc-Brake-Adapter-20P-for-PM-to-PM-p43632/ * don't use all the washers supplied unless needed.
https://www.bike-components.de/en/Trickstuff/Scheibenbremsadapter-PM-Gabel-auf-PM-Bremse-20-p32887/
https://www.bike-discount.de/en/buy/formula-adaptor-front-180mm-postmount-6-54443
https://www.bike-discount.de/en/buy/fsa-adapter-pm-f-180-mm-db020-419512


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## fmendes (Jun 25, 2016)

Old topic, I know. Since I googled the issue and this seems to be the most complete topic around, I'm adding a bit more of information.

I have used on the rear an adapter +20mm with two valve nuts (the round ones) for a 203mm ICE rotor. I had measured the thickness of the nuts in 2.95mm, or 1.45mm beyond recommended. Looking closely, it is further out than the 160 to 203 adapter I have on the front. Still the pads are sitting fully on the rotors.


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## FactoryMatt (Apr 25, 2018)

torontocycles sells trick 1.5mm drilled Titanium washer spacers that do the trick for inline adapters.


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## fmendes (Jun 25, 2016)

FactoryMatt said:


> torontocycles sells trick 1.5mm drilled Titanium washer spacers that do the trick for inline adapters.


Sounds good. However a new adapter costs USD 10, while the two washers cost USD 5+5 for delivery. My suggestion was using stuff that most people have at home.


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## FactoryMatt (Apr 25, 2018)

3mm is too thick imo - better off going to the hardware store. but yes.


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## fmendes (Jun 25, 2016)

I was afraid 3mm would be too thick. In my case it worked, but is not assured will work in every case. In all cases, I agree - a good set of washers in the right thickness would be better.


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## Scott In MD (Sep 28, 2008)

Just adding knowledge to the database >>

The new 2020 Pike Ultimate 35mm stanchion X 120-160mm travel forks use a native 180mm post brake mount, so this fork requires a 23mm adapter, or a 20mm adapter with a 1.5mm spacer to run 203 rotors. The Shimano adapter is better, in my opinion, than spacers for this structural function. Also, pay attention to the length of the hex-head mounting bolts. If you are upsizing from 180mm you will probably need longer bolts to go to 203mm … in my case 30mm length on bottom and 20mm on top since the top bridge on the adapter is not as wide as the bottom bridge. This will make sense when you look at your adapter.


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## Scott In MD (Sep 28, 2008)

2mm works fine. It shims the very top of the pad off the rotor but to the best of my judgement doesn't matter. However, I think the SHimano F203 adapter rather than a spacer is the way to go to prevent wobble-gobble.


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## ka81ua (Oct 14, 2014)

Hello.
Some questions bout adapters.
It's PM180 on chainstay of frame. I use 180 mm rotor.

What "4-bolt" adapter (links, please) do I need to install rotor through the adaptor?


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## cobba (Apr 5, 2007)

ka81ua said:


> Hello.
> Some questions bout adapters.
> It's PM180 on chainstay of frame. I use 180 mm rotor.
> 
> What "4-bolt" adapter (links, please) do I need to install rotor through the adaptor?


 "4-bolt" adapters for 180mm to 203mm

https://www.bike24.com/p211559.html

https://northshorebillet.com/products/post-mount-disk-brake-adapter?variant=16836948097

* With the "4-bolt" adapter, the brake caliper would be moved back closer to the axle.


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## ka81ua (Oct 14, 2014)

cobba said:


> "4-bolt" adapters for 180mm to 203mm
> 
> https://www.bike24.com/p211559.html
> 
> ...


Just to clarify that - using pm180to203 adaptor I will be able to use my 180mm rotor on my frame with 180mm clamp, right?


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## cobba (Apr 5, 2007)

ka81ua said:


> Just to clarify that - using pm180to203 adaptor I will be able to use my 180mm rotor on my frame with 180mm clamp, right?


No, if the frame has 180mm post mounts on the chainstay, you don't need an adapter for a 180mm rotor, the 180 to 203mm adapter is for using a 203mm rotor on 180mm post mounts.

This thread is about adapters for a 203mm rotor with 180mm post mounts, I thought that's what you wanted.


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## ka81ua (Oct 14, 2014)

cobba said:


> No, if the frame has 180mm post mounts on the chainstay, you don't need an adapter for a 180mm rotor, the 180 to 203mm adapter is for using a 203mm rotor on 180mm post mounts.
> 
> This thread is about adapters for a 203mm rotor with 180mm post mounts, I thought that's what you wanted.


I used that thread just to ask about 180mm adaptor.
Once again, I want to use 4-bolt adaptor to install caliper on frame with 180mm mount with using 180mm rotor!
I don't want to install caliper directly to the frame.


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## cobba (Apr 5, 2007)

ka81ua said:


> I don't want to install caliper directly to the frame.





> It's PM180 on chainstay of frame


If the frame has 180mm post mounts on the chainstay, you will have to directly attach the caliper to the frame to use a 180mm rotor..


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## ka81ua (Oct 14, 2014)

cobba said:


> If the frame has 180mm post mounts on the chainstay, you will have to *directly* attach the caliper to the frame to use a 180mm rotor..


As far as I know there are some options (some of adaptors) that may help me with my idea. Installing them I will move a caliper backward-or-forward a litle bit but still it'll do the job..


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## senorbanana (May 11, 2017)

but why, just bolt on the caliper to the frame


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## cobba (Apr 5, 2007)

ka81ua said:


> As far as I know there are some options (some of adaptors) that may help me with my idea. Installing them I will move a caliper backward-or-forward a litle bit but still it'll do the job..


Any adapter that you put on 180mm post mounts would probably stop the caliper from aligning properly with a 180mm rotor.

I don't see any sense in what you want to do.


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## ka81ua (Oct 14, 2014)

senorbanana said:


> but why, just bolt on the caliper to the frame





cobba said:


> I don't see any sense in what you want to do.


thread in PM mount of frame.
Couple of my friends already has a problem with it.

ANyway, the question is about adaptor options.


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## ka81ua (Oct 14, 2014)

cobba said:


> Any adapter that you put on 180mm post mounts would probably stop the caliper from aligning properly with a 180mm rotor.


+- 1 mm is not a big deal. )


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## cobba (Apr 5, 2007)

ka81ua said:


> thread in PM mount of frame.
> Couple of my friends already has a problem with it.
> 
> ANyway, the question is about adaptor options.


How often do you need to remove the brake calipers?

Do your friends ever use a torque wrench?



ka81ua said:


> +- 1 mm is not a big deal. )


What adapter supposedly does this?

Have you seen anyone with this setup before?


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## ka81ua (Oct 14, 2014)

cobba said:


> How often do you need to remove the brake calipers?


as often as needed



cobba said:


> Do your friends ever use a torque wrench?


seriously? )



cobba said:


> What adapter supposedly does this?


If I knew - I guess that thread would never exist )



cobba said:


> Have you seen anyone with this setup before?


Once again - if I'd have seen something ...
No, I haven't, that's why I ask..

Anyway, if someone has seen something according to my question - you're very welcome. )

P.S. sorry for bad english, not my native.


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## ka81ua (Oct 14, 2014)

For now, what I found out (if anyone else needs that kind of info):
1) any stock adaptors in theory wouldn't work
2) one of options - cut the mount to "160mm rotor depth" and use a 4-bolt adaptor 160 - 180
3) draw your own 4-bolt adaptor and CNC it.


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## syl3 (Apr 23, 2008)

you do not need any adaptor.

fix the broken frame thread with helicoil.

or cut new thread in the next bigger size (M7) and use m7 bolt.


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## ka81ua (Oct 14, 2014)

syl3 said:


> you do not need any adaptor.
> 
> fix the broken frame thread with helicoil.
> 
> or cut new thread in the next bigger size (M7) and use m7 bolt.


question is about a looking for a correct 4-b ADAPTOR only. thank you.


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## cobba (Apr 5, 2007)

ka81ua said:


> If I knew - I guess that thread would never exist )
> Once again - if I'd have seen something ...
> No, I haven't, that's why I ask..


When you said...


> +- 1 mm is not a big deal. )


I thought you might have seen or heard of someone doing this.



ka81ua said:


> For now, what I found out (if anyone else needs that kind of info):
> 1) any stock adaptors in theory wouldn't work
> 2) one of options - cut the mount to "160mm rotor depth" and use a 4-bolt adaptor 160 - 180
> 3) draw your own 4-bolt adaptor and CNC it.


1) correct
2) Probably not a good idea to cut around 10mm off each post mount
3) Here's some post mount specs, I don't think you'll be able to draw up and make what you want.
* measurements on the seat stay will be the same on the chain stay











ka81ua said:


> question is about a looking for a correct 4-b ADAPTOR only. thank you.


There is no correct adapter, attaching the caliper directly to the post mounts is the correct way to attach it.


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## slomtbr (Oct 9, 2010)

ka81ua said:


> For now, what I found out (if anyone else needs that kind of info):
> 1) any stock adaptors in theory wouldn't work
> 2) one of options - cut the mount to "160mm rotor depth" and use a 4-bolt adaptor 160 - 180
> 3) draw your own 4-bolt adaptor and CNC it.


If there's a problem with the the threads in the post mount, use a helicoil to repair them.
If you're trying to solve a problem you don't have yet, buy a torque wrench and tighten the bolts to spec, and you'll be fine.
All images I've seen of 2016 Reigns have a 160mm post, with a +20mm adapter. Can you post an image of your rear brake setup?
Asking for a 180mm to 180mm adapter is useless, there is no +0mm PM to PM adapter. Even if there were, you'd have to use the existing post mount threads to use it.


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## ka81ua (Oct 14, 2014)

cobba said:


> When you said...
> 
> I thought you might have seen or heard of someone doing this.
> 
> ...


Thank you very much for all that info.

P.s. By the way, i don't see it as a serious problem - cutting mount -10 mm (and, of course, facing it after).
But, it would be a last last last option, of course, and will never happen I guess. )


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## ka81ua (Oct 14, 2014)

slomtbr said:


> If there's a problem with the the threads in the post mount, use a helicoil to repair them.
> If you're trying to solve a problem you don't have yet, buy a torque wrench and tighten the bolts to spec, and you'll be fine.
> All images I've seen of 2016 Reigns have a 160mm post, with a +20mm adapter. Can you post an image of your rear brake setup?
> Asking for a 180mm to 180mm adapter is useless, there is no +0mm PM to PM adapter. Even if there were, you'd have to use the existing post mount threads to use it.


Post #50.


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