Planning to use a Hope 185 rotor on my new build.

Have a set of Formula RX discs brakes turning up with I believe are standard 74mm caliper spacing.

The brakes will go on a pair of DT Swiss forks which are PM.

As far as I can see I have the option of the following:-

Avid 185 PM-PM adapter (although i’ve read that avid rotors are sligtly different to everyone elses?)

Hope Mount-H with 1mm spacers beneath mount (or caliper) (183 adapter, so 185-183=2 divided by 2 = 1mm)

Any ideas?

you can get 185mm adapters but shimming a 183mm will probably be fine.

Just make sure you use a decent quality flat washer (not a cheap one that is stamped poorly so curved). The washers that normally come with brake caliper bolts are normally pretty flat or pick up some stainless ones for a £1 or so on ebay/toolstation.

Remember some adapters don’t just move the caliper away by 10mm at each hole so check the pad/disc contact is okay but 1mm on both holes shouldn’t be any problem.

185mm adapter (expensive): http://www.chainreactioncycles.com/Models.aspx?ModelID=50119

I had the same problem but ended up giving up on it.

Avid 185 PM-PM adapter

The Avid adapter is for Avid callipers and uses the tri-align cup/cone washer things to space it out. So if you stick an non-Avid calliper on there it won’t be in the right place. Also the surfaces aren’t flat so you can’t really space the calliper out with normal washers – I tried it but it wasn’t pretty and I didn’t fancy my luck with it so I took it off again without even testing it.

The NSB one linked to by andyl is the only 185mm PM-PM adapter for non Avid brakes that I’ve seen anywhere. It’s a bit pricey, you could probably flog your 185mm disc and buy a 180/183mm one for the difference.

“The Avid adapter is for Avid callipers and uses the tri-align cup/cone washer things to space it out. So if you stick an non-Avid calliper on there it won’t be in the right place.”

If that were true, how come you can bolt any ‘normal’ PM caliper straight onto (avid with tri-align conical washers) onto a ‘normal’ 160mm PM fork or frame?

My superstar PM 160-203mm adapter works with my avid elixir caliper (with tri-align conical washers) on a 203mm rotor?
As do my juicys (with tri-align conical washers) on shimano 180mm adapters on 180mm rotors?

If that were true, how come you can bolt any ‘normal’ PM caliper straight onto (avid with tri-align conical washers) onto a ‘normal’ 160mm PM fork or frame?

I must be misremembering what the problem was exactly (this was over a year ago) but certainly when I tried to fit a Shimano calliper to my Avid 185mm PM-PM adapter it didn’t work, the calliper fouled on the disc and didn’t sit flat on the adapter.

Firstly, are you sure it’s a Hope 183 disk? AFAIK, Hope only make 183’s, therefore you need a hope ‘H’ adaptor. If it’s an Avid 185 disk then you need the adaptor linked above by andyl, otherwise you can shim the hope ‘H’ or any non-avid 180 adaptor to fit, just make sure the bolts are long enough. Alternatively, buy a standard 180 rotor and a non-avid adaptor (Superstars are fine for a fiver).

The issue with Avid 180 & 185 PM-PM adaptors is that the faces of the adaptor are not flat and they rely on the CPS washers to account for the difference. You can use an Avid caliper & washers with any other manufacturer’s adaptor (as james said), however you can only use the Avid 180 & 185 PM-PM adaptors with Avid calipers & CPS washers.

it’s definitely a 185 rotor.

i have bought a H-mount from Wiggle (in black, so it will match the black formula mount on the back).

looking at it logically, if i add a 1mm washer between the mount and the caliper, it will move the caliper out 1mm at the correct angle. this should leave me with the correct spacing for a 185mm rotor (as per AndyL’s suggestion).

if you need more the retainer on presta valve stems works.

When I bought my new Pro3 AM4 wheels they only had 185mm rotors available so I did the “1mm washers under the caliper” mod and it’s working without issue.