I am confused about Hope 180/183mm rotors and what size rotor I really need.

To cut a long story about changing kit / upgrading forks and calipers I currently have a Fox 36 with a new(ish) post mount silver M4 caliper. The fork and new caliper were all sorted by my LBS. When the fork / caliper were upgraded I stayed with an old wheel that has an old 180mm Hope M4 rotor.

I have been sharing this wheel with my other bike with RS Pikes that also runs a 180mm front rotor but I am fed up of sharing the wheel between the 2 bikes.

So my thinking was just buy another 180mm rotor for my new wheel. Having looked closer I notice now Hope offer 183mm rotors. So what size should I really be buying for my Fox 36s + Hope post mount caliper?

Hope this makes sense.

Cheers

Rotor size has nothing to do with the brake, but the mount.

Shimano do good value floating rotors at 180mm and mounts to match.

Rotor size has nothing to do with the brake, but the mount.

My understanding is the opposite, the 3mm difference between 180/183 is set by the calliper, although in most cases it will just work. When I used a 200mm formula rotor with 203mm hope brakes is didn’t quite use all the brake pad made no difference when I also swapped over to a formula 200mm adaptor.

ps to the op, I think that hope used to be 203 but are now 200, best bet is to email hope with your model number, you will probably get the correct answer same day.

If you have post mount calipers then it’ll be set up for a 183mm rotor on the front, IS is 180mm.Due to production tolerances it may not make a difference as you’ve found, or it may mean your pads overhang the rotor’s edge, or it may mean that your caliper body touches the rotor edge, depending on which mix of parts you use.

I had Hope M4’s with 183mm floating rotors but they rubbed my forks. So I changed to Shimano 180mm floaters, but they didn’t quite reach the edge of the pads. So I got a Shimano 180mm mount and it’s fine.

So I didn’t change the caliper, just the mount.

I also recently noticed that adaptors can change the angle of the brake calliper slightly, effecting how the contact portion of the rotor passes through it. Also thinking about different widths of brake pads being matched up to different widths of the braking portion of the rotor. Although I didn’t used to think it mattered and could pretty match rotors, callipers and adaptors I would now always prefer to get a matching set to make sure everything is optimised.

Washers?

I’ve just had the opposite problem, and it is to do with the calipers.

I think that hope used to be 203 but are now 200

I think it’s the other way round: I have some old M4s, my newer 203 and 183 Hope rotors didnt fit so i had to get some old 2nd hand 200/180mm ones. Those helpful Hope tech guys told me over the phone that they changed a few years ago. It’s a pretty nasty bodge to make up the difference with washers.