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Brakes. Love ’em or hate ’em, they’re important. Single-speeders may do away with gears, but even they continue to use brakes. Wild, I know.

So, just like with anything scary, it’s best just to talk about it, get it all out in the open. Below we’ll outline some of the in’s and out’s of the brakes and brake mounting options you will find on Sour bikes! Let’s go!

Sour Bicycles Big Fun
ISO brake adapter on the Big Fun, enduro hardtail

Flat Mount. What is it? And why is it on my frame?

If you’re looking at a Purple Haze, a Clueless, or a Pasta Party then you’ll probably have noticed that the brake mount looks a little bit different than brake mounts of yesteryear. Flat mount has been around for roughly just as long as disc brakes have in the road/gravel world, but they are a new face in the MTB world.

Flat mount allows us as designers just a little bit of extra breathing room as far as angles goes. It also allows for more creative, compact, and fun dropouts… all while keeping the weight down. And because our frames are steel, our flat mounts are more stable than most!

Purple Haze FM160

Nowadays all the Sour frames using the flat mount brake standard are using the 160mm standard, or FM160 “Direct”. What this means is the when the FM caliper is mounted without an adapter, it will be mounted correctly for a 160mm disc rotor. It’s as simple as that!

The Purple Haze and Clueless are maxed out at 160mm rotors, but the Pasta Party can go to 180mm if you need to. To achieve this, just add a standard 20mm flat mount adapter to your caliper… the same one your caliper would use on a traditional FM140 frame.

But what about the other bikes?

All other Sour bikes use an ISO brake mount. This is the brake mount you probably know about if you have a MTB’ing background. ISO was more or less the first standardised disc brake mount for bicycles (ISO is short for International Organization for Standardization, why it isn’t IOS is a mystery).

ISO brake mounts require an adapter to mount a standard post mount brake caliper, these will vary depending on the disc rotor you’d like to use.

Below we have outlined all the brake mounts for our frames. Any questions? Please don’t hesitate to send us an email, or ask your local dealer!

Purple Haze / Clueless
Frame: FM160, max. 160mm disc
Fork: FM160/FM140

Pasta Party
Frame: FM160, max. 180mm disc
Magura part no. QM51 for 180mm disc
Fork: Depends on fork

Crumble / Big Fun / Double Choc
Frame: ISO/PM
Crumble, max. 180mm
Big Fun / Double Choc, max. 200mm