I like my Vanmoof B5, but one thing I find very poor is the braking performance. The bike comes stock with 140mm rotors and no-brand mechanical brakes.

I thought I'd upgrade the brakes, going quite a bit overkill for a commuter bike, purchasing a Shimano 180mm rotor for the front and Shimano SLX hydraulic brakes. With this kit, I also purchased a SM-MAF180 disc brake adapter.

How ever, when I mount the rotor and the adapter, the rotor still appears to be approx. 20 mm "too big".

Below is an image of the stock setup.

enter image description here

Does this fork have a non standard post mount, or have I just purchased the wrong adapter?

  • Be conscious that your new powered-up brake could cause the axle to come out of the dropouts under braking. Its good you have axle nuts, but be sure to do them up properly.
    – Criggie
    Aug 7, 2016 at 19:46

1 Answer 1


Mountain bike forks will normally direct mount to fit a 160mm rotor. The 180mm adapter you purchased will add 20mm to rotor size - so should (might) work with a 160mm rotor. You would need an adapter to increase 40mm rotor size ir you want to go to a 180mm rotor.

You could try a 203mm adapter or drop back to a 160mm rotor - either might work but I have not had experience with this setup.

Looking at the post mount, I would be a little concerned the mounts are up to the forces a 180 rotor could generate and would be checking the specs from the fork manufacturer.

  • 1
    That makes sense. I was wondering what the "normal" value was. I will order swap the 180mm disc for a 160mm and see how that goes. 180mm was indeed very overkill.
    – Theodor
    Aug 7, 2016 at 9:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.