Using a smaller disk rotor than suggested in a fork

Just putting together a mtb bike for the 9 yo and got the purchasing wrong so got 160mm rotors but the fork says minimum 180.

I will probably just end up buying the bigger rotor but before I do I was just wondering if the minimum size is typically some kind of geometry limitation or if it is solely weight related guidance. (Revelation 2016 fork).

If it is weight then obviously my kid is v light compared to an adult and he’s not going to be riding it hard so wondering if could get away with the 160 to start with until he grows a bit more??

Cheers for thoughts and info in advance!

If it’s minimum 180 then the caliper mount is likely not going to allow a 160 rotor

Something to do with the mounts I think.
My Rebas and Machette will take a 160 with no adapter, my Maz 66s take a 203 with no adapter.
I have seen adapters for going bigger but not sure it’s possible to fit one to go smaller.
[Edit] what he said three seconds earlier

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scotroutes
Full Member

If it’s minimum 180 then the caliper mount is likely not going to allow a 160 rotor

This

It will be the actual mount. When you attach the brake caliper without any adapters it will fit a 180mm rotor. You can go bigger by adding a +20mm adaptor but you can’t go smaller.

A lot of forks now have a 180mm rather than 160mm post mount as standard

I have seen adapters for going bigger but not sure it’s possible to fit one to go smaller.

Dremel make one 😉

Cheers for the replies, 180 it is!