Hi on my nimbus 26 muni i want to change the cranks from 165s to 150s from my Oracle 24 but i cant get the crank bolts to loosen i have put WD-40 on it and it hasn’t helped dose anyone know of a way to get them to undo i have used a long Allen key and put all my weight on it and didn’t do it 
what should i do?
Thank you,
Sam
Well my first question is always going to be are you doing it the right direction? Crank bolts don’t care about which direction is front or back. It’s lefty loosey, righty tighty.
Second question, is it happening on both sides or just one?
yes i am turning it the right way and yes it is on both sides
WD-40 isn’t really meant for that. It might work. Or, as you’ve seen, not. A penetrating oil like “liquid wrench” would be the thing.
Also, I’ve been told to tap it with a hammer to set up vibrations which are supposed to help breaking it loose.
Hopefully that works, because resorting to heat can be problematic.
I use the 8mm socket. You can get more leverage
Use the gorilla method. Put a pipe on the hex wrench, and give it a quick turn. If the bolts were torqued up tight, and haven’t loosened during riding, they will be pretty tight. Remember a hand-held L-shaped hex wrench provides a lot less power than a torque wrench with a long handle.
I don’t recommend heat in this application, and “Liquid Wrench” or similar products will be ineffective, IMHO.
(Strokin99 beat me to it. That tool, combined with a long-handled socket wrench or breaker bar, will make short work of it.)
Thank you to everyone for helping and thank you very much LanceB i didn’t have a pipe so i used a seat post to extend the Alan key 
I take that to mean you got the bolts off?