Depends, where are you flying from? we flew from Luton, she weighed the bikes but Mr MC has this knack of propping the bag up subtly with his foot so they don’t notice! coming back in Geneva they were insistent that I stood away from the belt to weigh the bags properly, Mr MC was 30k and mine was 28k however they didn’t charge us extra even though the TOTAL baggage allowance is 32k! And my 85litre rucksack clearly DIDN’T weigh 4k!!
If you fly from Gatwick they have these metal barriers over the conveyor belt which stops them from weighing the bikes.
Mates travelling from Bristol have had bikes weighed, this time they checked his bike knowing it was over weight. Allowed him to put bag on not saying anything. He was waiting in the departure lounge to go when his name was announced and he was taken out to tarmac saying his bag was too heavy, he had to take some stuff out and put it into his girlfriends bike bag! craziness!!
By paying for a bike your personal weight limit is 32k, if you have just a bag then the limit is 20k. the max you can fly is 50k and they will charge you (or may depends on how nice check-in people are).
So in short who knows! If they weigh it do the foot balancing trick! oh and good luck, let us know the answer from the airport you fly with!!