Just flown with Ryan air. The allowance for a bike is 30kg
Sporting or musical equipment including but not limited to large fishing rods, golf clubs, bikes* (bikes have a weight limit of 30 kilos), scooters, fencing equipment, pole vaults, javelin, surfboards, bodyboards, snowboards and skis and large musical instruments including but not limited to harps, double bass and drums are inherently unsuitable for carriage by airlines operating fast turnarounds such as Ryanair. However, these items may be carried in the hold of the aircraft in addition to your personal checked baggage allowance up to a limit of 20 kilos per item upon payment of a discounted online fee of £50/€50 per item, per one way flight. If the item is purchased at the airport or through a Ryanair call centre a higher fee of £60/€60 per item/per one way flight will apply). Any sporting and musical item weighing over the 20 kilos allowance will be charged for the excess at the applicable excess baggage rate per kilo.
From http://www.ryanair.com/en/terms-and-con ... kedbaggage
They never asked what was in the box or even weigh it just asked how much it weighed