Sportives are cycling events for cyclists who want to pretend to be in a race, but can't be bothered to join a club and/or become a member of the national sporting body.
They dress up in their fancy kit and ride round the course as fast as they can, knowing that they are being timed and those times will be on the internet for anyone to view.
Most Audax organisers set the Maximum speed to 30 kmh, as per ACP. For a 200 km ride, its pretty fast and not many get back before the final control opens. A 100 km ride however is about the right distance to hammer round and beat the 30 kmh limit.
For 100 km rides, many oganisers set the Max speed at 30 kmh simply because there are lots of raceboys without mudguards who chose not to pay the rediculous fee to ride a Sportive. It was 20 kmh once upon a time when mudguards were compulsory.
[One aspect that annoys me is the raising of the minimum speed by many organisers from 10 to 15 kmh. This discounts a lot of youngsters ( school age ) from enjoying a 100 km BP ]
Audax rides that are organised by cycle clubs usually have a competative slant in each of the distances. There will be rival clubs attending and speeds will be high. For anyone who want's a speedy 200, go on the Beacon Cotswold Expedition. Beacon, Halesowen, Wolverhampton, Solihull, Worcester, Evesham and Cheltenham will all be there. Tag along with the group if you dare.
As I have said before, there is NO helmet ruling. You could wear a blonde wig and be ushered to the front, and then to the back when they see your backside is a bloke's