This dratted kindy vacation season is cutting into my cash reserves, but at least I have a bit of time to play. Today I decided to see just how fast I could ride 22km. Turned out I got this..

http://www.endomondo.com/workouts/ogVAY_qz_bA

That gives an average speed of 28.3 km/h and a maximum speed (briefly) of 52.6 km/h. This on my mtb, But, I think I'm hitting a limit either physically or in terms of my ride. Its almost impossible to maintain a pace of more 39 km/h on the flat without spinning so fast I go anaerobic and have to slow down after a few minutes.
Anyone managed to get modified (wide tires) mtb moving faster than 40 km/h on the flat without hitting the redline? Running 44/11 and the largest gear and the bike weighs in about 16kg with a full water bottle. Flat bar (being an mtb and all...)