my 2 penneth

Ive run on a DD rolling road @ SCC I made 267bhp, I then ran at Track & Road
http://www.tracknroad.com/ it runs within 1.5% of HT's Proper SF901 Superflow Engine Dyno
http://www.dynoit.co.uk/ and I made 285bhp

Both roads are regarded as accurate and are calibrated on each run..... Rob runs in 4th with tyres enflated and its a twin roller jobby where as T&Rs is a single roller device and they run in 5th but according to Clint Gaskin this is fine as its all based around the ability of you car to accellerate the known mass of the drum. At T&R they run the car up so the roller was exactly spinning at 60mph then press a button, which callibrates something

I also ran at EA with no boost controller or manifold and made 295
as a joe public non techy I have no clue how much real power I have

and am not bothering running on a RR anymore
DD
T&R
EA