Here is a much better explanation, I would never be able to explain it so well.
(http://www.fordpower.org.uk/index.php?topic=10546.45)Grey mate forget about the wheel figures on MAHA dyno's or ones like them.
It's not a wheel figure like you understand it to be.
MAHA dyno's don't estimate the drag they actually measure it.
The tyre sits in between two small rollers & deforms a lot which creates huge drag!
Also drag increases with rotational speed not constant like most people or dyno calculations would have you believe.
I use a MAHA dyno, you set it up like most other dyno's but at the end of the run you dip in the clutch & let it coast down which don't take long as it's a resistance dyno.
It measures the drag from the clutch back including the huge drag at the tyres & then takes that away from the measured power that was calculated from a variable resistance setting calculated & controlled by time, then it gives you a wheel power figure but more importantly a crank figure that is actually measured rather than guessed!
For wheel figures they are useless for comparisons.
For crank figures they are probably the best chassis dyno on the market.
The MAHA 4wd dyno was developed in partnership with Audi/VW for their quattro cars & is the only dyno they recommend their cars to be used on. Even has an instruction manual & part numbers from Audi.
Also BMW, Merc. Porsche & Ferrari use them at the factories to test the high spec cars that come off the production line to see if they are within spec.
Makes them the only dyno they recommend too!
The crank figure will be with in 2% Jurgen unless the operator made a mistake which it don't look like it to me.
To sum up
MAHA wheel figures are useless for comparisons, crank figures are ultra accurate & are proven to be.