Difference between engine horsepower and wheel horsepower

We had a customer call in today with a Caliber SRT-4 that was suprised when I told him that his bone stock Caliber SRT4 probably has 255 wheel horsepower.

He stated that he bought his Caliber SRT-4 with 285 horsepower, not 255.

Just to clarify to anyone who may not know, there is a drop in power by about 10-15% on all cars between the engine and the tires. Why you might ask?

Its because of friction. Sure, the engine is rated at 285 horsepower, but by the time the power is put through the transmission, through two axles, two hubs, wheels and tires, you lose power.

Here are some interesting factory horsepower ratings and real world horsepower at the wheels we have seen:

2000 Ford Focus factory rating 130 hp, at the wheels 106 hp

1997 Dodge Neon 150 hp rating, at the wheels 121 hp

2003 Dodge SRT4 215 hp rating, at the wheels 225 (this is because the factory underrated the horsepower)

2008 Chevrolet Cobalt Turbo 260 hp rating, 242 hp at wheels

2008 Dodge Caliber SRT4 285 hp rating, 258 hp at wheels