rolling road

[spud]

wheel sizes:- would it make a difference if you put 15" or 17" on the same car to get a faster or slower result

 

[Prince]

Are we talking about bhp? If so, on the fly or at the wheels? Or are we talking about torque?

 

[spud]

bhp at the wheel

 

[Prince]

I don't know the difference between 15 and 17 inch rims, but I do know that a 16 inch rim with the same tyre profile as a 17 inch rim will put down more power. Not really sure why though.

 

[old-git]

I don't know the difference between 15 and 17 inch rims, but I do know that a 16 inch rim with the same tyre profile as a 17 inch rim will put down more power. Not really sure why though.

Assuming no tyre slip on the rollers and identical rolling circumference, the only variance would be the all up weight of tyre and wheel. The lighter combination will show a small increase in power transmitted to the rollers purely due to the reduction in weight that the engine has to turn.

IMHO

 

[obi_waynne]

Engine power would be unchanged but the reading might be altered.....

Does the gearing have a bearing on the power figure? Surely if the gearing is altered the power figure will slide up or down the RPM range.

For example a 17" wheel hitting 6000 rpm at 170nm
Compared to a 16" wheel hitting 5800 rpm at 170nm

I guess it depends if the RPM is based on engine speed or wheel speed and if this takes into account the gearing changes. (My head is still spinning from this one so put me right if i'm way out!)