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Dyno - Does Wheel Size Matter

NUT515

By NUT515,
in General Automotive Discussion

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NUT515

Posted
Posted

Hey guys just a quick question. We all know that increasing rim size and there fore overall rolling circumference of our tyres can throw our speedos out but can we make more horsepower and if yes is it signifigantly difference between different size tyres.

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adamskill Mentor

adamskill

Posted
Posted

Hey guys just a quick question. We all know that increasing rim size and there fore overall rolling circumference of our tyres can throw our speedos out but can we make more horsepower and if yes is it signifigantly difference between different size tyres.

yes in theory it can.

No, dont got and put 22's on your car.

*LOACH* Veteran

*LOACH*

Posted
Posted

I am interested how the wheel diameter difference affects the horsepower the dyno reads?

I understand the skinnier tyres/lighter wheels but if these are equal and the only difference is the actual diameter of the wheels why would the horsepower measured change?

Power=forcexdistance / time

Force in the dyno is calculated by the accelaration of the drums (not measured through the spark reading for engine RPM) and the weight of the drums which is a known constant as is the distance (the circumference of the drums).....I am probably missing something obvious but I really don't see how rim size affects horsepower.

mad082 Grand Master

mad082

Posted
Posted

you have a point regarding the equation. i was wondering the same thing about that. i think that is why using a different gear doesn't alter the readout by much. however i think there is still a slight variance in there. and going to bigger wheels gives a taller ratio which will have a small effect on power. but i think more of it probably comes from the weight difference of the bigger wheels.

and if it does make a difference, this may play a part in how some people are able to get higher readings from a car running a stock ecu/turbo, other than the usual "happy dyno" call.

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