will the size of wheel afect the h/p #, if you have 17"factory wheels or and factory 18"if so what whoud be the diffent

 

the heavier the weight, the more power you will lose trying to get them to spin...size doesnt matter, only weight...

 

there was a guy on here who posted something on this. he went from 17's to 20's and lost 8rwhp

 

I think size does matter, I could be wrong but if you turning a 20" wheel compared to a 17" wheel and the weight was the same I think the 17 woudl read higher. I think anyway.

 

No, it shouldnt change anything if they weight the same becuase they are the same diamete around...if you go for a bigger wheel, you get a smaller sidewall tire.

Loss in RWHP is typical if the wheel is heavier, which 20's usually are compared to a 17...

The Loss of RWHP is because the power is lost in trying to turn the heavier wheels. Its the same kind of theory behind the driveshaft...if you change out the driveshaft for something lighter, you are able to free up from extra hp.

This is just the same, except reverse. There is no such thing as a free lunch...if you want to do something to your car, you are going to have to give up something else. To ride on 20's you are going to give up a few ponies and maybe a little bit of gas mileage. Now i'm not saying that your engine will produce less power, its just that the power is lost in teh drivetrain and not put to the ground.

 

Yeah I know that the 20" does loss you hp to the engine, you just free up more hp to the wheels with a smaller rim.

 

Wish more people understood this concept... every mod is a compromise.

Anyway... just like was said, its the weight of the wheels that hurt, not the size. But I do want to add1 thing. Changing the overall diameter of the tire will change the effective gearing of the car also, and will have as great or greater effect than the weight can. taller overall tires will make your gears seem higher (i.e. make your 3.55's act like 3.31's). An shorter tire will do the exact opposite (3.55's maybe seem like 3.73's) Keep in mind that while what I am saying won't hurt you on the dyno, but when you have the car in the real world, on the street, its going to be very noticable.

 

Well said...!!