do you lose horsepower going from 17's to 18's??

[rsxballa]

The guy in my local auto accesories store told me that if you go 18s you lose some horsepower.. i was just wondering if anyone else has ever heard of this?

[goinbig]

yes, The larger the diameter, the more the vehicle has to work to make them turn. Going up just an inch wouldn't hardly be noticable. You can always just get a slightly lower profile tire to make up the difference though

[Dsilver]

I agree...

[airtight_python]

Not necessarily. If you use low profile tires and keep the same overall diameter as original it will probably be the same. If the wheel is a lighter aluminum wheel and there is less rubber then the overall wheel and tire combination will be lighter than a stock tire with all that rubber. Using a low profile and keeping original diameter will also keep the speedo in the right spot.

[Grant@Tirerack]

You would not loose horsepower by plus sizing since the aspect ratio will change to keep you at the correct O.D. . It's only when jumping up in O.D. that you run into problems. It has the same effect as changing your gear ratios on the back end of everything.

[Dsilver]

Listen to Grant, he is the man

[goinbig]

increase in diameter will cause a loss in power. weight does not matter. going up in tire diameter is like gearing up (higher gears). Smaller diameter is like gearing down (lower gears/higher numerical value). Trust me, when all you do is build vehicles for off-road, you will realize fast when you're running 44+" tires!

[Dsilver]

haha

[EH3Civic]

Originally Posted by goinbig

increase in diameter will cause a loss in power. weight does not matter.

PLEASE?! That sounds rediculous to say that weight, in a wheel, doesn't matter (if i understood you right). I noticed a positive change going from a 19lbs 14" steely to a 16.7 lbs 17" alloy. To say that weight doesn't matter, is to ignore physics and angular momentum.

[Soyo]

rim size has nothign to do with it, because the tire gets smaller as the rim gets bigger. the weight is the thing that effects it, so if your wheels and tires weight 25lbs at each corner with the 17's but weight 30lbs at each corner with 18's then yes your losing horsepower to the ground, but not at the crank ofcourse

[goinbig]

Originally Posted by Soyo

rim size has nothign to do with it, because the tire gets smaller as the rim gets bigger. the weight is the thing that effects it, so if your wheels and tires weight 25lbs at each corner with the 17's but weight 30lbs at each corner with 18's then yes your losing horsepower to the ground, but not at the crank ofcourse

So...if the tire gets smaller (I'm assuming you mean diameter) as the rim gets bigger, um...what happens when you go from 14" wheels to 27" wheels ?? Is the tire completely gone by then. Weight does play a big role on torque (at the wheels of course) but it wouldn't be noticable going from 17's to 18's. That's like when people install little gadgets on their cars, add 5 or so horsepower or torque, and say that they can feel the difference

[Dsilver]

Haha, good point goinbig

[Dsilver]

They say they can feel it, because they want to believe that it really made a noticeable difference, the mind can do many extraordinary things

[goinbig]

ya, I always like it when people say that they can feel the increase in horsepower, when torque is the thing that you can actually 'feel'. Torque is what makes the wheels spin and the car go.

Then, people come on here saying that they can feel this "horsepower," and how much they have gained by putting on lighter wheels, when I can almost bet they didn't put the car on a dynomometer to actually prove it.

[EH3Civic]

so wait, are you suggesting the wheel weight has nothing to do with acceleration, and speed and the such - that wheel weight has no effect on performance?