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tony

17`s

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have many got 17`s on there c , is it true that they can affect your performance?

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have many got 17`s on there c , is it true that they can affect your performance?

 

This is a common question and the answer is:

 

Probably!

 

It all depends on the new wheels' weight distribution. Going to bigger wheels is putting more metal further away from the centre of rotation = more energy required to spin it at a given speed = less energy available for propelling the car. The energy required is proportional to the square of the radius for a given mass which is why increasing the radius from 7.5" to 8.5" (i.e. 15" to 17" wheel diameter) you sometimes get a noticable effect.

 

(8.5/7.5)squared = 1.28 i.e 28% increase in energy required just to spin the wheel and this is per corner so times 4 for the whole car! And this is assuming the same style of wheel AND completely ignoring tyres!

 

If you could get bigger wheels that actually required less energy to spin them you would see a performance increase! i.e. some ultra-ultra-lite alloy.

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I run 17'now, I changed from the standard 15 inch speed line alloys on my VR, the car feels much steadier now, it feels tighter which Im sure is to do with the low profile tyres and generally I feel more of the road now which gives me more control.

 

The samller the wheel the quicker your starts are but the bigger your wheels are the slightly better top speed you get, thats what I have been told!

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My blurb above was assuming bigger wheels/lower profile tyres so the same rolling radius.

 

If you go to smaller wheels and a smaller rolling radius then yes, you will accelerate quicker, (it's just altering the overall gearing of the car), but at the expense of top speed.

 

Opposite is true for bigger wheels/bigger rolling radius - slower acceleration.

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have many got 17`s on there c , is it true that they can affect your performance?

 

This is a common question and the answer is:

 

Probably!

 

It all depends on the new wheels' weight distribution. Going to bigger wheels is putting more metal further away from the centre of rotation = more energy required to spin it at a given speed = less energy available for propelling the car. The energy required is proportional to the square of the radius for a given mass which is why increasing the radius from 7.5" to 8.5" (i.e. 15" to 17" wheel diameter) you sometimes get a noticable effect.

 

(8.5/7.5)squared = 1.28 i.e 28% increase in energy required just to spin the wheel and this is per corner so times 4 for the whole car! And this is assuming the same style of wheel AND completely ignoring tyres!

 

If you could get bigger wheels that actually required less energy to spin them you would see a performance increase! i.e. some ultra-ultra-lite alloy.

 

This just reminds me of that bit in Austin Powers II where they're trying to explain about Time Travel problems and he goes cross-eyed and just says "Oh well, don't worry viewers, it's just a movie :lol: )

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Oh yeah - and you've got to take into account the relative air density and the cooefficeint of friction of the particular road surface you're on....

 

 

 

 

:wink:

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