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Oohhhhhh yes :cool: .

3 caveats:

Wheel weight, watch what you buy otherwise you'll end up with a burden not a bonus.

Use extra load sidewall tyres, you've a convertible, they are heavy.

You will lose some ride smoothness and fuel economy may drop off a little too.
 

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I'm looking at a used set of Saab 5 spokes so I'm guessing the weight should be greater, but not significantly. The tires on the set are 215/50's so it will be a taller tire, which may offset part of the performance increases. One of my alternatives is to retire my current 16" 5 spokes with the Kumo 205/55 and put the saved $ toward the big three (6 point brace, rear stabilizer, rack brace).
 

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Larger wheels actually need to be lighter than the smaller wheels they replace for the effect on acceleration and braking to be a wash. Say for example you had two sets of wheels, and each weighed X lbs. One set was 16 and the other was 17. The 17s would accelerate and brake more slowly because as their mass is concentrated farther away from the axis of rotation, thus their rotational intertia will be greater.

Handling may feel sharpened with the larger wheels, but whether the car sticks better is really due to the tire choice. From a purely performance standpoint, I would use the lightest, smallest wheels that would fit over the brakes, with a very stiff sidewall tire with a sticky compound.

Of course 17/18" wheels look much better on our cars, so if thats what youre after then just realize that they will likely have a negative impact on performance ;)
 

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Good points...


I've driven 15", 16", 17" and 18" wheels and by far, the most comfortable are the 15 inch one.

The 16s are OK, but the 17s offer MUCH better handling due to the shorter sidewall height...buit, as everyone has said, there's a serious tradeoff in noise, vibration and comfort.

18" wheels look amazing, but the road feel is pretty harsh.
 

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redrum said:
Larger wheels actually need to be lighter than the smaller wheels they replace for the effect on acceleration and braking to be a wash. Say for example you had two sets of wheels, and each weighed X lbs. One set was 16 and the other was 17. The 17s would accelerate and brake more slowly because as their mass is concentrated farther away from the axis of rotation, thus their rotational intertia will be greater.
This is dependent entirely on the design/manufacture technique; and then factor in a steel rim is generally even lighter at the rim than alloy rims [most, not all].
Very good quality alloy rims have little mass in the rim but it comes at a price.

Also you haven't factored in tyre mass, this can be collosal with high side tyres.
 

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Rotational inertia will of course vary based on wheel design and manufacturing technique, but in broad terms two sizes of the same brand/model wheel, the larger will have the most rotational inertia.

Although dependent on wheel spoke and hub area design, most alloy rims contain the majority of their mass in the rim section between the two tire beads, which is also the area which creates the most inertia per kilo of mass.

Tire weights between wheel sizes (based on a plus-size technique, keeping the overall diameter the same) generally only vary 0.5-1.0 lb for each inch of rim size, with the larger rim size tire being lighter. This of course varies on the type of tire, but the difference is almost always less than that of the difference in rim weights of the two sizes.

Broadly speaking though, a 205 50 16 tire and wheel combo will have less rotational inertia than a 205 45 17 combo, using the same type of tires and rims. People often go with wider wheels and tires when they upsize, and while this will afford more grip than the same combination on the original smaller and narrower size, its rotational inertia will be that much larger.
 

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redrum said:
Rotational inertia will of course vary based on wheel design and manufacturing technique, but in broad terms two sizes of the same brand/model wheel, the larger will have the most rotational inertia.
How many people trade up [or down] in size and retain the same design?

From ownership experience, I have had a set of 17x7" rims that weighed more [with heavier rim section too] than the set of 17x7.5" rims still in use; so the narrower rim with its measured extra thickness was at static a heavier rim too.

They're not all broadly the same, there are massive variances out there. To massive for general fit all statements.
 

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Well I'm sure hardly anyone trades up or down for the same style rim, but that thats the only way to make an accurate statement on how size alone will affect inertia. :D

Unfortunately general statements are all that can be made with the countless wheel and tire combinations out there.
 
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