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Discussion Starter #1 (Edited)
So I’m thinking about some new wheels for the 2008 Aero I just bought. This particular car came with ALU59 wheels instead of the more typical ALU71’s, the original owner had them changed when the car was bought new.

I kind of like the looks of the ALU59’s but both right side wheels have pretty bad curb rash and the car is still on the original tires (car has only 21K miles, but the tires are from 2007). So at minimum I need either replace/refinish the 2 curbed wheels and get some new tires, OR replace the whole setup with some 18’s. If I do that, I am thinking about a set of ALU73’s to maintain an OE style look with some 235/45R18's.

On the one hand, the 17” wheel/tire package is probably at least 5 pounds lighter than an equivalent 18” setup so the suspension dynamics are probably better with the 17's. But the 18’s would look better. Any thoughts on this dilemma? I’m just wondering what the hit will be from a suspension harshness and handling point of view to jump up to the larger wheel and tire size. I know that TX wheels were 18”, but I don’t know the weight of the TX wheels relative to a set of 17’s or the ALU73’s.

Opinions/first hand experience are very welcome!
 

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Well it's not all wheel weight. The eighteens will have a shorter sidewall which will give you less sidewall flex making it better for corners. But I'm not sure what the best balance is for your car.
 

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Your problem is that you are retaining the same tyre width and sidewall height, so add the larger wheel and you're gonna REALLY fill the guards, maybe too much with rubbing etc.
 

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Discussion Starter #4
Thanks for the replies!
My thought was to stay with OEM sizing, I believe the TX uses 235/45 18. If I went with 235/40 18 that just about matches the diameter of the existing but the ride harshness will likely worsen.
 

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Discussion Starter #6
Thanks, I figured that if I went to 18's then I would change the tire size in Tech 2. I know that there are tradeoffs, I have upsized and downsized wheels in other cars. What I was curious about was how the 9-3 responded to a heavier wheel and tire combo, was there noticeable change to suspension dynamics and to a lesser extent vehicle acceleration.

Probably it is okay since SAAB offered the 18" size with 235/45 for the 9-3 in other markets and for the TX in the US. Maybe I am overthinking it...
 

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There's no free lunch here, you will struggle by just going up a size without reducing the sidewall.

Go here http://www.1010tires.com/Tools/Tire-Size-Calculator

That puts your circumference change at 4%, rule of thumb is to stay within 3% or your speedo and ABS etc start to get confused.

You can probably get away with it but make sure it fits.
Thanks, I figured that if I went to 18's then I would change the tire size in Tech 2. I know that there are tradeoffs, I have upsized and downsized wheels in other cars. What I was curious about was how the 9-3 responded to a heavier wheel and tire combo, was there noticeable change to suspension dynamics and to a lesser extent vehicle acceleration.

Probably it is okay since SAAB offered the 18" size with 235/45 for the 9-3 in other markets and for the TX in the US. Maybe I am overthinking it...
Does one really have to use Tech 2 to change the wheel/tire sizes in the ECU (or whatever else computers need the info) if the size discrepancies are < 3% from stock size ?

Also, jza80 ..... that 1010tires tire size calculator provides you all the different popular brands and models of tires available at each of the up-/down-sizing ....... useful to have and plan your purchase based on the options available at each size.
 

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Discussion Starter #8
Does one really have to use Tech 2 to change the wheel/tire sizes in the ECU (or whatever else computers need the info) if the size discrepancies are < 3% from stock size ?
Probably not, but I have a Tech 2 so it would be something that I can easily do. In fact, the car is about 2-3% off right now (45MPH indicated is about ~43MPH on radar) so I am going to adjust it whichever way I go.
 
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