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Discussion Starter #1
Forgive this if its a unintelligent question for a new car but I'm curious if there is a drop in toque/power with having the 18" rims over the 16". On my old Kicker mounting 18's killed my power (looks cool though) just wondering if its the same or if the design team countered this in some way.
 

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There should be no difference if you size the tires correctly.

[2 * width * profile% + rim dia] should be identical with whatever sets of rims/tires you put on a car.

Any difference between the old and new overall diameter will translate as a change in final gearing ratio and a change in performance. Smaller will equal faster acceleration lower top end, larger the opposite.

IIRC. Sold tires for a number of years, but that was some time ago.

Actually with the 18" rims the speedo probably reads 4% slower than with the 16" rims
Rim (in) Width (mm) Sidewall % Sidewall (mm) Sidewall (in) Total Dia (in) % difference
15" tires, P195/65 R15 15 195 65 126.75 4.99015748 24.98031496 0.0%
16" tires, P205/55 R16 16 205 55 112.75 4.438976378 24.87795276 -0.4%
18" tires, P225/45 R18 18 225 45 101.25 3.986220472 25.97244094 4.0%

http://www.tiresizecalculator.info/

How about 20" Rims and these?
http://www.tirerack.com/tires/Compa...e&pagelen=20&pagenum=1&pagemark=1&RunFlat=All
 

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Discussion Starter #3
Ok so if I understand it correctly you are saying the correct rim to tire ratio will equal the 16" having a higher profile tire and the 18" with a lower profile tire to equal the same stock height and not effect power or torque? I never could figure out tires/rim sizes so thanks for the info.
 

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It looks like the Soul was designed around the 18" wheel, with the 16" being thrown on afterward. The speedo seems to read slightly faster than the true speed (using GPS and radar), which leads me to believe that it's accurate using the 18" wheel and tire combo with its diameter. So, you might want to base tire sizing options against that to get your actual speedo accuracy.
 

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It looks like the Soul was designed around the 18" wheel, with the 16" being thrown on afterward. The speedo seems to read slightly faster than the true speed (using GPS and radar), which leads me to believe that it's accurate using the 18" wheel and tire combo with its diameter. So, you might want to base tire sizing options against that to get your actual speedo accuracy.
i wondered why that was! i knew i wasnt going 45 in a 35 with all those cars still passing me..
 

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I'm probably going to compromise and get the +, sell the rims and upgrade to 17". The price of 18" tires is a little scary.

Too bad those stock 16" rims are butt ugly, probably no resale value on em...
 

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I'm in one of those moods so I'm going to chomp right in and lay down the facts...

Up sizing your wheels will always affect your torque, power and performance!

The larger wheels (along with tires) have more mass. This means it takes more energy to speed them up and slow them down in comparison to smaller wheels and tires.

We must also consider the unsprung mass of the larger wheels & tires. This increase in mass effects ride quality and how effectively the suspension works to keep the tire in contact with the road.

In simple terms it is a lot easier for the engine & transmission, breaks and suspension to deal with lighter/smaller wheels and tires.

Hope this helps.
 

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I talked with the guys at our local dealership and got some good news.

I asked them about moving up to an 18 inch tire and wheel and was concerned about the speedo working correctly. They said it wasn't a problem and that the just needed the new wheel and tire sizes and they could reprogram the computer for the new setup. the speedo is electronic not manual so programming is fast and easy.

I have a new pair of ASA 18" wheels and tires picked out at tirerack.com
 

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Go for the 18" wheels if that is what you want. However, realize the trade-offs.

I leased my wife a Soul + because of the 16" wheels.

We live in NE Ohio where the roads are bad and full of holes in the late winter/early spring and nasty patches the rest of the year.

I ruined several low profile wheels on my former BMW M3. So much so that I now have a 328i with 16" tires and no problems.

Once I hit a hole with my wife's 18" winter tires. The wheel was destroyed and the tire was fine. The tire store told me that is the case with many low profile tires. The wheels get damaged before the tires!

So if you live in a part of the country with good roads, go for it.

If you live in a part of the country with bad roads, think twice.
 

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if you haqve the stock 16" you need 225/40R18 tires to match the diameter, the stock 18" have a slightely larger diameter..( 225/45R18 )
 

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in order to get a true indication for speed offset, you must know the overall diameter of the the tire. all things being equal, the offset is a proportion to the size difference. an important item of notation is whether the soul behaves differently due to speed offset not being the correct speed, besides the speedo.
 

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the 15" tires are 635mm diameter,
the 16" tires are 632mm diameter,
the 18" tires are 660mm diameter.
so you're looking at a maximum diameter change of 35mm for smallest to largest tire. 35mm = 1-1/4" diameter differnce. you can use math to calculate the speed difference from one size to another.

If you need more info, PM me.
 
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