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2010 SRX LUX
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...but you're just not going to feel either of these effects driving a 4,000 pound luxury car.

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V.D, don't worry about weight when choosing a size, it's not going to noticeably effect performance on these cars.
I'm not going to argue with you, if you drive like grandma, you are correct, and most likly won't notice a difference.

I do own a 4k performance vehicle, where it has been proven over and over, that larger, more heavy wheels greatly impede all performance aspects. Along with more break wear, more hub bearing wear, and a more heavy steering feel.

If you want to make your car slower, have fun, it's your car :)
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Just for grins and kicks, maintaining the proper tire outside diameter for the car, it might be instructional to weigh some different Cadillac wheel and tire assemblies for comparison.

The weight differences between a Seville 16" assembly, the 17" assembly, and the recommended tire on a Deville 18" assembly are so close to "none" that it isn't funny.

Tires (from the Tirerack spec sheets..........
A 235/60/16 all-season weighs 25#
An all-season 235/55/17 weighs 27#
A 235/50/18 weighs 28#

So what is the mass of an extra wheel inch of aluminum alloy ? Not much.

Aftermarket wheels do not enter the equation.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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I don't drive my STS like grandma, not even close.

The only thing that would impede performance and effect brake/hub wear is a larger wheel/tire WITH AN OUTSIDE DIAMETER LARGER THAN THE OE WHEEL/TIRE. This is because you're essentially changing the final drive ratio, and you're also changing the amount if leverage/torque that the brakes have over the wheel. A few extra pounds per wheel/tire makes an essentially immeasurable, totally unnoticeable performance difference. Brake and hub wear?? Do you notice more brake and hub wear with a bag of potting soil in the trunk? How about a small child in the back?.....

If larger and ever so slightly heavier rim/lower profile tire package decreased performance, then why do touring/performance models of many, MANY cars, come with larger rims/lower profile tires, with NO changes to engine performance, braking systems, or hubs?? Se body better tell the engineers they've been doing it wrong...
 

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1979 Coupe deVille, 1995 Sedan DeVille (sold)
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That may be true for a slightly heavier wheel.
However, a bigger weight difference can be very noticable.
I've taken the standard, steel wheels off a car and refitted it with factory alloy wheels. The difference is quite obvious.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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The placebo effect is strong. Just think of the physics of what you're saying. Add (let's say) 20 pounds to a car, and all if a sudden it feels and handles significantly worse??

Change the oil after adding larger wheels. All that "extra power" from the clean oil will compensate...
 

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98 DeVille, 97 DeVille d'Elegance
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Apples and oranges... A heavy steel rim replaced with a rim a bunch lighter you probably would feel some difference. More likely the new tires and the warm fuzzy feeling from shiny new alloy rims attributed also.
If we were talking an 8 second drag car absolutely every once of unsprung matters. But on a heavy car not a bit.
If you put big arse mudders and huge rims on a vehicle not designed for them the hubs do blow out not from extra couple pounds from rims or tires, dumbass offset yes though.
 

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1979 Coupe deVille, 1995 Sedan DeVille (sold)
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There is a big difference between adding 20 pounds to the trunk and adding it to the wheel.

I'm not talking about increased acceleration and faster turning. Think about the effect of that additional mass and inertia when the wheel experiences a sudden acceleration in the upward direction due to a bump in the road.

There is a reason automotive engineers talk a lot about "unsprung weight"

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When I swapped wheels on our old Chrysler, it did not accelerate faster or turn into a high performance sports car.
It was, however, noticably smoother than before.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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Unsprung weight has nothing to do with the inertia of a spinning wheel. As posted, Unsprung weight effects the action of the suspension. Wheel weight effects Unsprung weight, but again, 4,000 pound luxury car.
 

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1979 Coupe deVille, 1995 Sedan DeVille (sold)
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I think we are in agreement here, but don't realize it.
I wasn't talking about spinning inertia. When you suddenly push up on a wheel (against the spring, etc), spinning or not, there is still inertia to overcome.

Also, in my case, it was not a 4,000 lb luxury car.
 

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Discussion Starter #30
I don't think I'll ever be able , or want to turn my 4000 pound luxury car into a sports car! I'm a portly gentlemen so comfort is key! Haha! I figure I'll just go with a factory Dts 18 to be safe! Cuz u both make a lot of valid points! So I'll do like my fellow Italians and stay on the safe side!
 

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2010 SRX LUX
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One size larger wheel with a thinner tire doesn't always equate to more weight. Less tire sidewall = less weight, different designed wheel with thinner spokes, less weight.


and engineers are not perfect....the supercharger and ignition recalls come to mind.
 

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2001 DHS
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I recently put 18" STS wheels on mine with 245/45/18 , no issues what so ever even with 5 people in the car. Personally I wouldn't go bigger than 18", just to preserve that "OEM" look :

dev1.1.jpg


dev2.2.jpg
 

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I've been kicking the idea of different wheels around. But I want to shop by weight. It's very possible to shop for the right tire wheel combo with plus 2 wheel size and keep weight the same.

I wish you could sort wheel, and or tires when shopping by weight, like you can with cost. Lightest to heaviest.

But I wouldn't go bigger than 18".
 

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98 DeVille, 97 DeVille d'Elegance
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:yeah: Unless a rim is known to be a big heavy bastard I wouldn't worry about it and I don't think I would want a light weight tire...
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The alloy wheel weight difference in a 16, 17, 18" factory wheel is insignificant. IF each wheel/tire assembly was 4 pounds heavier than "stock", that's the equivalent of 2 cases of beer in the trunk. If the new tire diameter is within 0.3" of original, then braking force is absolutely unchanged.

If your original tire outside diameter was 27 " (close to ours) then you could run a 27" wheel (no tire) and NOTHING would change - except ride and traction.

USA, Please read the entire thread - all of it.
 

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I just changed a set of tires on a 2005 CTS 17" and they where pretty light (have to get scale for shop). Anyway I like the wheels I want to get a set for my 97 DeVille. Where do you guys suggest. Spaldings? I'm assuming they have the offset?
 

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I was looking at the Advanti Racing B2 Denaro, there light weight. I don't know if they will look good on the Caddy though.
 

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2007 Cadillac STS-V Black On Black
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Thanx a lot ! I really appreciate the help! And jealous that u guys get to do 60 mph on the highway ! Isn't that like 120k? All our highways are 100 k max and they write tickets like it's going out of style ! They take pictures with airplanes and everything! Anyway once again thanx very much! I've been wondering what my optons were , I may go with the 18 !
Haha here in the GTA highways we can drive about 130km/h without getting in trouble! :D

I recently put 18" STS wheels on mine with 245/45/18 , no issues what so ever even with 5 people in the car. Personally I wouldn't go bigger than 18", just to preserve that "OEM" look...
Love the light under the door handles on the DHS's! Wheels look great too. If I ever do anything to the wheels on my DTS it'd be 19" black or chrome rims.
 
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