Sunday, January 8, 2012

Does adding bigger wheels/tires to my car slow it down?

I have a cadillac cts that comes stock with 16inch alloy. I would like to upgrade to some 18inch black wheels but a friend of mines told me that i will lose a certain amount of horsepower/torque for every inch i go above the factory specs. A friend of mines had a 2000 pontiac grand prix that came with 16inch alloys and when he upgraded to 18inch wheels his car did seem a bit slower. What do you think? Do you think adding bigger wheels and tires to a car slow it down? If so, by how much?|||Just going to a larger rim will not "slow it down"your ride. Going to a larger tire OD will decrease torque, and make the speedometer read wrong.


I think what you are wanting to do (going to a larger rim and using + sized tires) will work. Be advised that while this may look better and increase handling, it will come at the expense of the ride.


By the way the combination that you are looking at (going from 16 to an 18 rim would be a +2 combination).|||the tires will not make the vehicle go any slower unless they are to big and they are rubbing your wheel wells. The only thing it will truly effect is your speedometer. It will be off. It will show that you are going slower than you actually are.|||It's a simple pysics thing to do with the rolling radius...





A larger diameter wheel (including tyre) will make you accelerate slower... But will eventually give you a higher speed..





A smaller diameter will do the opposite - Give you better acceleration, but at the cost of top speed|||I'll will not be too technical here for you to understand. Your friend told you that his car became slower but it didn't, because he was looking at the speedometer but it gave a false reading...Why you ask? Because the the calibration of the speedometer is made with the stock tires. That's why it looked and felt slower. It will make the car a bit faster and easier to handle..But don't go TOO big. The tire may scratch the inner walls That could destroy the body or tires/wheels.|||If you put bigger wheels and tyres on your car, it would feel a lot slower and the speedometer would be innacurate.





Like the last posters have said, when you fit your 18" rims you get low profile tyres so the wheels and tyres will be the same size as the originals. That will give you the best result.|||If you pick the new tire size correctly overall diameter (and thus gearing) will not be a problem. However, the new wheel and tire combination is likely to be much heavier than the stock setup. How much heavier (and thus how much effect) depends on the wheel and tire combination. That in turn requires more power to just turn the wheels so you end up with less power hitting the pavement. It also means it takes longer to slow down since there is greater mass for the brakes to overcome. The increased unsprung weight combined with the lower profile of the new tires will also adversely effect ride quality. It's gonna be stiff and harsh. If you go with a wider tire there will also be greater rolling resistance to overcome. This isn't helpful for straighline speed but can actually be a benefit in braking and cornering.





As for that tire size, your CTS probably has P225/55R16 94H or 94V sized tires on it at 33 psi front and rear. The sizes you will want to consider with the new tires are 225/45R18XL 95W to maintain the correct overall diameter of 25.7 inches inflated to 39 psi front and rear to maintain the correct load carrying capacity. Or you can use a wider tire 245/40R18 93W at a lower and more comfortable 36 psi front and rear. Either is virtually identical in overall diameter to the OE tire size so will introduce no errors in speedometer, odometer or change the gearing.|||well , first of all your not going to loose horsepower. what happens is when you change the wheel size it takes the vehicle a longer distance to make one revolution than the original. of course it may seem like you have lost torque and horsepower but actually its just more weight added to the vehicle,that's why the car doesn't seem to perform as well as before.(it will also change the calibration on your speedometer,causing it to gain or loose mph due to wheel size)

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