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Hi,Just installed a new set of rims with tires (20x9 rims with 255/45-20 tires) on my Evoque and the car feels a bit different while accelerating (slower acceleration). The original rims were 19x8 with 235/55-19 tires. I'm thinking it's due to the larger wheel size and weight. Has anyone experienced the same issue? Thanks
 

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Not that I'm an expert, but the car, regardless of wheel size, is engineered for a certain diameter tire/wheel combination. In other words, going to a 20 inch rim, you need tire with a smaller sidewall. With larger outside diameter, the engine and transmission are both
working harder. Maybe need to have transmission software re-done. I'll bet your speedometer is off too. Just a thought, like I said, I'm no expert. Good luck.
 

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Doing the math, you have a smaller rolling circumference with your 20" rims because of the '45' profile tire side wall. This should result in a slight feeling of lower gearing, more punch in each gear, shift points at a lower speeds, and higher rpm's than before to maintain a cruising speed (speedometer registering a slightly higher inaccurate speed.) The rim weight (increase?) is insignificant when considering acceleration. This would only affect aggressive handling but you are not going for best lap times driving your Evoque.
 

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Adding larger wheels and tires basically changed your gear ratio. You didn't mention the weight of the wheels but bigger is generally heavier and a larger tire is heavier as well. a 235/55/19 Yokahama weighs in at 29.5 lbs and 255/50/20 (no 45 aspec ratio listed) weighs 34.5 lbs. That's an extra 5lbs per tire not including the wheel difference, which is larger diameter and wider. The overall diameter for the tire sizes I mentioned above varies about 1 inch so the aspec ratio of 45 rather than the 50 I noted is 13.5 millimeters or approximately 1/2 inch.
 

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OK so one 20" wheel/tire combo weighs 5 lbs more than a 19" wheel/tire combo. Let's assume the the increase in mass comes in at the perimeter (in reality it doesn't, but let's take the "worst case" route).

Let's also assume the Evoque can do 0-60 mph in 6 seconds. Yes that's probably faster than it's rated, but this number gives us a nice 10 mph/second acceleration rate.

According to my calculations 5 lbs accelerating @ 10 mph/second would equal 136.6 pounds of force. Multiply this times 4 (there's 4 wheels) and you get 546.4 additional pounds of force against the drivetrain with the 20" wheels.

If we use the old saying "10 lbs equals 1 hp" than we could assume adding 20" wheels and tires could theoretically suck 54.6 hp from your vehicle. Of course I'm using all worst case theoretical numbers so actual results would likely be less, but I'd say even if I'm off 50% you're still losing 27 hp.
 

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I hoped you would jump in Engineer! I figured you would know the formula even in a worst case. Thanks!
 

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So when speccing a new Evoque with OEM 20" rim/ 245-45 wheel option, as opposed to the 19", you are giving up 27HP – horsepower measured at the wheels?
 

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So when speccing a new Evoque with OEM 20" rim/ 245-45 wheel option, as opposed to the 19", you are giving up 27HP – horsepower measured at the wheels?
Yes and No. The horsepower is still there, but the affect of acceleration lost is the equivalent of losing it. Towing, hills, etc would not be affected. Only acceleration and braking would be impacted.
 

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The 20" wheels definitely do not make that much of a difference. 0-60 is roughly 7 seconds, you might notice a .1 to .2 second difference from that, if that.
 
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