--Stock 19" Rims to 20" Aftmkt Question, ECU, Shift patterns, etc will be OK?-------- - Chevy Impala Forums
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post #1 of (permalink) Old 10-22-2019 Thread Starter
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--Stock 19" Rims to 20" Aftmkt Question, ECU, Shift patterns, etc will be OK?--------

2018 Impala 3.6, going to 20" rims, has 19" stock, was wondering if this would mess up anything ECU wise.


Thanks in advance
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post #2 of (permalink) Old 10-22-2019
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Depending on the tire size difference, the only thing I could think of that would be off would be your speedometer reading.

Here's a really handy website: https://tiresize.com/speedometer-calibration/

Just plug in your old tire size, your new tire size, and see how far off your speedometer reading will be from your actual speed.

Hope this helps!


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Depending on the overall size difference (tire+wheel), you could also alter shift points as well, since shift points are based on both pedal position and reported speed. Since the reported speed will be altered by the overall tire+wheel size difference, you actually alter the shift points too. Now very minor overall size differences wouldn't really be a problem, but something to keep in mind depending on how big of a difference there is in overall size.

Last edited by jtrosky; 10-23-2019 at 09:44 PM.
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Use the same sized tires that GM puts on the 20" Impala Rims and there will be no issue at all as the outer diameter stays the same, just a lower profile tire. The factory 20" is 245/40R20 as compared to the 245/45R19 on the 19" wheels. Overall diameter is 27.7" on both sizes.
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OK that makes sense, I thought the 20" wheel option from Chevy would have diff parameters but overall height like you mention is the same, good shit.
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How is the ride quality compared to the 19 inch rims?
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Quote:
Originally Posted by Dougie View Post
How is the ride quality compared to the 19 inch rims?
Less sidewall will always be a rougher ride.

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Its same except I used plastic "HUB CENTRIC" rings and two different tire shops, three different balances and there is still a vibration. Its very subtle, it does feel like the tires needs balanced but I doubt it(BF Goodrich.)



I have aluminum ones on the way, gonna swap them out soon to see if it makes a difference.
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The 20 inchers are quite susceptible to pothole damage. Beware.
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You know you need to balance them on the car.
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