OEM tires vs Duratracs and speedometer - Chevy Colorado & GMC Canyon
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post #1 of 9 (permalink) Old 05-18-2017, 03:39 PM Thread Starter
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OEM tires vs Duratracs and speedometer

So I just noticed my truck arrived from the factory with the OEM rims/tires and the dealership will be installing the black rims/Duratracs. Does the vehicle need its speedometer recalibrated as a result, and will the dealership just do it or will I need to ask? I've heard mixed messages here.

"Ragnar": 2017 Duramax 4x4 Z71
-----------------------------------
04/20: Ordered at dealer
04/25: Accepted by GM (2000)
04/26: TPW 05/08 given (3000)
04/29: Vehicle ready to build (3300)
05/05: Order sent to production (3400)
05/13: 0946 AM, Ragnar is born
05/17: Delivered to dealership (5000)
05/24: Delivered to me (6000)
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post #2 of 9 (permalink) Old 05-18-2017, 03:44 PM
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The difference in the tire size is so close that it doesn't really affect the speedometer (I think it was 1-2mph off at 65mph) and make sure the dealer gives you back your original set of wheels and tires. You paid for two sets

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post #3 of 9 (permalink) Old 05-18-2017, 04:23 PM
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I just wnet from stock tires to a more aggressive tire with a bigger rim size, I haven't noticed ANY difference in Speedo.

Went from stock to 265 70-R17's All-Terrain tires.

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post #4 of 9 (permalink) Old 05-19-2017, 11:01 AM
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There will most definitely be a difference in indicated speed and actual speed unless the dealer does a computer update.

Going from a 255/65/17 OEM Wrangler Adventure Kevlar to a P265/70/17 Duratrac produces and approx. 8% speedo error. Revolutions per mile went from 691 to 659 (full tread). So when my speedo reads 75mph I'm actually going closer to 71mph. If my odometer reads 360 miles on a tank, I actually drove 377.28 miles (360m x 1.048 = 377.2.

So even going up just 1 size to a 265/65/17 Duratrac will cause a speedo error. The difference appears quite small to unnoticeable at low speeds but becomes larger numerically as speed increases. So at 35mph it may only be a 1mph difference but at 80mph it may be as high as 3-4mph. Is it enough to be concerned about? That's totally up to you but I would advise adding that difference into your mpg calculations so you don't feel let down by fuel economy readings that are lower than they are in actuality. :) *Just make sure you get the actual specs on the tires you are comparing. Some 265/65/17 tires are larger in circumference than others.

Here is a calculator that allows you to plug in exact tire size info to find your error. *note, this does not account for any speedo error that is there from the factory. i.e. not all vehicles have an accurate speedo from the factory. Many feel this is a design feature for safety and fuel economy....

https://tiresize.com/comparison/
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2016 Canyon SLE CC LB All-Terrain 3.6L - RC 2" Kit | Goodyear Duratrac P265/70/17
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post #5 of 9 (permalink) Old 05-19-2017, 02:28 PM Thread Starter
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LOL this is why I asked. 3 different answers so far: No difference, nominal difference and significant difference. Either way I asked them to flash the computer. Assuming they have a trail boss setting or something.

"Ragnar": 2017 Duramax 4x4 Z71
-----------------------------------
04/20: Ordered at dealer
04/25: Accepted by GM (2000)
04/26: TPW 05/08 given (3000)
04/29: Vehicle ready to build (3300)
05/05: Order sent to production (3400)
05/13: 0946 AM, Ragnar is born
05/17: Delivered to dealership (5000)
05/24: Delivered to me (6000)

Last edited by ChaosTheory; 05-19-2017 at 05:07 PM.
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post #6 of 9 (permalink) Old 05-19-2017, 02:32 PM
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Quote:
Originally Posted by F8LZ71 View Post
...... any speedo error that is there from the factory. i.e. not all vehicles have an accurate speedo from the factory......
Our 2004 Ranger came with P225/70R15 tires, speed/mileage off.....replaced them with LT235/75R15 tires, speed/mileage almost correct afterwards......

Use measured mile markers or GPS to compare with odometer.
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post #7 of 9 (permalink) Old 05-19-2017, 03:17 PM
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Quote:
Originally Posted by ChaosTheory View Post
LOL this is why I asked. 3 different answers so far: No difference, nominal difference and significant difference. Either way I asked them to fla6sh the computer. Assuming they have a trail boss setting of something.
I didn't mean to suggest the difference would be significant. I just mean there would definitely be a difference. :)
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Quote:
Originally Posted by F8LZ71 View Post
...... any speedo error that is there from the factory. i.e. not all vehicles have an accurate speedo from the factory......
Our 2004 Ranger came with P225/70R15 tires, speed/mileage off.....replaced them with LT235/75R15 tires, speed/mileage almost correct afterwards......

Use measured mile markers or GPS to compare with odometer.
Totally! I always use a GPS to test my speed and I watch the accuracy range. This is usually in agreement with roadside speed traps. Or close enough anyway. Haha
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post #8 of 9 (permalink) Old 05-19-2017, 03:26 PM
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My winter tires are 265/65/17 and the Speedo is very close, with the oem 255/65/17 showed faster than the truck was actually going

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post #9 of 9 (permalink) Old 05-19-2017, 10:58 PM
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My midnight package came with Duratracs in 265/65/17. My Speedo reads 3% slow, meaning when I am indicating 68 I am actually going 70. The dealer said there was no calibration to fix it.
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