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11-20-2013, 05:19 PM #1
New tires - is a speedo adjustment necessary?
I tried using the search function, and I didn't find anything. So sorry if this has been asked a thousand times!
So within a 2 weeks of getting my 2014 (150 miles on her), I had the level kit and bigger Wrangler Duratracs put on.
My question is, going from a 265/60/18 to a 275/70/18 - is my speedometer / odometer off you think? I guess I could download some GPS app on my phone and test it...but thought I would ask here first.
If it is - what's the recommended point for getting the old tune and reflashing the ECM? If the speedo is off by just a little - would you still recommend? (Obviously if it's like 7+mph off, I think I would... but what if it's only 2-3mph off?)
Thanks!2014 Chevrolet Silverado Z71 4x4 | 2.5" level/lift | 275/70/18 Goodyear Wrangler Duratrac
ChevyFan liked this post11-20-2013, 05:38 PM #2
There are a couple of reasons you would want to have the Trucks Computer Re-Programmed to Correct your Speedometer Readings, which will Be Off with this change in Tire Size(As Shown Below).....as the Vehicle’s Computer Calculates your Speed based on the Diameter of the Stock Tires, and with this Change in Tire Size, the Vehicles Computer doesn’t know how Fast your Vehicle is going......also with this change in Tire Size, your Transmission may Not Shift Correctly......
Most Hand-held Programmers have the feature of Correcting the Speedometer Readings, when there's a Change in Tire Size and/or Change in Gear Ratio.
Edit:....IMO....you should have the Speedometer Corrected, for this Change in Tire Size.
Here are the Specs for Both Tire Sizes you've mentioned
Typical Weight ~ 26 lbs / 12 kg ~ 18 lbs / 8 kg Tires: Tire 1 Tire 2 Tire size 265/60-18 275/70-18 Section width 265 mm (10.4'') 275 mm (10.8'') Sidewall 159 mm (6.3'') 193 mm (7.6'') Tire Diameter
775 mm (30.5'') 843 mm (33.2'')
68 mm (8.8%) taller.
Rim sizes 18x7.5 to 18x10 18x7.5 to 18x10.5 Circumference 2434 mm (95.8'') 2647 mm (104.2'') Revs per mile 661.3 608 Speedometer Assuming that this is OEM tire and speedometer readings are correct >>> Speedometer reads 60mph actual speed will be 65.3mph 8.8% faster.
Last edited by 99'HEARTBEAT; 11-21-2013 at 05:33 PM. Reason: Added some more Infor.
5.3 l 3.73 l G80
BLACK BEAR CUSTOM TUNE
SNUGTOP l COLORMATCH l KATZKIN
ChevyFan thanked for this post11-20-2013, 07:47 PM #3
GPS tells you how fast, you are going! If not, GPS model? Yes.. Get a "SCT" programmer, http://www.sctflash.com/index.php I am not a rep, just a Owner of their product.2010 GMC SIERRA CREW CAB (Silver) 4x4, ReadyLift 2.5" Level Kit, 305/60/18 Dick Cepek Mud Country, Go Rhino Nerf Bars, Husky Liners front and rear, Bushwacker Bed Rail Caps, Custom tuned. 4:11's
11-21-2013, 12:12 AM #4
Sounds like an excuse for a custom tune with a diablo tuner from @06MonteSS to me!! There are a bunch of satisfied customers of his here.
1995 Silverado 4x4
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99'HEARTBEAT liked this post11-21-2013, 12:50 AM #5
2011 Chevrolet Silverado 5.3L LT
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11-21-2013, 04:07 PM #6
11-21-2013, 04:59 PM #7
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There are some iPhone / Android apps that will give you your speed and other driving information as well, they can be very useful in helping to determine how much off you are.
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