Got New Tires, Speedo Off 2-3mph
11-22-2015, 11:13 AM
#1
Got New Tires, Speedo Off 2-3mph
So I recently replaced the OEM Goodyear Wrangler SR-As with 4 Goodyear Wrangler ArmorTracs....I GOT THE SAME SIZE (275/65R18)....and now the speedometer reads off by 2-3mph....it's noticeable. So if I'm actually going 77mph, the speedo will show 79-80mph! Note: For accurate actual speed I have 2 sources, a Garmin GPS unit, and Escort's Smart Radar app, which I run on my phone.
Anyone care to tell me why this is happening?
Anyone care to tell me why this is happening?
11-22-2015, 11:32 AM
#2
Senior Member
One thing would be the wear on the old tires. Going from worn-out tires to brand new tires means you gained size - i.e. the old tires had a smaller circumference due to the wear. I've seen that this roughly could be a 2% difference. So, if your speedometer used to read 77, 2% more would be 78.5. So yes, could go from 77 to 79 quite easily.
In your case, assuming the calibration was set at the factory and not touched (i.e. by a tuner or anything else), there should be no difference at all since the tires are the same size. On Goodyear's site, both take 651 revolutions to go a mile. You might see a difference in MPH from your worn to your new tires, but should see no difference between what the old tires accuracy, when they were new, to the new tires.
In your case, assuming the calibration was set at the factory and not touched (i.e. by a tuner or anything else), there should be no difference at all since the tires are the same size. On Goodyear's site, both take 651 revolutions to go a mile. You might see a difference in MPH from your worn to your new tires, but should see no difference between what the old tires accuracy, when they were new, to the new tires.
