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2022 ram 2500 Cummins larger tire size and speedometer difference

Scuba312

Scuba312

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Question for yall out there. So I been trying to figure this out with my truck. I have a 2022 ram 2500 about 6 months ago I put 325/60R20 BFG mud terrain tires on it. While driving I started paying attention to the mph. It didn’t seem accurate. So my question is if you put larger tires on then the speed should show slower that what I’m actually going am I correct? If so then I’m lost cause it shows about an average of 6-7 mph faster than my actual speed. Why is that? I’ve downloaded gps speedometer to see what the difference is as well as used ways gps and it shows the same thing in both apps. Shows I’m actually driving slower than what my speedometer says.
 
Scuba312 said:
Question for yall out there. So I been trying to figure this out with my truck. I have a 2022 ram 2500 about 6 months ago I put 325/60R20 BFG mud terrain tires on it. While driving I started paying attention to the mph. It didn’t seem accurate. So my question is if you put larger tires on then the speed should show slower that what I’m actually going am I correct? If so then I’m lost cause it shows about an average of 6-7 mph faster than my actual speed. Why is that? I’ve downloaded gps speedometer to see what the difference is as well as used ways gps and it shows the same thing in both apps. Shows I’m actually driving slower than what my speedometer says.
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Yes, larger diameter tires will make it go faster than indicated. Did you buy the vehicle brand new? Any change in axle gearing ? Your tires are only about 6% larger, so at 75MPH indicated, you would actually be going about 80MPH. Keep in mind that many vehicles indicate 1-2MPH less than actual...
 
Make sure your mobile device isn't connected via Car Play or AA or it will simply match the truck NAV GPS speed.
 
johanh13 said:
Yes, larger diameter tires will make it go faster than indicated. Did you buy the vehicle brand new? Any change in axle gearing ? Your tires are only about 6% larger, so at 75MPH indicated, you would actually be going about 80MPH. Keep in mind that many vehicles indicate 1-2MPH less than actual...
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Yes I bought it brand new. Only put the larger tires in it. When driving the speedometer will say I’m driving 70mph but all the speedometer apps and navigation apps says I’m driving 64mph. So I’m lost. I would think I’d be driving faster as well but I’m not.
 
Any chance the tire shop tried to make a correction and got it off?
 
Like Brutal_HO said, make sure you phone is totally disconnected from the truck (bluetooth and wifi off). I had this exact same thing happen. I assumed the truck was wrong and the phone GPS (waze, gps app, etc.) was correct, but that wasnt the case. Something weird happens when they are paired that makes the phone GPS inacurate.
 
On the internet if you go to tiresiz.com the website will give you several options and one of the options is speed difference based on tire size.
 
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