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Discussion Starter #1
well i just installed a 6" lift kit and 35x12.50x20 nitto trail grapplers and I am wondering how far if at all the speedo is off? It seems that I am flying past everyone when doing the speed limit. that of course could be because I live in alabama and nobody here knows how to read a speed limit sign (sign says 55, they do 45). I am just trying to make sure the tires throw me off that much.
 

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It will very a little bit depending on tire size but with my 37" I was off by 7mph. Speedo was reading 45 and I was doing 52mph. But like i said it kinda varies vetween size and tread(so im told)Hope this helps.
 

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Dealer can easily set the speedo for the new tire size. Probably even do it for free.
 

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I just returned from the dealer (oil change and recall) and didnt think about even asking them. thanks for the info
 

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I took mine in after putting on 34" tires and they told me that they can only change the spedo to mach 17" stock wheel and tires or 20" stock w/t , they said the older trucks had a program to change the spedo for any size but the new ones dont.
 

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Ya I called my Dealer after i got my lift and my 37's put on to ask them if they could set my speedo becaue I bought new tires.They said sure bring it in.So I did,I pulled into the bay and the guy I talked to came out and said well sence you went like 5 tire sizes bigger there was noway of fixing my speedo.

I am just buying a predator Tuner next year.that will fix my speedo :).
 

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Discussion Starter #7
well that is just great lol, o well at least if i get pulled over i may get away with it as an excuse.
 

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u cant say you installed this and not show us any pictures!!!!!!!!!!!!!!!!!
 

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Dealer can easily set the speedo for the new tire size. Probably even do it for free.
when i went to my dealer they said they could do it.....for $100.00. i said now thank you.

It's a ratio, your speedo is off 2mph fast at like 30 and it's 5mph at 60, so at when your speedo is at 60 you're doing 65. because your bigger tires have to make less revs. to complete the same distance. i'm not sure if this makes sense the way it's written but i tried lol :4-dontknow:
 

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u cant say you installed this and not show us any pictures!!!!!!!!!!!!!!!!!
well i have posted pics in the correct spot on the forum lol. but here is the thread of some mods I have done.
http://www.ramforumz.com/showthread.php?t=63986

when i went to my dealer they said they could do it.....for $100.00. i said now thank you.

It's a ratio, your speedo is off 2mph fast at like 30 and it's 5mph at 60, so at when your speedo is at 60 you're doing 65. because your bigger tires have to make less revs. to complete the same distance. i'm not sure if this makes sense the way it's written but i tried lol :4-dontknow:
It does make sense, is that for 35's? i figure that all tires will be different due to tread and whatnot, am i correct? I guess I will use your ratio for now and get it fixed at some point.
 

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I would recommend getting it changed sooner then later. You will actually rack up more miles on your odometer the more you drive around. The truck thinks is going faster which means further then it is. So instead of 60miles your truck will say 65. After a while it will make a big difference.

I actually made my tire size on my Predator 28" tall hahaha from 35". This makes my mileage great! It thinks I am going 15% less then what I actually did.
 
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