This may be a dumb question, but this is my first time with larger-than-stock tires.

I used my Smarty to adjust the ABS for the larger 35's and checked my speed using a GPS today. I noticed (and expected) the speedo to be off (it reads 5 mph faster than the GPS at 70 mph) but I am wondering if the odometer is off as well now. If so, my warranty gets hosed since it will show that I have gone farther than actual.

Anyone got any experience on how to adjust properly with the larger tires?

 

You can adjust tire size by 1/4" inch using the smarty you just need to dial it in til it reads correct . I measured my 35/12.5/17's and they measured 34 1/4" so i set the smarty on that and it was dead on according to the gps

 

Cant the Dodge house dial in 35's?? i wanna say my friend said he could go up to 35's..

 

If the Odometer is off it would be the other way around with bigger tires, you would be driving more miles that your odometer would read so your warranty would last longer. If the speedo reads 70 and you are going 76 then you are traveling farther than it thinks.

 

I just put 315s on and used the Smarty to adjust my speedo. I don't have a GPS so I have no clue if it is actually correct. But I'm gonna take the word from everyone else and just assume it is correct and keep driving it.

 

Are you sure ? By entering a larger tire diameter than you actually have your speedo will read higher as it thinks it has covered more ground. I'm pretty sure if you measure your tire it will not come out at 35" Either way best just to set it to proper speed by fine tuning the smarty.

 

If you enter a larger size than you have it will chalk up more miles than you are driving, but if you don't correct your speedo after going to 35's then you will read less miles on the odomter. The SMARTY is easy to fine tune if you do as suggested and measure the true tire hight and check it with GPS if possible. If you program the truck back to stock and then reload a new SW form the smarty then you will need to redo the speedo correction or the highway patrol will let you know. I also don't think it is possible to hand calculate your fuel milage if your speedo is not correct.

 

i looked my tire spec up and they are 34.8 so i put that in the Smarty. My overhead reads more accurate with the Smarty also My Diablosport would have me getting 25+ MPG and it was off about 9-12 the Smarty has it at 16-19

 

Thanks for all the info. I set my Smarty to 35" tire size (not actual measurement - guess I need to do that) but obviously I did not get it right. Time to reset once I return home.

 

It's hard to believe that a 1/4" would make that much of a difference but I guess we woudn't be adjusting them in those increments if it didn't. When I picked up my takeoffs my Smarty jr was waiting for me when I got home.so fortunately I didn't have to drive with the speedo off. I just went to the bfg site and got the 34.5" from there. I guess I should actually go measure the tire and see if it jives up.