Engine/Transmission (1998.5 - 2002) Smarty and Tire size adj......HELP....

[ABossana]

Hello everyone, i have had my smarty for about 2 weeks now, and i have been trying to get my speedo dead on for a while and cant seem to nail it. My tire size is 285-75-16, the door sticker says stock was 245-75-16, and when i loaded the smarty for the first time the tire size was set at 29. 5 if i remember right. i had put my "new tire size to 32. 00" (measured from ground to top of tire) however if i set my cruise control to 60 mph and drive 1 mile according to the trip meter it only takes 55 sec. when it should take 60sec? I then tried going to 33" and 30" to see if i could get it to change one way or the other and it didn't seem to work... ... ... any ideas? anyone running 285-75-16 with a smarty who has their speedo dead on? what did you use for "new tire size"? thanks for the help in advance



on a side note: Smarty in general..... Unbelievable

Smarty on #9... ... ... . Priceless

Anthony

 

[NoSeeUm]

Tried using a GPS?



Marco has said there are some glitches in the ECM concerning tire size vs speed. So times a GPS or mile per minute calculation might be required for tuning.



Jim

 

[Gary - K7GLD]

I'm running new TOYO 285/75//16's - used the smarty to set new size at 32. 75 - was slightly off about 1 mile in 100 - so went to an even 33 - seems right on, but will know more on a longer road trip in a few weeks...

 

[ABossana]

my tires are brand new aswell, so i guess ill keep trying



Thanks, Anthony

 

[JR2]

I have 285-75-16 BFG AT/KO's and set my size to 33 and I am spot on. Verified with my GPS.

 

[ABossana]

ok i will try 33" again, thanks for the help.



Anthony

 

[Bucky205]

Tire Correction Formula

You should be able to correct it off the following if a 245 = 29. 5 in the Smarty. 285\245 = 1. 16, 1. 16 * 29. 5 = 34. 31. Gas mileage should be worked on the same formula with pen and paper. If you are spinning 285's, 245's were stock and you used 25. 2 gallons to travel 285 miles, your actual is 285*1. 16 = 330. 6/25. 2 = 13. 11. I think a lot of people would feel better about their mileage if they corrected their odometer for their tire size.

 

[Gary - K7GLD]

I finally got my truck out on a longer RV towing trip - and had to do more speed/distance correction with Smarty.



I ended up spot-on over long distance with 32. 25 with my Toyo 285's. I'm not sure if the added weight of the 5th wheel compromises the diameter of the rolling tire down the road, and will know more when we again travel a long distance with the truck unloaded.

 

[Beast2B]

Remember that you are also dealing with a speedo that is NOT accurate at all speeds from the factory. I can get my speedo dead on at 30mph (with a GPS) and be off at 60mph and vice versa. The gauge accuracy is crap through the entire range, so I suggest setting it correct for highway speeds. if you want dead on speedo and odo measurements, get a GPS and mount it on the dash!

 

[JTHosler]

Tire size

I tried changing my tire size yesterday, what is the current tire size supposed to be in the smarty the first time you use? Mine said 0. 00, was I supposed to put the stock tire size in first, then put in my upgraded tire size?



Thanks,

 

[Bob Wagner]

just go ahead and enter the new tire size

 

[JTHosler]

ok, thats what I did, now I just need to check for accuracy.



Thanks,

Justin

 

[Nate]

Yeah I don't pay much attention to the speedo since I have a GPS in the truck. My speedo is off about 5 mph at 65-70.

 

[NoSeeUm]

Remember that you are also dealing with a speedo that is NOT accurate at all speeds from the factory. I can get my speedo dead on at 30mph (with a GPS) and be off at 60mph and vice versa. The gauge accuracy is crap through the entire range, so I suggest setting it correct for highway speeds. if you want dead on speedo and odo measurements, get a GPS and mount it on the dash!

LOL



Used to have my GPS on all the time. I did this with my camper on once and did not check it for a few days. Well, I eventually picked it up and looked at it. The GPS told me that my position was somewhere about 500 miles SW of Hawaii and my altitude was -300 feet.



Jim

 

[rotohead]

The new generation gps recievers can acquire a better signal easier then units of just a year ago. My bro-in-laws, older but otherwise identical Garmin 60cs can't get a signal in his truck w/o a ext antenna but my month old 60csx has no problem from the middle of the cab. Big difference imo.

 

[NoSeeUm]

The new generation gps recievers can acquire a better signal easier then units of just a year ago. My bro-in-laws, older but otherwise identical Garmin 60cs can't get a signal in his truck w/o a ext antenna but my month old 60csx has no problem from the middle of the cab. Big difference imo.

Yeah, in my case it is the interference from the camper.



Jim

 

[RAndrae]

I have that size tire and programmed 33". DEAD ON