Any of you guys running 18" wheels change the setting on the SCT tuner to correct the speedo. Im looking for the right setting. I believe it has it in rev/minute or something along those lines. Thanks.
18" Wheel. Help with speedo correction (SCT)
- Thread starter Cravinmohead22
- Start date
i was told with the tire sizes on the 17 and 18 inch rims, the total diameter of the tire/wheel combo is the same and you don't need to recalibrate the speedometer. ie, the sidewall of the tire on the 17" rim (stockers) is taller than the sidewall of the tire on the 18" rim. the lower profile tire on the 18" rim supposedly compensates for the 1" increase on the wheel. i haven't measured anything so i could be wrong but im running 18's and my speedo is accurate with no calibration.
unless you are running some weird tire size it should be fine.
unless you are running some weird tire size it should be fine.
moonltgold
New Member
It's diameter of wheel that counts. Stocker is 25.7" so if you are close, (within 1/4") you won't see the difference. But if you have a 26.5" or 25" tire, you'll be off a few mph, maybe like 4-5 at 75 mph.
I just read the tire guide on Americanmuscle.com and it say 305/35/18 will be off 2.8% That is reading 60mph and actual 61.7 mph so now i have to figure out what to do. Thanks for all the replys
Go to nitto's site, get the revolutions/mile and then get into your tuner and set rev/mile to the closest number, but dont go over the number. that will get you your most accurate speedo setting. It will read a little faster than youre actually going, like maybe .00002mph faster than youre going but that way its not showing that youre going slower than you actually are. you catch my drift?
Yup. Im in my garage as we speak Going through the options. Also switching my fan speeds a little.:beer:
I wouldnt bother messing with those really. But yea, put it at 785 revolutions/mile and you'll be golden.
I set it to 765 because to tuner goes I increments of 5. That only one Rev/mile more than nitto's site says. It was set to stock which is 786 and was only 2.8% off so I think I'm good to go now. Thanks everyone.
Your speedo is going to be off still. 305 35 18's from nitto are 786 revolutions/mile so stock is 811. I dont know where you are getting your stock sizing from but stock is over 800. So set it to 785 and go with that. That is going to be your most accurate number.
I got the stock number from the link I posted in post #6. Its from American muscle.
PaladinMicro
Use this and put your tire size into the prompts and it will come out to 787 revolutions/mile so 785 would be your closest bet. 275 40 17 tires are 810 according to that calculator. The guy is a regular on Mustang Forums and is some sort of engineer genius.
Use this and put your tire size into the prompts and it will come out to 787 revolutions/mile so 785 would be your closest bet. 275 40 17 tires are 810 according to that calculator. The guy is a regular on Mustang Forums and is some sort of engineer genius.
You were 100% correct. Americanmuscle.com sheet wasnt even close. Thanks for the info and sorry for even thinking I was doing it right. :beer: I confirmed the speedo reading next to my GPS app on my phone.
Cool. just trying to help ya out mang. I think I'm going to call AM today and tell them that they need to revise their tire size menu to make it more accurate.
Called AM and informed them of the issue and they said that this issue will be taken care of as soon as possible. :thumbsup:
Good job. :beer: You will have saved alot of people time and maybe money on getting a ticket with them thinking their speedo is correct. :rockon:
^My thoughts exactly. Trying to save everyone a little bit of time, effort, and money...and maybe a couple points on their license. lol
Just an update, AM took the link down that the OP posted with wheel sizes and revs/mile and are probably currently fixing it. Gotta love AM and their awesome customer service!!! :thumbsup:
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