budders

Hey guys, so im just thinking forward here and i needed some opinions... again.

This weekend im going to be picking up a set of 18" saleens from a guy. stock wheel is 17" and these are 18s, so my speedo (and odo) is going to be off by a few mph.

I know that you can correct this with the SCT tuner, but i dont have one

So i was wondering what you guys suggest I should do. These are my options so far that i've come up with,

A. stop by a shop that has an SCT/Diablo tuner that can chage the tire size
B. Just flat out buy an SCT/Diablo for 399$ off american muscle.
C.... find someone with a tuner (dont know any body though)

A, would probably be the cheapest, but im not sure if shops even offer this. I emailed a mustang shop (evolution performance) near me, and its been about 2 days and still no response. (pretty sure they wouldn't wanna bother with my old stang though, heard they only cater to high paying customers, gt500s ect.)

I would hate to have to spend 400 bucks just to get my speedo to read right, but the positive side is that ill get a custom tune

What do you guys think I should do? If any one else has any other solutions or suggestions, please let me know! Thanks guys.

(posted this by accident in 4.6 general, mod can delete)

bopiela

As long as the overall tire diameter of your new wheels is close to your stockers you will have no issues. It is not the wheel size, but the overall tire diameter. So you should be ok, most likely, and not need any tuning!

budders

Thank you so much, i just realized that. i did that math and its only going to be about a half an inch off so i guess i dont have to worry, but maybe I should just get a tuner so i can have some fun

Mustang_NTriangle

1/2" will impact your speedo especially the faster you go. If you don't have a tuner go and get one you can benefit from it all around.

teej281

Whats the tire size on the tires youre buying??? My tires are 295-30-18's and they make my speedo read 61.7 when in reality im only going 60...so i mean youre putting unneeded mileage on your car. I would go ahead and get the tuner and put the canned high octane tune in it and roll with that that way you can get your speedo right and if you get gears you can compensate for those as well. Just my opinion.

budders

the tires I'm getting are 245-40-18 & 275-40-18. I think I can wait a little bit for the tuner. I might get it in a few months, closer to summer. My budjet for modding isn't too big, but I still wanna do some more stuff to it before summer, like lowering, tint all around, and finish installing the hood scoop + mach 1 chin spoiler (waiting for those warmer days).

teej281

I wouldnt get a 275 40 18 if youre going with that front size you mentioned. Try to find something like a 265 40 if you want to run 275 40's that way it wont be such a big difference between front and rear height. Or drop your profile down to a 275 35 instead of a 275 40 so they will be closer in diameter.

K Z

http://www.1010tires.com/TireSizeCal...bmit&reset=yes
This will help u out

soccerman002

http://www.miata.net/garage/tirecalc.html

Use this tool to determine your displayed versus actual speedometer reading. Helps in determining tire sizes if you'd like to avoid worrying about there being a slight percentage difference. In the long run, I don't think a 1% difference either way is really worth worrying about, especially if you plan on picking up a tuner later down the road that can make the adjustment. The tuner adjustment is meant more for aftermarket rear-end gear adjustments than tire/rim size adjustments.

budders

I just check the tire size on my car right now and they are 245-45-17s all around. the tires im getting are 275-40-18s. it says when im traveling at 60mph, ill actually be going 62mph. thanks guys for all the info