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View Full Version : New tire size: how do I tell the car that?


gdsqdcr
08-26-2010, 07:42 PM
I out new tires on the rear today, 265/50/18's. How can I tell the computer that the size is not stock soothe speedo reads correctly? I thought I could figure it out with the SCT2 that I have; but apparently I am not that good.

Thanks!
Anthony
FordNut
08-26-2010, 07:47 PM
You need to have your tuner change it and send you a new tune. You need to have the Pro Racer's Package or the Commercial/Professional Tuner's Software from SCT.
FordNut
08-26-2010, 07:48 PM
BTW, if the rears are the same diameter or smaller than the fronts you're going to have other problems with traction control and ABS, those problems can't be fixed in the tune.
TooManyFords
08-26-2010, 07:59 PM
Which tires did you go with? Are these the Nitto 420S's? How far off is your speedo with these on there?

I ask because I ordered a set of 235/55R18's for the front and the 265/50R18's for the rear.
gdsqdcr
08-26-2010, 08:31 PM
I have the stock size in the front and 265/50/18 in the rear. They are the Nitto 555 Extremes. Look nice. We shall see the handling in a bit -- has to wait since I got hit on the way home. Body shop time ... :)
FordNut
08-26-2010, 08:39 PM
Bummer....
dohc324ci
08-26-2010, 09:07 PM
What! Hope it won't be in there long. What happened?
gdsqdcr
08-26-2010, 09:28 PM
I was in the daycare parking lot with the back door open putting the boys in. The teacher saw me and we chatted a bit. She got in her truck and didn't realize my door was still open. She pinned it between her tire and fender well. Lots of paint off the door where it rubbed the tire. The concern is in two other places though: the hinges and the crease in the metal next to the quarter window. That crease is about 8 inches long and the bend is at the chrome. I am thinking a new door skin ... The door does shut, but leaks air now.

Her grandpa owns a bodyshop so I am going to check them out this weekend. Her words, if I am not comfortable, we call insurance first thing Monday and go from there. Nice teacher or I would Lready have called insurance.

Two parents watched it happen and she readily admits it being her fault so I am not concerned waiting till Monday.

Just sucks. N
FordNut
08-27-2010, 05:36 AM
Best bet, find a silver Crown Vic in a junkyard and swap the entire door. I believe the main difference is the exterior door handles on the CV are chrome and the MM are painted.
Marauder
08-29-2010, 09:17 AM
245/55-18 = 28.61" diameter
265/50-18 = 28.43" diameter
0.6% difference.
If your speedometer reads 65, you'll be traveling 64.6 mph.

I think you're ok. :)
BAD MERC
08-29-2010, 10:22 AM
I was in the daycare parking lot with the back door open putting the boys in. The teacher saw me and we chatted a bit. She got in her truck and didn't realize my door was still open. She pinned it between her tire and fender well. Lots of paint off the door where it rubbed the tire. The concern is in two other places though: the hinges and the crease in the metal next to the quarter window. That crease is about 8 inches long and the bend is at the chrome. I am thinking a new door skin ... The door does shut, but leaks air now.

Her grandpa owns a bodyshop so I am going to check them out this weekend. Her words, if I am not comfortable, we call insurance first thing Monday and go from there. Nice teacher or I would Lready have called insurance.

Two parents watched it happen and she readily admits it being her fault so I am not concerned waiting till Monday.

Just sucks. N


What door was hit? I have a WHOLE damaged LR door with perfect hinges and door handle in silver birch. If you need them they're yours free if you pay shipping!
Black Terror
08-29-2010, 10:22 AM
Sct 2 & 3 Tuners have menu to change revs/mile(705 to 710), use calculator below:

http://www.miata.net/garage/tirecalc.html
SC Cheesehead
08-29-2010, 10:26 AM
Sct 2 & 3 Tuners have menu to change revs/mile(705 to 710), use calculator below:

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

Good stuff, thanks for posting. :up:
gdsqdcr
08-29-2010, 04:21 PM
Bad Merc, it was my left rear door. I will keep this in mind. First I need to figure out with the offender what they want to do. Nice girl, but is my car she hit.

As for the SCT2, that is what I have and I could not figure it out. I will try again, cause I xo like it perfect.

Thanks!
Anthony