i wanted to do this with my factory 17” 5 spokers. factory size is 235 45 17 i believe. think i would be ok with some 255’s in the nitto nt05 flavor?

 

Look at Nitto's Website...

For "my rim" the 18" Chrome Bullits (sp?)

NT555 Tire
235/50-18 recommended rim is 6.5 (7.5) 8.5
255/45-18 recommended rim is 8.0 (8.5) 9.5
275/40-18 recommended rim is 9.0 (9.5) 11.0

Then you can use this to see the difference in rotation and width etc...
http://www.miata.net/garage/tirecalc.html

Now for your tires the;
235/45-17 it looks like you can go

The NT05
255/40-17 BUT THE recommended rim is 8.5 (9.0) 10.0

 

255/45-18 are the way to go I think. Ive got coopers on my stang in that size, and they seem to fit really well, they stick out slightly further than the wheel, unlike the stock size.

 

255/50-18

255 divided by 25.4
10.03937008 x .50 TREAD WIDTH
5.019685039 x 2 SIDEWALL HEIGHT
10.03937008 + 18 RIM DIAMETER
28.03937008 x 3.141592654 TIRE HEIGHT
88.08827905 ROUND
63360 divided by 88.08827905
713 REVS / MILE

Its just an example of the math. Dont let this confuse you.....

http://www.tacomaworld.com/forum/tirecalc.php
https://www.rsracing.com/tech-wheel.html
http://www.1010tires.com/TireSizeCal...?action=submit
http://www.miata.net/garage/tirecalcold.html

 

lost me 157db

we were talking about a 255/45 which is within 1/2" of the 235/50

 

235/50-18 vs 255/45-18 vs 255/50-18

235/50-18
Sidewall: 4.6
Radius: 13.6
Diameter: 27.3
Circumference: 85.6
Revs/Mile: 740

255/45-18
Sidewall: 4.5
Radius: 13.5
Diameter: 27
Circumference: 84.9
Revs/Mile: 746

255/50-18
Sidewall: 5.0
Radius: 14.0
Diameter: 28.0
Circumference: 88.1
Revs/Mile: 719

 

275/45 is 27.7" tall, half an inch or so taller than the OE sizes. This 45-series tire IS mfr-approved for mounting on 8.5" wide wheels. 275/40 generally is not (there is a tiny possibility that some mfr makes some tire model that they claim is OK on 8.5" but I'm not going to try to chase it down).


Being half an inch under the minimum mfr-approved wheel width will give away some of the tires' lateral stiffness, so it'll feel a bit "lazy" about cornering. (ps - the word "almost" bothers me, a lot, because sometimes poo does happen. If/when it does, it'll be too late to wish you'd done differently)

I'm less concerned with unseating the bead than I am with extra heat generation in the sidewall, and where specifically in the sidewall that the extra heat gets concentrated. Something called a "flex point" moves up/down over the sidewall as wheel width is varied. Not all portions of the sidewall are equally capable of handling this local flexing or the temperature that is developed.

That said, being half an inch "below spec" is something that you can get away with for short duration or low-speed driving where the tire temperatures remain low. But loading a car so equipped up to the gills with all sorts of gear and taking three of your friends on a long highway trip in the middle of a Texas summer heat wave is probably asking for trouble.


Norm