i was at the audi dealership last night and they had 275s on OEM 18s.

 

they're ordered.
i'll post pics when i get them.

i actually like the little bit of a bulge. now i'm not going to be so worried about curbing my wheels any more.

 

Sounds like my tard brother-in-law........285s on a 7" rim.....I told him it
wasn't a good idea..........the installer told him the same thing but he's
going to do what he wants! The 245s are good for the frontend but why
not just go with 255s out back.........no issues there.

 

yes you're right, 285's on a 7" rim does sound a big crazy.

the 275/35 ratio produces a sidewall that is closer to stock then a 255/35 mix, meaning your speedo won't be as off.

check it out.
a 245/40/19 tire has the following characteristics.
Sidewall: 3.9"
Radius: 13.4"
Diameter: 26.7"
Circumference: 83.9"
Revs/mile: 755

the 275/35/19's that I put on have these characteristics;
Sidewall: 3.8"
Radius: 13.3"
Diameter: 26.6"
Circumference: 83.5"
Revs/mile: 759

as you can see it's a little smaller, and that means that my speedometer is going to be a tad fast (ie, when my speedo reads 60 I'll be going 59.7)

now, as for the 255/35/19 you suggested
Sidewall: 3.5"
Radius: 13"
Diameter: 26"
Circumference: 81.8"
Revs/mile: 775

this is much smaller then the stock tires, so now, when your speedo is reading 60, you're really only going 58.5.

To get all this data I used the tires size calculator on this website.

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

 

Size Range OD Revs
255/40 ZR19 8.5-10" 27" 769

Gary didn't specify series, he just said 255. 255/40/19 specs for PS2s appear above. Only .3" difference in OD.

Lou

 

ahh, didn't know he was talking 18's

 

Don't know if this thread is dead, but I put 245/35's in front and 255/40's on the rear. Very satisfied. Live in Wisconsin and had to get a all season tires-Michilens. What a pain in the ****!- $1600.00 later

 

you got pics of the front?

 

My rear OEM 19 tires are almost gone, and I was thinking about replacing them with Toyo T1-R 275/35/19's, keeping the stock tires in the fronts. Do you think there will be issues with VDC with this setup?

 

I am running 275/35/19 in the rear and 245/35/19 in the front for about 6k miles on OEM 19s. no issues. FYI for everyone.

 

This thread is back from the dead.
I'm buying tires this week - Toyo T1R's.

Based on the info from http://www.miata.net/garage/tirecalc.html (thank you for posting this link, Madscientist!!!)....

255/35/19 Front and 275/35/19 Rear is closest to OEM in overall diameter, and thus the most accurate for the speedometer and odometer readings.

FRONT
225/40/19 OEM
Sidewall: 3.5 in
Radius: 13.0 in
Diameter: 26.1 in
Circumference: 82.0 in
Revolutions per mile: 773.0

255/34/19 comparison
Sidewall: 3.5 in (same as OEM)
Radius: 13.0 in (same as OEM)
Diameter: 26.0 in (-0.1 in)
Circumference: 81.8 in (-0.2 in)
Revolutions per mile: 775 (+ 2 rpm)

Speedometer reading with non-stock tire is 0.2% too fast. When your speedo reads 60mph, you are actually traveling 59.9mph

REAR
245/40/19 OEM
Sidewall: 3.9 in
Radius: 13.4 in
Diameter: 26.7 in
Circumference: 83.9 in
Revolutions per mile: 755.0

275/35/19 comparison
Sidewall: 3.8 in (-0.1 in)
Radius: 13.3 in (-0.1 in)
Diameter: 26.6 in (+0.1 in)
Circumference: 83.5 in (-0.4 in)
Revolutions per mile: 759.0 (+4 rpm)

Speedometer reading with non-stock tire is 0.5% too fast. When your speedo reads 60mph, you are actually traveling 59.7mph.


Based on this data, the choice is clear...bump up the 225/40/19's in the front to 255/35/19.

I'm very curious as to why no one on the forums has suggested this, if the calculations make it so evident that it's the correct way to go.

Are there any opinions on this setup? Has anyone tried it?

 

The reason most people won't suggest it is because a 255mm wide tire is out of the range specified for an 8" wide wheel, just like the 275's. There isn't going to be a significant advantage to going with wider tires on the stock wheels because contact patch is solely a function of weight, not tire width. The possible advantages lie with handling because a wider tire allows for more lateral grip, but is offset by the flex in the bulging tires

 

Whatever I do, I need to keep a 20mm stagger between front and back? 225 Front, 245 Rear being similar to 245 Front, 265 Rear?

 

Not necessarily true, alot of 350z guys run 275's all around with VDC, I think maintaining height stagger is more important than width stagger

 

Well a Bridgestone 275-35-19 re050 needs at least a 9" wheel. I don't think the oem 19" rear is 9"? I thought they were 8.5" wide?