The 275 vs. 245 is just measuring the width of the tread--NOT the width of the tire. You are measuring including the sidewalls. Look at the tires themselves, or your pics. See how the sidewalls on the 245 are a bit fatter? They bulge out a bit more. Try measuring the actual tread itself and compare those measurements.

 

that would be true if it was a 245 tire, but those are 255.




anyway in the pic side by side you can visually see that the inner treads on the 275 are wider than the 255. but at first glance i could see how easy you could think that the tires were the same size.

 

Thanks for the photos and captions. You have got to be a engineer.

 

Bleh, I guess your tires are fubar. I personally would run a 245 on the front and a 275 on back, but that's just me.

Where did you get them from? I like Tire Rack because if I need to ship back an incorrect size I'm only out a little shipping and they never hassle.

 

I got them from tirerack. Why would you go for a 245 in front versus a 255? Just curious. 245/275 seems to be a more popular combo on this site.

 

Haha! Yeah, it's a dead give-away; over analyazing stuff. I used to be a techie type, but now I am a program/project manager for techie stuff. Chief paper pusher now... I do miss the hands on. Still have those OCD tendencies...

 

Tread width measurements with a ruler are the real let-down here...

275 = 10"
255 = 9-3/4"

I am sure it'll be fine. They'll probably take acompletely different shape once mounted on the wheels and inflated.

It's just that logic did not prevail with the tires being so similarly sized, versus the true 20mm difference I was expecting.

 

that is a little disheartening. the 255 should be right at 10 inches, and the 275 should be 10.8 inches. Kinda sucks that you paid alot for these tires and didnt really get what you were expecting.

 

The picture of the level on top of the two tires balanced by coins is measuring the section width. If you check Bridgestone's web site, the published section width of a 255/40R18 RE050A PP is 10.2 inches and a 275/40R18's section width is 10.7 inches, a difference of about 12.7 mm.

The Tire Rack states, "[The section width's] measurement is made without any load placed upon the tire and after the tire has been properly mounted on its industry assigned measuring rim and has been inflated and reset to its test pressure after 24 hours." Also, "Because a tire's section width is influenced by the width of the rim upon which the tire is mounted, the correct industry assigned measuring rim width for the tire size being measured must be used."

Since these tires aren't properly mounted on the correct size measuring rim, 9.0 and 9.5 inches respectively, I think the difference in section width that was found is understandable. What's odd though, Bridgestone lists the tread width of both tires to be 9.3 inches.

 

Look at the size differences between the RE050A and the RE050A PP:

275/35/19 (SW=section width, TW=tread width)

RE050A - SW 10.9 TW 10.2

RE050A PP - SW 10.6 TW 9.1

ncdoc

 

Yep, I noticed that too. I think it's because they market the PP as a tire that does well in wet and dry. So they make it narrower so it's less likely to hydroplane (?).

I just don't get it...

we mounted them and the 255 looks perfect on an 8.5" rim. The 275 still looks a bit stretched on a 9.5" rim. Hmmm... I'll post pics in a few days.

 

Just some feedback.... After the wife has been driving on these for a week or two, I thought I'd take her car up hwy 84 - Woodside road.

HOLY ****!!!!!

This car is just crazy-fast on the corners with these tires. Handling is VERY neutral, especially when accelerating out of a corner. The fronts have grip for days!

I was pushing the car pretty hard and it was like, "That's all you've got?" to me! HAHAHA... what a blast. Feedback is also very good. I could not get the car to push (understeer) around the corners.

I really pissed off the TCS after trying a little deliberate throttle-oversteer coming out of a corner. It seriously cut the power and would not come back on its own until I slowed down about 15 mph and stayed there for a few seconds! Stupid TCS! Don't worry, I am used to hanging it out a _little_ on the rear-end. The M3 would let me get away with that maneuver much more before ASC kicked in. Oh well.. I may drop the rear pressure a couple PSI - they don't seem to be wearing out to the edge after the spirited driving. The rears are a higher load-rating than stock, so they might like less pressure...


Definitely impresssed with this tire in this size combo:
RE050a Pole Positions
255/40/18
275/40/18

Oh, and she's running spacers on her wheels that give her an effective +15 offset...

This thing would be fun at an auto-x!

Noticably more grip than my GT with:
RE050a (non pole positions)
245/40/18
265/35/19

Had me grinning from ear-to-ear


I wish I could put this setup on my AME circular spec-r's that are on their way, but Bridgestone does not a offer a 255/35/19, only a 245/35/19. And I am going 275/35/19 in the rear when my new wheels get here. Hmmm... I may have to go DS-D3 with my new wheels to get the sizes I want.. I wish the Pole Positions came in more sizes. I don't think I'd like a 245/275 setup... That would probably understeer noticably...

I don't care how big these measure or don't measure... it turned out to be a non-issue! THey don't look as big as they should, but form<function in my book.

 

Just thought I'd complete this thread with some pics...

BTW, her rims are 18x8.5 and 9.5, +35 all around with 20mm spacers for a final +15 all around...

 

Looks proper.

 

hey what wheels are those?

 

Appears to be the Sportmax well now XXR 962.