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      03-30-2013, 06:40 AM   #1
Vanne
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Tire sizes m coupe

Just wondering what the stock tire sizes are for the 18 inch rims?

Mines got 275/35 on the back??

Thought stock was 255?/40????

Will this have any impact on safety?
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      03-30-2013, 08:38 AM   #2
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the stock sizes on my 2008 3.0si are
255 35 R18 Rear
225 40 R18 Front

Not sure if these are the same on the M?
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      03-30-2013, 10:09 AM   #3
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Stock for ///M are:
225/45ZR18 front
255/40ZR18 rear

As long as the tire doesn't "rub" or comes in contact with anything during suspension compression, you should be fine. There are a few people running your indicated size without issues. However, some do report "rubbing". So, it may depend on the tire model as not all 275s are created equal
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      03-30-2013, 09:12 PM   #4
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interesting.. where would they be rubbing? inboard or outboard of the rim?
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      03-30-2013, 10:09 PM   #5
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What size:
Wheels and offsets?
Suspension?
Alignment (negative camber)?
Type of tire (PSS, RS-3)?

Tire size is just one variable. Need more info.
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      03-30-2013, 11:24 PM   #6
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That's the size I am planing to go to next time.
Just going for the bling factor.
Will add 15mm spacers just to insure no rub.
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      03-30-2013, 11:44 PM   #7
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Quote:
Originally Posted by NewZee View Post
the stock sizes on my 2008 3.0si are
255 35 R18 Rear
225 40 R18 Front

Not sure if these are the same on the M?
Quote:
Originally Posted by XMetal View Post
Stock for ///M are:
225/45ZR18 front
255/40ZR18
So stock 3.0si has lower profile tires vs. stock M?
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      03-30-2013, 11:51 PM   #8
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Entirely possible that the performance of the ///M requires more sidewall flex to keep them planted.
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      03-31-2013, 10:57 AM   #9
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Stock wheels, not sure on suspension, but its rock hard. Not sure on spacers and not sure on camber, but it looks great
There is no rubbing at all. Dunlop direzza 1dz101
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      03-31-2013, 12:23 PM   #10
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I'm assuming that you're also running Direzza dz101 on the front as well with 245/40ZR18 without issue? I'm also trying to decide if I want to stick with stock or go with this Direzza dz101 245/40 and 275/35 combo on an upcoming tire purchase.
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      03-31-2013, 12:25 PM   #11
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Common tire size combos are F/R 245/40 and 275/35, 235/40 and 265/35. The 275/35 is ~1.7 smaller in diameter than the stock tire. Which is just fine. No safety issues whatsoever.

The only negative with running that size tire is running it on the stock 9" wheel. That size tire belongs on a 9.5" or 10" wheel. Otherwise the tire is a bit pinched, and you're not realizing the full width of tire and not getting maximum potential out of the rubber.
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      04-01-2013, 11:46 PM   #12
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Quote:
Originally Posted by XMetal View Post
I'm assuming that you're also running Direzza dz101 on the front as well with 245/40ZR18 without issue? I'm also trying to decide if I want to stick with stock or go with this Direzza dz101 245/40 and 275/35 combo on an upcoming tire purchase.
Nope, 225/40r18 on the fronts.
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      04-04-2013, 03:44 PM   #13
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I just checked and realized that the tires on my M roadster were replaced with the lower profile tires... Any drawbacks other than incorrect speedometer?
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      04-04-2013, 04:01 PM   #14
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Quote:
Originally Posted by intoflatlines View Post
I just checked and realized that the tires on my M roadster were replaced with the lower profile tires... Any drawbacks other than incorrect speedometer?
Many people have replaced their stock tires with a lower profile tires and gone 10-20+ millimeters wider. It depends on the combination you choose, you can do this aggressively or conservatively.

To check any possible difference in overall circumference, and how it will affect your speedometer (and odometer), use one of the many online tire size calculators like this one: http://www.discounttire.com/dtcs/infoTireMath.dos
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      11-05-2013, 02:11 AM   #15
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xmetal did you decide what you wanted to do yet? I HAVE to buy new front tires,and am debating wether to go 235/40/r18 or 245/40/r18 for the front, stock for the M being 225/45/r18

i have 275/35R18 ON The back with no issues.

i have stock size INtercontinental on the front at the moment, but i hate how the tire looks, it round on the sidewall, especially towards the grippy part of the tire..

any suggestions?
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      11-05-2013, 06:53 AM   #16
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Like what Finnegan said, most go 245/275 or 235/265 combo. Since you already go 275 in the rear, 245 in the front will keep the difference front/rear in check. If you choose 235 in the front (which is fine), beside it's smaller than OE size, it'll also be smaller than the rear tire.

HTHs,
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      11-05-2013, 11:26 AM   #17
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Quote:
Originally Posted by Vanne View Post
xmetal did you decide what you wanted to do yet? I HAVE to buy new front tires,and am debating wether to go 235/40/r18 or 245/40/r18 for the front, stock for the M being 225/45/r18

i have 275/35R18 ON The back with no issues.

i have stock size INtercontinental on the front at the moment, but i hate how the tire looks, it round on the sidewall, especially towards the grippy part of the tire..

any suggestions?
I have decided to play it safe and stick with the stock sizes and just got the widest contact patch that I can find. I ended up with the Bridgestone Potenza S-04 Pole Position. It even look a tad bit wider than stock...almost as though I have 235/265 combo. The ratings on TireRack were good and it's priced relatively well.
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      11-05-2013, 01:21 PM   #18
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Isn't 245 on the front too wide for the OEM wheels? I will be buying new tires in the spring and will most likely go for Bridgestone RE-11 or similar in 235/40 front and 265/35 rear. Stock wheels and suspension. I'd like to go wider especially in front but I don't think it would be beneficial with the stock wheels.
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      11-05-2013, 01:57 PM   #19
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Quote:
Originally Posted by intoflatlines View Post
Isn't 245 on the front too wide for the OEM wheels? I will be buying new tires in the spring and will most likely go for Bridgestone RE-11 or similar in 235/40 front and 265/35 rear. Stock wheels and suspension. I'd like to go wider especially in front but I don't think it would be beneficial with the stock wheels.
I believe that is what Finnegan said. You can fit the larger 245F & 275R on the rims, but it isn't optimal. 235F & 265R is as big as you should go.
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      11-05-2013, 02:33 PM   #20
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Quote:
Originally Posted by intoflatlines View Post
Isn't 245 on the front too wide for the OEM wheels? I will be buying new tires in the spring and will most likely go for Bridgestone RE-11 or similar in 235/40 front and 265/35 rear. Stock wheels and suspension. I'd like to go wider especially in front but I don't think it would be beneficial with the stock wheels.
Depending on tire construct. You need to check the range of wheel rims allowed per manufacturer's specifics. Most 245 tires will require a minimum width of 8", with nominal width being 8.5" (and max width of 9") if my memory serves.
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      11-05-2013, 04:55 PM   #21
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Like the Hack said it depends on the tire. However, as a general rule, running a tire to meet the minimum width requirement of the rim may not yield good results.

My data with the pyrometer show that the center, or middle of the tire tread does most of the work. Basically the tire is "pinched". That extra rubber doesn't achieve the objective of more grip, rather it's counterproductive. That was the case in trying PSS 245/40 and 275/35 on the stock rims, with -2.5 up front. The tires were not happy. Put them on 8.5 and 9.5 inch rims and tire temps (and grip) showed a considerable improvement.

Some tires, particularly those that are square (Star Specs, etc.) and have stiff sidewalls may work "ok" at min. rim size. R comps or competition tires may work fine as well (different rules). But for street tires, if the goal is more grip and effective contact patch, wider may not equal better.

Personally I'd go with the 235/265 combo with stock sized rims. YMMD, I'm offering what I could see at the track with a pyrometer, not trying to describe absolutes.
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      11-05-2013, 10:49 PM   #22
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Yeah thx Finn and everyone else, I am going to go with 235/40r18. Probably dz101..
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