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Discussion Starter #1
alright, my mazdaspeed 6 had a run in with screws and nails and now i need new tires. i don't wanna spend $200 bucks a tire and tire rack has the Kumho ECSTA SPT for cheap. the 215 is $107 and the 225 is $95. my question is should i get the 225 and save the money even though OEM is 215? also, are the Kumho ECSTA SPT comporable to the potenzas? the potenzas seem to grip pretty good, so i don't wanna lose the performace there cause i drive pretty spirited. also, the Kumho Ecsta MX didn't do so well in the Car and Driver review. are the Kumho Ecsta MX and the SPT pretty much the same?

what i really want are the Goodyear Eagle F1, but they don't seem to make those in 18"

any other recomendations on tires $140 or less would be appreciated.
 

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Are you planning to change out that one tire or all 4?

For AWD, you should either get the same tires or tires of equal size. If you get one pretty different from the rest of the others, it'll throw off the sensor readings and might think it's slipping. It'll cause a bind in the transfer case.

Not all 215/45-18"s are made equally as well.
 

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You cannot use 225/40R18 on the stock MS6 wheel. It is only 7 inches wide and 225/40R18 requires at least a 7.5 inch wheel. Your options are 215/45R18 or 225/45R18. While you're searching, consider the Toyo Proxes T1R, which is available in 215/45R18.

 

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Discussion Starter #5
You cannot use 225/40R18 on the stock MS6 wheel.

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I know this. I am comparing the 225/45WR18 to the stock size 215/45WR18. I want to know the disadvantages of changing sizes to just save the $50 on the cheaper 225/45WR18.

I am going to change all four tires.

PS
Mazda put all the fucking finger bolts on the damn spare and jack so fucking tight i had to get a wrench to undo them. Even then it was hard. If i was on the fucking high way changing the spare I would be so fucking pissed it would tempt me to roll my car off a hill.
 

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I know this. I am comparing the 225/45WR18 to the stock size 215/45WR18. I want to know the disadvantages of changing sizes to just save the $50 on the cheaper 225/45WR18.
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Ok, cool. I don't really see any advantage to going to 225/45R18. Your speedo will be off a bit. If it were me, I'd stick to the oe size.
 

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With the larger tire you speedo will be off...

It will read that you are going slower than you actually are.... technically this means less miles on your car ;)
 

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It is a minimal size change. Maybe a pinky width wider in the tread section and less than half of that in height. The speedo runs just slightly fast stock anyway, so you'll likely just be making it read accurately.
 

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It is a minimal size change. Maybe a pinky width wider in the tread section and less than half of that in height. The speedo runs just slightly fast stock anyway, so you'll likely just be making it read accurately.
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True. It's within guidelines. Difference is about 1.2%, so at speedo reading of 70 mph, actual speed is about 71 mph.
 

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You cannot use 225/40R18 on the stock MS6 wheel. It is only 7 inches wide and 225/40R18 requires at least a 7.5 inch wheel. Your options are 215/45R18 or 225/45R18. While you're searching, consider the Toyo Proxes T1R, which is available in 215/45R18.
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I'm a little bit lost on your reasoning here. You stated that 225/40R18 requires at least a 7.5 inch wheel but yet you then said your options are 215/45R18 OR 225/45R18.

Wouldn't the 225/45R18 require at least a 7.5 wheel too since it has the same width?
 

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I'm a little bit lost on your reasoning here. You stated that 225/40R18 requires at least a 7.5 inch wheel but yet you then said your options are 215/45R18 OR 225/45R18.

Wouldn't the 225/45R18 require at least a 7.5 wheel too since it has the same width?
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No, because the taller sidewall of the 225/45 allows it to be fitted to a narrower wheel. I'm quoting RMA specifications and they say 225/40 needs 7.5 inch wheel and 225/45 can be mounted on 7 inch. But like I said before, I think the better choice is the 215/45 anyway.
 

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The speedo runs just slightly fast stock anyway.
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I was amazed at how accurate it is.

We purchased our '6 used with the stock Michelins on it, and decided to let the stock tires (pumped to 35 psi) take the summer beating on the back U.S. Forest Service and Yakama Indian Nation roads that we frequent in the summertime (before swapping to real tires for our wet winter months); so I have had a lot of chances to check out how accurate the odometer is with the stock tires mounted.

There is a 21.17-mile stretch of Washington Highway 14 (two lanes, no place to deviate) from just east of Washougal to just west of the Bridge of the Gods where the mileage markers at both ends are calibrated in hundredths of a mile, 19.63 at one end of the stretch and 40.80 at the other. I have watched the odo driving that stretch four times now, and each reading showed 21.1 miles, with even tenths of a mile being the limit of resolution of the digital odometer. On a statistical basis, I would expect one or more of those readings to be 21.2 if the odometer was exactly correct, but my readings do suggest that the odo is in error by no more than .07 mile over a 21 mile stretch, which works out to 99.9967% accuracy.
 

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Discussion Starter #13
i got the kumho 225/40R/18. they did a quick calculation and said they would fit no prob and they seem to be right. i have only tested dry traction and it seems to be just as good as the potenzas.

i paid $549 with the hazard warranty at discount tire.

it was very fun pulling out of the discount tire with slippery new tires. it's pretty funny cause the exit from the lot has rubber where people got the back end squirrely just like me. good time.
 
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