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Discussion Starter · #1 ·
I'm looking to replace my rear tires and the current ones are blizzak 245 / 40 / R18 s ,,, a bit confused because some websites have the tire size as 245 / 45 / R18 ... I bought the car about a year and a half ago so I'm not the original owner. What is the correct tire size, and since I'm only replacing the rears, do you guys think I would have handling problems from front to back? If both my rears are 245 / 45 and my fronts are 245 / 40 .. how would that affect handling? Do you guys know why the original owner would switch the ratio? I wonder if my speedo has been off this whole time.. I don't think it was kuz I'm pretty sure I've gone through the radars and it's accurate on the gauge.



thanks:gears:
 

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Stock size for the 18" wheel is 245/45/18.

The Sport 19's were 245/40/19.
 

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It's not much of a difference. 1-3 mph from actual versus what your speedo says. And that 1-3 range is dependent upon how fast you're going. It's further off at higher speeds. I'd be willing to bet your speedo has been off while running the 40. As in, it was never adjusted for them.

The car shouldn't handle any differently, aside from you're going to a higher sidewall, so it should ride better. The type/brand of tire would have more impact as well.
 
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Discussion Starter · #6 ·
It's not much of a difference. 1-3 mph from actual versus what your speedo says. And that 1-3 range is dependent upon how fast you're going. It's further off at higher speeds. I'd be willing to bet your speedo has been off while running the 40. As in, it was never adjusted for them.

The car shouldn't handle any differently, aside from you're going to a higher sidewall, so it should ride better. The type/brand of tire would have more impact as well.

cool, ty ebg8gt !! :pir_flag:


the 45s are half the price of 40s... I'm going with Blizzaks because that's what's on there now and they look ok. My Jeep needs a new tire and caliper so for now I have to drive my baby in the snow. I've been driving on two bald rear tires for a few months now lol. But it's getting a bit a crazy... I got caught in a snowstorm and the rear was sliding around like Stevie ray vaugh on a strat
 

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I've heard some people report the ABS system freaks out when different tire diameters are used on front and rears, since the wheels are turning at different speeds. I don't know what the threshold is though.

If you haven't bought tires yet, take a good look at the Michelin Pilot Sport A/S 3+. I took mine into the snow for 4 days and had great results on all kinds of snow/ice, never took the chains out of the trunk even though lots of other people had to use chains.

Rant mode - on

I also know that my speedo consistently reads about 3 mph high on the OEM wheels and OEM size tires (245/45/18) and has read high from day 1, making me wonder if the dealer recalibrated my car for different wheels/tires and then put back on the OEM ones when I bought it without putting the speedo calibration back to stock. I suspect the speedo would read correctly if using the sport package wheels/tires, not sure why the dealer would mess with a non-sport car like that.

Of course, I recently had a collision guy tell me that my hood had been repainted even though I never had it painted myself, so maybe the car had a "colorful" history in its first 20ish miles and the original dealer never told me about it. I hate to say it but with that kind of nonsense at the dealer level and cars being badly damaged even before the cars got to the dealer lots, Pontiac deserved to die.

Uh.. rant over :)
 

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Discussion Starter · #8 ·
The ABS system has been fine with 40s on the front and 45s on the back but I should have definitely gone with the 40s again. The look is way better. I actually did get the same tires you have by coincidence and yes they do great. I have been a fan of Michelins tires since I swapped some Bf goodrich tires out for Michelins my 05 GSX-R600. The difference in terms of grip and ride comfort was night and day on a motorcycle.

I have the Blizzaks still on front and I think they look better than the Michelins but the Michelins have a better ride and noise level.

If I could do it over I'd buy the Blizzak 40s all around but the michelins are not too bad.
 
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