Look like 18's to me. You can put up to 19's and still be safe if you were wondering. I had 17's on mine. Look at the size difference from my main profile pic.
About an inch and the ride quality! Sorry had to get smart on that one. You'de have to get a smaller profile tire for the 18 than the 17. It lessens the ride quality, but I wouldn't assume it would be too awful of a difference.
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You can put up to 19's and still be safe if you were wondering. I had 17's on mine. Look at the size difference from my main profile pic. 
You'de have to get a smaller profile tire for the 18 than the 17. It lessens the ride quality, but I wouldn't assume it would be too awful of a difference. 
