You can swtich to a 180 no problem. It was said that it improves handling slightly if you change both tires to the 00-02 spec, thats a 120/65 front and the 180/55 and thats what i did. Its hard to tell if its better, but so far it works great for me.
If you can change the tire without changing the rim or anything else I say go for it. What's the worse that could happen, it doesn't handle as good as it did before? You'll still be able to turn and everything; it shouldn't be that bad, and if you hate it just do lots of burnouts
That's if you have the money to experiment. If not you're probably not missing much of a positive difference, and I wouldn't worry about it
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