You are only feeling the stiffer/lack of sidewall because you are on street tires with soft sidewalls to begine with. If you were running Honda Challenge or Speed Channel Touring I could see that big of a wheel to clear big breaks. But, just buy running that wheel you are way down on HP and Torque. This is because even if the rim and tire of 15inch wheels weights the same as 17inch wheels. The weight is farther away from the center takeing more ummph to get it rolling and sucking up power.

If you have a set or can get a set of 15x7 or even 15x7.5 if you want to spend alittle more slap on some cheap (low $) V700 Ectas from Kumho and go.

If you want a tire to drive to and from the event on you cant go wrong with the Azenis or the Kumho MX. I have had them both and figure they are extremely close. View my thread about the Hankook tire if you can hold off untill early September.

Just my .02$

Michael