Capri is right about load, but I wouldn't say you shouldn't do it. My stock tires are 195/65R15 and I got 185/65R15's for the winter. I did pay attention to the lower load capacity, but it was within limits. I hauled quite a few things on them and had no problems. When I'll need to replace my summer tires they'll also be 185/65R15's, no doubt about it.
So my advice is to first check whether the weight limits will be OK, and if so then go for some skinny low RR's
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e·co·mod·ding: the art of turning vehicles into what they should be
What matters is
where you're going, not
how fast.
"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell
[Old] Piwoslaw's Peugeot 307sw modding thread