I run 245/40-17 PPS03s on SSR comps. Lowered to 25"...had to roll fenders though.

...wheel offset can make a big difference

Remember rim width effects rubbing as much as tire width.
 

Go to the tirerack and shop through the tires, then compare specs of actual measured tire width on different rim widths, you can have two different size tires on wide and narrow rims that measure out to the SAME size..........

Inflated Tire Width...
 

All sizes are 255x35x18:

Toyo Proxes T1S
10.2 inches

Bridegstone Potenza S03 PP
10.3 inches

Yokohama AVS Sport
no 255x35x18

Yokohama AO32R
no 255x35x18

Kumho ECSTA 712
10.0 inches

Yes, you are right that the Kumho's are narrow, 0.3 inches over the S03, and 0.2 over the T1S. But the SO3 and T1S are not far off at 0.1" difference.

FWIW...

When you're walking on razors, 1-2mm can be the go-nogo detail.
 

I spent 4 hours installing 245/35-19's on a Benz yesterday, Yoko's had to be removed and S0-3's installed in order to clear the uppper A arm bolt in the front, with both tires 245/35-19!!!!

Which is why people are racing HARD on Kumies without rubbing.

Not if you don't lower too much.

I am running 235 35 19s... will I rub with H&R Streets? How low can I go?

what offset are you rims?

SSR GT3s, I think I am running 10mm spacers..