245/35/19, 275/30/19, has anybody had frequent flats while using these low profile tires? how many? How much harsher if at all do they ride when compared to the 245/40/18 dunlop RFT's ?

 

Most people think that 19" NRF = 18" RF in ride.

I never had 18" RFs, but I think that my 19" NRFs with the low profile tires of the specs that you named are no worse than my OEM 17" NRF tires.

I think that a lot also has to do with the kind of tire that you use. If you go to any discount tire site (e.g., TireRack), the comments made among the different brands will greatly differ among the same size tires.

If you are asking if you should worry about 19" tires, you shouldn't at all.

 

Just put on my Blizzak RFT winter tires (245/40R18) on the stock style 124 18" sport rims. They ride harsher then the 19" they replaced in the sizes you quoted. This made me remember how much better the ride was when I installed the 19's over the stock 18" RFT's. The other big difference was weight. My 19" wheel/tire combo is much, almost half the weight of the stockers with RFT's.

Get the 19's you will have zero problems unless you hit every pot-hole on the street. Well even 18's won't last doing that.

BP

 

The short answer is no to frequent flats. I ran a set of michelinPilot sports down to the cord and never got a flat. I also unavoidably ran over a bumper in the left lane of rt 80 at 75mph and got a flat in 6mos old tires. RF's are appreciably harsher in ride imo than NRF regardless of the size. 19" NRFT is going to ride nicer than 19"RFT and maybe even the 18 RFT's as well.
You have to decide what's more important for you, personally I'm not sure they are worth it.

 

no frequent flats at all. only flat tire i had was due to a nail in the sidewall from an alley. some bumps are felt more but the ride is not harsh at all in my opinion.

 

Thats how I feel about my 18" setup, I'm running the standard 530 s.p. combo (245/40/18 rft's all around, mounted on style 123's) and even though you feel the bumps more that usual, I equate it to the ride you might expect from and any sports car, tight, not harsh. I assume then, that the aforementioned, staggard 19" setup mounted on style 166's would give me a simmilar, if not a "slightly" softer ride, and pot hole damage would not necessarily increase dramaticaly. Am I reading you and the other posters correctly?