If you read the V720's tire rack description, the exact words are

"Because its design focus is street use and specifically to excel in the short runs seen during autocross competition, the Ecsta V720 should not be driven on a race track."

Also, the old Excsta XS are on sale for $90/ea for 255/40/17 right now.

 

Interesting on the v720. Must be a new updated disclaimer. Didn't see that listed before.

 

The Achilles 123s don't come in a 255/4r17, rather they come in a 255/35r17. They'd still work but as OP suggested, their are concerns with the potential failure of those tires.

 

That is what I would buy then. I loved the Kumho Ecsta XS throughout my HPDE journey. One set lasted me from HPDE1 to my competition license.

 

They're probably the outright stickiest DRY tyres of their time. IIRC, they existed in the era of RE01R and Z1SS. I had a set of 215/45/16 on my EM1.

I remember that they were awful in any kind of water lol.

Seemed to wear pretty ok.

 

A buddy uses the Kumho XS on his chump car, and swears by them. They wear like iron.

 

They're probably the outright stickiest DRY tyres of their time. IIRC, they existed in the era of RE01R and Z1SS. I had a set of 215/45/16 on my EM1.

I remember that they were awful in any kind of water lol.

Seemed to wear pretty ok.
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I'm still using these for track and street, on the last know set now. Next year I will have to switch up. These tires have treated me pretty well over the years, excellent dry traction for the wear. I set near record times with them at the 2.5 mile Ridge moorsports park last year. Not bad for a tire that was produced like 10 years ago.

 

I have had the NS2-R (120 TW) on the car for the last 5k or so with one track day.. Before that I had the Federal RS-R. I personally find the Nankang to be much better during normal and extreme driving conditions. More cold grip, more all out grip, less road noise, and equal (if not better) durability. Not sure what they are going for right now but I paid around $140 each for 255/35/18's last year and would definitely recommend them as an alternative to the more well known performance tires.

 

^Thanks for the feedback. A lot of the reviews I've read for the Nankang NS-2Rs have been pretty positive but I can see how people can be skeptical since they are relatively unknown brand and not sold on TireRack. How do they run width wise compared to the Federal RSRs? I believe I've read the RSRs run very wide. What size wheel/tire do you have? Any pics of them or how they wear?

Unfortunately, there is only (1) Kumho XS tire in TireRack's warehouses, that is why the price is so cheap.

 

I'll try to post some pics when I get home.. Such a pain to do on this forum lol... but I would say they may be just slightly narrower than the RSR. I run them on 18x10 forgestars and there is definitely some slight stretch with the 255.