Driving and handling notes with Kumo ACR tires

[LCatGA]

Had old Micheline Pilot SS on the Snake and they were hard(2015 date codes). Just had Kumo V720 ACR 355 mounted on the rear and Kumo V730 275s on front(same tread, similar compound). Weather today was in low 50s so I made sure to warm tires up with spirited use of my driveway before making any notes. Was not able to do much of "at the edge" driving but was able to push it in a few turns.
Here are some of my observations.
Obviously, car has changed but not necessarily for better in all the aspects. There are definitely more traction and back feels more planted under acceleration. But surprisingly to me there are more body roll and less precise steering feeling. Car lost some of it's nervousness but also became much more pedestrian in a sense. It feels more fluid in some aspects but less of the surgical knife feel I got in the beginning. So here is some of the things I need to do to it
Coilovers. While Car can definitely use a set of high quality Coilovers, preferably with short helper springs. I think MCS single adjustable is a minimum I'll need on it to get control of body roll while preserving some road comfort.
Solid bushings and steering rack links. Adjustable sway bars - I would like to preload rear a bit. Bump Steering correction - need to give a nose a better sense of direction especially considering how heavy it is.
LSD - maybe I did not had to get one, Gen 4 LSD preformed good enough with new tires, but with a lower gearing and some bolt on mods it should be relevant.
But so far, definitely a bit less thrills and less smile on my face

I guess hard old rubber might have some benefits.

[Aevus]

Good to know.
Not gonna buy front V730...

as for the rear 355, if you ever find a streetable tire with more traction (summer weather) let us know!

[LCatGA]

I'm not sure if its V730s but you might be right

[Aevus]

even old and dry, Michelin tires are probably still very decent... especially if not pushed on a track


also, I remember reading somewehere about the V730 and it was not very tempting.

and that new (2022) Tirerack test isnt helping...

https://www.tirerack.com/tires/tests...y.jsp?ttid=302

[Aevus]

I think the real good options in these 19/18 sizes:

Michelin 4S on all corners
or
Falken RT660 (crisp steering feel) mix n matched with 720ACR rear
or
Yoko A052 (massive grip) mix n matched with 720ACR rear


Oh, and make sure you're testing and comparing with the proper tire pressures.

720ACR rear = 27-29 (cold)
Yoko A052 = 35-37 (cold)

[Siciliano15]

Yea I think overall the Michelin 4S tires would prob be the best they are also much lighter weight than the Kumhos. Michelin also makes the sport cup 2 connect in our sizes too so thats probably the best track or warm climate option. Mine came with the Nittos on it, they have pretty great dry traction actually but they ride and handle like a Nitto, cheap feeling. Gonna go with the 4S tires in 285/35 front 355/30 rear when these Nittos get to about 6 years old.

[Fatman2006]

I have V720 all the way around. 355 in the rear and 285 up front, I think the car still feels precise. I have zero wheel spin in first gear, the car just goes!

[LCatGA]

I could not find V720 ACR in 285 R18

[LCatGA]

According to tire experts it's better to match V720 ACR with V730 rather than regular V720(NON ACR)

- - - Updated - - -

Yes, the grip on 720 ACR is marvelous.

[Fatman2006]

I should have clarified, my tires are V720 ACR.

[Aevus]

I should have clarified, my tires are V720 ACR.

https://www.tirerack.com/tires/kumho-ecsta-v720-acr


only available in these sizes tho

[Siciliano15]

Did it feel like your car got slower with the Kumhos? The rears alone are like 8 pounds heavier each than the same size Michelin tires so I feel like thats a lot especially for rotating weight...

[LCatGA]

Car does not feel slower, if anything it just got a bit more of the body roll. It lost some of it's jumpiness/nervousness and traction on the rear its just out of this world. I cant loose rear in 2nd gear and I have to do something really stupid to do it in first. I no longer feel I need LSD. How ether front moves too eagerly for my taste exhibiting a lot of understeer and suspension feels less precise. Even with prior problems related to older/harder tires I could take it through roadcorse faster - this reflecting more on a style of driving I'm familiar with. I preffer a lot of steering feedback, precision and neutral handling. If I have a choice of oversteer I'd take it over understeer any day of the week. All my cars exhibit more of the oversteer behavior. My 996 GT2 started out with a lot of understeer but suspention were screwed on it. We got it extremely neutral with no over or understeer.
Now raising preassure on front from 29 to 33PSI did helped a lot. I'll try to raise it to 35 psi tomorrow if it's warm out

[Aevus]

Car does not feel slower, if anything it just got a bit more of the body roll. It lost some of it's jumpiness/nervousness and traction on the rear its just out of this world. I cant loose rear in 2nd gear and I have to do something really stupid to do it in first. I no longer feel I need LSD. How ether front moves too eagerly for my taste exhibiting a lot of understeer and suspension feels less precise. Even with prior problems related to older/harder tires I could take it through roadcorse faster - this reflecting more on a style of driving I'm familiar with. I preffer a lot of steering feedback, precision and neutral handling. If I have a choice of oversteer I'd take it over understeer any day of the week. All my cars exhibit more of the oversteer behavior. My 996 GT2 started out with a lot of understeer but suspention were screwed on it. We got it extremely neutral with no over or understeer.
Now raising preassure on front from 29 to 33PSI did helped a lot. I'll try to raise it to 35 psi tomorrow if it's warm out

then, probably in the same situation as I am:

Falken RT660 (crisp steering feel) mix n matched with 720ACR rear
or
Yoko A052 (massive grip) mix n matched with 720ACR rear

I have a brand new set of RT660 ready to be installed, but I'll wait for warmer weather to test and compare with the Yokos

I expect a great deal from the RT660, should be precise and nervous as I like. Will I miss the A052 grip? Maybe.

[Siciliano15]

sounds like those tires are practically like a drag radial how they are softer around turns but great straight traction

[Aevus]

Just so you all know:

The Kumho 720 ACR tire is only available in TWO sizes.

https://www.tirerack.com/tires/kumho-ecsta-v720-acr

The tire was developped for the Dodge Viper ACR (gen 5) so it's 19'' front.
Obviously, if you have Kumho front 18's, it's not the same tire.