[ICTsccaCamaro]

Originally Posted by EDFHOBBIES

What rim do you run the 355s on? And the dimensions and offset? Any spacers?

Stock 19's, rear camber is at about -2.2 and the wiring harness is relocated in the left wheel well.

[TheRealJA105]

Originally Posted by Mountain

They aren't specifically listed in the SCCA Time Trials list, but the way their tire rules are written make them illegal:


The Viper versions are 6/32, they are "variations differing from standard specification", and are only offered in two sizes.

Now, why Kumho decided to use a different (much, much, much crappier), autox-specific compound on their regular version is beeeeeyond me, as if their normal was anything close to what the Viper version was, they'd be selling a lot more.

Yes they are specifically listed on the SCCA Time Trial Exclusion list. I copy and pasted right from the page.
Kumho probably isn't making the other tire sizes in the ACR compound because it clearly isn't a 200TW. That's the real reason most competition groups are excluding them. They are the ultimate 200TW cheater tires. The tread depth/size availability is just the politically correct way of excluding them.

[ICTsccaCamaro]

355's ACR's on stock 19's with -2.2 rear camber

[EDFHOBBIES]

Nice!

[ICTsccaCamaro]

Originally Posted by EDFHOBBIES

Nice!

They do just hit the inside lip of the fender during really hard compression though, I just put a few layers of xpel tracwrap on the edge of the fender.

[RUQWIKR]

Originally Posted by ICTsccaCamaro

They do just hit the inside lip of the fender during really hard compression though, I just put a few layers of xpel tracwrap on the edge of the fender.

What fronts do you run with them?

[ICTsccaCamaro]

Originally Posted by RUQWIKR

What fronts do you run with them?

305 RE-71r'S

[TheRealJA105]

Originally Posted by ICTsccaCamaro

They do just hit the inside lip of the fender during really hard compression though, I just put a few layers of xpel tracwrap on the edge of the fender.

Any room inboard if you went with a higher offset than OEM?

[Mountain]

Originally Posted by TheRealJA105

Yes they are specifically listed on the SCCA Time Trial Exclusion list. I copy and pasted right from the page.
Kumho probably isn't making the other tire sizes in the ACR compound because it clearly isn't a 200TW. That's the real reason most competition groups are excluding them. They are the ultimate 200TW cheater tires. The tread depth/size availability is just the politically correct way of excluding them.

My bad. I mis-read and thought you had posted about SCCA Solo.

You think tires like the RE71R and A052 are really any different in the mentality you state? This is and has been the big topic with these tires* for the past few years in the autox scene... The A052 basically went through the near-exact exercise: Yokohama took one of their "streetable track tires" that could meet the 200tw "rating", making a little adjustment to the compound, increasing tread depth and keeping essentially the same tread pattern.

Pre-2019 A052
"Streetable Track Tire"
TW: 200
TD: 6/32"
TP:

2019+ A052
"Extreme Performance Tire"
TW: 200
TD: 7/32"
TP:

ACR V720
"Streetable Track Tire"
TW: 200
TD: 6/32"
TP:

Mainstreme (post ARC) V720
"Extreme Performance Tire"
TW: 200
TD: 8/32"
TP:

ACR V720 version + 7/32" + more sizes... why not? Kumho essentially dug themselves into a very specific corner (regional-level autox) with their mainstream V720.


*"these tires" = the recent top "extreme performance tires"

[ICTsccaCamaro]

Originally Posted by TheRealJA105

Any room inboard if you went with a higher offset than OEM?

I would like to think you could move them inboard 1 or 2mm but when I pulled the wheels off before winter I thought I remembered very slight rubbing on the fabric liner that must happen during compression, I will hopefully uncover the car next month and try to take a picture of this.

[TheRealJA105]

Originally Posted by Mountain

My bad. I mis-read and thought you had posted about SCCA Solo.

You think tires like the RE71R and A052 are really any different in the mentality you state? This is and has been the big topic with these tires* for the past few years in the autox scene... The A052 basically went through the near-exact exercise: Yokohama took one of their "streetable track tires" that could meet the 200tw "rating", making a little adjustment to the compound, increasing tread depth and keeping essentially the same tread pattern.

Pre-2019 A052
"Streetable Track Tire"
TW: 200
TD: 6/32"
TP:

2019+ A052
"Extreme Performance Tire"
TW: 200
TD: 7/32"
TP:

ACR V720
"Streetable Track Tire"
TW: 200
TD: 6/32"
TP:

Mainstreme (post ARC) V720
"Extreme Performance Tire"
TW: 200
TD: 8/32"
TP:

ACR V720 version + 7/32" + more sizes... why not? Kumho essentially dug themselves into a very specific corner (regional-level autox) with their mainstream V720.


*"these tires" = the recent top "extreme performance tires"

I don't think they are much different as the RE-71 was the original cheater tire, but it has become accepted. I still think the ACR compound is different. Why else would Kumho say you shouldn't track the new V720 compound, but the ACR was made to set track records?
Isn't the Yokohama under review for being legal?

[Mountain]

Originally Posted by TheRealJA105

I don't think they are much different as the RE-71 was the original cheater tire, but it has become accepted. I still think the ACR compound is different. Why else would Kumho say you shouldn't track the new V720 compound, but the ACR was made to set track records?
Isn't the Yokohama under review for being legal?

Oh, I agree with you: the regular V720 has to be different than the ACR V720. I have never heard of anyone with chunking, de-laminating, and/or separation issues on the ACR version like people do with the regular V720. I know some people claim that they have run the regular V720 on track with no issues but I have personally seen quite a few different people run them in autox and several people in Lemons or track days have issues with them. They have good pace, but severely lack the durability. Sad because the old Kumho tire from late 2000's/early 2010's was awesome (forget that tires name XS-something).

The Yokohamas were under some review, but last I read (end of last month), the case has been dropped.

[EDFHOBBIES]

I also saw the pirelli corsa pcz4 305 19a for dirt cheap

[EDFHOBBIES]

Originally Posted by ICTsccaCamaro

I am running 305 RE-71's in the front and the 355 Viper Kumho's in the rear, it is the best grip i have had so far and I have ran a lot of different sizes in my short 1800 miles of ownership.
305/30R19 front
325/30R19 rear

285/35R19 front
285/35R19 rear

305/30R19 front
305/30R19 rear

325/30R19 front
325/30R19 rear

305/30R19 front
355/30R19 rear

Will it mess with stability track having the 355s on rear and lets say the the 295 vipers on front?