Number 23

ok i'm in a bit of delima about replacing my tires on my Z06. Currently they still have the stock Goodyears on them. I'll be doing a decent amount of autocrossing this year and was looking for a good sticky tire to replace them with. The Three i'm considering are:
-Toyo R888's
-Kumho Escta XS KU36
http://www.kumhousa.com/Tire.aspx?id...466bd5c&cat=18
-Nitto NT01 or NT555RII
I've looked on there websites and found that they don't make the exact same tire sizes as the stock goodyears. My buddy told me to go with this size:
Front 275/40ZR 17
Rear 305/35ZR 18
which are fairly close to stock.

I will be driving this car on the street. Car gets about 3000 miles a year put on it. So any recommendations on size and tire would be helpful.

Kubs

Out of those three I have heard the Kumho is excellent, but I have not used it myself. Not to mention I think the Kumho is a bit less expensive.

argonaut

I tried the NT01's in AX. They work ok but not ideal, I felt like they don't heat up quick enough. For street use they also pick up and throw an amazing amount of rocks onto your quarter panels.

Where do you AX - with the Central PA region? (I've been to many of their events)

Any interest in hitting the race track? - my buddies and I live in Mechanicsburg area and we frequently head down 81 to Summit Point, WV. Pocono Raceway is another place I go quite a bit. Let me know if you want to try it.

c4cruiser

I have run the older Kumho Escta MX on my 87 for autocross, track days and on the street. They have done very well although now that they are down to about 40% tread left, they do get somewhat greasy until I get heat in them. The Kumho will let you know when it's at the edge of grip.

I only use the MX's for autocross in cold weather, fun events or if the course surface is rough. Otherwise I usually run Hoosier A6's. I trailer my car to events so race tires are not a problem.

From what I have read, the XS is even better than the MX tires were. For autocross, it will be a matter of finding the right tire pressures and a good autocross alignment.

The sizes you show will fit on Z06 wheels.

shakedown067

I'm looking at the Nitto NT555R II extremes as they are the only tire i can find with both a 275/40/17 and a 305/35/18.

http://www.discounttiredirect.com/di...%2FPerformance

eschantra

A buddy of mine rus 555RIIs on his C5Z that has some modifications and runs SSM. They seem to be competitive and he drives them daily. I'm thinking of trying R888s as a dual purpose tire for when it's raining too hard to run A6s.

KBRVETTE93

I think you would have a hard time finding a better value for dual purpose tire than the 555RII. These are an older design, but are reliable, predictable and wear nicely. I have run these for autox in the past and was very pleased.

I run Kumho V710s for track only. If I were to select a single tire for dual purpose I'd choose the Nitto 555RII

Z07coupe

# 23,
Be aware that most autox sanctioning bodies have technical rules that will penalize you if you run wider rims or tires than stock. NCCC will not permit you to run in group1S with a tire more than 1 size larger in width. Larger wheels can also cause a class change. Check the NCCC web site for the 2010 changes to the rulebook. They have a chart now to show what you can run. SCCA also has limits, but I don't know what they are.
Are you planning on putting a 275 tire on an 8 1/2" rim?
And a 305 on a 9 1/2" rim?

eschantra

Z06 is 9.5 and 10.5, and the SCCA stock class rules allow you to run any size tire that will physically fit. I've seen 315s squeezed on the front stock wheels

l98tpi

There were 2 different tire test conducted last year in GrassRoots Mag and the Kumho XS beat the competitors in both test. As well, I know that a member of our Vette club purchased the xs tires and seemed to have lowered his autox times.

Z07coupe

Eschantra, Thanks for correcting me. I didn't remember the Z06 had wider rims (I should have). The NCCC web site shows that for an 03 Z06:
acceptable size range front - 255-275/35-45/17
acceptable size range rear - 285-305/30-40/18

So #23 is within the parameters for NCCC events, also.

Did the SCCA have a rule change on tire size? I remember about 5 years ago at a SCCA autox, a C4 with ZR1 rims (wearing rear 305 or 315) was placed in a different class than I because of the wider wheels and tires. Would this have been done because of the wheels?

96CELT4

That is because he was running a rim that was not available for the way his particular C4 was optioned. If his C4 was not a ZR1 and he was running ZR1 offset rims in the rear, then that is what bumped him out of stock class. Had he been using the stock size/width/offset rim that matched what came on his C4, and somehow was able to squeeze a 305 on it, he would have been within the guidelines of the rules.

The rule that any size tire that can be made to fit the stock rim has been in place for at least the past 11 years that I've been autocrossing with the SCCA.

Number 23

I did two autox events through the national council last year one hosted by Cumberland Valley and the other Hosted by Lancaster County. Ever since then I've been hooked. I'm heading over memorial Day to Pocono Raceway to obtain my High Speed license. I do want to try a few of the SCCA events this year and some road coarses as well. I could tag along a few times with you as long as my work doesn't go with mandatory OT on weekends.

Ok it seems that a few people have recommend the Kumho's and nobody really has to much experience with the R888's yet. I called one place about the Toyo's and they want for:

CJ's Tire and Automotive in Mechanicsburg,Pa
275/40ZR 17 231.99 per tire
305/35ZR 18 371.99 per tire

I'll call about the Kumho's and see what there running.


Also I've seen about the Issue with potential cracking in temps of 15 degrees and below. My car gets stored in the winter time in wooden shed but it doesn't have heat. Pa can get cold do you guys think I'll be alright if I leave those tires on over winter?


Thank you for all the help guys

waktasz

Don't forget about the Falken rt615. Might not be as fast as the best street tire for autocross but definitely cheaper. Might be on par or better than the r888 or Nittos, which I've NEVER seen a fast car have at an autocross.

gkmccready

That's because the Toyo and Nittos are considered DOT-Rs... not a street tire, so if you're required to run a street tire, you can't run them. And if you're going to be fast and run DOT-Rs you're going to choose a Hoosier or Kuhmo and not drive them to the events. You can't blame the tires for the way the rules are written.

waktasz

oh, I am a mega failure then.

I was mixing up the r1r with the r888. People I've talked to that ran the r1r were not pleased.

Anyway, just ignore me

vettehardt

In NCCC we do allow some C4s to run the ZR-1 wheels even if they weren't stock to the car. You can run any wheel that is stock for your class. So any class 1G or 1GS car, 92-96 with LT1 or LT4, can run the ZR-1 or grand sport wheels since they were offered on the grand sports. In group 1 You are allowed to run any size tire you can get to fit on those rims. Once you move up to group 2 or above, you only have a minimum diameter of 16" on the wheels. Group 2 still has to run a DOT tire, but can run any size. Group 3 or RP cars can run any tire/wheel they want with a minimum diameter of 16".

The street tire classes are different and you do have to run the right size tire with in the tollereance allowed. The ZR-1 wheels are allowed in the street tire class also. Becarefull of some tires since they are not made with a minimum of 8/32" tread depth. They can qualify as a street tire in every other way, but they are not made with the required tread depth and it will put you in to group 1 with the race tires.
Here is the wording in the rule book for group 1S:
1984-NEWER - Any type wheel with correct diameter & width for class & axle;
adapters allowed.

Factory original tires, and replacement STREET tires with MINIMUM DOT
wear rating of 110 manufactured with MINIMUM 8/32” tread depth NEW &
HAVING 2/32” or more tread remaining (i.e., tread must be ABOVE wear bars).
+/- 10 mm tire width and/or +/- 5 aspect ratio allowed (01/10)
Group-1S tires not meeting minimum tread depth specification move car to
Group-1
1982-OLDER - All four tires must be same size & construction, minimum
profile is Series 60.
1984-NEWER - Tire size (diameter, width, & profile) MUST be correct for class
& axle.

No Go

I run the Nitto R II's and highly recommend them (4 sets thus far). I get 10,000 street/autocross/track miles out of them on average. They ride a bit rougher than a true street tire, don't pick up any garbage to throw against your paint, and put me from a mid pack finish to typical top 10 for autocross events.

The tread wear is 100 so yes...they get classed different than a true street tire (normal cut off is 140?)...so I normally run in the race car class...with slicks and Hoosiers.

Cold temps: they do now include a warning about below 32 degrees-don't drive/move or risk cracking of the carcass. If you car just sits I see not problem with them...I would expect you put your car on jackstands? This would be better.

Hope that helps.

Number 23

Ok called about the kumho Mx's and the newer XS's. I was told they are phasing out the Mx's and being replaced by the XS's. I think I will go with the Kumhmo's got a price of 998.00 total for 4 tires and 25.00 a tire mount and balance. That was for:

275/40 17's
305/30 18's



No Go:
I forgot about putting the car up on Jack Stands. Yes I do have a set and will get that done.


Thank You everyone for all of your input on this matter. When it comes time for a full slick I will definitely have to purchase a extra set of wheels!

96CELT4

Yep that all sounds correct for the NCCC rules as I remember them.

Except I wasn't talking about NCCC. I was answering a question Z07coupe had about SCCA rules.

It would be nice though if stock classing rules in these regards were more closely matched between the two organizations. Would have kept me from having to run group IIJ in NCCC for the past 8 or 9 years just because of my Penske shocks.