3rd gear started spinning today around 5500 rpm (peak torque) in 60*F weather.... looks like I am going to need new tires sooner rather than later too. Tires are Toyo T1 Sport, 240 tw. A year ago with the same setup they hooked pretty well, I think age/heat cycle has just got to them. Honestly did better than I was expecting, I got them at the time because they were super cheap and had 265/40/17 front size.

Think I am gonna do R888R all the way around. Getting something less sticky up front doesn't really save much money and I don't drive this thing all that often so price difference shouldn't be huge either. I like the idea of running the same compound all around if possible.

 

I think the only other tire to talk about (mentioned in OP) is the ET Street S/S. Obviously a much more serious drag radial. I've never ran them, but read the sidewall is soft as expected so expect handling to feel a little meh, especially when compared to a road course tire such as the R888R or NT01.

NT05R would probably be a great compromise if it were offered in the right size for C5Z wheels.

 

I ran 275/40/17 and 305/35/18 R888s on OEM Z06 wheels for the past year. The Sumitomos that I bought the car with were a joke, I wanted something that I didn't have to risk ice skating with on accident with stock power and gearing. I had the R888s on before and after having 4.10s installed. Before, I had to try really hard to break them loose...kind of killed some fun. After, still hooked 95% of the time punching it from any gear/rpm. After the blower, I was still very impressed with how they hooked. They hooked most of 1st and all of 2nd gear, no problem. With the newsed wheels came 345/30/19 R888s, but they're 5-6 years old and have been to the track an unknown amount of times. I still thought they'd hook better given they're nearly 2" wider...nope. At WOT, they skate 1st, most of 2nd, and sometimes some of 3rd. FRESH tires make a significant difference. I also have a pair of 305/45/17 Et Street S/S that I'm hoping to mount on a set of classics tomorrow. These tires are significantly softer than my R888s were brand new. I know they'll be good...but I don't plan on trusting them whatsoever in high speed corners. Goes back to what I said earlier: can't have your cake and eat it too haha. Although when I'm done with the 345 R888s, I plan to try the 355/30/19 Kumho 720 ACR (OEM ACR Viper tire). They have great reviews, are significantly cheaper than the R888R, and appear to be more street friendly as well.

 

The 355 Kumhos might be a lot cheaper but the 345 R888R's are actually wider, 13.1" tread width vs 12.5", and feature a lot stickier compound.

 

Yep, we're definitely at that point where everything is a compromise of some sort. Curious to hear how the ET streets feel, please report back. I understand it's not really apples to apples being different size, 19 vs 17 tire sidewall difference etc, but still curious. I'm also a believer that compound > width generally.

Where do you live/what's the climate? I don't expect any tire to really grip well below let's say 50. It gets pretty cold here in the winter (30s), but summer time, 100s are pretty common. That's probably my biggest friend for traction... High DA, high heat, and hot asphalt lol.

 

Tire Rack has sec width of 14.2" and tread width of 12.5", and 13.5"/13.1", respectively. I see what you're saying about tread width, but it boggles me that the sec width is THAT much larger with LESS tread? Especially considering the Kumho's tread appears to wrap to the side wall just as much as the R888Rs...very strange. I've actually read that the Kumho's are stickier, despite treadwear ratings. For a ~$200/tire savings, I'm definitely willing to try them out either way haha.

Absolutely, will do. I anticipate them being much better, even cold. I don't intend to ever fully heat them up and test exactly how much they can grip...I'm still on 100% stock drivetrain (except the p/p 4.10s and C6 Z06 left output shaft), I would anticipate finding a weak link pretty quickly if I tried a hard launch. I'll at least wait until I'm ready to replace the clutch until I feel like testing them haha. I also agree with you on compound>width. A 275 DR would do the job just fine, but 305s will fit the 17x11s better.

I'm in SoCal, so not TOO different from you it appears. We're seeing lows of 40s/50s right now and I definitely see 100-110 in the summer. I haven't used these 345 R888s in 80+ weather yet, but I didn't see an extreme difference in my 305 R888s. A little obviously, but not enough that I think these 345s are going to significantly soften up in a few months.

 

I've ran Kumhos before and I agree that they tend to sandbag their tread wear ratings. Their tires with 200tw ratings are probably closer to a 140tw.

A supercharged Z06 is probably over-geared with a 4.10 cog, due to the amount of torque a blower adds. Your car would probably hook harder, with a taller rear cog. (3.42?)

 

Mine is just a coupe, so 4.10s are only slightly steeper than a Z06's effective gearing with the M12. The 3.42s were extremely too long legged for me, so that was the first "major" mod I did. Still wasn't enough oomph for me and I came across a good deal on the SC. The 4.10s aren't ideal with the SC, but keeping them is cheaper than redoing them...and it still keeps the car fun to drive on the street. And the 27-28" tires help knock the gearing down enough for the strip when I decide to give it a go.

 

There had never been an SAE, or ASTM UNIVERSAL tread wear standard.
thread wear ratings are for individual internal manufacturers comparisons only... Compairing one Kumho tire to another Kumho tire. Or one Michelin to another Michelin... but NEVER CROSS REFERENCED.

A100 RATING from one manufacturer could easily mean the same as a 200 from another manufacturer... Its for manufacturers internal comparison only.

 

Great thread. Just ordered the 305/35r18 R888R tires for the FRC after reviewing it.

I have the OEM zo6 speedlines on the car, 4.10’s and 622 RWHP.

Until I saw this I was unaware how much HP guys were able to “corral” with these tires or what my options were.

 

What are you guys running for alignment? I still have a track (road course) alignment on mine so that probably isn't helping a ton either with some extra neg camber. Seems like most in here are kind of on the same page... looking for good all around setup that can still turn decently well.

Curious to hear what you guys have done. How important is rear toe?