kbreese

First time I heard someone call MPSS "Garbage"

They are almost universally known as one of the best UHP summer street tires, if not the best.

DeweyD

I autocross the car. I think the mismatch can work well. There just aren't good choices out there for 200 TW tires that perform well. (Unless you go RE71R but these aren't available in good sizes) I autocrossed the MPSS twice and they were awful. Very little grip either lateral or straight line. Then again MPSS aren't meant for autocross.

I do agree though, I would be hesitant to run mismatched tires in a HPDE, but that does not automatically mean that a mismatch will always be bad. You just want to make sure the compounds and structure are as similar as possible and test the setup before committing to it.

I blame tire manufactures for not making good tires in big Vette sizes!

DeweyD

I think that's the problem for me, they are UHP. Which you are right, they probably are the best UHP and maybe better than some Extreme Summer tires. But I have always had traction issues with the MPSS. I can't be the only one here. It roasted the tires in first and second was still squirrelly in a straight line. On other cars I was never impressed with MPSS either. But I have been spoiled rotten by a variety of extreme summer tires.

My definition of garbage in this case is a tire that doesn't allow the car to do close to what it was meant to. With the Kuhmos on there I can now give it quite a lot of throttle coming out of a turn in first without white knuckles or a puckered butthole.

kbreese

I hear you. At least you 19" wheel guys have a decent amount of options. The tire manufacturers absolutely suck when it comes to 20" options for these cars. Although I actually like my Invo's on the street (345/25/20 & 285/25/20) They are very smooth and quiet and the traction isn't that bad. Still, I wish there were options that offered more grip. On the highway they are perfect but If I pull up to something worthy at a stop light, it's not going to be an easy task if you know what I mean. But truth is that's going to be extremely rare. And even then, I might not be in the mood. I don't mess around any where near as much as I used to. Age does that

AzDave47

Autocross tire demands are not close to street or road course performance needs. The A7 is a great autocross tire, but it will overheat and slide badly after 2-3 road course laps.

My HCI Z (602/489) with OEM size PSS hook up well in a straight line at 40 and above with 60-70* temps, no problem on the 1-2 or 2-3 shift with traction. The PSS do not hook up like drag radials in a straight line or my R-compound tires for road course, but work well as a general street tire that will corner and hook up well and last a long time.

The Kumho 720 ACR with 6/32" treat and 200 treadwear won't get 10K miles of street tread wear and you have to mis-match the fronts with another tire, which would not be my choice.

DeweyD

I agree with most of your points, and I'm not actually suggesting that everyone should go out and get the Kuhmos. They are a one-trick tire, not well rounded.

I just really don't get the hype with MPSS. I never had the success you seemed to have with them. I ran them at a range of temps and pressures. At 70 or below they would spin and slide in 2nd gear once the tach hit 4,500rpm at WOT. In first they would never hookup at those rpms.

I had them on my Evo X that was street driven and autocrossed as well, and they were okay. They only thing that really impressed me was the longevity, though for all the times I have spun out at autocross the MPSS are the only tires I have ever flat spotted.

I seem to be one of the only ones that dislikes the MPSS. they aren't necessarily bad tires, but I wouldn't personally recommend them based on my own experiences. Count me in the minority.

kbreese

For what it's worth I have MPSS on my 2012 5.0 in sizes 285/40/19 and 255/40/19, and I was very impressed with their traction. Sometimes they hook like a damn DR! Granted it's only about 400whp and a heavier car, but they seem very sticky. They pick up stones like crazy. The rear tires were actually Porsche specific, but wouldn't think that would matter. I previously had Conti DW's, and the MPSS are better. My ONE complaint is I don't find the ride quality to be great. They aren't all that soft and kinda jarring on bumps. They have this kind of "boing" to them, hard to describe. My experiences are all street, no track. My 5.0 is tuned and an auto and the shifts hit HARD, especially the 1-2 shift which just a spins little and then is off and running.

pokerpro

FWIW when I'm bringing my Z up to its top speed (204 so far) you had better believe I'm not using Korean made tires.

.gearhead.

I have 345's and 295's. No rubbing whatsoever.

AzDave47

I know I was down on power in Ely, NV (elev. 6500', 55*) but when I ran the mile trap speed event two months ago with the 325 PSS, I rolled off the line in 1st, then full throttle, quick shift to 2nd at 7100-7300 rpm and full throttle, quick shift to 3rd, 4th, 5th and no hookup problems on a narrow two lane with old paving, good enough for 3rd place behind a 2000 HP Lambo, C6 ZR1 with pully and ahead of two C7 Calloway Z06s, one with mods, the other hit 203 at the Mojave 1 1/2 mile a year ago. I'm sure they had problems getting tires to hook and I was the only NA car in the top six. Speeds were down due to elevation (mid-170s and low reporting by the organization on all speeds).

I do know my first PSS set nearing 5 years old did not hook as well stock as the new ones after HCI work, so maybe age was a factor in your situation. On road courses, the OEM size PSS will understeer in steady state mid-speed corners.

mggray87

so trying to order tomorrow. PSS 275/325. 275/345 or 285/345. Which would be best

kbreese

I would stick with stock sizes, particularly up front, for crisper handling, but I doubt it's going to make a huge difference either way.

If you prefer a little more beefy/ bulged look then go with the 345's out back. I would guess it might give a little better straight line traction too. Personally I do think the 345's look better out back. One other minor consideration though is more weight & rotational mass with the bigger tire. In a nutshell it will essentially rob a few HP.

Unreal

345s will not give better straight line traction, as the amount of rubber on the road does not increase over a 325. They will look different, fit different, cost different, and provide different turn in/handling, but won't add straight line traction.

kbreese

I know it's a topic of debate the whole contact patch thing with wider tires, but I was mostly considering the taller sidewall, and the increased rotational mass, that could likely add a little more traction over the 325's.

TXGS507

I am running the MPSS up front 285/35/18... out back is the Sport Cup II's.. 345/30/19.. Love the combo, handles, and rides nice and quiet...... I too am coming from the GYF1's... My Z is making 560 to the tire.

AzDave47

from the other tire post running now:

You have alluded several times to the look of the tires and no concern for performance. If you can put up with the trammeling Michael D mentions the 285/345 would look best and suit your needs. They would also be a better cornering balanced set than the 275/345s, and understeer about the same or slightly more than the 275/325s, which is mild unless on a road course (which is not in your plans) on mid-speed long corners. The 295s are recommended for a 10" minimum rim and mounted on a 9 1/2" tire the sidewalls would bulge and look a little funny

mggray87

thanks dave. sorry to beat a dead horse. I'm rookie sport car guy who just came up on my first z06. and since its more of a garage queen, I'm just making sure myself spends money where id be happy since the tires will wear out from TIME opposed to mileage..

Titan C6Z

Here's a few more pics to show how MPSS stock sizes look:

rio95

I was in the same boat and went with stock size mpss. They are an excellent street tire that can handle some track duty. I considered the bigger sizes to make them fill the wheel well better but my stock size tires look pretty good especially with 1/4 spacers which stock rims need at a minimum in my opinion. Weight is another consideration no one mentioned. More cost and more weight for probably no more traction and worse road tracking didn't seem worth filling the wheel wells to me. I don't think you can go wrong either way though. Both are good options.

mggray87

Here is a question for you. I heard about the ground force balancer. 2 places near me have it dealership and discount tire Co. The guy asked me if I want force matched as well. No idea what it was. But he said it's pretty expensive they do it on the lambos and stuff. It's basically an extra 150 to do the match force wheels. I'm in bay area. Not sure current prices in my area and todays time. But it was like 160-200 jist to mount balance valve stems and all that. And if I wanted it force matched with rims it was like 350 out the door. He said he said moat people don't. Vettes he said I might be the first. But Lambos. They do since they feel everything in road or vib. What's your take.

He even said i am probably alright jist mounting and balancing but it's up to me.