In reply to dallasreed :
I'm actually in the market for new tires this week and would actually quite like to try the P1s. The Z06/Z07 wears 285/35/19 front and 335/25/20 rears. I do not have a set of 19" wheels for the rear, unfortunately, or else I'd give that a run; I'm a little reticent to go with a narrower and taller rear. Is there something I'm missing?
EDIT: I'm running Forgeline wheels but in stock sizes. I'd be willing to play with fitment if it meant an improvement. Right now I'm running Cup 2s but am not tracking the car as often and would like something with better wear characteristics. Currently I have a set of Extreme Contacts in my tirerack shopping cart.
In reply to docwyte :
245/40/18 will be here at the end of the month
315/30/18 is available now
They can both be ordered already https://vitourp1.com
In reply to brandonsmash :
For C7Z since I just had this conversation with someone else.
A few fitment options keeping in mind stagger to keep the ABS happy. Compared to A7's 315/30/18 335/30/19 which are known to work without having ABS issues.
Front to rear is
Hoosier 4.58%
Vitour 295/345-18 is 4.68%
Vitour 295/345-19 is 4.72%
The 295/345-19 is also what everyone with C8Z is currently running
Vitour 295/30/18 345/25/19 3.92%
Vitour 285/35/19 325/30/20 2.93%
Vitour 275/35/19 325/30/20 4.05%
Not sure how close it needs to be but I imagine any of those would play nice with the ABS.
I think when your laptimes drop substantially compared to Cup 2 or EC's you'll be quite a bit less worried about the size changes.
Dallas, I'm going to shoot you an email through GRM's system - I have some questions about rears in particular.
dallasreed said:
Not sure how close it needs to be but I imagine any of those would play nice with the ABS.
For most modern cars using a Bosch controller (which Corvette does) keeping the stagger within 6% of the OE stagger will work with OE ABS and stability control. And the units will recal quickly just driving down the road in a straight line.
This info from folks that work at Bosch.
Note that this does not mean a 6% stagger, it means +/- 6% relative to the OE stagger. So if you go up in OD by 3% at one end and down by 3% at the other end, you'd be right on the hairy edge.
I have spreadsheets I use to calculate various combinations relative to stock.
Where did you find the 8.7 inch tread width data, or do you measure before testing?
I only ask because the one spec sheet I could find stated a 9.1 inch tread width for 245/40/17.
Also, great article! Just in time, as I was about to order more Nankangs...
vertigo said:
Where did you find the 8.7 inch tread width data, or do you measure before testing?
I only ask because the one spec sheet I could find stated a 9.1 inch tread width for 245/40/17.
Also, great article! Just in time, as I was about to order more Nankangs...
Unlike the other typical specs (OD, Section width, etc) tread width is not standardized. We typically use Tire Rack's measurements, since they do the measurements themselves which gives consistency across all brands. But Tire Rack does not yet carry the P1, so we compared to the other known quantities we had on hand (pretty much everything fast) and measured/estimated. Have a look at the picture in the story of the three tires side-by-side and you'll see.
Also note that tread width specs can be highly influenced by the shape of the tire. A square-shouldered tire will typically measure wider than a crowned tire, even though the effective width is the same. A good example is CRS V2 vs RE71RS. The former is more square, while the latter is rounded. So RE71RS always look to have narrower tread widths when they really aren't when in actual use.
Andy Hollis said:
Also note that tread width specs can be highly influenced by the shape of the tire. A square-shouldered tire will typically measure wider than a crowned tire, even though the effective width is the same. A good example is CRS V2 vs RE71RS. The former is more square, while the latter is rounded. So RE71RS always look to have narrower tread widths when they really aren't when in actual use.
And shape really depends a lot on the wheels you put it on. A 265/35R18 Maxxis RC-1 will fit the NASA 266mm template if you mount it on a 9" wheel, but not on a 9.5", for example.
"Don't buy into the first model year" is the conventional wisdom.
Ahem.
I bought a first-model-year S550 Mustang GT new.
And a FMY C7 Z51.
And a FMY C7 Z06.
And a FMY Honda África Twin.
And a FMY GX550.
My Ducati SFV4 is at least a second model year, so there's that, but it's still pretty close.
So, given that history, why not? I placed my order for a set of P1s today based largely on this thread. Let's roll.
I'm curious if there has been any concern with tariffs on these? They are Chinese right? I put in an order to make sure I got a set before any of that nonsense kicks in, if it does. I wonder what other brands will be impacted?
codrus (Forum Supporter) said:
Andy Hollis said:
Also note that tread width specs can be highly influenced by the shape of the tire. A square-shouldered tire will typically measure wider than a crowned tire, even though the effective width is the same. A good example is CRS V2 vs RE71RS. The former is more square, while the latter is rounded. So RE71RS always look to have narrower tread widths when they really aren't when in actual use.
And shape really depends a lot on the wheels you put it on. A 265/35R18 Maxxis RC-1 will fit the NASA 266mm template if you mount it on a 9" wheel, but not on a 9.5", for example.
NASA templates are more of a section width thing, which absolutely does change with rim width. That's also why there's a spec called Measuring Width which goes with Section Width, both of which are standardized for any given size.
Tread width when measured as TR does, does not change with wheel width. Which is why they measure it bare tire.
BTW, when I say "standardized" I am talking about for members of the Tire and Rim Association, a US tire industry trade org and watchdog group which manages/monitors all the standardized specs for both wheels and tires. That way, you know a replacement tire or wheel of the same size as OE will fit on your car.
All the big guys are TRA members, plus many of the little guys. Vitour is not a member. Nor was Hoosier when it designed the "fat boi" A7/R7 duo. Hoosier are now via parent Continental. Note that the TAP meets all the normal specs per sizing.
ETRTO is the European version of TRA.
Andy Hollis said:
All the big guys are TRA members, plus many of the little guys. Vitour is not a member. Nor was Hoosier when it designed the "fat boi" A7/R7 duo. Hoosier are now via parent Continental. Note that the TAP meets all the normal specs per sizing.
Hm, interesting. In the R7 it's the 245/40R18 that fits the 266 template best (on a 9.5" wheel) and that's what I was thinking of trying with the TAP when they come out, but it sounds like that'll probably be too small.
I guess Hankook probably wasn't a member when the RS2 came out? I had a set of those on an Audi once that turned out to be 3/4" wider than the factory Continentals.
codrus (Forum Supporter) said:
Hm, interesting. In the R7 it's the 245/40R18 that fits the 266 template best (on a 9.5" wheel) and that's what I was thinking of trying with the TAP when they come out, but it sounds like that'll probably be too small.
I guess Hankook probably wasn't a member when the RS2 came out? I had a set of those on an Audi once that turned out to be 3/4" wider than the factory Continentals.
R7/A7 are the big outliers. Everything else is fairly consistent. Note that there is a bit of wiggle room in those standards, which results in things like A052 running wide (but not A7/R7 wide) and Bridgestone S001 running narrow (ND Miata OE tire). According to the designers, TAP physical sizing was aimed squarely for the middle of the road.
Oh yeah, the Goodyear Eagle RS line follows the Hoosier A7/R7 girth lead. Which seems odd since they are a TRA member. But, while those tires carry a DOT mark, they also say Not for Highway Use. And they are made by Goodyear's race shop -- not normal production. So I suppose that's how they get away with it.
In reply to theruleslawyer :
If the tariff increase is implemented as outlined by Trump at 10%, it’s not a concern. However, if the increase is much higher, there are contingency plans and options to address it.
Vitour, along with many other companies, have imported a large amount of product ahead of any changes taking effect. As a result, I’m doubtful that tariffs will have any impact on supply, regardless of the scenario.
Vitour has multiple product lines of premium passenger tires made on the same production lines as the P1, and in China they are positioned as a competitor to Michelin's premium tires at a much favorable price.
If these products were in the USA I suspect they would be very well received and very successful. For better or worse tariffs keep this from becoming a reality. Vitour does have trailer tires, truck and bus, and offroad/commercial product lines in the USA which for various reasons are not subject to the high tariffs.
A tariff increase effects basically everyone, even if the tire is not made in China, if materials are, then there will still be an effect.
dallasreed said:
In reply to docwyte :
245/40/18 will be here at the end of the month
315/30/18 is available now
They can both be ordered already https://vitourp1.com
Any word on a 295/35/18?
This is a popular size for many ATS-V, CT4-V Blackwing, M3, M4 etc.
Dallas, what is the shipping time from your warehouse to Seattle? I am going to the Rolex 24, and want to be home when the tires arrive (I don't want them sitting on my porch for days!).
In reply to goingnowherefast :
295/35/18 is in stock now https://vitourp1.com
In reply to RacerBoy75 :
Last ones I shipped to a certain SCCA lap-time leader in Washington state took 5 days after UPS picked them up.
Anyone tried these outside of a autox or TT type of event? We do 20-30 minute races in AZ where it can get quite warm. I see they have a "D" heat tolerance rating. Would I regret running them?
In reply to spedracer :
I ran an endurance race with Lucky Dog in exhibition on the Vitour P1 in a 150whp Miata. We got 10 hours out of them and we were setting fast laps in some stints on lap 30.
https://vitourp1.com/blogs/news/is-the-vitour-p1-qualified-as-an-endurance-tire
In reply to roadracer :
So here is my take running autoX Stock class last year with the P1.
I ran a 2017 Ford focus RS with the same set up on both P1 And RE71rs other then the sizes 2354017 for the re and 2454017 on the P1, on a 18x8 wheels the P1 was pinched on the wheel a little and If i did it again would go down a size so they were not. The Re71 was more predictable with my set up and I preferred them but on a day when I ran both tires back to back the p1 was faster. but for me and this is a car with zero camber adjustment I had better luck when the P1 was cold compared to the RE needed a little heat in it. I do plan on running the P1s on my hill climb car once I Kill the A052s that are on that. my personal opinion is they like a little camber and try not to pinch them onto wheels but they did last a lot longer then my RE71s did.
