Street tires in IT? My Review

Chip42

New member
As promised, I ran a set of 205/50R15 Dunlop Direzza ZIIs at Sebring for the traditional Thanksgiving weekend "Turkey Trot" races 11/30-12/1. My car is a mild prep ITB MR2 at 2335 min weight, about 2340-2380# as raced depending on fuel load.

the rain gods were unhappy with us, and every time our group was headed to grid the skies would start to spit on us - just enough to make everything slick, not enough water to exploit the treads on the Dunlops. oh well. so I didn't really develop a feel for the tires until the races on sunday, the later of which started dry.

My impressions:
little to no noise. none of that 1982 showroom stock tire howl many people seemed to expect.

amazing braking feel. I could lock them up but it wasn't like I was constantly feeling for that line. 9/10ths driving there was no issue, 10/10s it was still impressive how much brake I could use.

Cornering grip is certainly less than a hoosier, but I think the marked difference is a slightly slower response time to inputs on the wheel. I wasn't logging actual Gs but I didn't feel wanting. slip angles were obviously higher, and I found myself throwing a lot more at the wheel than I would normally with hoosiers. simple to get used to, and it was fun chucking the car around a bit. optimizing the suspension and alignment for these tires would help, with near zero toe the car was a bit floaty. shaving the tread might help response but goes contrary to my experiment to evaluate the tires as delivered.

They are very linear - breakaway is not sharp, though it is still sudden. recovery is easier than on a hoosier for this reason.

speed - I'm no SARRC champ but I was able to keep up with the same pack of cars I usually run with, and actually made up ground in the corners as usual for my rather underpowered car. I honestly don't think I was more than 2s off my personal Hoosier pace.

overall I really enjoyed them. more forgiving, require a bit more input, handle great, and feel very racy. At roughly half the price of a set of R6s in the same size... I'm a convert.

I ran Street Tire Challenge livery on my hood that will match the decals I'll be offering for IT racers in the CFR, or other divisional/regional series that wish to make use of them, to run a race within a race for IT cars - 100% optional, scored separately by volunteers, not the local SCCA event organizers, so it's invisible to the T&S folks and thus easier to implement on the fly. 100% IT rules with an added 180+ tread wear minimum to the tire rules. sign up, slap on a sticker, go have fun.

current offerings in popular IT sizes that fit the bill are the ZII I ran along with the BFG Rival, Hankook RS3, and Yokohama AD08R. there are some others in fewer sizes and I'll bet more are on the way.

stay tuned for more on the Street Tire Challenge series. I urge everyone to try these out, I think you'll be surprised how good they are. I think they are likely to be farther off the pace as the class speeds go up, so ITS might be 5-6s a lap off, where ITB is maybe 2-3s.

anyhow, I'd like to hear other's impressions. I think these have the potential to make for a lot of fun, lower cost racing.
 
This same weekend I pulled the older 195/60x14 dunlop Z1 tires off my street car. They were a lot of fun. I was unable to get any real comparable data as the runs were in the damp and the reat was on new 225 R6. I hope more regions think about it. There was a decent group of people that came by and was interested. Ranging from ITS to ITC. Not many ITR cars there.

I plan on getting a set of Z2s or rivals and run cfr races. Hoosiers are great but if you are not getting contingency (finishing position or lack of competitors) then this is a great solution.
 
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Congrats on your win!!

I have a pile(20+) of 205/50/15 Dunlops. Z1, 160$ for 4. some are very nice. The new Z2 are supposed to grease up more than the last version. I dont know for sure tho.
The new Chumper needs some 265x 17s.

Add the HP class to the ITA cars and I'll bring a Golf. It wont keep up with the ITA cars tho but I can try.
 
I'm not getting into class mix n' match. if you want to run the HP car on 180s, we can work a group for that, but it'd an ITX or SPU, not an ITCS class.

they really were impressive though. to bad I wasn't as much, but cobwebs and all that.
 
FWIW we run the Rivals on our crapcan Miata, and I'm happier with them than I am Z1s in the same size. we ran a full 24hr event and used up maybe 25% of the tire. I never ran that car with DOT-Rs, but I was quite happy with how it handles on the Rivals and was keeping up with well-known SM builders & racers in their 'cheater SM car'. (they were also on Rivals).
 
This is great to hear! I am glad someone else has given this try and realizes how great this type of tire can be especially on IT cars. I still think it is hard to get off the purple crack when you have a car that you know can win, but if you can get enough people to race with you'll have a ton of fun!

Stephen
 
I also don't think ITS or ITR cars would be 6+ seconds slower. If that was the case I could get people crack and get a lot of track records! We have found 2-3 seconds the norm (for us) and we are running under 4 seconds off the track record. With our ITR car we are running about a second faster than a SM track record. not sure if that helps in your comparison. I find the biggest loss in time (using our data, not a hunch) is actually getting the power down at exit. On Hoosiers you can get on the throttle sooner and harder making up time all the way down the straight.

Stephen
 
I also don't think ITS or ITR cars would be 6+ seconds slower.

You're in ITR though and can get properly sized street tires. Without changes in the wheel rule for ITS, ITS times are going to be quite a bit slower. 205-15 street tires are smaller than what most of us in ITS use. I use 245-15 tires on all four corners, and will be experimenting with a larger size this spring. A couple other ITS cars use larger than 225 as well.
 
What size street tires and you fit and work well on 7" wide rims. I was using Hoosier 225s on 6" wide wheels, and the Hoosiers are known to be on the larger variance of the 225 specs.
 
Here in PR in an attemp to lower competition costs and attract more competitor we decided to go with street tires. After receiving different proposals we decided to go(for 2 years) with the Kumho XS as the local distributor offered them in 205/50-15 at $100ea with monting and balancing for racers.

Many people criticized the decision, but when everybody got to the track, the club started receiving complements on the decision and now everyone love them. To the point that some of the GT3 racers are considering it. As racers setup their suspension I am certain times will continue to drop and so far we're getting two full weekend out a new set.

There are other very good options like the Hankook RS3, Dunlop ZII, Toyo R1R.
 
the hoosiers fit smaller wheels better than most street tires due to the real street tires having real street carcasses where the DOT-"R" tires have just enough to get by. a 225 street will fit a 7" rim no worries, and should fit a 6" wheel but you'd need to test for diminishing and negative returns from flexing the tire to the wheel. there are no 245 15's though. that's true. but at least everyone is in the same situation so it's not as much a detriment if you look at it that way. there are 225's from BFG and some others.

Stephen - you and your brother's experience, as well as that of a bunch of guys named Rob who have driven the RX8 is of huge importance to me. your team sort of pioneered the Street Tire IT thing and have the most experience with it that I'm aware of. I know we are taking different approaches to getting people interested, but I'd like our efforts to help each others with data and contacts.
 
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I find the biggest loss in time (using our data, not a hunch) is actually getting the power down at exit. On Hoosiers you can get on the throttle sooner and harder making up time all the way down the straight.

Stephen

**Hodge-podge post to follow**

1. On the other forum, there was a thread posted about a test with an autox Vette comparing street tires and A6s. Very similar DATA was found: the peak g-loading between the tires were similar, both laterally and longitudinally. The streets were nowhere near as good at doing two things at once. You could see it pretty starkly in the g-meter scatter plots that read like a friction circle.

2. The available sizes are probably an issue. I think there would be some that would argue that the bigger problem would be with the B and C cars, not as much the S cars, because in the little cars the diametrical difference is more, street vs R. Hell, for them, it would be a bigger setup change, because even ride height is grossly effected. Counter to that argument could be that **most** cars in the same class run on similar diameter wheels/tires. So you could say that it would effect everyone evenly, for the most part.

3. On a 15X7, you can run a 225/45-15, which is available in the Rival. There was a test in the last GRM of this tire. It was faster on the 8 and 9, but whatever.

4. On the ME front. I run all sorts of tires on my car. For pdx, I've run a 13" V710, a 205 Ecsta XS on a 15X7, and a Azenis 615K on a 15X6. I also ran the ARRC on a combo of the Azenis on the 6 for a rain quali session, and an SM6 take-off on a 15X7. I'm not married to any of the above. They all "feel good." Right now, what I'm planning on doing next year is to run at least one SCCA endurance race on the Rival, a Chump on the Rival on 8s, and a Major which will probably be on some sort of R6 take off, to better keep up in the STL/FProd groups.

Unfortunately because my car has been through tons of changes, I don't have comparative data, but I ran high 1:45s at the ARRC on the SM6s, and at a late season pdx at Lime Rock I ran a high 1:05 on the Ecta XS. ITA car, VERY light prep. Honestly, I felt 1:05s at LRP on streets was very strong, I'm pretty sure with even just a smidge of development in the car, and newer streets, I'd be able to find someone to race with in even a mid sized field.

5. Why does the data matter {Devil's Advocate}? If you have a group on streets, how they compare to a class on rcomps is immaterial. I think the Blethen's experience, and from what I've seen from #4, even in a mixed group, a street tire shod car won't be dangerous or in the way. The guy or girl inside it will just be retaining a few more of his/her earned dollars.

6. Chip: I'd like to see a pic of your car with the STC livery. And maybe info on where to get me some. Or maybe just make the graphics files available? I'm borderline agnostic on the whole thing, as running the SM6 take-offs was frickin cheap for me too. But otoh, they were trash after only the ARRC weekend, and it would be easier to not have to put new tires on all the time, no matter the cost of them.


Good discussion. I have no interest in changing anyone's mind at this point, or pushing for rules changes. The organic movement that could come out of Chip's idea is compelling, though.

Will
 
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Rival 225/45/R15... $121 from tirerack. wow

Up until a week or so ago, they were also offering a $50 rebate when you buy 4... then there's the Dunlop Z2 at $109 each... and Bridgestone with the RE-11A and a $70 rebate. :D

Like I've said before: the current crop of street tires don't have the same absolute limits as R-comps but they're a crap ton cheaper as long as you have a tire that doesn't need or benefit greatly from shaving.
 
I think this is a really cool idea. I'd like to encourage any and all of my STL competitors to try out these tires, too.
 
The livery as. Run on my car:

IMG_20131124_164531.jpg


Decals will be red where this is green. "Racing for fun" is a placeholder. I'm accepting alternate suggestions for that. Right now I'm thinking a play on words about the tread like. "race with depth" or simply "groovy".

I'll share the art on the website which is forthcoming. I hope to have it all up and running by 1/1/14

and thanks to Marc Dana (MazMarc) for the design and vinyl work. he makes my bad ideas look good.
 
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I'm surprised you're not getting more out of them. I thought street tires have a much longer life span?

+1, cheese grater track?

I have ~18 hours on my Azenis 615Ks, other than one that's sort of flat spotted, they have at least another half that left, or more.

I have probably 20+ hours on my Ecsta XS (which don't meet the 200tw requirements for most street tire series, but ARE streets), and they came to me as a completely unknown quantity. I'd use them another 2 pdx days, AT LEAST. A novice or inter PDX driver could probably go another 10-12 hours on them with no trouble.

I did a Lemons with another team on the Dunlop Z1s, 14 hours and they had at least another 6+ hours on them with no issues, E30 BMW.

I'm pretty sure others are seeing the same numbers out of the Z2s and the Rivals. IE if you're somewhat diligent with them re flat spotting (to which streets are pretty resistant) and rotation, 24 hard track hours are not out of the qustion for a set.

Notable with at least the ones I've had direct experience with, the 615k, XS and Z1, the tires are very very consistent along it's life. Example, the Z1 on the E30 was at Lightning. I ran my fastest laps of the event in the cool on the second day after the tires had been run for ~9-10 hours. And that was well into my stint.
 
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