Hoosier / Continental Slick Questions

[KBBOSS1086]

Does anyone know the difference between the Continental EC-DR's and GT-O's? My understanding is that the EC-DR's are Extreme Contact Dry tires (with 275/35/18 being used on the 302R's in the Continental GS class). I'm thinking the GT in GT-O stands for the GT class in the Rolex series Does anyone know if this is accurate and if the "O" is important? Are the EC-DR's & GT-O's the same compound?

Also, I searched all over the net to find out how to conver the 3 digit aspect ratio in, for example the 285/645R/18 GT-O's but could not figure out how to convert this to a standard tire size (xxx/xx/18). I assume the larger the 3 digit number the taller the sidewall, but does anyone have any idea what a 285/645R/18 would be comparable too?

I'm considering getting a set of these from Hoosier but have no idea how tall the sidewalls will be and what compound they are. I emailed Hoosier a couple days ago but haven't heard back and my next track day is approaching quickly.

Thanks
Sean

 

[steveespo]

Sean
The 645 is the overall height in millimeters. 25.393" tall tire.
Steve

 

[Senderofan]

Does anyone know the difference between the Continental EC-DR's and GT-O's? My understanding is that the EC-DR's are Extreme Contact Dry tires (with 275/35/18 being used on the 302R's in the Continental GS class). I'm thinking the GT in GT-O stands for the GT class in the Rolex series Does anyone know if this is accurate and if the "O" is important? Are the EC-DR's & GT-O's the same compound?

Also, I searched all over the net to find out how to conver the 3 digit aspect ratio in, for example the 285/645R/18 GT-O's but could not figure out how to convert this to a standard tire size (xxx/xx/18). I assume the larger the 3 digit number the taller the sidewall, but does anyone have any idea what a 285/645R/18 would be comparable too?

I'm considering getting a set of these from Hoosier but have no idea how tall the sidewalls will be and what compound they are. I emailed Hoosier a couple days ago but haven't heard back and my next track day is approaching quickly.

Thanks
Sean

Sean:

I just received a set ( 4 ) of Hoosiers / branded "Continental"....305 / 650 /18". The second number refers to the aspect or side wall. From what I can gather from the Hoosier website....My "650's" would equate to a 40 side profile in street tires. I'm thinking the 645...depending on width...would be 35-40. Unmounted my sidewall is 3 3/8" with a width of 11 1/2" plus.

Have you checked the Hoosier website?? They have several of their road racing slicks on sale....got mine at a substantial discount: https://www.hoosiertire.com/discontinuedtires.htm Scroll down to the second to the last offering...highlight the size section and choose tire size.

Good Luck,

Wayne

 

[KBBOSS1086]

Thanks for the info Steve & Wayne.

I ordered 2 sets of the A6's from the Hoosier sale back in March and am ready to try the continentals now. The deals are very good on the discontinued tires and shipping is even better ($15 flat no matter how many you order).

When I talked to the rep at Hoosier in March he told me to expect the prices to drop even more later on in the year.

 

[further]

The tire code is as T/A/W.
T = Tire width (mm)
A = Aspect ration (%)
W = Wheel size (inches)

For example, for the stock Boss Pirellis:
Front - 255/40/19
Rear - 285/35/19

The parameters are as follows:
Front -
T = 255 mm
A = 40 %
W = 19 inches
Rear-
T = 285 mm
A = 35 %
W = 19 inches

To calculate overall tire height (from WIKI):
For a size shown as "T/A/W" use (2×T×A/100) + (W×25.4) for a result in millimeters

Therefore the front stock Boss tire is
(2x255x40/100) + (19x25.4) = 686.6 mm

The rear stock Boss tire is
(2x285x35/100) + (19x25.4) = 682.1 mm

Your 285/645/18 tire is 645 mm tall, as they have already calculated the height.

Regarding the GT – O classification, I have ordered and used the following slicks from Turnermotorsports (for Bimmers):

275/650/18 Continental Grand slick (Hoosier knock-off) GT- O compound.
305/650/18 Pirelli Grand Am Slick D2 compound.

I have ready to go for my next event(s):
305/650/18 Continental Grand slick (Hoosier knock-off) GT- O compound.
305/650/18 Pirelli Grand Am Slick D2 compound (second set)

They both performed very well and are true slicks. Start at about 20 PSI and shoot for 30 hot. Ran both sets for 16 heat cycles then tossed them. They still had tread based on the little dimples but I wasn’t sure how many cycles I could go, so I ditched them. They are all used and were mounted on 18 x 10 inch D Force wheels from Vorshlag. The 275 Conti’s were a tad narrow for the wheel (prolly better mated on 9.5’s) but the Pirellis were just about right (maybe a tad wide). The 305 Conti’s are really wide (wider than the Pirelli’s) but I know some have ran them (Vorshlag and customers). I use a 5 mm spacer up front with 2.6 degrees negative camber.

BTW, thanks for the link to the Hoosier discontinued tires. I’ll def put them in the mental Rolodex.

 

[blacksheep-1]

FWIW try to get the "Indy" compound tires (used last year) or the standard Conti used this year, which is the "Indy" compound, they are slightly softer to prevent heat buildup at some of the tracks. I suspect however that those tires will be the "old" GS compound which is harder. As far as heat cycles go like most tires the first 5 laps will always be the best, the ones "broken in" slowly will last longer. You can get quite a few heat cycles out of them, they will however cycle out before they wear out. I have a couple of sets out back, let me look at the designation in a bit and I'll post it. (Indy vs Old).

OK the "old" (2012) tires said Extreme Contact Dr on them, the "Indy" tires said exactly the same thing except under the "DR" was stamped GS-I assuming that was for GS class, Indy spec. I honestly haven't noted the side of the new tires since they are a "spec" tire in GS.

 

[2012YellowBoss]

Does anyone know the difference between the Continental EC-DR's and GT-O's? My understanding is that the EC-DR's are Extreme Contact Dry tires (with 275/35/18 being used on the 302R's in the Continental GS class). I'm thinking the GT in GT-O stands for the GT class in the Rolex series Does anyone know if this is accurate and if the "O" is important? Are the EC-DR's & GT-O's the same compound?

In the Rolex series
The GT-O was used at Daytona, O for Oval.
The GT-I was used at Daytona, Indy and Wakins Glen this year, I for Indy.
GT-R compound is for other road courses R for Road course.

The GT-I in the Contenental Series was used at the Indy race last year and the compound is used at all tracks this year. Last year the 275's were marked GT-I for the Indy race, before this there was no markings. At the start of this year I think they were all marked GT-I and now they just have GT on them.

Also I have been told the GT-O is very close or the same as the GT-I compound. The EC-DR (last year's unmarked tire) will be a little different then the GT-O but it is not enought to make a difference for track use.

 

[neema]

my goodness. just when I was telling myself that my NT01s were overkill and I should learn how to drive on some less sticky/smaller, Hoosier decides to sell 305 sized slicks at $130 a pop.

If I run across any of you and have a horrible driving line on track, I apologize in advance!

 

[KBBOSS1086]

Awesome information guys and pretty much spot on to what the Hoosier Rep told me. I emailed them a similar line of questioning to what I asked here and this is the response I received. PS - Hoosier is a great company to deal with. I've been very impressed! The service they provide and knowledge they share is second to none.

Sean,

Thanks for returning to purchase more track day tires. First, the GT – O tires are designed as pure slick tires with a pretty durable tread compound. The EC – Dry tires are more designed as a DOT track tire, but offers a slick tread pattern.

Both compounds – EC-Dry and GT-O are pretty hard compounds and would take 1 – 2 laps more, compared to the A6, to come up to temperature. Don’t be surprised when running these Conti tires take a bit to warm up.

Next, the GT slick tires are labeled with a European designation where both the Width(285) and Diameter(645) are listed in Millimeters. I have listed two Conti Tire options below.


275/35R-18 EC(Extreme Contact) – Dry - $221.00 each

Diameter – 25.6” x Tread Width – 10.3”


285/645R-18 GT-O - $191.00 each

Diameter – 25.5” x Tread Width – 10.6”

The EC-Dry tire would need 30 – 32 psi COLD / 40 – 42 psi HOT pressures

The GT-O tire would need 24 – 26 psi COLD / 32 – 43 psi HOT pressures.

Any more questions after reading this, please feel free to write

Jeff Speer, HRT

 

[neema]

Great info. Interesting that the GT-O compound has such a large pressure operating range compared to the ECs

 

[cloud9]

Awesome information guys and pretty much spot on to what the Hoosier Rep told me. I emailed them a similar line of questioning to what I asked here and this is the response I received. PS - Hoosier is a great company to deal with. I've been very impressed! The service they provide and knowledge they share is second to none.

Sean,

Thanks for returning to purchase more track day tires. First, the GT – O tires are designed as pure slick tires with a pretty durable tread compound. The EC – Dry tires are more designed as a DOT track tire, but offers a slick tread pattern.

Both compounds – EC-Dry and GT-O are pretty hard compounds and would take 1 – 2 laps more, compared to the A6, to come up to temperature. Don’t be surprised when running these Conti tires take a bit to warm up.

Next, the GT slick tires are labeled with a European designation where both the Width(285) and Diameter(645) are listed in Millimeters. I have listed two Conti Tire options below.


275/35R-18 EC(Extreme Contact) – Dry - $221.00 each

Diameter – 25.6” x Tread Width – 10.3”


285/645R-18 GT-O - $191.00 each

Diameter – 25.5” x Tread Width – 10.6”

The EC-Dry tire would need 30 – 32 psi COLD / 40 – 42 psi HOT pressures

The GT-O tire would need 24 – 26 psi COLD / 32 – 43 psi HOT pressures.

Any more questions after reading this, please feel free to write

Jeff Speer, HRT

No wonder I was rolling the front edges, the recommended hot pressures are much higher than I was told by the place I bought used ones. Good info. I was emailing with Hoosier today on recommended R6 fitment and you're right they are very helpful.