255/35-18 Hoosiers or 245/40?
12-13-2008, 05:56 PM
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255/35-18 Hoosiers or 245/40? A week ago I spun a bearing in my autocross car. Today I ran the V in STU, a street tire class, as a backup. The car actually did much better than I expected, so I'm considering trying out some R-comps on this car next year. I've been running on Hoosiers for 2 years and see no need to change, so my question is whether a 255/35R18 Hoosier will fit without rubbing on the spindle, fender or anything else. Hoosier says an 8.5-inch wheel is on the small side of their recommended wheel size for this tire but still acceptable. So...if I actually go through with this which tire should I pick? I'd love to hear from any of the guys with track or autoX experience, especially on race tires.
For what it's worth, I'd be running this car regularly in E Street Prepared class in SCCA Solo next year along with all the pony cars and the WRX. I'm not looking for a nationally competitive car here, just something fun.
For what it's worth, I'd be running this car regularly in E Street Prepared class in SCCA Solo next year along with all the pony cars and the WRX. I'm not looking for a nationally competitive car here, just something fun.
12-13-2008, 07:30 PM
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I'm not sure about the 255/35, but I have 2 sets of R-compounds. Toyo R888s and Hankook Z214s. Both are 245/40/18. I have no issues at all and the car handles like it's on rails.
I've run about 4 events with my R888s and took first in class every time. For comparison, the other cars in my class included M5s, Mustangs, stock Miatas, stock S2000s, etc...
And a pic for fun
I've run about 4 events with my R888s and took first in class every time. For comparison, the other cars in my class included M5s, Mustangs, stock Miatas, stock S2000s, etc...
And a pic for fun
12-13-2008, 10:33 PM
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Thats what I'm looking for as well 245/40s. I autox'd mine last week for the first time (first time ever autoxing) and it seemed like the front end wanted to push pretty hard. I did find it pretty interesting that I got the lateral g force to .97 on the G/Y F1 GS3s. Of course I did spin out so it may have been the end of the grip level.
12-13-2008, 11:11 PM
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I ran today on the GSD3s as well. Either my co-driver or I hit 1.10/1.13 with the air pressure set to 44 front/40 rear. Dropping rear air pressure should reduce understeer a bit.
12-14-2008, 08:34 AM
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Mine were 40-42F/38-40R Gained pressure during the run obviously. The lot that we were on had ALOT of sandy debris on it and the surface was very cold... Cool to see that there is more potential out of them! Are those OE G Force meters very accurate or is it just a typical gauge?
12-14-2008, 08:48 AM
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My guess would be that the G-meter measures instantaneous G, not continuous G. Spikes well above 1G likely come from a car breaking loose and then snapping back the other way, in my opinion. Virtually any car can exceed 1G for a split second under these conditions. I could be wrong, but I refuse to believe a car this big can actually pull a constant 1.13G when last year's national F Stock champion in a Shelby GT told me he was datalogging 1.2G on Hoosier A6s and running on a better surface.
Now R comps like Hoosiers, R888s, V710s and so on are easily capable of >1.1G on a CTS-V. But street tires? I have my doubts...FWIW, the Lotus Elise pulls 1.07 on its stock tires.
Now R comps like Hoosiers, R888s, V710s and so on are easily capable of >1.1G on a CTS-V. But street tires? I have my doubts...FWIW, the Lotus Elise pulls 1.07 on its stock tires.
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12-14-2008, 12:52 PM
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My guess would be that the G-meter measures instantaneous G, not continuous G. Spikes well above 1G likely come from a car breaking loose and then snapping back the other way, in my opinion. Virtually any car can exceed 1G for a split second under these conditions. I could be wrong, but I refuse to believe a car this big can actually pull a constant 1.13G when last year's national F Stock champion in a Shelby GT told me he was datalogging 1.2G on Hoosier A6s and running on a better surface.
Now R comps like Hoosiers, R888s, V710s and so on are easily capable of >1.1G on a CTS-V. But street tires? I have my doubts...FWIW, the Lotus Elise pulls 1.07 on its stock tires.
Now R comps like Hoosiers, R888s, V710s and so on are easily capable of >1.1G on a CTS-V. But street tires? I have my doubts...FWIW, the Lotus Elise pulls 1.07 on its stock tires.
12-15-2008, 10:55 AM
#9
I also run 245/40 Hoosier R compounds. (got the out of stock rolex GT compound, not R/A6's).
I compared them to the 275/35/R18 Falken Street tires, that I run on the street, and they are the same width. I think if you went wider you might have rubbing issues up front.
The 245/40's don't rub. These were on stock 8.5" rims.
-Chris
I compared them to the 275/35/R18 Falken Street tires, that I run on the street, and they are the same width. I think if you went wider you might have rubbing issues up front.
The 245/40's don't rub. These were on stock 8.5" rims.
-Chris
12-16-2008, 09:58 AM
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There is a yaw sensor under console. Its listed as vehicle yaw sensor (w/veh latl acclrm). I believe this is the sensor that monitors your driving and engages the stabilitrac when you step the car out of shape. I believe that this sensor also reports the vehicles lateral load on the gauge in the cluster.
I tossed my V into a clover leaf getting off of the highway and registered 1.18g. It was a short moment that there was alot of load but it retains peak load. The car had a gross amount of understeer and the tires were confirming my assesment. Too much fun! This car rips!
On topic: Any tire with minimal tread grooves and a lowest treadwear rating will be an improvement.
I tossed my V into a clover leaf getting off of the highway and registered 1.18g. It was a short moment that there was alot of load but it retains peak load. The car had a gross amount of understeer and the tires were confirming my assesment. Too much fun! This car rips!
On topic: Any tire with minimal tread grooves and a lowest treadwear rating will be an improvement.
Last edited by CORNER CARVER; 12-16-2008 at 10:24 AM.
12-17-2008, 07:08 AM
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Wow, I used to run my Iroc in F-stock. There is no way I would put my V up against a stock Iroc. I was figuring SS or something. Is the weight its big dis-advantage on the autocross course?
12-17-2008, 07:15 AM
#14
I also run 245/40 Hoosier R compounds. (got the out of stock rolex GT compound, not R/A6's).
I compared them to the 275/35/R18 Falken Street tires, that I run on the street, and they are the same width. I think if you went wider you might have rubbing issues up front.
The 245/40's don't rub. These were on stock 8.5" rims.
-Chris
I compared them to the 275/35/R18 Falken Street tires, that I run on the street, and they are the same width. I think if you went wider you might have rubbing issues up front.
The 245/40's don't rub. These were on stock 8.5" rims.
-Chris
-Chris
12-17-2008, 08:01 AM
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You got it. Weight and the inability to fit a large tire kill the V for serious autocross. Besides, not every car in a given class has a chance to be competitive. The AMC Javelin is still classed in F Stock just because that's where--for the most part--RWD, American V8 4-seaters go. The current king of F Stock is the Shelby GT (not the GT500!). Compared to the V it's down about 80 hp but it can fit much larger tires (295s) and weighs about 500 pounds less. Also, IRS isn't a huge advantage on a surface that's always flat and smooth.
01-13-2009, 10:03 AM
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I'm reviving my thread because I'm getting closer to ordering tires. Is there much chance that a 255 or 275 that's shorter than stock might fit up front without rubbing, or is it the width itself that's the issue? To anyone who has had rubbing problems, where exactly did the tire rub--fender lip, spindle, plastic inner fender...?
