Are those 275's on 9" or 10" wheels?
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Originally Posted by TNTUBA
(Post 776663)
Are those 275's on 9" or 10" wheels?
Bob |
Bob if you end up having an extra set of 9's you need to unload i'll buy em :)
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Originally Posted by Savington
(Post 770919)
You've left this part out the last couple of times, and it's fairly important. If Hoosier designed the tire to fit and work on an 8" wheel because that's the max width for a racing class (taking a shot in the dark here - SCCA T3)
So what's the point of running the radial slicks? Other than spending lots of money to go really fast? Are they legal for any of the classes people are running? |
For NASA, the ST classes and any of the TT classes.
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Tann3r is correct. For NASA TTS for example, one just uses a different weight/power correction factor to account for wider, non-DOT tires. As long as your corrected weight/power does not exceed the limit, 8.7 for TTS, then you can use slicks. In my case I will have to reduce power slightly over being able to run full engine power with say 225/45-15 NT01s. It is all in the NASA TT classification rules.
Tires>horsepower (within reason) so I think I will come out ahead. We will see. The real question in my mind is if for me the slicks are better and/or more cost effective than an A6/R6. Either will almost certainly be a lot faster than slightly more power on NT-01s. But also more expensive. Sorry to the OP if we have completely jacked this thread at this point. |
Originally Posted by ZX-Tex
(Post 777112)
Tires>horsepower (within reason) so I think I will come out ahead. We will see. The real question in my mind is if for me the slicks are better and/or more cost effective than an A6/R6. Either will almost certainly be a lot faster than slightly more power on NT-01s. But also more expensive. 30whp doesn't make a 2 second difference, but going from a 225 R-comp to a 245 radial slick sure will :giggle: |
For TT/PT the Conti tire seems to be the way to go. They score it the same as the R6 but in my experience it's a better tire. I doubt it's worth 2s like the r80 but it's at least as fast as the R6 and has better life.
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Originally Posted by Savington
(Post 777139)
30whp doesn't make a 2 second difference, but going from a 225 R-comp to a 245 radial slick sure will :giggle:
Anyway I plan to try this very soon, and in fact will be at TWS in November for a TT event. If this tire versus power tradeoff works out well at TWS, it will work at any of the other tracks we run at. TWS is the most horsepower oriented track we have in this area, at least until COTA is finished. |
Originally Posted by ZX-Tex
(Post 777213)
WORD. Exactly what I am thinking. I have been playing what-if scenarios with the NASA TT scoring. I would go from 325WHP to "only" 290-300WHP. I doubt I would miss it that much, even at the faster tracks like TWS.
Anyway I plan to try this very soon, and in fact will be at TWS in November for a TT event. If this tire versus power tradeoff works out well at TWS, it will work at any of the other tracks we run at. TWS is the most horsepower oriented track we have in this area, at least until COTA is finished. Bob |
We have to go to a shop with a Dynojet Dyno, use the NASA correction factors in the rules, and do three back-to-back runs measuring WHP (not BHP). You send the plots in to the National Director, and keep a copy with you at the track.
The vehicle is also subject to dyno verification testing at the track. It has not happened to me yet but I have seen it happen. There are ways for the cheats to cheat of course but that is the system. |
So long story short I tested the Hoosier 23.0x9.5-R15 (Formula Atlantic) slicks on Sunday at Harris Hill in San Marcos. These were mounted on 15x9 6ULs. I ran Saturday afternoon and most of Sunday on NT-01s (15x8 6ULs) due to the track being wet. Sunday was the Texas Miata Challenge.
On Sunday afternoon the track dried off and finally became fast again. So I switched to the Hoosiers and went out for three separate sessions about 6-9 laps each. Between sessions I was checking tread temperatures and temperature distributions, and adjusting pressures. Probe type Longacre pyrometer. I had to add pressure to get them to heat up but each time I added pressure they were faster and felt better. In the last session I had them into the 1:28.X range which was about 3-3.5 seconds faster than the NT-01s I had just removed. But after the 3rd or 4th lap the grip started falling off. They did not feel like they were getting greasy, just a bit less grip everywhere, with about a 2 second fall off on lap times. I tired taking a lap at a 10 second slower pace but it made no difference. After that I gave up and came in. Overall they were not any faster than the Hankook Z214 C51 (225/45-15) I had used there before. Same car, same driver, same direction. I am allowing for the different track conditions by looking at the lap times of the other TxMC competitors compared to what they and I had done before at the same track in the same direction. My unadjusted best time for the Hankooks is actually 3 seconds FASTER than the Hoosiers, but the track was probably 2-3 seconds slower that day for everyone. So roughly speaking it is a wash. |
Originally Posted by ZX-Tex
(Post 781913)
So long story short I tested the Hoosier 23.0x9.5-R15 (Formula Atlantic) slicks on Sunday at Harris Hill in San Marcos. These were mounted on 15x9 6ULs. I ran Saturday afternoon and most of Sunday on NT-01s (15x8 6ULs) due to the track being wet. Sunday was the Texas Miata Challenge.
On Sunday afternoon the track dried off and finally became fast again. So I switched to the Hoosiers and went out for three separate sessions about 6-9 laps each. Between sessions I was checking tread temperatures and temperature distributions, and adjusting pressures. Probe type Longacre pyrometer. I had to add pressure to get them to heat up but each time I added pressure they were faster and felt better. In the last session I had them into the 1:28.X range which was about 3-3.5 seconds faster than the NT-01s I had just removed. But after the 3rd or 4th lap the grip started falling off. They did not feel like they were getting greasy, just a bit less grip everywhere, with about a 2 second fall off on lap times. I tired taking a lap at a 10 second slower pace but it made no difference. After that I gave up and came in. Overall they were not any faster than the Hankook Z214 C51 (225/45-15) I had used there before. Same car, same driver, same direction. I am allowing for the different track conditions by looking at the lap times of the other TxMC competitors compared to what they and I had done before at the same track in the same direction. My unadjusted best time for the Hankooks is actually 3 seconds FASTER than the Hoosiers, but the track was probably 2-3 seconds slower that day for everyone. So roughly speaking it is a wash. I’m still sticking to my plan of building a car around 23.5X11 R16 tires in an R75 compound. Bob |
Yep. I tried these since they were available in barely used scrubs at a cheap price. Now I am thinking maybe I should try the 245/580R15 R80 next though availability other than new is TBD.
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Originally Posted by bbundy
(Post 781952)
I’m still sticking to my plan of building a car around 23.5X11 R16 tires in an R75 compound.
Bob |
Also, Trackdayhookey had 245/580 Hoosiers at WSIR this weekend. They are PINCHED on a 9" wheel. No doubt that they need a 10".
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Originally Posted by Savington
(Post 781976)
Bob, why not the 23.5x12R16?
FWIW. V8 track miata build with 23.5x11R16 http://www.roadraceautox.com/showthr...450#post956450 I think it needs some inner fender work to get the ride height as low as I’m running now and have the suspension optimized for height and travel. Bob |
Originally Posted by ZX-Tex
(Post 781913)
So long story short I tested the Hoosier 23.0x9.5-R15 (Formula Atlantic) slicks on Sunday at Harris Hill in San Marcos. These were mounted on 15x9 6ULs. I ran Saturday afternoon and most of Sunday on NT-01s (15x8 6ULs) due to the track being wet. Sunday was the Texas Miata Challenge.
On Sunday afternoon the track dried off and finally became fast again. So I switched to the Hoosiers and went out for three separate sessions about 6-9 laps each. Between sessions I was checking tread temperatures and temperature distributions, and adjusting pressures. Probe type Longacre pyrometer. I had to add pressure to get them to heat up but each time I added pressure they were faster and felt better. In the last session I had them into the 1:28.X range which was about 3-3.5 seconds faster than the NT-01s I had just removed. But after the 3rd or 4th lap the grip started falling off. They did not feel like they were getting greasy, just a bit less grip everywhere, with about a 2 second fall off on lap times. I tired taking a lap at a 10 second slower pace but it made no difference. After that I gave up and came in. Overall they were not any faster than the Hankook Z214 C51 (225/45-15) I had used there before. Same car, same driver, same direction. I am allowing for the different track conditions by looking at the lap times of the other TxMC competitors compared to what they and I had done before at the same track in the same direction. My unadjusted best time for the Hankooks is actually 3 seconds FASTER than the Hoosiers, but the track was probably 2-3 seconds slower that day for everyone. So roughly speaking it is a wash. |
C71 Hankooks can kiss my ass. I don't understand how a tire can go from 13-seconds under SM record pace, to 7-seconds off my previous best NT-01 laptime, in one session.
My previous best at WSIR was a 1:27.0. I couldn't get under a 1:33.4 on cycled-out C71s. Switched back to a set of old NT-01s, with a single newer tire on the LR corner (important corner), and with a car that pushed slightly I was able to get straight down to a 1:27.7. I cannot wait for 15x10s and 245/580 glory. |
In my case I have C51 compounds. I am not surprised that an NT01 was faster than a cycled out anything.
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