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Old 09-27-2011, 08:32 PM   #41
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Are those 275's on 9" or 10" wheels?
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Old 09-28-2011, 11:47 AM   #42
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Are those 275's on 9" or 10" wheels?
They are on 9". Looks like the 10's wont arrive untill all my racing is done for the year.

Bob
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Old 09-28-2011, 11:48 AM   #43
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Bob if you end up having an extra set of 9's you need to unload i'll buy em
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Old 09-28-2011, 02:19 PM   #44
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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)
Only R6, A6 legal in T3. Tires must be D.O.T. to run in touring classes.

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?
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Old 09-28-2011, 02:49 PM   #45
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For NASA, the ST classes and any of the TT classes.
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Old 09-28-2011, 03:45 PM   #46
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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.
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Old 09-28-2011, 04:45 PM   #47
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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.
I did the math a while ago for ST2 and my car. With a 225 NT01, I was allowed ~260whp. With a 245/580 Hoosier R80, I was "only" allowed 230whp.

30whp doesn't make a 2 second difference, but going from a 225 R-comp to a 245 radial slick sure will
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Old 09-28-2011, 04:49 PM   #48
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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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Old 09-28-2011, 06:37 PM   #49
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30whp doesn't make a 2 second difference, but going from a 225 R-comp to a 245 radial slick sure will
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.
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Old 09-30-2011, 06:06 PM   #50
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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.
How do they verify your hp? I think I might still make over 300 hp with my waste gate safety wired full open. I loose all the spool but up top it wont make less than about 14 psi.

Bob
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Old 09-30-2011, 07:00 PM   #51
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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.
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Old 10-10-2011, 06:14 PM   #52
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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.
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Old 10-10-2011, 07:46 PM   #53
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Quote:
Originally Posted by ZX-Tex View Post
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.
Those are Formula Atalatic front tires. R25 or R35 compound. Iíd imagine super soft more sated for doing autocross run with a Miata. Most of the GT sedan type cars run on R75, R80, or R100 compound Id guess they would be more suited for the application. What I donít understand is EP cars run on 23X9.5 R15 cantilevered Bias ply tires in R35 or R45 compound and are fast as hell.

Iím still sticking to my plan of building a car around 23.5X11 R16 tires in an R75 compound.

Bob
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Old 10-10-2011, 08:25 PM   #54
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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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Old 10-10-2011, 08:31 PM   #55
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Iím still sticking to my plan of building a car around 23.5X11 R16 tires in an R75 compound.

Bob
Bob, why not the 23.5x12R16?
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Old 10-10-2011, 08:37 PM   #56
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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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Old 10-10-2011, 11:34 PM   #57
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Bob, why not the 23.5x12R16?
That’s a good question. It would probably require some testing. I’m thinking it would require a lot of cutting into sill area to on the aft side of the front wheel opening to fit them and be able to turn if you put them on the front. The 11's aren’t that much bigger than 275's but I think they still will need a bit some clearance by getting the pinch weld out of the way.

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
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Old 10-12-2011, 05:14 AM   #58
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Quote:
Originally Posted by ZX-Tex View Post
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've also had great experience with the kooks. Price for longevity and lap times beats the r6 any day. I'm not really a huge fan of the r6 have used then s few times road racing a integra itr this summer.
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Old 10-12-2011, 05:24 AM   #59
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C71 Hankooks can kiss my ***. 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.
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Old 10-12-2011, 10:27 AM   #60
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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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