bbundy

Hoosier 275/35/15 R6 DOT tires
or
245/580/R15 R80 slicks.

Anybody have any experiance to compare the two in terms of performance, longevity, driveability etc on the track?

k24madness

iTrader: (6)

Here is what I got for you Bob.

A good friend with a V8 Miata ran 275 R6's on 9's. He was never really wowed by the tires. He tried my 245 R80's one day and was blow away at the grip difference. Times were significantly better but his R6's were at the end of the life (at that time) and the R80's were new so not a good comparison.

Another friend who runs American Iron has a 600hp mustang. He ran R6's for a long time. He switched to R100's. He claims longer life and better grip. Very consistent from stickers to cords.

I ran my first set of R80's out 12 heat cycles before cording due to poor setup. I now have good alignment numbers (NB sub frame) and a new set of R100's. I only got 3 heat cycles in em so not much info there. The difference between the R80 and R100 is not very much IMHO. I am a bit of a hack so take it for what it's worth. I felt a pretty big drop off around 6 heat cycles with the R80's.

I did a LOT of research before pulling the trigger on R100's. The Porsche guys claim very little grip difference but much longer life out of the 100's. The big diff seems to be how quick they come up to temp. The R100's are a bit scary out of the gate.

Check with Orion. He has run the R80's quite a bit.

bbundy

keep the info coming. I've won some free tires through solo contigencies trying to decide if I want to get something diferent instead of more Solo tires for next year.

Kind of looking at NASA TT since we have a region as of this year but havent even figured out how I could class this little beast.

Savington

iTrader: (31)

Your car would probably be a NASA TT2 car.

bbundy

any reccomendations for which Hoosier tires?

Savington

iTrader: (31)

You're allowed more power on the 275/35s. A6/R6 is counted as the same tire, as are the R80/R100s. Up to you to decide whether it's worth it or not.

orion4096

iTrader: (22)

I'm not going to be any help. I've only ever run 225 ra1s, 225 nt01s, and 245 R80s at the track. Never been on a A6 or R6 on any car. The R80s were amazing, though. Turn-in felt so good. The only annoying thing is warming them up and the $1000 missing from my wallet.

bbundy

Interesting if Im reading right Non DOT would bump my adjusted wt/hp into TT1 without turning the boost about as low as I can. -.75 versus +.4 is a big differance in adjustment.

k24madness

iTrader: (6)

Also consider race strategy. With A6's you have grip right out of the gate when most of the shuffling goes on. That seems to be the best time to secure a good position. On the other hand R80's will come in later so you have to defend out of the gate and try and gain positions later. Restarts etc play a role too.

Savington

iTrader: (31)

Non-DOT slicks between 244mm and 267mm get +0.4 added back, so the 245/580 R80s are counted as a combined -0.35, and the 275/35 R6s are counted as a combined +0.4.

In the real world, for a 2351lb comp weight (NASA ST rules favor curb weights ending in "51"), you take a 25whp hit if you decide to run 245/580 R80s instead of 275/35 A6s, or about a 9% power hit.

k24madness

iTrader: (6)

In ST2 for my car (2,200lbs with driver)

273 HP 245 A6-R6
260 HP 275 A6-R6
237 HP 245 R80-R100

I can't imagine the 13HP advantage of the 245 R6-A6 being worth the trade. The 275 is a no brainer there IMHO
The 23HP hit of the slicks is pretty steep. What I have to look at is avg HP across the RPM band. With my setup that 23HP delta may end up being half or less when looking at avg HP from 5k-8k. In that case the R80 should be the better choice.

bbundy

I would be running TT Time trial only with this car. I am assuming you can run a HPDE car with proper bolt in roll bar in NASA Time trials. Non wheel to wheel. I have a Spec Miata for wheel to wheel but going about 10 seconds faster than I can in my Spec is a lot of fun too.

The other Use I have for this car is Autocross. Where I take the roll bar and some chassis bracing off swap on a bigger wing and splitter. And go win Hoosiers and Mazda money contingencies at National tour autocross and Pro Solos. Minimum weight without the roll bar and no driver is 2080 lbs and It has to have interior in tact. So add 100 lbs worth of roll bar bracing and accusump system plus 200 lb driver and I’m over 2350 weight probably more like 2400. It would probably take a bad tune and a safety wired open waste gate to get the car to make much less than 300 hp with the current setup I could probably make 320 to 380 very comfortably and Its really happy at about 360 whp with around 17 lbs of boost.

k24madness

iTrader: (6)

Hey Bob come join us at Thunderhill Oct 23rd. One of my friends rented the track for the day. Only two run groups so LOTS of track time. I could use another Miata to help fend off those mustang guys.

bbundy

Wow I'm going to have to figure out how to make less hp.

245 or under DOT 331 HP
275 DOT 314 HP
245 Non DOT 287 HP.

287 HP I think is out of my range

Somwhere I herd Hoosier was making a 245/40/15 A6/R6 not in the catalog. is that true?

k24madness

iTrader: (6)

I heard the same but have not seen em yet.

bbundy

oh it was in an email I got from Emillio

bbundy

Seeing how the last dyno tuning session my car it made ~325 HP on just the can boost at ~12.5 to 13 psi and at peak power RPM it would probably still make that much boost if I safety wired the internal waste gate wide open and it would just have really crappy spool . Looks like it might take 245 DOT tires to get me into TT2 with my heavy but powerful miata.

Looking at the TT results after the first season NASA raced up here in the northwest looks like I would have won TT2 running my 225 Nittos If I would have showed up and put down my typical lap times. 5 car class would mean tire contingencies if running Hoosiers.

k24madness

iTrader: (6)

I love the 245/580's on the 10's. Can't imagine a better rim for em. I wonder how the R6/A6 will look with the way they do the sidewalls on those tires. It seems like they are cantilevered to allow running a larger tire on a smaller rim. I think the guys with stock body work with 9's are gonna be in heaven with the new sizes.

Double O 86

sixshooter

iTrader: (12)

I see something in a new 2013 catalog on Hoosier's website that you might be interested in.

Under the category "SPORTS CAR D.O.T. - RADIAL (A6 & R6)"

Item #46521 P245/40ZR15

Hoosier Racing Tire - Tires Designed For Champions