Measured Performance Differences Between 275 vs 225 Hoosier A6's
#1
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All,
I'm looking to buy a set of 275 A6's for autocross. I had a set of 225 A6's on 15x9's and the tires measure only about 1" narrower than the 275's. Before I invest in flaring or cutting fenders, I wanted to see if anyone in the community has made a jump from 225 to 275 A6's and what kind of improvements they saw in grip, lap times, driving impressions, etc.
Thanks.
I'm looking to buy a set of 275 A6's for autocross. I had a set of 225 A6's on 15x9's and the tires measure only about 1" narrower than the 275's. Before I invest in flaring or cutting fenders, I wanted to see if anyone in the community has made a jump from 225 to 275 A6's and what kind of improvements they saw in grip, lap times, driving impressions, etc.
Thanks.
#2
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I know the difference between 255R13 and the 275 man meats is worth the time if you compete at more than a local level. But its not enough time that if I just ran with the local miata club and occasionally the scca that I would cut up the car to fit the 275s.
If you run the 275s on 6ULs you can get away with just running a 5mm spacer up from, and cutting the front fenders. And using a fender roller to pull the **** out of the rears. Although some people report not being able to pull the rears enough but being able to pull the fronts enough. Try both and see if they fit. You wont be able to pull the car far enough to fit the 275s on 15x10s.
IMO its worth it if you are competing regionally or nationally. But if its just local I'd probably go with the 255 13x9 combo and not cut. I dont think anyone is going to have the data of going 225 to 275, maybe Bundy did it a long time ago, or maybe someone who's been in CSP for a long time would know.
If you run the 275s on 6ULs you can get away with just running a 5mm spacer up from, and cutting the front fenders. And using a fender roller to pull the **** out of the rears. Although some people report not being able to pull the rears enough but being able to pull the fronts enough. Try both and see if they fit. You wont be able to pull the car far enough to fit the 275s on 15x10s.
IMO its worth it if you are competing regionally or nationally. But if its just local I'd probably go with the 255 13x9 combo and not cut. I dont think anyone is going to have the data of going 225 to 275, maybe Bundy did it a long time ago, or maybe someone who's been in CSP for a long time would know.
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Those look like 15x9s. Which arent too bad, but maybe half a tenth slower than the 15x10s. I MIGHT have been able to pull my front fenders more if I had more patience but I started to tear the metal on mine. It was easier to just cut them and put some sheet metal edging on them.
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To the original poster - can't quote times but the grip of the 275 is noticeably more than the 225
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His name was Mike Perry and he did a L33 swap NB. He found that Hoosier 275 were around $300 each and The Official Site for American Racer® Racing Tires 275 were around $160 each with the difference to be around a sec slower than his fastest time.
http://www.v8rspec.com/forum/viewtopic.php?f=10&t=15
http://www.v8rspec.com/forum/viewtopic.php?f=10&t=15
![](https://www.miataturbo.net/attachments/race-prep-75/80991-measured-performance-differences-between-275-vs-225-hoosier-a6s-track2.jpg?dateline=1372468030)
#10
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Perhaps a set of 12" wide midget tires? Needs a 13" Dia rim though...12" is 305s
Micro Sprints Asphalt Racing Tires
Micro Sprints Asphalt Racing Tires
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MARK Perry
I also tested the American Racer tires. More info here:
New 275 racing tire option !!! - Page 2 - MX-5 Miata Forum
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I also tested the American Racer tires. More info here:
New 275 racing tire option !!! - Page 2 - MX-5 Miata Forum
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Thanks for the input. The fitment info sounds promising. I went ahead and ordered a set of used 275 r6's for trial and fitment. The tires aren't much wider than the 225's and the unmounted tire bead width is 9.5" so I'll have to pinch them slightly to fit on 15x9's.
Emilio - the 245 size looks enticing, but I'm surprised to see how similar in dimension it is to the 225. Almost the same. I would have thought Hoosier would have placed the sizing closer to the middle of the 225 and 275.
Emilio - the 245 size looks enticing, but I'm surprised to see how similar in dimension it is to the 225. Almost the same. I would have thought Hoosier would have placed the sizing closer to the middle of the 225 and 275.
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IMO the spacer is required for 6ULs in the front even with the 15x9s on xidas. And I have the built up hoosier on my upper shock mounts to prove it. And the wear on the plastic spring isolator. It also puts a nice purple ring on the hoosier and will cut down to the cord in a couple auto-x's. If you're not doing that you either have less compression travel than I do or you arent cornering very hard. Or I guess you could be running higher than 850 pound springs.
The other question, is there an Avon A11 compound thick kevlar construction tire in ~23" diameter that is this width? Because that will be WAY faster than an A6 if you didnt need the tire to be DOT.
The other question, is there an Avon A11 compound thick kevlar construction tire in ~23" diameter that is this width? Because that will be WAY faster than an A6 if you didnt need the tire to be DOT.
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The tread width differences between a 225 and a 275 are pretty significant.
This pic is of 225/45/15 Hoosier H2O wets on 15x9's vs 275/35/15's on 15x10's.
![](https://www.miataturbo.net/attachments/race-prep-75/81097-measured-performance-differences-between-275-vs-225-hoosier-a6s-420948_10150650776544242_500104241_9076494_276238332_n.jpg?dateline=1372591687)
That said if you aren't going to run 15x10's then sick with 225's. 9" wheels pinch the sidewall of the 275. You will see significantly more shoulder wear and less overall performance. Keep in mind too that to optimize the 275's vs 225's would at minimum require some shock adjusting and more than likely require a change in spring rate. So even doing a back to back test on the same day(without optimizing both setups) isn't going to provide you any usable data.
This picture show's 275s on 15x10's vs 275's on 15x9's
This pic is of 225/45/15 Hoosier H2O wets on 15x9's vs 275/35/15's on 15x10's.
![](https://www.miataturbo.net/attachments/race-prep-75/81097-measured-performance-differences-between-275-vs-225-hoosier-a6s-420948_10150650776544242_500104241_9076494_276238332_n.jpg?dateline=1372591687)
That said if you aren't going to run 15x10's then sick with 225's. 9" wheels pinch the sidewall of the 275. You will see significantly more shoulder wear and less overall performance. Keep in mind too that to optimize the 275's vs 225's would at minimum require some shock adjusting and more than likely require a change in spring rate. So even doing a back to back test on the same day(without optimizing both setups) isn't going to provide you any usable data.
This picture show's 275s on 15x10's vs 275's on 15x9's
![](https://www.miataturbo.net/attachments/race-prep-75/81098-measured-performance-differences-between-275-vs-225-hoosier-a6s-imag0267.jpg?dateline=1372591687)
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Lots of us are going from fast HPDEers that would have loved to try 245s, to TT/PTers that need the soft and skinnies for points. It will be fun to watch Emilio and Andrew try the 245s in the higher classes maybe?