I’ve noticed Miata guys seem to love sticking 275/35/15 Hoosiers under their cars. Considering how light, well-balanced, and relatively underpowered they are ... do they really benefit from having so much rubber on the ground?
Is there a functional reason for this, or is it a “just because you can” type of thing?
Coming from the BMW world, I’m used to seeing cars that are much heavier and significantly more powerful that run 225 and 245 tires.
In reply to LanEvo :
I knew someone who loved E30s for autocross because he could fit 275s in the wheelwells without very much drama. He always sang the praises of the E30 due in large part to its unusually large wheelwells. "Try to fit that much tire under anything else its size!", he'd say.
He also liked to run so much boost in the six that block integrity was a regular failing point.
For autocross, in anything built to a class that allows that much width, power is way beyond stock.
My underbuilt SSM Miata is making about 235 RWHP and traction is scarce with 225s. I really should go another inch or two wider and flare it.
I like 275s on my ae86. Lighter than a lot of other cars but also makes good power. The width is awesome for grip
In reply to Duke :
E46 M3 track cars generally run 265 rear tires and don’t seem to have any trouble with grip even at some 300 rwhp. Does the Miata need more because the track is narrow? Again, I’m genuinely trying to understand.
Fitzauto said:I like 275s on my ae86. Lighter than a lot of other cars but also makes good power. The width is awesome for grip
I’m building my TR6 into a weekend/track toy. I love the look of steamroller tires tucked under flared arches. I guess I’m trying to justify doing something that I know in my heart is probably kind of dumb
I run 275s on the back of my Beetle and still regularly break them loose at launch and under heavy trail braking.
LanEvo said:In reply to Duke :
E46 M3 track cars generally run 265 rear tires and don’t seem to have any trouble with grip even at some 300 rwhp. Does the Miata need more because the track is narrow? Again, I’m genuinely trying to understand.
TRACK cars, yes? Not trying to get max grip in 1st or 2nd gear?
What about the idea that such a wide tire won't get warm enough to really hook up at an autocross event?
In reply to Knurled. :
Yes, I only have experience with trackdays and wheel-to-wheel racing. I know autocross guys need huge tires, but I’ve seen Miatas on track with them as well.
In reply to Fitzauto :
Autocross or open track?
In reply to LanEvo :
Yeah, that doesn't make sense to me either, then. When people find that tires much wider than 285mm hurt lap times, with 600+hp engines, one starts to wonder...
In competitive events? If so, the reason they run them is that they are faster.
Wide tires hurting laptimes is usually an aero thing, and Miata guys have figured out how to make 275s work well by now. Now if someone is doing it on a stock body car and a low power motor, I would question why.
In reply to LanEvo :
I’ve had autocross ridealongs in well-prepped Miatas on 275 A7s. You wouldn’t believe the violence of the transitions, or the sustained midcorner grip. It’s an astounding amount of mechanical traction. When you can stay flat through a 5 or 6 cone slalom and just snap the car back and forth through the gates, you can carry a lot of speed.
Duke gets it. Grip is king.
^^^ does that hold true on an open track as well?
The wider the tire the more frontal area it has. If you have Watkins Glen length straights the lower top speed caused by the drag more than offsets the faster corners. Lime Rock not so much. Now with your TR6, if it still has stock suspension your geometry is not good enough to take advantage of that much tire, and the chassis will fail at the suspension mounts if you could produce that much grip.
Say what you want about CSP Miata's running huge tires but the top CSP Miata in 2017 would have placed 3rd in EM, arguably a much quicker class
LanEvo said:^^^ does that hold true on an open track as well?
It’s like downforce. It keeps making you faster until it doesn’t anymore.
The one time i drove a stock-power miata on wide R-comps, it was eye opening. The only thing you had to do 90% of the time was steer.
Keith Tanner said:LanEvo said:^^^ does that hold true on an open track as well?
It’s like downforce. It keeps making you faster until it doesn’t anymore.
That is a very eloquent way of describing it.
My CSPish Miata with older 275 hohos data logged 1.45G in some corners. On better tires, and more developed the next year I know that was significantly higher. High enough I started having trouble keeping my alignment bolts correct on a smooth asphalt site.
They are trade offs of course, braking is actually worse, but a properly set up car can get away with so much on steamroller tires. Mine now runs -3.5 camber all round, 21/19 pounds of air in the tires, weighs 2,000 lbs, and is actually too softly sprung with SM springs (700/325).
For no other reason than to thread jack I have received the 16x8s, 16x9s, 205/50s and 245/50s for the Miata suspended Panhard. I think AI will mount them to push the donor tub around on 
For track and autocross, that's been covered very, very well.
For not, though, I hate driving on flat, wide tires on real roads- especially any roads that have worn a wheel lane in them, as the tires will wander around in those gullies. Drives me nuts.
Also, if you actually wanted to over drive a little on real roads- it's a lot easier to do (which means it's slightly less not legal) with normal width tires.
On my Alfa, I'd race all day on 225's. But normal driving, anything wider than 195's suck.
Which is to say, if the cars that have the wide tires are not racing, they are just posing as such.
LanEvoComing from the BMW world, I’m used to seeing cars that are much heavier and significantly more powerful that run 225 and 245 tires.
The big question is, can you shove bigger tires under the BMW's and stay legal for the class, and if you do, do they get faster? Miatas do this because they're faster with more tire, as Keith says, until they're not. I personally love Miatas with low grip, but I do acknowledge that they're slow that way.
You'll need to log in to post.
