GRM white NA Miata

Hey, I read the recent article about adding new suspension to the NA Miata and buying new tires in some monster widths, but I didn't see much further info on the tire fitment.

I desperately need more wheel/tire width, but I do not want to do more than roll the fenders (at most; preferably not). As with anything on teh intarweb I am getting conflicting reports about what is necessary to get serious width in a 15" size.

The car currently sports ancient 205/55(?)/15 V710s. Even accounting for the thousand heat cycles on them, with the blower it is just too easy to overwhelm the available traction. Next spring I want to get wider wheels and tires if possible. The car has an FM coilover kit on Koni sports, unknown (but stiff) spring rates, FM sways, and a has been lowered a bit using the perch adjustments. Don't have ride heights at hand.

Some say the 275/35/15 Hoosiers fit fine on 15x9 6ULs but others say you need 15x10 or 10.5 and a sawzall. I've heard Hoosiers run wide; is a 225/45/15 A6 substantially wider than my Kumho 205s?

Or, since I am budget-challenged after buying the car anyway, is there some other combination I should be looking at that is 90% of the grip for 70% of the price? Longevity is also a question - while I don't expect to be more than locally competitive, I definitely cannot afford fresh tires every 4 or 5 events.

Thanks...

Duke wrote: Hey, I read the recent article about adding new suspension to the NA Miata and buying new tires in some monster widths, but I didn't see much further info on the tire fitment. I desperately need more wheel/tire width, but I do not want to do more than roll the fenders (at most; preferably not). As with anything on teh intarweb I am getting conflicting reports about what is necessary to get serious width in a 15" size. The car currently sports ancient 205/55(?)/15 V710s. Even accounting for the thousand heat cycles on them, with the blower it is just too easy to overwhelm the available traction. Next spring I want to get wider wheels and tires if possible. The car has an FM coilover kit on Koni sports, unknown (but stiff) spring rates, FM sways, and a has been lowered a bit using the perch adjustments. Don't have ride heights at hand. Some say the 275/35/15 Hoosiers fit fine on 15x9 6ULs but others say you need 15x10 or 10.5 and a sawzall. I've heard Hoosiers run wide; is a 225/45/15 A6 substantially wider than my Kumho 205s? Or, since I am budget-challenged after buying the car anyway, is there some other combination I should be looking at that is 90% of the grip for 70% of the price? Longevity is also a question - while I don't expect to be more than locally competitive, I definitely cannot afford fresh tires every 4 or 5 events. Thanks...

It's funny...I see NA Miata and I think "naturally aspirated".

Anyhow, it's my car. Before the 15x9 wheels even arrived, I rolled the fender lips. It was easy, and with a little bit of heat I didn't even damage the paint. I tried to make a video of the process, but had an equipment failure that ruined it. Now that I have a new camera, I'll try again next time the need arises.

When we were doing the suspension testing, we were using 15x9 6UL wheels and the 245/45R15 Nitto NT-01s, and there's only the slightest of rub against the control arm at full lock.

Later, when I moved to the 275/50r15 Hoosiers, I get the slightest bit of rub when the tires deflect under hard cornering. It's very slight, but affects both the lower spring perch (inside) and the edge of the fender lip. It's slight enough that I don't have any plans to "fix" it. It really is very minor.

I've been told that other coilovers that user larger diameter springs have much more serious rub issues, but no direct experience with them.

I know, that NA Miata thing is ambiguous if you're supernaturally aspirated, but it sounds hipper than "first-gen".

How was the grip on the Nittos?

Do you know the diameter of your springs? I could compare to mine.

My budget option it to put something fresh on the current 15x7 Kosei K1s There is a set of mildly-used A6s available for ~$400 in 225/45/15. How do you think those would fit on the 7" K1s? I guess they would be a little wide and would roll the sidewalls.

If I'm spending $X for tires only and am still going to be seriously compromised by section width, shopping around for wider wheels and paying $2X for the package makes more sense if it results in more speed.

Not that I am that fast myself but I'm competent enough to know the car would benefit from more dig. But I really have to think before dropping a grand or more just to see if it helps. Thanks for your prompt response.

The 225 hoosiers run really wide. They are as wide as many 245 width tires. I'd say that's your best option if you want to avoid hacking the fenders or raising your ride height a bunch.

225/45R15 Hankooks on 15x9 TR Motorsports C3Ms. Tires are actually a bit stretched, so I can go bigger with the race rubber

First off the Hoosier A6s are 275/35R15 and will require rolling and a slight pulling of the fenders on an NA Miata. On the NB they simply require a rolled fender. 15x10 rims are ideal for the 275s but I would recommend you try the 225/45R15 Hoosiers on a 15x9 rim. You give up a small amount of tread width but you won't have near the rubbing problems.

EvoRoadster wrote: First off the Hoosier A6s are 275/35R15 and will require rolling and a slight pulling of the fenders on an NA Miata. On the NB they simply require a rolled fender. 15x10 rims are ideal for the 275s but I would recommend you try the 225/45R15 Hoosiers on a 15x9 rim. You give up a small amount of tread width but you won't have near the rubbing problems.

You are right sir! The 225/45/15 Hoosier R6 has a 9" tread width, and not surprisingly they recommend you match that to the wheel width. I just picked up a set of those on 9" rims for my NA. The Hoosiers run 5/8" wider tread and a full inch wider carcass than the 225/45/15 Hankooks (on 8" rims) they're replacing.

I rented a fender rolling tool and will be fitting them up this weekend.

Excellent, thank you. Time to start hitting the classifieds and saving up.

EvoRoadster wrote: First off the Hoosier A6s are 275/35R15 and will require rolling and a slight pulling of the fenders on an NA Miata. On the NB they simply require a rolled fender. 15x10 rims are ideal for the 275s but I would recommend you try the 225/45R15 Hoosiers on a 15x9 rim. You give up a small amount of tread width but you won't have near the rubbing problems.

^^ This.

The Miata lips are easy to roll, though.

The Nitto NT-01s are great tires, and my #1 choice for R-compounds that will endure street duty. Ultimately, they don't provide the level of grip that a set of 225 Hoosiers do however, even if they are a little bigger. If you're planning to compete it's Hoosiers for the win.

Tom Heath wrote: The Nitto NT-01s are great tires, and my #1 choice for R-compounds that will endure street duty. Ultimately, they don't provide the level of grip that a set of 225 Hoosiers do however, even if they are a little bigger. If you're planning to compete it's Hoosiers for the win.

Are you saying the Nittos are bigger than the 225/45 hoosiers? I don't think so. The hosiers will be MUCH wider.

edit I just looked it up and though Nitto doesnt list tread width the section width is 8.86" compared to hoosiers' 9.8"

Huge differece!

FYI - almost every coilover setup for the Miata uses a 2.5" spring. There's one from FCM that use a 3.5" (stock diameter) spring, the AFCOs are technically 2.625" but often run a 2.5", and the V-Maxx are a 2.25" (actually 60mm). But as long as you have 2.5" you should be fine for clearance.

Tom: I have street tires and plan on picking up a hitch and trailer, so I only need competition tires. I guess the long-range plan is to get 225/45 A6s on 15x9 wheels for autocross duty, then put something that will fit on 15x7s and is suitable for track days / HPDE on the existing 15x7 K1s. It has Toyo street tires on some unknown Motegi 15x7s, too.

Keith: thanks for that info, too.

Duke, I'm up the road from you by the philly airport, i have a fender roller that can be used in exchange for a little liquid bread.

Wes

Hey, that sounds like a deal! Thanks.