Hey guys,

I’ve been reading, searching, and lurking for a while. Finding myself in need of advice:

I’m doing a LS3 swap in a 94 NA. It’ll end up making around 370hp/tq at the wheels. Like most high power NA Miata builds, I’m having trouble picking a wheel and tire set up. I am willing to roll, pull, flare, and wide body. Whatever it takes to make it work. Handling and balance are a high priority. The car will be 85% street driven, doing a few track days per year. At the moment, I’m considering two options:

1. 15x9’s with 245/45’s all around. Tire selection is very small with 15’s at 225 or 245, and I’d be restricted to 200tw tires. My concerns here are that 200tw tires will not be a great street option. I’m considering noise, hydroplane resistance, cold temp performance, the tire kicking up every rock and pebble on the road, etc. Also, I’m not sure what a 245 on a 9” wheel will give me that a 225 on an 8” will not…

2. 16x8 with 245/45’s all around. These will be heavier and very tall, as tall of a tire that’ll fit really. But tire options range from 200tw to 300tw, many of which would make a decent street tire. I can get wheels that weigh 13lbs, so it won’t be a horrible weight penalty. My main concern here are the effects on ride quality and handling.

This is an important decision as the wheels and tires will dictate the length of shock and spring rates I pick. All advice is appreciated.

thanks!

 

I'll give my opinion. I mostly lurk on here too as I don't drive a Miata, just run the same size wheel/tires. I have a Lotus Europa with 1100lbs on the rear axle, similar to a Miata, with a turbo 3.5, conservatively 430hp/330tq crank so similar to yours but less wtq but probably same power to weight. I run a 15x9 in the rear with a 245 BFG Rival S. Mine is a weekend street car that I autocross once a month in the on season. The Rivals are as quit as any tire I have ever had. Rock pickup is not bad though it does pick up some. I would never consider driving in the rain or with a dark cloud in sight so can't comment on hydroplaning. I've had other light, high HP/TQ cars and have run MT DR's RA1's, V700's, Nitto DR's, anything other than regular tires. It is no fun when you can't get the torque down. I've read every tire article and follow AX. If you only want a 225, the A052 is softer but doesn't come in a 245. The CR-1 comes in both and seems softer than the Rival S from reviews. From reviews, the Rival S take a few turns before optimum compared to the other two but I can't say, it works though and they are hard enough to use for track days, The A052 seems to be geared to AX as it comes up fast so not the best for track unless it TT. I'm happy with the Rival's but I will try the CR-1 next. Some like the RT-660 too and many Cam guys AX with them but they aren't a top tire for AX. If you are doing track days too the Rival S or RT-660 would be my pick.

 

Thanks!

What size (diameter) wheel are you on? Have you ever experimented with different diameters?

 

The fattest you can stick in is my advice, as another 94 with LS3 owner. I'm still on 205 15x8, and can only push the car reasonably 4/10, have a set of 245 RS4's sitting in the corner and I'm begrudgingly looking at flares (annoyed, because I also did paint and body during the swap so I get to do it again - also why I've procrastinated doing the work). Low end torque is through the roof with V8, and if you sneeze and bump the throttle while making a right hand turn into traffic, the rear end will step out. I wouldn't worry too much about treadwear, just consider it a cost of ownership, and maybe the miata's light weight will keep the wear down.

 

15x9". It's all I've run on this since finishing it.

 

My car was like this, like a switch. I ended up getting a Pedal Commander and setting it to economy mode. It just slows the first 1/4 input or so but still allows WOT. It made it much easier and safer. I don't know if you guys are cable or drive by wire though.

 

Thanks for all the comments!

One of my hesitations is that I could wide body the car and set it up for 17’s with 35 profile and get really wide in the rear. But then I’ll lose a lot in terms of handling, ride, and balance. I’d also be willing to go down to 14’s but there is no tire option there either.

It’s sounding more and more like 245’s are the route to go. I’m still curious if the better tire options with the 16” make it a worth while route.

Carbon Miata flares with 15x9’s and rs3’s in 245….? Anyone know a good flare option I can mold in to the body?

 

Carbon Miata's seem like the most subtle / closest to OEM bodylines I've seen, though I've heard fitment usually needs tweaking. Like to see if someone else chimes in with another option that isn't OMG FLARES aesthetic.

I could probably tune the DBW throttle response down a bit, but I think fixing the root cause (mechanical grip) is more rewarding. Camaro's are running 305's, so anything to approach that contact patch probably helps.

 

275/35-17 is, theoretically, the tallest diameter that could fit in the rear. It would have to be paired with a 245/45-16 front. But it would work on paper.

Again, I am not sure if the increased grip is worth the loss of ride quality and handling balance. But I really have no idea….

 

Here is a guy that went all in with 315’s on the rear….

https://www.v8miata.net/general-moto...ck-2242/page2/

 

Just an update:

After talking with good-win, 949, super Miata, and reading a few flyin Miata posts, the consensus seems to be that anything taller than a 15” wheel is going to compromise the suspensions ability to do its job too much for the added width to be worth it. One even suggested a 15x10 with 245’s will comprise ride quality too much on the street and suggested 15x8’s with 225’s for street duty. He also admitted I’d be spinning them all over the place.

Apparently you can do a 15x9.5 without a flare, but it takes a big roll and pull. 15x10’s will require a flare.

I’m considering the 15x10’s, I just need to find a flare I like. I’d prefer to mold it in, but there are not many that will allow it.

 

You don't need more than 9" to for a 245. You aren't tracking the car and even then you can run a 9" with a 245, yeah 10 is faster. You just need a soft tire that will hook cold. It isn't the width that hooks.

 

I get it’s not needed. My current thinking is that permanent modification is required to the car no matter what. Flares are more work, but it’s just as permanent as rolling and pulling the rear quarter.

Your point on width is well received. I’m guessing that’s why one of the guys suggested 225’s for the street. And I’m looking very hard at the Rivals per your suggestion.

 

As Clifton says, if you want traction, you want the grippiest tyres (lowest TWI), that don't require lots of warmup to produce grip. The price of that will be tyre life, at least on the rear. You will become good friends with your tyre dealer - but you knew that already, right?!

 

FYI - I've run 245's on my modestly-powered NB1 (250whp) for years with 15x9's. They'll fit with a flat roll and the front's will probably contact the inner liner at full lock - that is, if you've still got 'em. I've run 200tw Maxxis, RS4's and now RT660's. The Maxxis' were tricky in the wet, the RS4's lasted the longest (2 years, 4-5 track days per year) and handled everything but cold with aplomb and I'm new to the Falkens...we'll see. None of them are you would call "comfortable" but, if you know my car, you'll know that comfort is NOT my primary concern.

I have no idea how any of them would react on a high-hp car like yours.

 

Excuse my ignorance, but what makes a tire not comfortable? Just less compliance from stiffer sidewall?

 

"Comfort" means different things to different people; ride quality, NVH (noise, vibration, harshness), stability (tramlining over rain grooves and/or roads with exaggerated crowns), etc...

Contributing factors to dis-comfort are; large, aggressive tread blocks, sidewall stiffness, excessive flex, tread design, wear characteristics, etc...

One "man's" ideal tire can be another's dream. For me, I don't care too much about NVH or ride quality (there are enough other noises and vibrations going on to cancel out much of the contribution of any tire). My goals are handling, traction and stability - in that order. So, I'd take my advice with that in mind.

 

I run my 99 LS1 with 15x8 225/45 RS4-s and I have no complaints. It's brutally hot down here in the Keys so traction is hardly an issue. The noise and ride are not that bad. Obviously, it's not gonna be stock comfort or noise, but that's par of the course when you cut up a car to triple it's horsepower. Since it's a street car like mine just go with what wheels look best to you and get a 200tw tire. 15's are fine.

 

15x10 with 245/40/15 with flares is going to be the easiest solution. You may not know which shop I run, but we know a bit about this.
NA/NB tolerate additional tire width pretty well but don't handle additional height well. So you'll want to stick with a combo that's 23" or so. Even a little latter causes major fitment headaches.
Lots of good choices in 245/40/15 and more coming.

The 15x10 6UL wheel pictured is no longer in production but there at least two other companies that replicated the fitment.

 

If you're really willing to anything, you can make 285/30/18 fit. But I suspect this level of fender modification is beyond what you mean.

https://www.miataturbo.net/general-m...8/#post1405078