Not quite SSM Miata

Hello ll,

So about a year ago last October, I found myself the owner of a 1999 NB Miata with a fairly extensive list of mods, not the least of which was a full Flying Miata FMII with all of the upgrades. It has FCM bilsteins, 500# front springs, 350# rear with 1 1/8" front bar and an 11mm rear. It made 278 RWHP on a local dyno, it drives great and puts down power fairly well( other than violent wheel hop on launch) with the help of an OS Giken rear diff. Wheels are 15x9 6UL with now 4 year old 225 Hoosier A7 front and rear.

I had previously been autocrossing my air cooled 1988 911 carerra, and enjoying it, until I had a ride in a well prepped NA with a turbo and ABS.....

My driving improved immensely during the first season in the Miata. I was regularly a runner up for FTD, and the car was alot of fun but PAX tells a different story and it seems like I should be alot quicker than I am if I really want to be competetive. I know there is still alot of room for improvement with my driving and I'm working on that, but I also know that the car is under prepped for SSM and I want to make a few tweaks and need some help deciding on whats next. As far as the current set up, the car stops great, turn in is crisp, and mid corner grip is excellent once the car takes a set. Corner exit the back end tends to wash out and I'm finding it hard to go faster due to the oversteer at the limit.

Tires are due for replacement, so I am thinking about also making the move to 11" 6UL's and 275 A7's, but I feel that I may be under sprung for the level of grip that would provide. 

 This is where I am at a crossroads. I do not want to re invent the wheel and start over and replace everything, so whats the best plan?  Can the current set up handle the increased grip 11' wheels and 275's would provide? Should I make the move to a street tire like the rivals for the slightly more favourable index? Keep the 15x9's and just bump to 245's?

I'm hoping that with the help of the hive I can drill down and come up with a plan to make the car more capable as my driving improves and start to PAX better that I currently do.

Thanks for any feedback

Your undersprung for sticky 225's imo.

Be aware that 11s and 275s will require carving up the fenders if you haven't done that already.  Not just rolled, but flares.

My Miata was pretty similar when I autocrossed it regularly about 5 or 6 years ago -- NB1 w/ FM2 making 270 at the wheels, 15x9s, 225 A6s, FCMs with a little bit more spring rate.  No way would I go back to 200tw street tires on that car after experiencing the Hoosiers.

kevlarcorolla said:

Your undersprung for sticky 225's imo.

Agreed. My SSM Miata on 225 series Rival S 1.5s with no rear sway bars and the same spring rates (on FM VMAXX Classics) picks the inner rear tire up on hard corners and just annihilates the inner tire (thanks Torsen diff)

Before you go to extremes try some fresh tires first. What you describe is more from a rock hard old tire than the need for more rubber. Basically the tire is too hard to grip under power on corner exit and causing the rear to wash out. 

bmw88rider said:

Before you go to extremes try some fresh tires first. What you describe is more from a rock hard old tire than the need for more rubber. Basically the tire is too hard to grip under power on corner exit and causing the rear to wash out. 

I have had a few people suggest that, and also several say I am undersprung for 225's and definitely way undersprung for 275's. The car does work fairly well as is, and seems to be happy absorbing the bumps and surface changes at our local venue. New tires and an oil change is the easy button for sure, I'm just not sure how much quicker I can be with the current spring rates and FCM. The car does have an OS Giken, and I have never experienced it picking up the inside wheel, but perhaps it is and I am not noticing it.

I have been thinking that there may be a market for the current FCM/ 6UL combo which may partially fund the upgrades to a full SSM set up. If I was to go that route, what would folks recommend for coil overs and spring rates?

tripower4speed said:

I have been thinking that there may be a market for the current FCM/ 6UL combo which may partially fund the upgrades to a full SSM set up. If I was to go that route, what would folks recommend for coil overs and spring rates?

The Fox/Flyin' Miata coilovers are supposed to be the cat's pajamas. Pricey, but well worth it. They were what I was planning to install this offseason until my transmission failure torpedoed my shock budget. As somebody told me, if you're serious, don't buy something just a little better. Go straight to the top of the heap. In the long run, it'll save you money versus buying something slightly better, then maxing out that setup, then upgrading again to something just a little bit better, then maxing that out and so on and so forth. 

SSM is full on stupid prep, you'll never get a street driven car to the level where you'll PAX well in that class.  Like, you're at half the HP and spring rate of a legit SSM car without even getting into the crazy aero the class demands these days.  

But since it doesn't sound like you're a Nats sort of guy, my vote is to keep your setup as is and slap on a set of fresh 245 hoosiers.  R-comps cycle out really quickly so you'll be stupid fast (locally) for about 80-100 runs.  4 year old tires are your biggest handicap.

Next is alignment.  If you aren't at -3 to -3.5 degrees all around you're leaving speed on the table.  Finally experiment with air pressure, my CSP car is happiest down around 21/19 psi.  It's way different than street tire pressures.

KyAllroad (Jeremy) said:

SSM is full on stupid prep, you'll never get a street driven car to the level where you'll PAX well in that class.  Like, you're at half the HP and spring rate of a legit SSM car without even getting into the crazy aero the class demands these days.  

But since it doesn't sound like you're a Nats sort of guy, my vote is to keep your setup as is and slap on a set of fresh 245 hoosiers.  R-comps cycle out really quickly so you'll be stupid fast (locally) for about 80-100 runs.  4 year old tires are your biggest handicap.

Next is alignment.  If you aren't at -3 to -3.5 degrees all around you're leaving speed on the table.  Finally experiment with air pressure, my CSP car is happiest down around 21/19 psi.  It's way different than street tire pressures.

That's an interesting point. I have no idea where the alignment is currently, and I have been playing with tires pressures. I started at 32 square, and had settled on 28 front and 26 rear, but this isn't the first time I have heard that going lower is possible. I ended up where I am using chalk, and kept lowering until it was rubbing off during a run to the right spot. I guess though I could keep going lower until its rolling over too far and then increase slowly?

So much to learn!! This car is so much better than my last two autocross cars ( 72 Firebird455/ 88 Porsche 911 ) that its been mostly about getting my driving up to speed and not wanting to change the car. I think that's still a big part of the plan, but I want to address the obvious shortcoming and give myself the best chance for success.

In reply to tripower4speed :

Without the big negative camber you can’t let the tire pressure down so low.  These things work together.  But the softer tire means larger contact patch and way more grip.  TBH, the added hp is nice and on a big course it helps but Autocross is so much about transition speed and maximum cornering that’s where you’ll see big results.

Don’t overlook your brakes.  The better your brakes the later you can wait before using them.   I drove a friends’ car last year and when I came to a braking zone (or what I thought was the braking zone in my car) I realized I couldn’t slow down nearly enough.  When asked he told me he was running OEM pads on an NC, huge time he’s been leaving on the table!