Hey autocrossers: what are some significant mods?

[slugg]

So without a doubt, the single most significant upgrade for autocross is tires. Stickier tires beat any other mod out there. But after tires, what's next?

My local autocross club allows minor mods in the stock category, but as soon as you alter the ride height in any way, you're thrown in with the fully modded cars, but not full out race cars. Kinda like street-prepared class. Is lowering your car really that big of an advantage? Obviously not slamming it...

What are some other significant upgrades? I've pretty much got this stock class on lock. I might go into the mod class, but as it stands, I'm about 2 seconds slower from the fastest guy in the equivalent mod class. Then again, he sets FTD from time to time...

 

[jlee]

If you want to compete, I'd stick in the stock class with epic tires. My MR2 was built for a fun street/weekend race car and is not remotely competitive in the class I'd be in for autox. If you want to build the car for pure enjoyment and then autox for fun on the side, I hear turbos are nice. :awe:

 

[Fenixgoon]

tires are always #1. after that, look at suspension mods. then power.

if you're looking to AX for fun anyway. if you actually want to do SCCA-type competitive stuff..no clue

 

[RKS]

upgraded sway bars? I know on my car they made a much bigger difference than Eibach springs or the front strut tower bar.

 

[Imported]

Upgrade to Hoosier A6s, as wide as you can fit. Then get a new diff (OS Giken, Cusco, Carbonetics), though that may push you into the "mod" class. In stock classes for most group, you can still change shocks if you don't change the springs.

 

[slugg]

What kind of difference would I see from lowering the car a bit onto stiffer springs? Is it minor, huge, or what?

 

[Viperoni]

Don't forget the importance of an alignment as well.

 

[HarryLui]

Smallest/lightest wheels you can find.

 

[HybridSquirrel]

Driver -> tires -> driver -> driver -> suspension -> driver

 

[thedarkwolf]

In the stock class you are allowed to upgrade the front sway bar and that should be a pretty cheap and easy mod. If anybody in your group can help you with an autox alignment that will also make a good difference. One of the guys I run with did mine for me the old fashioned way which is apparently more accurate than most of the machine since he actually gave a crap and didn't just do close enough.

I run my miata in STR since I've upgraded the suspension/wheels and I don't have a good way bring r-comp tires with me other than driving on them. I'll just stick to the street tire class for now. I'm running koni sports with coil over sleeves and 450lb front and 270lb rear springs and yes they make a huge difference over stock. Saying that I am regularly beat by a guy running a stock 99 miata on r-comp tires because he is a just a lot better driver than me. I do usually beat his daughter now though .

 

[Black2na]

your miata? and i would built it to STS2 or STR standards allows for classic bolt ons without jumping to the full blown race class. if not koni shocks and a front sway.

 

[thedarkwolf]

I don't have the rule book in front of me but just from memory
STS and STR are basically the same. Don't think there is a STS2 anymore.
STS = miata with an open diff and I think the older 90-93 with the VLSD
STR = miata with torsen rear
I think STR is allowed a wider rim too 9" for STR and 7.5" for STS but I'm the diff is the big thing.

STR/STS do allow headers/intakes/exhaust the basic stuff none of which I'm going to bother to do since the bang for the buck is pretty lousy. The suspension and tires have a lot better payback. You can go pretty crazy with the suspension stuff in STR/STS other than frame rails which I believe bump you up to CSP. You can run Koni shocks and a big front sway bar in stock. You just have to run the stock springs. Once you change out the springs you are bumped out of stock.

 

[slugg]

My local autocross club doesn't follow SCCA rules to the T. It's completely independent and a bit more laid back. Basically, in the stock class, you're allowed to change your intake, exhaust, sway bars, shocks, any cosmetic mods (like a carbon fiber hood), and must run a street tire (140 treadwear or greater). The mod class allows unlimited modification as long as the car is streetable and ALL major body panels and interior bits are original, except for the seats. You're allowed to use racing seats in the mod class, and if you have rear seats, you're allowed to remove them. Gutting the car and/or putting a full roll cage in it puts you in our racecar class. R-compound tires put you in the equivalent race-tire class.

My car has an eBay tube intake (probably not the best performance, but sounds cool), stock exhaust, upgraded front sway bar, and some of the best tires you can get. I'm consistently winning my class and I'm exploring the idea of going into the mod class. As it stands, in a typical 45 second course, I'm roughly 1.5 seconds slower than the first-place car in the mod class I'd be switching to. What I'm trying to figure out is how much money I'd need to close that gap, LOL!

Yes, I know it's 90% driver. I don't need that speech. I'm curious about the other 10% right now...

Thanks

 

[JCH13]

Don't forget the importance of an alignment as well.

This! Alignment is huge! What I suggest:

-1.5 to -2* front camber (i'm at -1.75)
4 to 5* caster (i'm at 4.5)
1/8-1/4in total toe out (i'm at 1/8)

-1.25 to -1.75* rear camber (i'm at -1.5)
1/8-1/4in total toe in (i'm at 1/8)

My alignment shop let me sit in the car while they did it, makes a BIG difference in such a small car.

I hear really good things about disconnecting the rear sway bar too, helps keep the rear end planted so you can throttle out of turns much earlier. I'm going to try it this year.

If you can get mods like FM frame rails in the stock class, do it. I'd also do a roll bar. These two mods really tighten up the chassis.

Bolt-on headers are supposed to gain a few HP, 3-5, which is significant on a ~100whp car. A regular tune-up never hurts. You could also advance base timing by moving the CAS to squeeze a few more HP out of it.

Many swear by 13/14in wheels with wide, short, tires. Not sure if that puts you out of stock class though.

I'm amazed a stock Miata is within 1.5s of the race-prep cars at your autox group, unless you're looking at PAX-corrected times.

 

[slugg]

The times aren't PAX corrected, that's raw. Sometimes it's 2 seconds, sometimes 1.

I already have a pretty good alignment. Things are a bit different on the NB Miatas: I can only get 1.2* camber in the front while at stock height. I've got 2* in the rear and 5* caster up front. The frame rails don't make a huge difference in the NB's. I forgot to mention that I already have a roll bar and an NB2 header, which is as good as most aftermarket options. I'm not too interested in having a loud exhaust...

So what's next: full coilovers? I have 205/50/15 tires... I'm thinking about 225/45/15 on 15x8 wheels maybe. I can still do that while in stock class, but that'd be some serious sandbagging. LOL!

 

[JCH13]

The times aren't PAX corrected, that's raw. Sometimes it's 2 seconds, sometimes 1.

I already have a pretty good alignment. Things are a bit different on the NB Miatas: I can only get 1.2* camber in the front while at stock height. I've got 2* in the rear and 5* caster up front. The frame rails don't make a huge difference in the NB's. I forgot to mention that I already have a roll bar and an NB2 header, which is as good as most aftermarket options. I'm not too interested in having a loud exhaust...

So what's next: full coilovers? I have 205/50/15 tires... I'm thinking about 225/45/15 on 15x8 wheels maybe. I can still do that while in stock class, but that'd be some serious sandbagging. LOL!

Silly, your race guys must be a little special, or you must be the next Senna! Stock -> race fastest times are 4-6s difference on a 60s course with my autox club. What sort of cars are they driving?

Do the toe adjustments, it will really help turn in and rear end stability.

225s would be overkill until you're pushing 200whp.

You're already on coilovers, but some FM springs and adjustable shocks never killed anyone :awe:

Other mods: lightweight flywheel, AC/PS deletes, better steering wheel, install hardtop and remove soft top (drops weight, stiffens chassis), better brake pads, stainless brake and clutch lines, race pipe/test pipe/cat delete pipe.

 

[Imported]

225s aren't overkill I'm running 225 RS3s on a 15x9 wheel for my NB. It seems to be the standard around here for the STR Miatas.

 

[JCH13]

225s aren't overkill I'm running 225 RS3s on a 15x9 wheel for my NB. It seems to be the standard around here for the STR Miatas.

I'm running on what I've read from national-level SCCA racers and the prevailing knowledge of the many track racers from Miataturbo.net

Stock NBs in my autox club are generally 205s, they're right next to the V8 miata with 15x9s and 225 RS3s.

 

[Imported]

Maybe the NAs? I know some have problems fitting the 225 without massive rubbing. Although I imagine the 195 Toyo would be a better tire for the NA and they could keep in.. STS? I forget how the new ST- classes work again.

 

[JCH13]

Maybe the NAs? I know some have problems fitting the 225 without massive rubbing. Although I imagine the 195 Toyo would be a better tire for the NA and they could keep in.. STS? I forget how the new ST- classes work again.

Nah, both guys have NBs, routinely top 4 or so in performance stock in the club.

I have zero idea how the new classing works, heh, I just know that 195s/205s with 15x7 or 15x7.5s are plenty of grip when you're at stock power levels, and feel way more responsive than 225s and 15x9s. I say that having 195 street tires, and 205 and 225 race tires

My NA has 225 RS3s, lowered, and all I did was a quick fender roll with my jack handle at the autox when they started rubbing. But I also have ~220whp when boost is turned up.

 

[thedarkwolf]

I run 225 RS3s on my 95 with a totally stock drivetrain. I only have 8" wide rims so I'm not getting the full benefit of the 225s but they were the best deal when I bought them.

I ran with my rear sway bar unhooked for the first time last month. I don't know how much it helped but I liked how it felt. I'm not making 200hp so spinning the rear tires coming out of turns isn't a huge problem for my 95.

Slugg what shocks are on your car now? Some of them can get away with a lot stiffer springs and some can't.

 

[slugg]

KYB AGX shocks right now. It can probably handle slightly stiffer rates (Flyin Miata sold it as a kit with their springs a few years ago), but they're not the best shocks out there.

I can't seem to find a clear answer for whether or not a 15x9 with 225/45/15 tires will fit a stock NB. If I go with new springs and shocks, I REALLY don't want to lower the car too much. I need to be able to handle the speed bumps around my house. So is there a competitive setup that still allows the car to be daily driven? My understanding is that 15x9 wheels will only fit with smaller diameter springs, like Flyin Miata's. Oh and I don't mind rolling the fenders.

I may have to re-post this on Miata.net. I apologize for turning this thread into something so specific, lol.

 

[JCH13]

KYB AGX shocks right now. It can probably handle slightly stiffer rates (Flyin Miata sold it as a kit with their springs a few years ago), but they're not the best shocks out there.

I can't seem to find a clear answer for whether or not a 15x9 with 225/45/15 tires will fit a stock NB. If I go with new springs and shocks, I REALLY don't want to lower the car too much. I need to be able to handle the speed bumps around my house. So is there a competitive setup that still allows the car to be daily driven? My understanding is that 15x9 wheels will only fit with smaller diameter springs, like Flyin Miata's. Oh and I don't mind rolling the fenders.

I may have to re-post this on Miata.net. I apologize for turning this thread into something so specific, lol.

I've got FM springs on KYB AGX shocks. It's a very good combination, but probably not the most durable shocks ever made.

If you get 15x9 TR Motorsports wheels from Tire Rack they should fit fine. One of the TR reps is on Miata.net and will answer PMs super fast.

 

[slugg]

I've got FM springs on KYB AGX shocks. It's a very good combination, but probably not the most durable shocks ever made.

If you get 15x9 TR Motorsports wheels from Tire Rack they should fit fine. One of the TR reps is on Miata.net and will answer PMs super fast.

So they fit with the stock springs, or do you mean with the FM springs? Because if I could make my purchases in stages, that'd be awesome. Also, they're 15.8 lbs per wheel; combine that with the bigger tire and we have some serious unsprung weight added to the car. How detrimental would it be to the handling? What differences would I expect? More grip, but harder for the suspension to do its thing. Hmm...

Back to the lowering/springs topic... I understand that going too low is bad because we need some suspension travel. Not low enough and we don't have any added benefit. Where is that sweet spot? Is that sweet spot high enough not to scrape on speed bumps?

I'm thinking out loud here. I'm interested in making my car more racecar, because racecar, but I don't want to give up being able to drive over speed bumps, up driveways, etc. Also, if it turns out that to be competitive with these guys will cost way too much money, then I'll bail from the idea.

 

[thedarkwolf]

It comes down to what do you want to spend and how rough of a ride you can live with. My 450lb fronts springs aren't bad but I'm use to it. The crazy guys run 700lb fronts and 300lb rears and I doubt I would want to deal with that on a daily driver.

The FM springs are cheap and a nice upgrade over stock for a daily driver/autox car but they lean more to the daily driver side and they aren't height adjustable. Then there are all the Tiawan adjustable coilover clones that vary from $300(racelands) to $1000 or so, some are crap and some get decent reviews. After that you start getting into the big name coilovers and the sky is the limit there. There is also the ebay coilover setup which has a huge thread on miata.net in the suspension section and is the way I went. Koni sports $500 + ebay sleeves $80 + top hats + bump stops + new springs = around $1000. You wouldn't need new top hats since the NBs already have good top hats and you can get away with the KYBs for a while but they can't handle super stiff springs, think they can go to 300lbs?.

Most of the ride height guides say to shoot for 12" front and 12.5" rear measured from the center of the wheel hub to the bottom of the fender or 4" and 4.5" measured from the ground to the pinch welds. Mine is slightly higher than that now and was slightly lower than that before. Lower was a pita daily driving but slightly higher is fine.

I had to roll my front fenders a bit running 15x8 with the 225mm wide tires and remove the front fender liners.