1993 Miata Spring Rates

[ChristoMX5]

In the process of switching to Ground Controls with Koni Sport (yellows) on the '93 Miata and wanted to know what a good spring rate for the car would be given I do a lot of street driving / autocross / back roads with some good sized bumps.

I'm reading the "standard" spring rate for konis are

Front: 6 / 2.5 / 375 Rear: 7 / 2.5 / 250

First number = spring length
second number = inner diameter
third number = spring rate.

Can anyone with experience in tuning Miata suspension chime in and give me the autocrossers perspective? (Lots of experts on the internet, don't know who to trust). I will be using the stock sway bars for a while, but may upgrade to the racing beat hollow front bar soon. Polyurethane bushings all throughout the car.

I'd like to car to be able to handle 3-5" bumps under cornering load at 80-100mph without being out of control, but still able to handle well at autocross events where there are minimum bumps and smooth pavement. Would 400 lb/in front and 300lb/in rear be a good compromise?

The guys are Flyin Miata are running 391 lb/in front and 258 lb/in in the rear on one of their setups that falls in between street and track.

Can anyone help with recommendations?

Thanks!

-Chris

[Max Hayter]

Autocross setup is usually in the 700/350 range!

[Steve Coe]

I had 700/350 on my old STS Miata. I had Koni Race on the front and Koni Sports on the rear 15/16 solid front bar and stock rear bar. The ride was very good except on freeway tar strips. That was the only time it wasn't very good. Even Brian of Goodwin Racing thought it was very good ride.
I think the only way you could get better than that is to use his Ohlins Coil Over set up.
BTW Koni Sports are only good to about 350lbs

good luck,

Steve

[Max Hayter]

I had 700/350 on my old STS Miata. I had Koni Race on the front and Koni Sports on the rear 15/16 solid front bar and stock rear bar. The ride was very good except on freeway tar strips. That was the only time it wasn't very good. Even Brian of Goodwin Racing thought it was very good ride.
I think the only way you could get better than that is to use his Ohlins Coil Over set up.
BTW Koni Sports are only good to about 350lbs

good luck,

Steve

I had the same setup on mine - quite was quite acceptable for a daily driver.

[Craig Naylor]

I'm at 700/375, elsewise what Steve posted.

IMHO, it's ok on the street as an occasional driver. It's brutal as a daily driver / commuter car if you have a real commute on LA freeways with upheaval on bridges (if you have a stiff suspension, you know what I'm taking about). The I10 from DT LA to Covina will bring a grown man to tears, especially Rosemead to I605 section. There are upheavals, I'd swear compress on impact, then leave the ground on rebound, there so bad. The car shouldn't chirp at constant 65-70, but it does on those overpasses. Don't really notice them at all in the Jetta or Fit.

[ChristoMX5]

I've read that the max is 400, the max is 450, the max is 500, the max is 500 and now the max is 350. Does anyone know this for sure or are these scientific guestimations?

As I stated the car will see double duty as a street car and I drive a lot of back roads with decent bumps mid corner, and some pot holes. A full autocross setup of 700 lb/in seems like it would be a bit extreme for my requirements. I found a picture of a guy with 500/300 with the RB hollow front bar and the car looks like it still has some compliance. We're going to check into what springs are on the car and go from there. I'll keep you guys posted.

Thanks!

[Max Hayter]

blah blah blah 500/300 blah blah

Pussy

[Ed Holley]

I've read that the max is 400, the max is 450, the max is 500, the max is 500 and now the max is 350. Does anyone know this for sure or are these scientific guestimations?

500

[Steve Coe]

I got my info from George Doganis, multi Nat champ (in a Miata)

Steve

[Bill Schenker]

I got my info from George Doganis, multi Nat champ (in a Miata)

Steve

That hack?

[Steve Coe]

LOL, yeah that hack.
Call KONI at 859-586-4100 ask for Lee Grimes and let us know what he says.

Steve

[Bill Schenker]

LOL, yeah that hack.
Call KONI at 859-586-4100 ask for Lee Grimes and let us know what he says.

Steve

He's in Lincoln right now (Lee, not George).

[ChristoMX5]

I'll give them a call when I get a chance guys, appreciate it.

Right now the ground control sleeves are stuck on the KYB AGX shocks and we are having a hell of a time separating them. Very little information found online, does anyone have a trick to doing this? We have a 20 ton press, but are hesitant to use it because the sleeves are aluminum. Don't want to bend or crack anything ($$$).

Anyone have experience in this?

[Jayson Woodruff]

Lots of pentrating oil. And anti-cease next time.

Depends on your tolerance for $$$. I don't find the sleeves to be overly expensive each.

Jay W

I'll give them a call when I get a chance guys, appreciate it.

Right now the ground control sleeves are stuck on the KYB AGX shocks and we are having a hell of a time separating them. Very little information found online, does anyone have a trick to doing this? We have a 20 ton press, but are hesitant to use it because the sleeves are aluminum. Don't want to bend or crack anything ($$$).

Anyone have experience in this?

[KJ Christopher]

Lots of pentrating oil.

I recommend Kroil. http://www.kanolabs.com

[ChristoMX5]

Lots of pentrating oil. And anti-cease next time.

Depends on your tolerance for $$$. I don't find the sleeves to be overly expensive each.

Jay W

I'll give them a call when I get a chance guys, appreciate it.

Right now the ground control sleeves are stuck on the KYB AGX shocks and we are having a hell of a time separating them. Very little information found online, does anyone have a trick to doing this? We have a 20 ton press, but are hesitant to use it because the sleeves are aluminum. Don't want to bend or crack anything ($$$).

Anyone have experience in this?

Can I send them into GC to have them remove it if we are unable to? I'd really like to do this myself, but the guy working on my car is saying they are really stuck on. I'd like to spend as little as possible since the goal for this build was under 7k including the purchase price of the car, though I've probably exceeded it at this point

[Anthony P.]

I was on 600/375 and it rode better than stock, but that was with more shock. (and my car is porky) Since your a genius run up a simulation on Chassis Sim for 5 bucks on their 7 post shaker rig and tell us. You can get average traction or something like that. Inputting the info can be a PITA. I dont know that engineering as its above my wage...

[ChristoMX5]

I got my info from George Doganis, multi Nat champ (in a Miata)

Steve

Thanks for the info Steve, makes me wonder if the max is 500, but the way it feels with 350 is the "max" per driver feel. Since I'm running the standard rates of 350 and 250 I guess I'm in the clear either way. Appreciate the heads up. Nice to know it's coming from a source that has credibility behind it.

Anythony-
Since I'm kind of stuck with what I have right now (translation: my budget is becoming thinner and thinner) I will probably go by way of the butt dyno. Cool to know there is a chassis sim out there for that cheap though. Makes me wish I was back in tech school again....free access to chassis dyno and Roehrig shock dyno 5 days a week. Might be a fun project to do and cross reference with real world lap times. Would be a cool feature for the youtube channel we're working on! Thanks!

[Bill Martin]

Chris, what wheels and tires will you be autocrossing on, and where do you place your priority between street comfort and autocross competitiveness?

[ChristoMX5]

Chris, what wheels and tires will you be autocrossing on, and where do you place your priority between street comfort and autocross competitiveness?

For the time being I am running on Kosei K1s in a 15x7 size with 205/50/15 Direzza Z2 tires. As for where I place my priority between street comfort and autocross:

Street comfort wouldn't matter to me except for the fact that I live about 10 minutes from some of the best back roads in the area and really enjoy driving them. They have some pretty good bumps and aren't always the best of paved at times. It's not safe to have a suspension setup that is too stiff so I really need something in between what would work for street, Targa Rally (example of the types of roads around here) and autocross.

Anythony and I met driving these roads and he will attest to how a setup too stiff can really punish you (and the car) on them. It will take some experimenting to get perfect over time, but I figured asking here would be a decent start. As stated before the rates will be 6" x 2.5" x 350 lb/in springs in the front and 7" x 2.5" x 250 lb/in springs in the rear.

I am running stock sway bars, polyurethane bushings everywhere, Koni yellows, FM frame rails, stock brakes, and the engine is stock as well.

[Bill Martin]

I'd have to guess that there won't be a good compromise available. With those wheels and tires you're in STS territory, and 700/400 is considered the sweet spot by many in that class. But 700 would be too high for your Sport shocks anyway. You'd need the shock combo Steve Coe suggested. You may want to go with upgrade bump stops because you'll probably be on them a lot at higher G corners. FCM seems to put the most effort into providing premium bump stops.

[ChristoMX5]

Will the car be hitting the bump stops even with the Flyin Miata rear shock mounts that allow 1.5" more travel? Not sure if I mentioned those are installed on the car.

I do tend to drive the cars I own very hard and the car will be seeing a lot of heavy cornering / transitions. I don't want to be hitting the bump stops constantly and have been told by several people now that shock travel is essential to getting these cars to handle well.

Let me know if the extra travel in your opinion is enough. What exactly is the purpose of an upgraded bump stop? From my understanding I thought a car wasn't supposed to really touch the bumps stops ever in an ideal situation. Can you elaborate?

[Bill Martin]

Competition cars regularly hit bump stops. Spring and anti-roll rates are chosen to minimize, but not eliminate contact because that would be unnecessarily harsh. For your tires, a prepared Miata needs about 700/400 to only occasionally contact the stops. Since your chosen rates are about half that...

I don't know how you can have a setup to successfully handle 3" to 5" bumps at speed and still be effective on smooth track. I've got this rally-prepped Cherokee I could sell you.

Suggest Google "MCU bump stops".

[ChristoMX5]

Didn't realize that Bill. The suspension felt pretty stiff to me compared to what I'm used to, but this is the first care I've actually had modified springs on.

Suppose there is no setup that will accommodate the bumps and be great on autocross since the nature of the two are essentially opposites. I was just wondering if the community had some ideas about what a good compromise would be. When I first got it I hit a decent sized bump and caught a considerable amount of air. Guess I'll just have to adjust my style for those sections and learn to drive around it. It feels like a good setup and sounds like the standard rates will work for my application.

Spoke to Keith Tanner from Flyin Miata and he recommended staying with the rates I have for what I need the car to do. That Jeep sounds pretty cool though. Would love to see pictures. Dad had an old Cherokee when I was little, my first memory of a car is opening the door on the freeway when I was 4 or so and learning out the car door. I remember being really calm, but my Dad and Brother screaming at me. 22 years later I still don't see what the fuss was about.

Thanks again.