Modifications to Tatjana

		Koni Shocks with Ground Control Spring System The Decision Why upgrade the suspension? The shocks are a given as the OEM Showa shocks don't last more the n 50K miles (as most OEM shocks do not). Removing the shocks in a miata is not a 1 hour procedure, and involved compressing the springs off the old shocks and onto the new shocks. Should you want to upgrade to firmer springs (which will help with turn in, steady state cornering, while also firming up the ride, which is a personal taste issue) this would be the time to do it. Othewise, you are doubling your labor. In my case, its just my time. But if you lack the time/skills/tools to DIY, that is several hundred dollars going to a mechanic. I open myself up to a big old flame by stating my 92 does not handle as well as my FWD Honda. Its the truth. My Integra GS-R is fitted with a set of Ground Control (GC) springs that allow it to handle better at the limits then my basically stock Miata. The integra does ride a bit firm, and is about as firm as I like it for a street car. When I decided to go with a set of GCs, I was concerned about making the miata too stiff for even my tastes. Before I go into specifics, let me give some background on GC. Ground Control Springs Ground Control is a small company that specializes in suspension upgrades for street and race vehicles. Although their web page does not actually list the miata in their applications guide, they can fit a set of GC springs to the miata. Marketing calls these sets 'coil overs'. Technically, that is a bit incorrect as the miata suspension already is a coil over, with coil springs surrounding the shocks. What GC offers is an adjustable spring perch that allows ride height to be changed, and the car corner weighted. Better yet, GC uses only Eibach ERS springs. ERS is short for Eibach Race Springs, which is a product line that is used in just about every type of race car. Spring rates can be selected usually in 25lb increments, and the springs are linear rate, not progressive rate. In my case, I wanted to upgrade the rear springs on my integra. The were 8" springs at 250 lbs each. After calling up GC, and speaking with Tony, then Adam, they informed my their 'normal' recommended street kit for a miata was 375# 6" front springs, and 275# 7" rear springs. Adam was a bit concerned about me using an 8" spring in the rear. I told him that I would be using thel ower Koni spring perch which gives me about .75" drop, and that I also was not worried about slamming the car, as that is not my taste. About 1-1.5" off the rear was all I wanted. He agreed that the 8" spring in the rear would be no problem. I also ordered a 350# spring for the front rather then a 375 as I was 25# softer in the rear already. Adam then allowed me to get a pair of 10" springs for the integra in that miata order. Now that is customer service. Not too many large operations would even consider this type of order. Adam and Tony did not flinch. The Big Day After waiting several months to schedule some time in DB94 to do the install, I was more then ready. I had loosely participated in one miata shock swap already, with Chris and Jac doing the wrenching for that and another one without me. Using the Cardell BFH method, the front ball joints had not given us too much trouble in the past. When it came down to the install, I did most of it myself. Being patient, and shooting it around with the other guys (who were working on their miatae at the same time) it took about 4 hours of labor to finish the entire job. I think I was a bit lucky that nothing really gave me any problems. The cotter pins slid out, the ball joints did not take too much percussion engineering to get apart. Chris has a decent spring compressor, though its hooks were too large to get at the narrow rear springs. Had to use an el-cheapo set of spring compressors on those. An impact gun is a very good thing to have when removing a few of the suspension bolts. Beg, borrow, and plead to get one when you do any work on the suspension if you can. Unfortunately, Chris's Mavica is currently getting repaired so we did not document the entire install. Its really not that exciting. I do have a few pics to show the GCs in my findings later on. Skip to the bottom if you are impatient. The Initial Test Drive Having done a few suspension upgrades before, I should have known better. But I foolishly went off and started beating the miata around. A quick snap fishtail woke me up and I drove a lot more conservatively. Remember: whenever making suspension modifications, no matter how trivial, take it easy on the initial test drive. That car felt good. Damn good. Ride quality was firm. No more bouncing over bumps as I had before. I really did not fully appreciate how shot my old shocks were until I rode around in with the Konis. I dialed in the Konis to be 1/2 turn from full soft in the rear, and 1 turn from full soft in the front. The reasoning for this was twofold: a stiffer front end would tend to dial out oversteer (hey, I was at least aware of it, even if I did not drive that way initially). Second, I was running stiffer springs all around, so some extra dampning was called for, rather then running the Konis on full soft. Even set like this the car was far too neutral for my tastes on the street. We went to a large deserted parking lot and began to do our normal suspension testing, consisting of medium speed loops, similar to a skidpad. Previously, I would have to really try to get the rear end out. 5000 RPM turns with heavy throttle application was the only way to wiggle the tail given my SP8000 rubber and a dry road. Now, the slightest addition of throttle mid turn got the car loose. Fun? Certainly. Safe? Not a chance. Something had to be done to dial out the oversteer. Back to the garage Dialing in my Setup, Part 1 Any suspension system is just that: a system. All the parts must work together. Previous additions to my suspension were a set of FM sway bars, and SP8000 tires. I had adjusted my FM sway bars to the soft setting in the front, and the medium (middle hole) in the rear. Since after the springs were added the car became more neutral, softening the rear sway bar would helpd dial some understeer back in, leaving all other settings the same. I had two options here: use the softest setting on the FM rear sway bar, or swap in the smaller stock bar. The softer setting on the FM sway bar is the first logical step as its a small change compared to going back to the smaller diameter rear bar. This change helped get the car back to a slight understeer at the limits. Using the same test loops in the parking lot, it was not harder to get the rear end out in the middle of the turn. I still could be being stupid, such as hammering the throttle while at the full capability of the tires in the middle of the turn, but it was not nearly as sensitive as before. It also was not as 'safe' as it had been prior to the springs. To help matters a bit more, I dialed the front shocks up another 1/2 turn stiffer. So far, the car feels great for me. My main concern is when I lend the car to a friend (friend's are always trying to borrow a miata, haven't you noticed?) and they are not accustomed to a car set up this way. A good Porsche driver should have no problem, but someone who regularly drives a Stupid Ugly Vehicle is another story (yes, you have to question my judgement when I lend my miata to a SUV owner in the first place). I will report further test/tune findings as I discover them. Dialing in my Setup, Part Deux After spending some more quality time with the GCs, specifically with various weather patterns, I really need to put the stock sway bar back in the rear. The car is fun, but you cannot be sloppy. A recent 60 degree day with rain showed that despite my SP8000s, any throttle application above 3000 RPM when you are exiting a turn will unsettle the rear end. How much depends upon how sharp you are turning, and how heavy your foot is. Is it fun? Sure. Is it what I want for the street? No. I miss the ability to take a good line through my favorite corners, and mash the throttle as I begin my turn out. It was really hard to get the car loose this way, meaning even those that don't drive RWD well would find it difficult to get into trouble. Dialing in my Setup, Part Three After getting my stock sway bars out of the basement I had left them in when I first installed them almost a year ago (thanks Wookie :), I jacked up the rear and began to work on putting the stock rear back in. As I mentioned in Part Deux, the car is still too loose for the street IMHO. With winter coming, that means black ice and my A/S Brickstones. Not a great combination in a miata. So, I have a moment of silence for the RB rear sway bar (she did well) and put back the puny stock bar. Feels like a toothpick I note. At the same time, I also raise the car about .75" for the winter, and throw on the RE-930s. The test drive was very revealing: I no longer had a too loose car. Even with the lousy traction of the RE-930s (who I could get to break away in the rear quicker then the SP8000s) I was having difficulty getting the rear end out by hammering the throttle too early on turnouts. This is good I thought. I would not describe the car as a understeering pig, but it was a step up from where I was with the RB rear sway bar. The GC springs still feel great, and the car handled surprising well with the RE-930s in the dry. They make noise, so I know I am working them a bit, but its not near the edge of traction. Mistakes made with throttle application won't bite you in the ass as much. This is good for other drivers, as well as me. Nobody is perfect :) Pictures of how the GCs look on Tatjana Here is a view of the GC's installed on a front side. You are seeing a 6" Eibach ERS spring coiled over a Koni single adjustble shock with the spring perch set to the lowest setting. The car is lowered about 1" from where this particular miata sat with its stock spring and shocks. Note that the adjustable collar has plenty of travel both up and down left on its 4" collar. Where the collar is set now, the spring is just barely loaded when the car is raised in the air. The bump stops were cut as directed by the Ground Control instructions, which said to cut the lowest bump stop, and trip the upper portion of the bump stop to fit into the center of the supplied poly shock mounts. Here is a view of the GC's installed on a rear side. This is with an 8" Eibach ERS spring, Koni single adjustable shock set to the lowest perch setting, and the bump stops cut as per Ground Control's instructions. Note that the adjustable collar is adjusted to the bottom. I cannot lower the car anymore. At this perch setting, the 8" spring is slightly unloaded when the car is lifted. This means I can move the spring up and down a few millimeters when the car is jacked up. Makes it easy to adjust (if I wanted to raise it, I would not need the tool as there is no loading of the spring against the perch), but if the rear end becomes unloaded, the spring will slam up and down a bit as the car's weight loads it again. Not much of an issue on my car, but if there was an inch or two of free space here, I think a tender spring would be in order. A tender spring is useful on suspension with short, stiff springs that want to provide some decent travel. The tender spring is a flat coil spring that does not have a hight spring rate. Its sole purpose in life is to keep the coil spring planted to the bottom of the spring perch, with the tender spring pushing against the top of the shock mount. This prevents any free play if the suspension becomes un-loaded.

Koni Shocks with Ground Control Spring System

The Decision

Why upgrade the suspension? The shocks are a given as the OEM Showa shocks don't last more the n 50K miles (as most OEM shocks do not). Removing the shocks in a miata is not a 1 hour procedure, and involved compressing the springs off the old shocks and onto the new shocks. Should you want to upgrade to firmer springs (which will help with turn in, steady state cornering, while also firming up the ride, which is a personal taste issue) this would be the time to do it. Othewise, you are doubling your labor. In my case, its just my time. But if you lack the time/skills/tools to DIY, that is several hundred dollars going to a mechanic. I open myself up to a big old flame by stating my 92 does not handle as well as my FWD Honda. Its the truth. My Integra GS-R is fitted with a set of Ground Control (GC) springs that allow it to handle better at the limits then my basically stock Miata. The integra does ride a bit firm, and is about as firm as I like it for a street car. When I decided to go with a set of GCs, I was concerned about making the miata too stiff for even my tastes. Before I go into specifics, let me give some background on GC.

Ground Control Springs

Ground Control is a small company that specializes in suspension upgrades for street and race vehicles. Although their web page does not actually list the miata in their applications guide, they can fit a set of GC springs to the miata. Marketing calls these sets 'coil overs'. Technically, that is a bit incorrect as the miata suspension already is a coil over, with coil springs surrounding the shocks. What GC offers is an adjustable spring perch that allows ride height to be changed, and the car corner weighted. Better yet, GC uses only Eibach ERS springs. ERS is short for Eibach Race Springs, which is a product line that is used in just about every type of race car. Spring rates can be selected usually in 25lb increments, and the springs are linear rate, not progressive rate. In my case, I wanted to upgrade the rear springs on my integra. The were 8" springs at 250 lbs each. After calling up GC, and speaking with Tony, then Adam, they informed my their 'normal' recommended street kit for a miata was 375# 6" front springs, and 275# 7" rear springs. Adam was a bit concerned about me using an 8" spring in the rear. I told him that I would be using thel ower Koni spring perch which gives me about .75" drop, and that I also was not worried about slamming the car, as that is not my taste. About 1-1.5" off the rear was all I wanted. He agreed that the 8" spring in the rear would be no problem. I also ordered a 350# spring for the front rather then a 375 as I was 25# softer in the rear already. Adam then allowed me to get a pair of 10" springs for the integra in that miata order. Now *that* is customer service. Not too many large operations would even consider this type of order. Adam and Tony did not flinch.

The Big Day

After waiting several months to schedule some time in DB94 to do the install, I was more then ready. I had loosely participated in one miata shock swap already, with Chris and Jac doing the wrenching for that and another one without me. Using the Cardell BFH method, the front ball joints had not given us too much trouble in the past. When it came down to the install, I did most of it myself. Being patient, and shooting it around with the other guys (who were working on their miatae at the same time) it took about 4 hours of labor to finish the entire job. I think I was a bit lucky that nothing really gave me any problems. The cotter pins slid out, the ball joints did not take too much percussion engineering to get apart. Chris has a decent spring compressor, though its hooks were too large to get at the narrow rear springs. Had to use an el-cheapo set of spring compressors on those. An impact gun is a *very* good thing to have when removing a few of the suspension bolts. Beg, borrow, and plead to get one when you do any work on the suspension if you can. Unfortunately, Chris's Mavica is currently getting repaired so we did not document the entire install. Its really not that exciting. I do have a few pics to show the GCs in my findings later on. Skip to the bottom if you are impatient.

The Initial Test Drive

Having done a few suspension upgrades before, I should have known better. But I foolishly went off and started beating the miata around. A quick snap fishtail woke me up and I drove a lot more conservatively. Remember: whenever making suspension modifications, no matter how trivial, take it easy on the initial test drive. That car felt good. Damn good. Ride quality was firm. No more bouncing over bumps as I had before. I really did not fully appreciate how shot my old shocks were until I rode around in with the Konis. I dialed in the Konis to be 1/2 turn from full soft in the rear, and 1 turn from full soft in the front. The reasoning for this was twofold: a stiffer front end would tend to dial out oversteer (hey, I was at least aware of it, even if I did not drive that way initially). Second, I was running stiffer springs all around, so some extra dampning was called for, rather then running the Konis on full soft. Even set like this the car was far too neutral for my tastes on the street. We went to a large deserted parking lot and began to do our normal suspension testing, consisting of medium speed loops, similar to a skidpad. Previously, I would have to really try to get the rear end out. 5000 RPM turns with heavy throttle application was the only way to wiggle the tail given my SP8000 rubber and a dry road. Now, the *slightest* addition of throttle mid turn got the car loose. Fun? Certainly. Safe? Not a chance. Something had to be done to dial out the oversteer. Back to the garage

Dialing in my Setup, Part 1

Any suspension system is just that: a system. All the parts must work together. Previous additions to my suspension were a set of FM sway bars, and SP8000 tires. I had adjusted my FM sway bars to the soft setting in the front, and the medium (middle hole) in the rear. Since after the springs were added the car became more neutral, softening the rear sway bar would helpd dial some understeer back in, leaving *all* other settings the same. I had two options here: use the softest setting on the FM rear sway bar, or swap in the smaller stock bar. The softer setting on the FM sway bar is the first logical step as its a small change compared to going back to the smaller diameter rear bar. This change helped get the car back to a slight understeer at the limits. Using the same test loops in the parking lot, it was not harder to get the rear end out in the middle of the turn. I still could be being stupid, such as hammering the throttle while at the full capability of the tires in the middle of the turn, but it was not nearly as sensitive as before. It also was not as 'safe' as it had been prior to the springs. To help matters a bit more, I dialed the front shocks up another 1/2 turn stiffer. So far, the car feels great for me. My main concern is when I lend the car to a friend (friend's are always trying to borrow a miata, haven't you noticed?) and they are not accustomed to a car set up this way. A good Porsche driver should have no problem, but someone who regularly drives a Stupid Ugly Vehicle is another story (yes, you have to question my judgement when I lend my miata to a SUV owner in the first place). I will report further test/tune findings as I discover them.

Dialing in my Setup, Part Deux

After spending some more quality time with the GCs, specifically with various weather patterns, I really need to put the stock sway bar back in the rear. The car is fun, but you cannot be sloppy. A recent 60 degree day with rain showed that despite my SP8000s, *any* throttle application above 3000 RPM when you are exiting a turn will unsettle the rear end. How much depends upon how sharp you are turning, and how heavy your foot is. Is it fun? Sure. Is it what I want for the street? No. I miss the ability to take a good line through my favorite corners, and mash the throttle as I begin my turn out. It was really hard to get the car loose this way, meaning even those that don't drive RWD well would find it difficult to get into trouble.

Dialing in my Setup, Part Three

After getting my stock sway bars out of the basement I had left them in when I first installed them almost a year ago (thanks Wookie :), I jacked up the rear and began to work on putting the stock rear back in. As I mentioned in Part Deux, the car is still too loose for the street IMHO. With winter coming, that means black ice and my A/S Brickstones. Not a great combination in a miata. So, I have a moment of silence for the RB rear sway bar (she did well) and put back the puny stock bar. Feels like a toothpick I note. At the same time, I also raise the car about .75" for the winter, and throw on the RE-930s. The test drive was very revealing: I no longer had a too loose car. Even with the lousy traction of the RE-930s (who I could get to break away in the rear quicker then the SP8000s) I was having difficulty getting the rear end out by hammering the throttle too early on turnouts. This is good I thought. I would not describe the car as a understeering pig, but it was a step up from where I was with the RB rear sway bar. The GC springs still feel great, and the car handled surprising well with the RE-930s in the dry. They make noise, so I know I am working them a bit, but its not near the edge of traction. Mistakes made with throttle application won't bite you in the ass as much. This is good for other drivers, as well as me. Nobody is perfect :)

Pictures of how the GCs look on Tatjana

Here is a view of the GC's installed on a front side. You are seeing a 6" Eibach ERS spring coiled over a Koni single adjustble shock with the spring perch set to the lowest setting. The car is lowered about 1" from where this particular miata sat with its stock spring and shocks. Note that the adjustable collar has plenty of travel both up and down left on its 4" collar. Where the collar is set now, the spring is just barely loaded when the car is raised in the air. The bump stops were cut as directed by the Ground Control instructions, which said to cut the lowest bump stop, and trip the upper portion of the bump stop to fit into the center of the supplied poly shock mounts.

Here is a view of the GC's installed on a rear side. This is with an 8" Eibach ERS spring, Koni single adjustable shock set to the lowest perch setting, and the bump stops cut as per Ground Control's instructions. Note that the adjustable collar is adjusted to the bottom. I cannot lower the car anymore. At this perch setting, the 8" spring is slightly unloaded when the car is lifted. This means I can move the spring up and down a few millimeters when the car is jacked up. Makes it easy to adjust (if I wanted to raise it, I would not need the tool as there is no loading of the spring against the perch), but if the rear end becomes unloaded, the spring will slam up and down a bit as the car's weight loads it again. Not much of an issue on my car, but if there was an inch or two of free space here, I think a tender spring would be in order. A tender spring is useful on suspension with short, stiff springs that want to provide some decent travel. The tender spring is a flat coil spring that does not have a hight spring rate. Its sole purpose in life is to keep the coil spring planted to the bottom of the spring perch, with the tender spring pushing against the top of the shock mount. This prevents any free play if the suspension becomes un-loaded.

http://www.eclipse.net/~magnum/miata/ground_control.html
Last updated: Mon Aug 6 8:16:58 2001
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