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Old 09-25-2006, 11:46 PM   #1
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Default Ground control ?'s

I've got a set of Koni yellows which I love. I set the front to mid perch and the rear to the lowest perch. I don't hit the bumpstops in the rear, which is curious. I'm really curious as to why my car looks no lower than before the konis? I wasnt expecting a huge drop...but it doesn't look lower at all!

I have been thinking about a set of ground control coilovers as I have read quite a few posts with people being happy with that setup. I REALLY love the look of a slammed miata, and I would be lying if I didn't say most of my want for them wasn't the look. I do have some body roll and would like to upgrade my suspension anyway.

My problem is I can't find much info on them. So far Good-win racing is the only place I can find to buy them. I would most likly get the 375/250 kit correct? What about corner weighting? Basically, tell me EVERYTHING about them or point me to the post which already does and I couldn't find by myself. Thanks.
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Old 09-26-2006, 07:43 AM   #2
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You probably can't find much on them because you'll never see them on street-driven Miatas. Maybe try the autocross forum at m.net.

But, ever the voice of reason... Have you driven a car with them installed? Ride in one with the stock springs compressed down the full two inches. You need to do that before spending $400 bucks.
If all you're interested in doing is lowering the car, get a set of lowering springs. I never thought compressing stock springs to lower the ride height was a good idea from a performance standpoint.

These RB's drop you an inch from $169 and they go for cheaper all the time in the classifieds: http://www.good-win-racing.com/mazda/miata/20-1028.html I'd try that before the Ground Controls.
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Old 09-26-2006, 11:41 AM   #3
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I have the GCs... with 450/350 spring rates. Personally, I like them... although, the issue is, you still really need the FM mounts in the rear to help with your shock travel, regardless of what springs you have. I would definately say, go for some higher than stock rates though. You'd be suprised what a non-bumpstop ride is like. With my setup, I've been back and forth to the gap, with the SO in the pax seat, with no complaints.... I autox on them too, and they have survived the track days....

Remember, you lower the car, you lower the amount of shock travel, that's what can change the ride considerably. I found the FM mounts made a huge difference with the way the car was controlled, specially over bumps while cornering.

The GCs are great though, you can swap springs, etc... you can control the ride height to where you want it.... You can also corner weight them too if you want to.

If I was to do it all over again, on a fresh car, without the koni's, I would just get the tien flex. <G> By the time you add up all the prices you are damn close to the price for the "full coil" setup... with the adjustable bodies.

I know somebody with the RB springs, and he likes them with the AGXs, but personally, you have no control over the ride height, so you can't make minor adjustments for things. And I've found that I had too much drop with my apex springs prior to the GCs.... definately not something I would repeat.

Do it once, get something you'll stick with.

Dave
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Old 09-26-2006, 11:52 AM   #4
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I've got GC/KYB on my car. Stock spring rates (375/250), and a ride height of about 12/12.5 (maybe a little less). I also have the FM rear shock mounts. Ride is as good as it was on just the KYB and stock springs and stock ride height. The only time it is worse is over really harsh pavement, but the RB solid sway bars probably contribute as much or more than the GC setup.

MANY MANY people use this setup on the street. It's an awesome budget coilover setup. The springs are excellent quality Eibach ERS, not to be confused with the crappy Eibach lowering springs.

The RB springs are crap. They are known to sag over time and lower the car too much with out increasing the spring rate. I beleive they are also a progressive spring, which in my opinion isn't good either. Makes for less than predictable handling.

If you want to just go with a spring the only one I would recommend is the FM springs, although I have no experience with the latest redesign.

The great thing about the GC setup is you can choose your spring rates when you order or you can change them after by ordering new ERS springs. You can also change your ride height, so in a month if you decide that a slammed Miata is no fun on the street you can raise it up with only the cost of a new wheel alignment. I'd seriously recommend something like the FM rear shock mounts to gain back the precious shock travel in the rear. When I installed mine I trimmed the supplied bump stops that come with the FM mounts, and trimmed the OEM bumpstops on the front. At 12/12.5 I've never had an issue with running out of travel.

Corner weighting isn't totally necessary, but in an ideal world you would want to do it. If I had access to scales I would do it for sure.

If you didn't have the Konis I'd say look into a full coilover from Tein. But since you already do I think the GC setup is the way to go.

Sam, have you driven a car on the GC setup? How about the RB springs? I've driven both and the GC setup is FAR better in my opinion.

Jay
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Old 09-26-2006, 11:53 AM   #5
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There you go, the same exact opinion from two different people, Dave just beat me to it
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Old 09-26-2006, 10:00 PM   #6
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Awsome! I personally love a stiff suspension. Its good to hear the setup works well. The FM rear mounts were something I thought about when I first got my konis, but after some measurements I decided against them. With the GC for sure I will pick a set up.

How do these install? I read an article about them, but it was for a MacPhearson strut assembly. Anyone know why there is such little info on them?

As for spring rates, I will admit I only see 2 or 3 autocrosses a year. I hope to hit gingerman raceway at least once next year. I dont need a racing set up, but I would like a sporty feel. Would you suggest stock rates or something a bit higher? Thanks, I love this forum.
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Old 09-26-2006, 10:17 PM   #7
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Im lovin my setup, but I havent riden in any other setup. I am interested to see how some KYB AGX's handle
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Old 09-27-2006, 10:09 AM   #8
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Essentially, the priciple with the GCs is, you replace the lower perch on the shock (at least with the koni's), and just put the GC threaded sleeve on the c-clip that holds the perch for the koni lower spring cup.

Then on the top you have either the stock perch, or the FM mounts in the rear if you want. (That's what I did). NOTE to install the springs (since they are smaller diameter than the stockers) you need to trim the bumpstops to get them to fit. You might want some spares to cut up.....

The FM Mounts essetially replace the stock rear tops on the shocks. When you pull the shocks, there's the upper perch that sits with the two 14mm bolts going through the body. You take those off (to get them out), then loosen the upper bolt on the shock, replace the whole mount. You have to order the right ones from FM though, Konis have the larger shock shaft.....

Otherwise, it's basically just like a shock/spring change on any miata.... If you have done it once, you'll know what 90% of the job intailes.... <G>

I agree with Jay, GCs are not for autox only. My car is the daily driver in summer... and even with the crappy roads it does fine. For that matter in the style NYC roads of Montreal.... (3' holes.... you can fall into completely).... the car did good.... for rim safety, I just tried to avoid the holes.... I didn't want to fall through to china. <VBG>

Dave,
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Old 09-27-2006, 10:50 AM   #9
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I just installed GC's (440/350) with revalved bilsteins with fat cat bumps and FM rear mounts. I bought them through car doman for $380 shipped (call gc first though and let them know what spring rates you're ordering). You can score the dampers for $80 each if you search (www.eshocks.com). Tein's sound like a good idea at first, until you realize a lack of product support (no services in the USA apparently), they won't warranty unless you buy from an authorized dealer who only sells at the very high msrp through an agreement, and they will only warranty the crappy twin-tube damper for 1 year (not the springs, perches, or pillow *****), and charge $120 to revalve each, after you send them to japan and wait 4-6 months. Bilstein offers a lifetime warranty, and can be easily revalved by shops all over the nation, many of which will be local. Eibach offers the same on any ERS spring.

I would only buy dampers from bilstein, koni, ohlins, and penske because thats just about it for a monotube design. Monotubes are great because you can have them revalved by any motorcycle shop or damper shop and typically have this done locally for about $60 each. Monotubes tend to last much longer than other designs, and thats from both personal experience and friends who've campaigned race cars for decades. The only drawback to a monotube is a lack of comfort in big cruiser sedans; so you can surf your cadillacs. Thats the whole reason why they were created according to a guy from bilstein.

I drive my car 80% of the time (my daily is slammed on 10 year old monotube H&R coilovers too) and I will agree that the 440/350 rates are not for the "faint of heart," but its a sports car, and you have alot to benefit from a linear, firm spring with appropriate dampening. I'm at 13" all the way arround now waiting to see if the springs settle, but that allows for a good ammount of travel, and the bumpstops go a long way in these cars from what I understand.

People don't give bilstein and GC enough credit. They are both good companies with a strong presence in the USA. I attempted to speak with many vendors before I made this purchase, and some didn't know thier head from thier ***, bilstein and ground control answered my questions and provide very usefull recomendations. Actually, I was assured I would make the right purchase after talking to a guy a bilstein and a guy at ground control. When both of thier answers to my numerous questions coincided, I knew I made the right decisions.
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Old 09-27-2006, 12:40 PM   #10
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I have GC/AGX/Chikara top mounts.

pretty kick *** if you ask me. Im running 450/375 and I havent measured how low I am really. pretty low but not dumped.
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Old 09-27-2006, 12:48 PM   #11
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Thanks guys, GC's are the way to go for me.
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Old 09-27-2006, 02:27 PM   #12
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I just put Tein Basics on my car along with the superior NB upper spring/shock mounts for ~$750-800. About the same price as just Ground Controls and 4 Konis, plus it includes boots, bumpstops, has greater potential travel (due to the NB uppers and shorter Tein shock bodies), has threaded bodies instead of sleeves that can slip/shift under load, has superior low-speed damping, and superior damping in general, when paired with ~350-450lb springs, etc.

Also, it's $75/ea. to rebuild/overhaul the shocks ($120/ea for their monotube models), and I have no worries about service since I bought them through Adrenaline Racing, a very stand-up, Miata-centric vendor.

Being monotube does not gaurantee a better shock, nor does it mean the shock will work well with springs, perches, etc. for which it was not originally designed. A good twin-tube design is superior to an average monotube design. The sum of the parts is greater...well you know the rest.
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Old 10-01-2006, 09:39 PM   #13
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The Ground Control coil-overs are great and you can also order them through Mazda Competition (assuming you have some proof of participation in at least two competitions in the past year).

I recommend *against* "slamming" your Miata if you are looking for improved handling. If only for looks, fine. If you are lowering your Miata for looks, then save your money and buy a set of lowering springs (much cheaper than a set of Ground Controls). Be aware that lowering a Miata literally screws up the suspension geometry (particularly the roll center) and you end up with a car that is actually slower through a corner than a stock Miata.

If you want to lower the car, then I recommend you only take it to the lowest Mazda-recommended height (there's a reason they pay multiple suspension engineers big bucks every year to design suspension geometry). Also, the front should be 20mm lower than the rear (+/- 10mm) to maintain proper roll center.

There has been much discussion on M.net concerning front roll couple and the interrelationship between suspension travel, ride height and caster/camber (lower height, more camber. More caster, less camber), spring rate ratios front and rear, and the relationship between understeer/oversteer characteristics and the spring rates front/rear and the sway bars front/rear. There are some good spreadsheets available that can give you an idea of what various combinations of spring rates and sway bars will do to your understeer/oversteer characteristics.

Would type more but this has been covered in detail over and over again on the other Forum. Do a search on "front roll center" and you'll have reading for hours....

Also, depending upon the power available, you can adjust the understeer/oversteer characteristics. With my turbo, I prefer a slight understeer (plus the car feels more stable at high speeds). Remember, everything is a tradeoff, fast turn-in at low speeds can equal twitchy and unsettling at high speeds.

Best of luck to you.
Barry
(Who found the hard way that "lowered" does not equal "better handling".)
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Old 10-01-2006, 09:46 PM   #14
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how did you find out the hard way that lowered didnt equal better handling? I know it doesnt but I am Just curious
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Old 10-02-2006, 12:10 AM   #15
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Short and simple answer? I drove pretty much only city streets after I lowered my car. Then I moved to the country and drove my car to work for a year through the same S-turn every day (I was totally ignorant of suspensions then) thinking I had a fast turbo Miata that was low to the ground. Generally exited the S-turn somewhere about 35 mph.

Then I bought a second Miata for my wife's use. Box stock. Original worn out shocks and suspension. Put a set of tires on it identical to the set on my turbo Miata and took the same S-turns. I was exiting somewhere around 40-45 mph even though it was leaning like crazy. I started thinking "Hmmmm...".

Began reading and learning. Modified my turbo Miata's suspension based upon what I learned. Now I exit that S-turn at a reasonable enough speed that the Sheriff's Deputy indicated I needed to slow down while traversing that turn. :-)

If someone prefers a lowered look, then good for them. I prefer my car to have more suspension travel, less bump steer, and handling characteristics I can adjust.

Regards,
Barry
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Old 10-02-2006, 12:24 AM   #16
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It probably has more to do with the type of suspesion than the ride height that has made the difference and experience you have.

My car handles MUCH better than it did on the stock suspension, autocross times tell the tale. My car is as low as possible for a street driven car, as it is some speed bumps and driveways have to be navigated very carefully. I've never experience bump steer and only at the very extreme have I run out of suspension travel, a stock Miata would likely have had the same problem.

Lowering the car with out retaining suspension travel and increasing spring rates will certainly screw things up. But doing it correcly can be like heaven.
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Old 10-02-2006, 09:43 AM   #17
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Yes, but therein lies the rub: most people lower their car with not regard to lost bump travel. They either use springs that aren't stiff enough to avoid being on the bumpstops all the time, don't use shorter bumpstops or both.
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