Brant's 99 Miata Set Up

Post your questions or tips about wheels, tires, alignment, or anything related to preparing an autocross car here.

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Brant Rakoski
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Brant's 99 Miata Set Up

Postby BrantR » Wed Oct 04, 2017 11:28 am

I finally got to debut my new Miata last weekend and man was it a tail-happy experience. I spun out on my first two runs (too much speed into the 180) and generally did a whole lot of sliding.

I've got RE-71s on it, but I'm feeling that alignment is way off and I'm due for some shocks. I took it to a shop to check on the tie rods and they pointed out that it's still on the original shocks with 167k miles on them! Also when I had somebody more experienced drive my car, they bottomed out something in the suspension going around the 180 (there was a distinctive CLUNK). I'm assuming that's bump stops but I don't know enough to be sure.

Sally's thread is chock full of information but I'm still feeling pretty lost on how to choose shocks.

I think the alignment is the most important thing to take care of first, but now I'm swimming through numbers. -2 camber? -1.75? To toe or not to toe? Etc. Also, should I hold off on the alignment until I get the shocks installed? Are there other suspension components that should also be replaced?

Any other setup tips or things I should keep in mind?
This is the first car I've put real work in to, and it's a bit overwhelming.
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Brant's 99 Miata Set Up

Postby Loren » Wed Oct 04, 2017 12:01 pm

NB Miatas have rear bump stops that are made of a really weird red poly foam that literally crumbles to dust after about 3 years. Your rear bump stops probably don't exist. That's what's causing your snap oversteer.

And read Sally's thread again. :thumbwink:

If you're paying someone to do your alignment, you'll likely want to do it again after replacing the shocks. New shocks will almost always raise the ride height by about a half inch or so, which affects the static camber, which affects the static toe. At the very least, you should reset the front toe after changing the shocks. If everything else was "right" before that, it's probably close enough. But, always check front toe.
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Brant's 99 Miata Set Up

Postby twistedwankel » Wed Oct 04, 2017 2:08 pm

BrantR wrote: Also, should I hold off on the alignment until I get the shocks installed?
Yes. Just throwing money away. But some tire stores will do a free check to give you a base line of how bad it is.
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Brant's 99 Miata Set Up

Postby jev61 » Wed Oct 04, 2017 4:30 pm

Hello Brant, everything Loren has said is correct. There are three things that matter: tires, shocks, and alignment. If I may be so bold, might I suggest an order of operation for your suspension:
1) Pick a set of shocks. Koni Yellow and Bilstein B6 are high performance choices, KYB GR2/Excel and SACHS are budget choices. All are better than what you have.
2) Pick a set of bumpstops. Fatcat Motorsports 58mm, Flyin Miata 54mm, or RE Suspension COT Series 58mm. Medium front, soft rear.
3) Pick a front swaybar. Flyin Miata 1-inch front bar or Racing Beat 1.125-inch front bar with Brace Kit. Hollow bars weigh less than solid bars.
4) Get an alignment. With a stock suspension, you will be front camber limited:
Front camber: -1.4°
Caster: >4.5°
Front total toe: zero
Rear camber : -1°
Rear total toe: +1/8"

I added a front swaybar to the list because an aggressive alignment can make the car tail happy, if you don't want to buy a larger front bar then have the rear camber dialed up to half a degree more camber than the front. If you do buy the front bar and the car is too tail happy, dail up the rear camber. Someone will suggest you unhook your rear sway bar; you can try it, but I don't think you will like it. I tried it with a stock suspension, the springs are too soft and the car rolls like a drunken sailor on shore leave.

Joe Brannon can help you with the suspension install and alignment if needed. Or Vortex Motorsports can do installs and custom alignments.
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Brant's 99 Miata Set Up

Postby BrantR » Wed Oct 04, 2017 4:52 pm

jev61 wrote:Hello Brant, everything Loren has said is correct. There are three things that matter: tires, shocks, and alignment. If I may be so bold, might I suggest an order of operation for your suspension:
1) Pick a set of shocks. Koni Yellow and Bilstein B6 are high performance choices, KYB GR2/Excel and SACHS are budget choices. All are better than what you have.
2) Pick a set of bumpstops. Fatcat Motorsports 58mm, Flyin Miata 54mm, or RE Suspension COT Series 58mm. Medium front, soft rear.
3) Pick a front swaybar. Flyin Miata 1-inch front bar or Racing Beat 1.125-inch front bar with Brace Kit. Hollow bars weigh less than solid bars.
4) Get an alignment. With a stock suspension, you will be front camber limited:
Front camber: -1.4°
Caster: >4.5°
Front total toe: zero
Rear camber : -1°
Rear total toe: +1/8"

I added a front swaybar to the list because an aggressive alignment can make the car tail happy, if you don't want to buy a larger front bar then have the rear camber dialed up to half a degree more camber than the front. If you do buy the front bar and the car is too tail happy, dail up the rear camber. Someone will suggest you unhook your rear sway bar; you can try it, but I don't think you will like it. I tried it with a stock suspension, the springs are too soft and the car rolls like a drunken sailor on shore leave.

Joe Brannon can help you with the suspension install and alignment if needed. Or Vortex Motorsports can do installs and custom alignments.
This was exactly what I needed to hear. Thank you so much.

I know everybody has an opinion on the Koni vs Bilstein, but I've had a hard time understanding what's really different.
Assuming stock springs, primarily autocross driving, and only the modifications/alignment you suggested, what would be the major differences between the two?
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Brant's 99 Miata Set Up

Postby Loren » Wed Oct 04, 2017 4:59 pm

Konis are adjustable, Bilsteins are not.

The adjustment on the Koni is "rebound" damping, so it doesn't affect compression. Konis have considerably softer compression damping than Bilsteins. But, you can adjust the rebound to suit your needs and a lot of people have proven them to be very capable for autocross. (and you can adjust them down a little bit for street use to make your wife happy)

Bilsteins are great, too! They have very crisp firm compression damping. Steering response is RIGHT NOW, it's awesome. But, that exact same characteristic makes them miserable to drive over "washboard" surfaces. Little bumps just get transmitted right through to you. The valving is "digressive", meaning that as the shock shaft speed increases (you hit a larger bump rather than a baby bump, or a steering input) they will go soft and absorb the bump. So, that's good. But, if street comfort is high on your list... you might not be crazy about Bilsteins. But, the feel Sooooo Goooood.

Best bet... try to find a good example of a stock Miata with each option and drive it a little bit. Be sure to take note of how the Konis are adjusted if you do this. Konis set near soft are downright plush.
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Brant's 99 Miata Set Up

Postby BrantR » Wed Oct 04, 2017 5:05 pm

Loren wrote:Konis are adjustable, Bilsteins are not.

The adjustment on the Koni is "rebound" damping, so it doesn't affect compression. Konis have considerably softer compression damping than Bilsteins. But, you can adjust the rebound to suit your needs and a lot of people have proven them to be very capable for autocross. (and you can adjust them down a little bit for street use to make your wife happy)

Bilsteins are great, too! They have very crisp firm compression damping. Steering response is RIGHT NOW, it's awesome. But, that exact same characteristic makes them miserable to drive over "washboard" surfaces. Little bumps just get transmitted right through to you. The valving is "digressive", meaning that as the shock shaft speed increases (you hit a larger bump rather than a baby bump, or a steering input) they will go soft and absorb the bump. So, that's good. But, if street comfort is high on your list... you might not be crazy about Bilsteins. But, the feel Sooooo Goooood.

Best bet... try to find a good example of a stock Miata with each option and drive it a little bit. Be sure to take note of how the Konis are adjusted if you do this. Konis set near soft are downright plush.
Beautiful summary. I'll have to ask around the Miata drivers this weekend to see who's on what. It sounds like Bilsteins might be a better fit since I already have a comfortable daily driver and that NOW response is going to make things fun. Not having to adjust them is also a bonus.

Last question for now: Is there any meaningful difference between the different brands/sources/sizes of bump stop? It seems like such a small part to comparison shop.
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Brant's 99 Miata Set Up

Postby twistedwankel » Wed Oct 04, 2017 5:16 pm

Koni Yellows and Bilsteins both have a lifetime warrantee to the original buyer. Save your receipts forever. My bilsteins came from the factory with bump stops included. Koni's did not.
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Brant's 99 Miata Set Up

Postby Loren » Wed Oct 04, 2017 5:17 pm

I go cheap and get bump stops from a 2000 Honda Civic. They can be had for about $6/each. They're too long for a Miata. (Actually, I did put them full length on one Miata. They just barely make contact at static ride height, meaning they started to engage immediately. But, they are VERY progressive, so it worked well enough.

Another thing you need to consider is whether or not you want to be "legal" for any particular SCCA class. FAST stock class is pretty liberal. We don't care about things like bump stops. Knock yerself out! But, if you're trying to be fully compatible with SCCA Stock (Street) class, they require that your bump stops be the same length as stock. How long is that? Idunno. You'd have to research that.

But, if you do the Honda bump stops, just trim the top segment out of them. They'll work. Everything is a compromise.

Or spend (much) more and get a "tried and true" combination from one of the outfits like FatCat. Maybe it will make you faster. Maybe it won't.
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Postby jev61 » Wed Oct 04, 2017 5:20 pm

BrantR wrote:Last question for now: Is there any meaningful difference between the different brands/sources/sizes of bump stop? It seems like such a small part to comparison shop.
Short answer: not from the three I listed. Loren can tell you how to cut Honda stops to fit for less. Bottom line: get new stops.
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Postby Native » Wed Oct 04, 2017 8:50 pm

Brant, I'm the "somebody more experienced" that drove your car at the last event - an "instructor run."
I hate to tell you this, but your snap oversteer is not the car.
If there's worn parts that need to be replaced (what was that thunk when I hit the brakes at the turnaround?), then by all means, replace them, and sure, upgrade! :thumbwink:
But practice, practice, practice. Don't throw a ton of mod-money at the car and expect it to equal seat-time.

And, this may be blasphemy, but KYB AGX are an inexpensive, functional, adjustable (easily) shock that might be good to "learn" with. Especially if you plan to stick with stock springs.
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Postby BrantR » Wed Oct 04, 2017 9:07 pm

Native wrote:Brant, I'm the "somebody more experienced" that drove your car at the last event - an "instructor run."
I hate to tell you this, but your snap oversteer is not the car.
If there's worn parts that need to be replaced (what was that thunk when I hit the brakes at the turnaround?), then by all means, replace them, and sure, upgrade! :thumbwink:
But practice, practice, practice. Don't throw a ton of mod-money at the car and expect it to equal seat-time.

And, this may be blasphemy, but KYB AGX are an inexpensive, functional, adjustable (easily) shock that might be good to "learn" with. Especially if you plan to stick with stock springs.
You're absolutely right that I need a whole lot more practice. I'm planning on hitting every autocross event I can for the foreseeable future.

I'm only throwing "mod-money" at the things that need replacing anyway, and I figure while I'm at it, I may as well get the good stuff.

Your advice was awesome and after your instructor run I didn't spin again. Thanks again for the help!
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Brant's 99 Miata Set Up

Postby Jamie » Wed Oct 04, 2017 9:51 pm

Native wrote:And, this may be blasphemy, but KYB AGX are an inexpensive, functional, adjustable (easily) shock that might be good to "learn" with. Especially if you plan to stick with stock springs.
On the other hand, shocks don't get replaced often, especially if it's not a daily driver. Shocks aren't that much fun to change -- whatever you put on, you're going to live with for awhile. The KYBs are fine if money's not available to go with Bilsteins or Konis, but get the best you can afford and be done with it.

That "thunk" could be a broken sway bar end link, or possibly a broken motor mount. Both easy to check.

While Joe's a big fan of changing the front sway bar, I'd hold off. No two Miatas seem to be exactly alike. Many benefit from a heavier front bar, but not all. Make necessary repairs, get a good alignment, a decent set of tires, and see how it feels.
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Brant's 99 Miata Set Up

Postby Loren » Wed Oct 04, 2017 10:10 pm

Check all of the undercar bracing. A lose brace will clunk like crazy under autocross stress.

Alignment bolts that are not sufficiently tight (hint: most alignment shops don't tighten them enough) will allow a little bit of movement and clunking under hard braking or cornering.

Basically, you need to thoroughly go over the car with somebody who know's Miatas!
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Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Brant's 99 Miata Set Up

Postby BrantR » Wed Oct 04, 2017 10:14 pm

I'll likely go with Joe Brannon for the install if he allows me to throw money at him. I'll see if he can give it a good inspection while he's at it. This has all been invaluable. I'm glad to have joined such an enthusiastic and helpful community.
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Brant's 99 Miata Set Up

Postby Native » Thu Oct 05, 2017 7:12 am

The thunk occurred at the turn around. Hit the brakes, the nose set, wheels straight, a single, heavy, thunk - metal to metal it seemed - made the turn, no "unthunk" and that was that.
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