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Old 09-10-2010, 12:46 AM   #1
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Default Adjusting ride height is a pain

At this point I am a whiz at taking my suspension apart. With multiple combination of spacers. I was able to attain a ride height of 12"F and 12.5"R. While this does not seem ideal, it appeared better than the 12.25"F and 13.25"R; 11.5F and 11.75R; and the 12"F and 13.75" combinations.

If it were really worth it, I could get 12.25"F and something around 12.5"R if I cut one of my FCM spacers.

What is typically considered the ideal ride height that the suspension geometry isn't compromised?

Last edited by miatauser884; 09-10-2010 at 03:42 PM.
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Old 09-10-2010, 02:09 AM   #2
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So did my spacers work out for you eventually?
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Old 09-10-2010, 02:12 AM   #3
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As low as you can go without compromising shock travel. With a shock designed to optimize travel in a Miata (i.e. XIDA, custom Koni 28/30, etc) you want to run the car very, very low, like 11.3-11.4" front ride height.
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Old 09-10-2010, 10:22 AM   #4
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Quote:
Originally Posted by curly View Post
So did my spacers work out for you eventually?
I would say the spacers are ultimately a win. I used all four spacers.

In the rear I removed the FCM spacers that were there to minimize dropping the car with NB tophats.

I remeasured this morning with a better method for pinpointing the wheel center. I'm 12" front and 12.75" R I think I am going to bring it to 12.5"F and 12.75" Rear or 12.25F and 12.5R

I can't decide which to do. My initial ride height of 11.5F and 11.75R was too low. The wheels rubbed the lip, and I scraped the car on everything. IF it were a track car only, then it would have been fine. As a daily, it's embarrassing when you scrape on every dip.

What's the vote between these two: 12.5F and 12.75" Rear or 12.25F and 12.5R.

BTW: I'm running revalved bilsteins
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Old 09-10-2010, 10:47 AM   #5
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Take the spring off, pull the bumpstop down, put a zip tie on top of the bump stop, attach the shock, attach the wheel, jack the wheel up until it hits something.

Now you can remove the shock, look at the zip tie, and see if you're limited by wheel clearance or by suspension travel (you may have to do this again without the bump-stop. Now go as low as you can respecting SavingAIDZ' advice. When I dropped my car down to 11.25 and 11.5" and changed the alignment, the car came alive.

I think its safe to say that if you're not using that bump stop before the wheel hits the fender, you better have a strong spring.
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Old 09-10-2010, 11:07 AM   #6
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Quote:
Originally Posted by Savington View Post
you want to run the car very, very low, like 11.3-11.4" front ride height.
, respectfully. I've been grappling with this lately, and come to a partial conclusion that going very low may be antithetical to really good handling because the roll center introduces a pretty large moment arm v the CofG, making the car roll more and become sluggish in transition. If you have the ability to raise roll center and work to minimize bump steer, then getting CofG low may be of benefit. If not, you are working against yourself a bit.

“The roll center establishes the force coupling point between the unsprung and sprung masses. When a car corners, the centrifugal force at the center of gravity is reacted by the tires. The lateral force at the CG can be translated to the roll center (RC) if the appropriate force and moment (about the roll center) are shown. The higher the roll center the smaller the rolling moment about the roll center (which must resisted by the springs); the lower the roll center the larger the rolling moment. You will also notice that with higher roll centers the lateral force acting at the roll center is higher off the ground. This lateral force x the distance to the ground can be called the nonrolling overturning moment.” (Race Car Vehicle Dynamics, William F. Milliken and Douglas L. Milliken 1995.)
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Old 09-10-2010, 11:20 AM   #7
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Quote:
Originally Posted by webby459 View Post
, respectfully. I've been grappling with this lately, and come to a partial conclusion that going very low may be antithetical to really good handling because the roll center introduces a pretty large moment arm v the CofG, making the car roll more and become sluggish in transition. If you have the ability to raise roll center and work to minimize bump steer, then getting CofG low may be of benefit. If not, you are working against yourself a bit.

“The roll center establishes the force coupling point between the unsprung and sprung masses. When a car corners, the centrifugal force at the center of gravity is reacted by the tires. The lateral force at the CG can be translated to the roll center (RC) if the appropriate force and moment (about the roll center) are shown. The higher the roll center the smaller the rolling moment about the roll center (which must resisted by the springs); the lower the roll center the larger the rolling moment. You will also notice that with higher roll centers the lateral force acting at the roll center is higher off the ground. This lateral force x the distance to the ground can be called the nonrolling overturning moment.” (Race Car Vehicle Dynamics, William F. Milliken and Douglas L. Milliken 1995.)
I have read that the miata has a fantastic well engineered suspension geometry at factory ride height. Lowering the car gains center of gravity, but does something to the suspension geometry that makes lowering not a good idea. Obviously I am no miata suspension guru and I do believe Sav's ride height recommendation's. There has to be some clarification to these conflicting views.

Remember, my car is a DD with occasional track duty. I don't like scraping the front lip around town and the frame rails out of my driveway. I can roll the fenders to avoid that contact with tire when turning. My ride height must be above 12" F and R

My driveway is steep. Standing at the top of the driveway is in line with the roof. My care scrapes when I pull out of driveway at 11.5/11.75




Sorry about indirect pictures, but it is all I have here at work.

Last edited by miatauser884; 09-10-2010 at 11:31 AM.
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Old 09-10-2010, 11:32 AM   #8
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I know the rears are limited by travel however when you get shorter bodies, higher rates, and pressurize the piston chamber to 375psi, you can run lower.
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Old 09-10-2010, 11:36 AM   #9
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Quote:
Originally Posted by djp0623 View Post


Sorry about indirect pictures, but it is all I have here at work.
Tell me about your flood insurance premium.
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Old 09-10-2010, 11:37 AM   #10
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I hate measurements of center to fender... never gives me a way to compare approximately where mine are compared to others...
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Old 09-10-2010, 11:37 AM   #11
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Quote:
Originally Posted by Splitime View Post
I hate measurements of center to fender... never gives me a way to compare approximately where mine are compared to others...
me too

I run 4.0 and 4.25 at the pinch welds.
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Old 09-10-2010, 11:42 AM   #12
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Quote:
Originally Posted by djp0623 View Post
There has to be some clarification to these conflicting views.
No conflict unless Savington refutes my analysis .

Quote:
Originally Posted by djp0623 View Post
My ride height must be above 12" F and R
12.25/12.50. IMO no reason to go lower on a street car. Keep in mind that even if you have short shocks and/or magic top hats, the rear suspension won't allow travel beyond ~10" because a-arm hit chassis. So every .25" you give up represents a large percentage loss of precious travel.

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Pretty shocks don't fix suspension geometry. If they did I'd be running 11".
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Old 09-10-2010, 11:50 AM   #13
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Quote:
Originally Posted by webby459 View Post
No conflict unless Savington refutes my analysis .



12.25/12.50. IMO no reason to go lower on a street car. Keep in mind that even if you have short shocks and/or magic top hats, the rear suspension won't allow travel beyond ~10" because a-arm hit chassis. So every .25" you give up represents a large percentage loss of precious travel.



Pretty shocks don't fix suspension geometry. If they did I'd be running 11".
I assume you're referring to bump-steer? I'm pretty low and its not a problem. Pretty shocks do fix geometry if they maximize travel.
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Old 09-10-2010, 11:57 AM   #14
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I've got NB tophats front and rear, FCM bumpstops, bilstein shocks, fm springs.

No flood insurance. I'm not at the bottom of the hill, and landscape design drains water appropriately around the house. I've contacted shaike so he can give some input. I'll report back with his recommendation. I also probed him for some alignment numbers. I want to be as aggressive as possible with out tire wear issues
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Old 09-10-2010, 11:58 AM   #15
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Quote:
Originally Posted by hustler View Post
I assume you're referring to bump-steer? I'm pretty low and its not a problem. Pretty shocks do fix geometry if they maximize travel.
Bump steer is only one problem. The other is the fact that when there is a greater distance between the roll center and the center of gravity, the car basically has more body roll. No roll is not the objective, but when you roll too much the body takes longer to take a set, and can become lazy particularly in transition. With no roll the car will become numb and difficult for us mortals to "feel."

Despite appearances, I'm not just baiting for a fight here. I'm dealing with these issues in earnest in real life, and would love for someone here to come up with a canned setup for me. But I think that without understanding how roll center plays into how the car's mass reacts under cornering, we are pretty much coming up with ride heights randomly.
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Old 09-10-2010, 12:08 PM   #16
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I like the Shaikh guy and I'd love to give him money...but are any of the cars with his shocks and set-up philosophy going fast? I've bought-up the 949 set-up kool-aid and I think its working better than what I had previously which was 1.5" higher with 1.5* less camber with softer springs and the 60* hotter tire shoulder temps aren't the way to go in my opinion.


Edit: I'm very interested in this thread (although not an engineer) because I'm putting my car on the scales next week and I want to set it up right, the first time. Its going to cost me about $750 to get the car balanced and aligned so I'm not looking forward to a change in theory in the future.
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Old 09-10-2010, 12:26 PM   #17
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Quote:
Originally Posted by hustler View Post
I like the Shaikh guy and I'd love to give him money...but are any of the cars with his shocks and set-up philosophy going fast? I've bought-up the 949 set-up kool-aid and I think its working better than what I had previously which was 1.5" higher with 1.5* less camber with softer springs and the 60* hotter tire shoulder temps aren't the way to go in my opinion.


Edit: I'm very interested in this thread (although not an engineer) because I'm putting my car on the scales next week and I want to set it up right, the first time. Its going to cost me about $750 to get the car balanced and aligned so I'm not looking forward to a change in theory in the future.
****, that means I should just put my car back where it was at 11.5 and 11.75. Do you measure at the bottom of the pinch weld, or the point where the pinch weld meets the rocker?

What alignment numbers are you running on your street car?
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Old 09-10-2010, 12:29 PM   #18
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Quote:
Originally Posted by hustler View Post
I like the Shaikh guy and I'd love to give him money...but are any of the cars with his shocks and set-up philosophy going fast? I've bought-up the 949 set-up kool-aid and I think its working better than what I had previously which was 1.5" higher with 1.5* less camber with softer springs and the 60* hotter tire shoulder temps aren't the way to go in my opinion.


Edit: I'm very interested in this thread (although not an engineer) because I'm putting my car on the scales next week and I want to set it up right, the first time. Its going to cost me about $750 to get the car balanced and aligned so I'm not looking forward to a change in theory in the future.
You lost me on the first part. You were at 6" at the rear pinch before? I don't know about Shaikh's setup philosophy, but there are at least autocrossers going fast on his shock package. I wouldn't necessarily call myself one of the fast guys in the big world, I do know that my car is handling very very well on my FCMs. Could I do better? Probably, but at a substantial cost. Could Bernie do better? Maybe.

As far as alignment, I don't see it as a philosophy as much as a somewhat amorphous science. If you're 60* hotter outside after pulling off track, you obviously need much more neg camber. On a racetrack, when you have "enough" camber you may well see a little higher temps at the inside edge because that's where you're rolling when you come in to hot pit. You need to go onto the rack knowing that you'll probably want all of -2.0* rear and -2.5* front if you can get it. Turbo guys want a little rear toe in to get stability, I went straight ahead n/a to liven the rear up and help it roll freer. In the front, a little in if you want it super stable on the highway, zero if you want it lively, a little out if you want it to turn in like a Lotus.

Set your ride heights with a little rake, like .25" higher rear, and scale for even % cross.

Will this setup be "right." It depends. Depends on tire, track, ambient conditions, when you're checking temps, what you've done right before checking temps (long straight vs. right sweeper), AND HOW YOU DRIVE. If you drive like my grandmother, you're not gonna need all that camber. There are probably tons and tons of Miatas "going fast" right now with -1.0 to -1.5 all around. Put Jim Daniels in the car and he'll roast the outside edge in three laps.

Interesting discussion.
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Old 09-10-2010, 12:33 PM   #19
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I guessed at the collar height when I was installing the new suspension this past weekend and was pleasantly surprised at where it settled down:

Name:  rideheight.jpg
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Apologies for terrible pic, it was taken in direct sunlight with my phone.

I think the rear end needs to go up just a hair, but other than that I think it's just about where I want it.
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Old 09-10-2010, 12:39 PM   #20
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I measure at the bottom of the weld, but you need to check travel first because that's a touch too low for the Tein Flex I have now. I run 2.75f2.5r camber, 3.5 caster, 1/16" total toe in (keeps rear tire temps down). Even with these numbers on the Teins I'm experiencing 20* higher outside tire temps and maxed on camber. I rarely drive this car on the street anymore (maybe because it was so hot this summer) so I don't know what to tell you about tire wear. I think that if I were tracking a daily driver, I'd subscribe to the soft spring/more travel logic to take advantage of dynamic camber rather than my current stiff set-up with 700/400lb springs

I'm genuinely talking out of my *** though and I wish someone who knew heads from tails would make a recommendation rather than you listen to me.

Quote:
Originally Posted by webby459 View Post
I don't know about Shaikh's setup philosophy, but there are at least autocrossers going fast on his shock package.
Is this an auto-x thread or a manly roadrace thread?

loaded up at 1g getting off the brake in steady state cornering:

Slammed in the front and I still need to move weight to the rear.

Here's a pic of the car higher and softer to grab some of that "dynamic camber":

You can visibly see very little camber in the rear, and heinous temp range to boot.

Last edited by hustler; 09-10-2010 at 12:50 PM.
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