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Old 09-10-2010, 12:45 PM   #21
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Quote:
Originally Posted by webby459 View Post
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.
Add a full degree to that camber all the way around and you're getting closer to even temps.
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Old 09-10-2010, 01:42 PM   #22
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Back to my DD problem. What does everyone think is a decent ride height that won't scrape the front of the car over every dip?

What are god aggressive DD alignment numbers that won't wear the tires funny?

12.5/12.75 seems good, but 12.25/12.5 is doable.
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Old 09-10-2010, 01:50 PM   #23
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Really should use the pinch weld height...I mean we're all running the same diameter tires, right? Within a couple tenths of an inch?

I hate trying to measure hub to fender lip.
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Old 09-10-2010, 01:59 PM   #24
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Quote:
Originally Posted by mgeoffriau View Post
Really should use the pinch weld height...I mean we're all running the same diameter tires, right? Within a couple tenths of an inch?

I hate trying to measure hub to fender lip.
Tough for those of us without fender metal left also.

Tire height and inflation will come into play though... so its only really good for own personal measurements. LCA angle would probably be more universal... but harder to measure.
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Old 09-10-2010, 03:38 PM   #25
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With extreme lowering the roll centers are lowered to the point where other tweaks become necessary to compensate (stiffer springs), the Miata is still faster. IOW, the losses bot actual and theoretical are more than offset by the gains in lower CG, ideal active camber, reduced pitch sensitivity, reduced caster change, etc.

Most of our track cars start at about 4" front, 4.25" rear without driver. The rear will drop a skosh on the scales with a driver in. We'll still tweak from there depending on the track and that includes running one side higher or lower on tracks like WSIR. For a street car that needs grounhd clearance, a good compromise is about 4.75" front, 5" rear to start. In the end, you have to start somewhere and adjust to suit your needs. The only constant is that .25" or so of front to rear rake. Miatas seem to like their roll center axis in the similar location as stock.
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Old 09-10-2010, 03:44 PM   #26
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Quote:
Originally Posted by emilio700 View Post
With extreme lowering the roll centers are lowered to the point where other tweaks become necessary to compensate (stiffer springs), the Miata is still faster. IOW, the losses bot actual and theoretical are more than offset by the gains in lower CG, ideal active camber, reduced pitch sensitivity, reduced caster change, etc.

Most of our track cars start at about 4" front, 4.25" rear without driver. The rear will drop a skosh on the scales with a driver in. We'll still tweak from there depending on the track and that includes running one side higher or lower on tracks like WSIR. For a street car that needs grounhd clearance, a good compromise is about 4.75" front, 5" rear to start. In the end, you have to start somewhere and adjust to suit your needs. The only constant is that .25" or so of front to rear rake. Miatas seem to like their roll center axis in the similar location as stock.
Alright, I'll start measuring at the pinch welds. I'll see how close I am to 4.75/5.0.

What to you recommend for an alignment with fm springs?
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Old 09-10-2010, 03:59 PM   #27
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Thanks for chiming in, Dad. You've made my car a lot faster over the last year.
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Old 09-10-2010, 05:11 PM   #28
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Can someone explain where the pinch welds are to this old fart?
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Old 09-10-2010, 05:34 PM   #29
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Where you put the OEM scissor jack.
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Old 09-10-2010, 11:16 PM   #30
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Quote:
Originally Posted by djp0623 View Post
Alright, I'll start measuring at the pinch welds. I'll see how close I am to 4.75/5.0.

What to you recommend for an alignment with fm springs?
Race alignment
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Old 09-11-2010, 12:21 PM   #31
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After the car has had two days to settle without me messing with the suspension. My pinch weld measurements are 4.875"F/5.125"R

Unless this seems overwhelmingly excessive I am going to leave it alone. I retain my .25" rake and Emilio's 4.75" alignment numbers should work for this.

Here is the recommendation from FCM for those that are interested.

"11.5" is too low on FM springs unless you live on glass-smooth roads.
12.5" f / 12.75" rear would be my recommendation for an optimal ride
height if you want decent ride and good handling. The alignment depends
upon what bars you have. If you have stock stock sways, I would remove
the rear bar and use caster 4.5 deg camber -1.5 front, -1.5 rear, zero
toe front and rear. If you have a larger front sway, then same values
but use -1.5 front camber and -1.2 rear. "

Last edited by miatauser884; 09-11-2010 at 12:44 PM.
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Old 09-11-2010, 12:44 PM   #32
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Pictures? Watch out for uneven surfaces, they'll obviously affect ride height, and have fooled me a time or two before.
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Old 09-11-2010, 12:51 PM   #33
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I will have to watch for that as my garage is probably not the most level spot to check. I like the pinch weld measurements because it became obvious how much variation you can get from the fender lip. For example. My front fender lips are bent downward do to tire rub. I really don't know what the fender looked like when new,so there could be a lot of variation from one car to the next.

I feel pretty good about my measurements since I was getting pretty consistent measurements. I'm going to remeasure again on a different surface to double check.
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Old 09-11-2010, 11:21 PM   #34
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I just measured mine and it's 5" both front and rear with 215/45R16 tyres. Tein SS with MSM front and rear sways. What kind of difference should I expect if I drop the front by 0.25 inches?

I still have the stock sways in storage so I could try the stock 99 rear one, but to be honest the car feels really good at the moment.
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Old 09-11-2010, 11:25 PM   #35
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This is a great thread. On MSM springs and bilsteins I am at 12.75 in the rear and 12.5 in the front. I think the nb tophats lowered it down.
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Old 09-11-2010, 11:38 PM   #36
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Quote:
Originally Posted by chicksdigmiatas View Post
This is a great thread. On MSM springs and bilsteins I am at 12.75 in the rear and 12.5 in the front. I think the NB tophats lowered it down.
I think I had a combination of things I didn't take into account for calculating ride height when I changed suspension components. 1) Different shocks have different spring perch locations. 2) NB tophats.

Please measure your ride height at pinch welds. I'd like to see your values. There really is too much variation with the center wheel to fender lip method.

On a DD, I really can't see the .25" rake playing a huge role. Everyone pushes their car different, so maybe it will make a difference to some people. During my attempt at finding the optimum balance between front and rear. I did end up with a 1" rake at one point. It was noticeable, but not obnoxious. I think it is more for aesthetics in a DD car. Check the link provided by Emilio. Good stuff.
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Old 09-15-2010, 12:18 PM   #37
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Quote:
Originally Posted by emilio700 View Post
With extreme lowering the roll centers are lowered to the point where other tweaks become necessary to compensate (stiffer springs), the Miata is still faster. IOW, the losses bot actual and theoretical are more than offset by the gains in lower CG, ideal active camber, reduced pitch sensitivity, reduced caster change, etc.
Thanks for the info, Emilio. I'm hesitant to buy into the stiffer spring kool-aid (on 550/350 now), but I'm rolling too much and the body takes too long to take a set in transition. But, there must be a reason the fast guys are all on 750/475ish splits or more. I'll probably be calling you soon to pick your brain a little more. I just gotta make some changes .
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Old 09-15-2010, 12:58 PM   #38
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Wirelessly posted

I'd rather drive on stiff springs rather than door handle scrapers.
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