Adjusting ride height is a pain
09-10-2010, 11:45 AM
#21
Tour de Franzia
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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.
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09-10-2010, 02:38 PM
#25
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.
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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09-10-2010, 02:44 PM
#26
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.
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.
What to you recommend for an alignment with fm springs?
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09-11-2010, 11:21 AM
#31
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. "
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 11:44 AM.
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09-11-2010, 11:51 AM
#33
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.
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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09-11-2010, 10:21 PM
#34
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Join Date: Dec 2004
Location: Brisbane, Australia
Posts: 1,278
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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.
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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09-11-2010, 10:38 PM
#36
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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09-15-2010, 11:18 AM
#37
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.
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