Well, it has been a while since I last posted! I noticed that afew weekends ago in a autoX I was running in, my Miata was understeering a lot. The front tires would just push under tight turns such as a hairpin, even at more than decent entry speeds. I have a suspiction that it is my OEM end links. That is the only part of the suspension that I have not got to yet. Every other part is a SM type setup with 450/350 springs. Could the understeer be caused by the OEM end links? Both sway bars are parallel with the ground, BTW.
What bars are you running?
http://www.fatcatmotorsports.com/FRC_1_6NA/FCM_MSDS_1_6NA.htm
use this and tell us what your FRC is, if its close to 60 this will explain your understeer
Is this a change in behavior?
Entering a hairpin at more than decent entry speeds sounds like a recipe for understeer to me...
I have the Eibach sway bars in the front and rear. By entering a hairpin with more than decent speed, I meant tjat I wasnt going in too fast. More than decent meaning acceptable speed. Sorry for the bad wording on that.
Jaynen wrote:
What bars are you running?
http://www.fatcatmotorsports.com/FRC_1_6NA/FCM_MSDS_1_6NA.htm
use this and tell us what your FRC is, if its close to 60 this will explain your understeer
The link wouldnt pull up for some reason
Ignore the calculator, how does the car behave in a steady-state sweeper?
I can't say I've ever been able to blame understeer on end links. But there's always something to learn.
In a steady state sweeper, it handles just fine. Doesn't feel off balanced or anything. The Eibach sway bars are set at a "Medium" setting for both bars as the OEM endlinks wouldn't reach any of the other holes.
The nut behind the wheel might be loose; did you check that? 
The first turn of the autoX course was a steady left sweeper and I could take it easily at full throttle after a few runs. Had plenty of room to get up to 35-40 mph. Car had no issues with understeer through that turn.
FSP_ZX2 wrote:
The nut behind the wheel might be loose; did you check that?
That loose nut had settled in and was being patient. Hahaha!
ransom wrote:
Is this a change in behavior?
^^^ This is the important question. Is it doing something different from usual? Have other drivers driven the car and had the same issue? Have you driven other well-set-up cars and not had the issue?
My gut reaction is that it is most likely your technique, but possibly alignment settings.
What speeds is this occurring at? Auto-X speed? Track speed (e.g. final turn at Infineon)? Different speeds will likely prefer different alignment settings, and what may be quick at an auto-x could be squirelly on a full track or even the freeway.
If it took you several runs to get comfortable pushing hard through a steady state sweeper, that points to you still building skill. I think the most likely scenario is that you just have work to do on proper trail-braking technique to maximize front traction, or possibly are just cutting the wheel in too abruptly (which goes into the first one).
Any idea what your caster numbers are? Caster will increase camber as you turn the wheel, so more caster might help in tighter turns.
I nearly doubled the caster on my ZX2SR and really improved the handling
Nice thing with caster is that improves camber on both wheels. Negative on the outside, positive on the inside.
If you are running the 24mm eibach front with the 15mm eibach rear and 450/300lb springs your FRC is actually very low at 47.9% which should actually mean your car will tend to oversteer. My guess is it is an alignment issue or a driver issue (hard braking and turning at the same time easily causes understeer for me)
Currently 375F 250R with a racing beat front bar and stock or no rear bar (depending on surface).
Stock endlinks on my car.
Handles great, but upping the rates to 550F 375R
check alignment.
Are you trailbraking? remember that miatas are massively front biased. (at least non-abs like mine) and this would cause plow initiation.
Caster is 4.5 with zero toe front and back with 1.7 front and 2.3 camber rear. I will look into trail braking for sjre as I have not really looked into it much. Suspension stuff is all still a vast unknown but I have started reading up on it. My Miata is non-abs. I make sure to finish braking before turning always.
In reply to miataman86:
Do you have issues with any other types of turns? Slaloms?
Does it plow immediately? Or accept some steering then run out of front grip?
Do you have any in car video that shows your hands?
In slaloms, I can get zip right through it and keep nice and tidy in the cones. Car feels planted and solid through it. I havent yet got to the in car video yet. It is on my list of things. In a really tight autoX hairpin, it will turn in upon me rolling the steering wheel (not throwing the car into it), but then plow forward and with a light tap of the brakes, gets back in track with turning like a champ. The understeer seems to come in between the initial turn in and apex. For those wondering, yes I am taking the out-in-out line on a harpin to stay on the driving line
No problems with sweepers, slaloms, long corners, or cut backs
This Tuesday, I am going to a shop that a friend of mine runs to have the AC and PS removed. I have a Sparco seat with a PCI seat mount and the interior has been almost stripped of the carpet except for the bulkhead behind the seats. I have a Hard Dog M1 Hardcore roll bar and the radio and speakers have been removed as well. Thought I I would mention those weight reductions to see if rhere could be a change in the weight balance of the car. I also take out the spare tire and jack out of the trunk before I start any runs. Would changing the alignment of any sort (camber and caster) help the handling any once the PS is depowered?
You might not like as much caster once it's depowered. That makes the steering heavier.
What would be a good figure to have for caster once the rack is depowered?
1.7 front and 2.3 camber rear
There's your problem. You need more camber up front.
I was thinking more Camber up front would help the issue of any understeer occuring as well. I do drive the Miata daily and I dont want to be shelling out money for new tires every so often. What would be a good figure to run camber wise so that I have as much grip for autoX but still be sensable for DD?
I daily drove mine with -2.3 front -2.0 back without any strange wear. I ran more than a full season of autocross (including 2 schools and a hillclimb) and daily driving out of a set of 195 Toyo R1Rs. Sold them with the car and they still had half a season left on them.
