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Discussion Starter #1
I've been collecting some data for the purpose of tuning suspension alignment on my car. The alignment I'm using now is -1.2 degrees camber front and rear as recommended by GWR, but I think there may be some room for improvement. I will be getting a new alignment done tomorrow and thought I'd share my approach on what specs I will go for next, and maybe get some input from those with experience.


Below is some data I collected from my track day at TMP Cayuga. It's a clockwise track so left side tires heat up more. I used a tyre pyrometer to measure inner, mid, and outer core temps across the tire tread. I used shapes on the tire tread as reference to ensure that I'm measuring the same position each time and for each tire. I also measured tire pressure. After a few sessions tuning my tire pressure, this is what I have:
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Note: temperature is in C and pressure is in psi

Since there are more right turns than left turns, I care more about the left side tires than the right side. From this data you can clearly see that the LF tire appear to camber more than LR tire. Not only that but I can see on my front tires that there is much more wear on the inside. This would make sense if the double wishbone front suspension cambers more than the multilink rear suspension does under compression. After all, factory alignment specs call for more static camber in the rear.
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I don't know how exactly the factory alignment specs are created, but I assume the manufacturer intend for the wheels to sit flat on the ground during cornering. Hence, I want to see if I can mimic the factory spec for my next alignment. My ride height is way below the lowest ride height for which factory specs are available (I have Progress springs with 1.3" drop), so I will have to extrapolate. By plotting factory alignment vs. ride height and getting a best fit curve, I arrive at the following specs:

Front camber: -0.92
Front caster: 8.67
Rear camber: -1.85
I will leave toe angles stock.
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These specs look very unconventional and I have a feeling it may not work out as I expected, but you'll never know unless you try. I will know by next track day (in few weeks maybe?) how the car will handle with these specs.
 

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Discussion Starter #2
Something just hit me. I've been doing it wrong. I shouldn't take measurements on the track because there are both left and right turns and that would skew the temperature readings. What I really needed was to test this on a skidpad, or in my case, an empty parking lot.

Just came back from said parking lot after jumping out of bed to do this. Here are my results:

Front:
Inner: 32.5, Mid: 38.0, Outer: 42.3

Rear:
Inner: 23.3, Mid: 28.3, Outer: 31.8

So looks like I actually need more camber for both front and rear.
 

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Do you used 245/40 tires?
 

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I’m currently negative 3 all around and need more . Tire psi also seems too high and you’re tires may be getting greasy . On a 40 tire we’re now starting 30psi cold mornings , and as it warms up ( 80 degrees ) 27-28 prior to going out so the temps never shoot up to even the high 30s . Here’s a cool video of one of the most talented racing alignment specialists in LA . And my front alignment example as an advanced set up that allows the car to rotate at higher speeds . My tire wear is almost perfect now but deff could use another half degree

 

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I saw some -1.1 and -1.5 replacement bushings for the UCA on Goodwin Racing. A little work involved but not too bad.
 

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Discussion Starter #7
Thanks for the input guys, alignment in 2 hours, I was ---> this close <--- to settling on some really messed up specs. Tire data from the track can be misleading and it doesn't help that there are websites out there telling you to equalize temperatures across the tread on a race track when in fact you need to do that on a skidpad. The stock alignment is pretty weird too, I guess the OEM wanted to build some serious understeer into the car so people don't spin out on a perfectly straight road (happens a lot where I live) :rolleyes:
 

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Discussion Starter #9
40PSI is a lot!
True. This was also a result of me being misled by the interwebs; I remember reading somewhere that you should increase pressure until mid and inner temps are the same, and that it's fine for outer temps to be lower. That's what I was aiming for, but now I know this approach is simply wrong. I found that the car had the best yaw authority when tire pressures are in the mid 30s warmed up, and that gradually fades away as pressures got higher.
 

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For autocross, which is a totally different animal, you dial in the camber to get the inside and outside shoulders of the tire as close to 5 degrees or less difference. then you adjust tire pressure from there to get the center where it needs to be....or to induce under or oversteer. I frequently end up with 28-29PSI up front and drop the rears to 25 or 26 to get it from stepping out so much under throttle. I'd start in the 29-31 range and see where that gets you.
 

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I have spent a lot of time testing tire pressures and tire temps. One benefit of racing on a .9 mile KART track with 13 turns is that it taxes all the tires harshly. One thing I learned is that nothing is exactly repeatable. I could be a whole second slower or faster with the exact same set up from a previous session depending on track temperature. Understeer was terrible under 50 F ambient and oversteer got worse over 100 F with 200 treadwear tires. There is no perfect set up. You cannot dial out all understeer and oversteer. You have to make compromises.

Best grip came at 30 PSI hot tire. I would not fill my tires back on the drive home and would measure them cold the next morning. They varied about .6 PSI between the four tires in the 26 PSI range when cooled back down.

I run the Flyin' Miata alignment specs. These specs are probably too agressive for a gently driven street car. The GWR specs would be better for that. But for the track and canyons they are very good. But it takes a couple of track sections to see the heat distribute across the tires evenly while making very small adjustments to air pressure.

I can usually dial in the correct air pressure by the end of the second session. Once I see the temps are even across the entire surface of the tire I know I need to switch to coilover and/or sway bar adjustments to correct the most severe problems. Like I said earlier, you have to make compromises. I prioritized the turns that let me carry the most speed and made adjustments for those turns. My -1.8 camber usually works for my 50-60 MPH corners but for @Spoolin32 a much more aggressive camber, like he has, is what is needed for the 100 mph corners. I wouldn't want to daily drive a -3 camber because you would just eat the inside of the tires up. At -1.8 I have perfectly even tire wear across all four tires.

And in case you are wondering how hot can a tire get on a KART track.

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Discussion Starter #12
I told my shop to max out camber and was surprised how much the stock suspension is capable of. Was going to test it out on the skidpad again but it started snowing!

Ideally I wanted slightly more camber up front than rear but the shop said they can't get down to 0.1 degree accuracy. Oh well, I guess a few tenths of a degree is not going to matter that much.
 

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I told my shop to max out camber and was surprised how much the stock suspension is capable of. Was going to test it out on the skidpad again but it started snowing!

Ideally I wanted slightly more camber up front than rear but the shop said they can't get down to 0.1 degree accuracy. Oh well, I guess a few tenths of a degree is not going to matter that much.

Have fun , excited to hear your impression. I don’t remember your entire set up outside the springs but should make more grip and rotate nicely . If you’re going to get heat into the tires few laps start them 28 / maybe 30 if it’s really cold and you won’t get enough lap time to get heat into them ( not sure if you’re just gonna play in the parking lot or hit a track . and see where the pressure goes.
 

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Discussion Starter #14
Have fun , excited to hear your impression. I don’t remember your entire set up outside the springs but should make more grip and rotate nicely . If you’re going to get heat into the tires few laps start them 28 / maybe 30 if it’s really cold and you won’t get enough lap time to get heat into them ( not sure if you’re just gonna play in the parking lot or hit a track . and see where the pressure goes.
Thanks. I intend to test it out on both the parking lot skidpad and the track, just need to wait for the ground to dry up and then for the track to open if they ever do.
 

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I told my shop to max out camber and was surprised how much the stock suspension is capable of. Was going to test it out on the skidpad again but it started snowing!

Ideally I wanted slightly more camber up front than rear but the shop said they can't get down to 0.1 degree accuracy. Oh well, I guess a few tenths of a degree is not going to matter that much.
How are you able to get that much camber on the stock setup??? Literally every person running C Street in an ND MX5 or Fiata is maxing out between -1.2 and -1.6.
 

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That makes sense. It was the "and was surprised how much the stock suspension is capable of. " in his post that threw me.
 

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Discussion Starter #19
Sorry by stock I meant stock suspension links. Even on stock springs if you maxed out your camber and then compress by 1.3" under hard cornering you should arrive at the same 2.6 degree camber that I have.
 

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I run just over -2 at all four corners on the street just fine.

My Volvo is running -3 in the front and -2 in the rear and I drive that in all conditions. It's toe that wears tires faster not camber.
 
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