How does adjusting ride height affect toe?
 

So, I know lowering tends to increase negative camber, but I'm a bit confused about how toe is affected. For example, if I lowered my coilovers 1/4 inch, would it cause the wheels to toe in or toe out? I always do alignments after making changes, but I'm just curious how it works.

When I lowered mine 1" with springs, the front toe went out. Inside of tires started to show the wear eventually.

What about the rear toe?

Out of spec. Both the front and rear will toe in under compression, I'm guessing the front will change less than the rear. I have yet to see anyone publish camber and toe curves.

I'm pretty sure that when you lower it, the car toes in

Edit: in the rear for sure

I would suggest reading this if you want to know what the suspension is doing under loads and what lowering it would do. Very informative MotoIQ post.

Thanks for the link! This makes me want to install a Whiteline roll center kit even more. Only problem is that it would knock me out of STX for AutoX. :(

When ever you change one thing it will affect others. That's a given for suspension. When you lower your car, you are affecting other parts of the suspension, i.e. Toe, camber, and roll centers. This is why is crucial to get alignment when changing anyone of them. Unless you're ok with spending more on tires and have worse handling. :)
However in saying that, apparently if you lower the car 15 mm (aka STi lowering springs) it's the optimum ride height for handling.

What about camber in the front, how does it affect toe?

Let's say I have e.g. -2 degs set and when I go to the track, I increase to e.g. -2.5 degs. How much (approx) and in which direction would it change my toe?

Also, if I mark up the -2 degs on my camber plates, would it be possible to reset it accurately to -2 degs? And would the toe subsequently come back to it's originally aligned value?

Changing the camber by that little amount I think would have a negligible effect on toe. We are talking maybe an increase of 1/10th of a degree of toe in, most likely less.

I am not an expert in suspensions, but I'm willing to share what I've learned from working on my car...

I installed Tein Street Flex coilovers front and rear on my car, and lowered it just under an inch front and rear. I saw no noticeable effect on toe or camber on either the front or rear. I'm not saying the toe wasn't changed, i'm just saying it wasn't noticeable to the eye if it was. When I adjusted the fronts for camber, again, I saw no noticeable change in toe. To be able to adjust camber in the rear, I installed a set of Megan lower control arms. When I adjusted them to get the camber I wanted, I saw a very noticeable effect on toe - the wheels toed in. A lot. I had managed to 'eye ball' a camber setting of -2 degrees on the fronts, and -3 degrees on the rears, +/- 0.5 degrees, just by using a tape measure and making lots of careful measurements. The drive to the alignment shop was 'interesting' to say the least, with the rear wanting to move around a lot in the straights, but entering corners was great!

I watched the tech make the initial measurements, and asked him to tell me how close I managed to get everything. The front toe was barely out. The rear toe was waaaay out. Don't remember the exact number, but it took a while to get it back in line. Know this - as he adjusted the toe rod to get it back into spec, it was affecting the camber. So he was going back and forth between them to get both 'in spec'. 'In spec' in my case being the camber I desired, and the factory toe spec.

Right now, my camber settings are -2 degrees front and -3 degrees rear. From what I saw, and from what I gleaned from my conversation with the tech, a change in the rear camber of +/-1 degree would definitely require a toe adjustment. You could probably get by with 0.5 degrees of camber adjustment in the rear if it's just a temp thing for an autox day, and you're going to return it to it's previous setting for the road. But I would make sure I had some method in place that would allow me to make those adjustments repeatable, reliably. I don't know what kind of rear suspension setup you're using, but mine doesn't have camber plates with markings that I can use as a reference the way my fronts do. I suppose very careful, accurate measurements of the length of the LCAs and toe rods could be used...

Again. I'm no expert. I'm just sharing the limited knowledge I have from working on my car and talking to folks much smarter than me on the subject.

1/10th of a degree is a LOT. Enough to make the car change lanes within ~100 feet.

When I had mine on the alignment rack, I noticed that adjusting the camber via cam bolt had no effect on toe. The top plate, though, would have an effect.

I lowered my Tarmac 2's by 2 full turns today in the rear. It appears the rear wheels now have just a little bit of toe in now. Before I lowered them the were zeroed out. When I get my next alignment done before AutoX starts I'll see how much it changed.

1/10th(0.1) a degree is not much when its equal on both sides in the front. You wont be tracking enough either side to notice. In fact it would help the car to be stable with toe in on the front where the camber plates the OP was asking about are. Adjusting the camber by .5 in the front ONLY will not cause what you are claiming.

Rear toe in is a different thing yes 1/10th would be a noticeable change in the rear. It could cause the rear to be very unstable at higher speeds. Changing camber with out adjusting toe is not advised. The OP was not asking about rear camber adjustments as we don't have an option of camber plates in the rear.