Rear Alignment Questions

#21

It’s a 26 or 27 mm adjuster. None of the thin wrenches I had on hand were able to fit. I was able to move it somewhat using the needle nose vice grips, but couldn’t get a good enough grip/angle on it to continue. I should be able to adjust it better once the tool gets here.

I thought about asking the shop for a re-do, but it’s such a pain in the ass to go get the trailer, load it up, drop off the car, etc. I had to take a day off of work for it the first time. If I can get them to do it on Thursday on my way to VIR, it might work, but I can’t take the additional time off right now.

Besides, I need to learn how to do this anyway.

#22

[quote=“juliancates” post=64302]It’s a 26 or 27 mm adjuster. None of the thin wrenches I had on hand were able to fit. I was able to move it somewhat using the needle nose vice grips, but couldn’t get a good enough grip/angle on it to continue. I should be able to adjust it better once the tool gets here.

I thought about asking the shop for a re-do, but it’s such a pain in the ass to go get the trailer, load it up, drop off the car, etc. I had to take a day off of work for it the first time. If I can get them to do it on Thursday on my way to VIR, it might work, but I can’t take the additional time off right now.

Besides, I need to learn how to do this anyway.[/quote]

The shop has a wrench that will fit? Back when I had the eccentric rtabs my shop had to use my wrench. Don’t hesitate to take a standard wrench and grind it thin. Over time you’ll accumulate lots of “special tools” that you had to make to do a certain task.

#23

Fix the calibration, come on man, use your imagination. Identify a perfectly horiz surface, maybe the shop’s alignment rig, and sit your digital level on it. Then wrap tape or something around one end until it reads level.

Alternately, tap the side of the digital level in 2 spots right where screws will hit a 15" rim in the best place. With some locktite on the screws, sit the device on the perfectly horiz location and turn the screws until it reads 0 deg.

The beauty of the latter is you will be set up to measure camber at the rim rather than the tire. Measuring camber by setting a level across the tire has obvious problems because the tire bulges at the bottom.

#24

I use this “toe stick” from ICM which is set up for measuring toe with a string system directly on a 15" rim:

http://www.ironcanyonmotorsports.com/tools-and-setup-equipment/icm-spec-miata-toestick.html

One nice thing about it is that there’s a spot in the middle for attaching an angle gauge, such as this one:

http://www.ironcanyonmotorsports.com/tools-and-setup-equipment/digital-angle-gauge.html

So you can use it measure camber right on the rim, in addition to toe.

The angle gauge will work with the toe stick, or with the wheel plates:

http://www.ironcanyonmotorsports.com/tools-and-setup-equipment/icm-wheel-plates-4x100.html

I haven’t tried the wheel plates with the SE30 yet to verify that they fit. They use standoffs which attach to two of the wheel studs per wheel. Might be a good platform for the laser setup you describe, Ranger.

#25

That Iron Mountain outfit spoke highly of this http://www.amazon.com/gp/product/B001PTGBRQ/ref=ox_ya_os_product
So I bought one. That will make it easy enough to make a 2nd camber gauge for when I want a 2nd opinion.

Re. strings vs. laser. One of the reasons I like my laser idea better is the magnification of error. I don’t know that I could tell 1mm from 2mm using strings, but I can certainly tell 6mm from 12mm. And that’s what you get when the error is x6. The laser method allows really precise adjustments.

#26

I agree that you can get a magnification of alignment changes with a laser, but how do you find the the zero point? I could see how this could work if you had a precision target that mounts to the front wheel hub and a precision mount for the laser on the rear wheel. Even then you’d probably have to zero the rig somehow. It would also seem to matter if the front wheel wasn’t set precisely for straight ahead.

If the frame of the car is straight and suspension parts aren’t bent setting the strings is just a matter of getting them equidistant from the centers of the front and rear hubs. And the cross check is that the strings on both sides of the car will be parallel. If you use fishing line for the strings 1/32" is easy to read and 1/64" isn’t difficult as measured at the wheel rim.

#27

[quote=“Ranger” post=64304][quote=“turbo329is” post=64301]
I bought a cheap digital level to do my alignment and it was horribly inaccurate. You could buy 10 alignments for the price of a good one. I wouldn’t trust a spinning construction laser either. Maybe a pen laser that you verified to be straight attached to the rim somehow would work.
[/quote]
Fix the calibration, come on man, use your imagination. Identify a perfectly horiz surface, maybe the shop’s alignment rig, and sit your digital level on it. Then wrap tape or something around one end until it reads level.

Alternately, tap the side of the digital level in 2 spots right where screws will hit a 15" rim in the best place. With some locktite on the screws, sit the device on the perfectly horiz location and turn the screws until it reads 0 deg.

The beauty of the latter is you will be set up to measure camber at the rim rather than the tire. Measuring camber by setting a level across the tire has obvious problems because the tire bulges at the bottom.[/quote]

Sorry I meant precision not accuracy. Something that can’t be fixed.

#28

[quote=“jlevie” post=64309]I agree that you can get a magnification of alignment changes with a laser, but how do you find the the zero point? I could see how this could work if you had a precision target that mounts to the front wheel hub and a precision mount for the laser on the rear wheel. Even then you’d probably have to zero the rig somehow. It would also seem to matter if the front wheel wasn’t set precisely for straight ahead.

If the frame of the car is straight and suspension parts aren’t bent setting the strings is just a matter of getting them equidistant from the centers of the front and rear hubs. And the cross check is that the strings on both sides of the car will be parallel. If you use fishing line for the strings 1/32" is easy to read and 1/64" isn’t difficult as measured at the wheel rim.[/quote]

That’s the main concern with mounting something to the body.

The strings are poor man, but they work every time…unless you have bent suspension pieces. Then again, you should know when they are bent if you started with a straight car.

#29

[quote=“jlevie” post=64309]I agree that you can get a magnification of alignment changes with a laser, but how do you find the the zero point? I could see how this could work if you had a precision target that mounts to the front wheel hub and a precision mount for the laser on the rear wheel. Even then you’d probably have to zero the rig somehow. It would also seem to matter if the front wheel wasn’t set precisely for straight ahead.
[/quote]
Slap some masking tape on to the center of a front wheel and eyeball the front wheels being exactly straight. Even if the front wheels aren’t exactly straight, they will be pretty close. And since the front hubs don’t change position much the accuracy of the mark you make on the tape will be close enough. A thick felt pen used to make the mark will be the accuracy problem, not the position of the front wheels.

When a single mm of rear toe shows up as 6mm laser delta up front, if a person can’t get their rear toe set to an accuracy of 0.5mm, they’re blind.

#30

[quote=“Ranger” post=64314][quote=“jlevie” post=64309]I agree that you can get a magnification of alignment changes with a laser, but how do you find the the zero point? I could see how this could work if you had a precision target that mounts to the front wheel hub and a precision mount for the laser on the rear wheel. Even then you’d probably have to zero the rig somehow. It would also seem to matter if the front wheel wasn’t set precisely for straight ahead.
[/quote]
Slap some masking tape on to the center of a front wheel and eyeball the front wheels being exactly straight. Even if the front wheels aren’t exactly straight, they will be pretty close. And since the front hubs don’t change position much the accuracy of the mark you make on the tape will be close enough. A thick felt pen used to make the mark will be the accuracy problem, not the position of the front wheels.

When a single mm of rear toe shows up as 6mm laser delta up front, if a person can’t get their rear toe set to an accuracy of 0.5mm, they’re blind.[/quote]
Okay, but that means that your zero is relative to the front wheels and there is no cross check for a damage caused error in a wheel position. That may be a minor thing, but it is possible. With strings this usually becomes obvious. Once the strings are set up they’ll be parallel unless something has been damaged.

#31

I accept that, but ultimately, everything can be screwed up by damage. Or damaged by screwing it up. Damage is, ah, well, damaging.

#32

I accept that, but ultimately, everything can be screwed up by damage. Or damaged by screwing it up. Damage is, ah, well, damaging.[/quote]
I agree, but it is nice to have a way to tell that it has happened.

#33

Well, good news on the alignment front. I got the adjustment tool via overnight FedEx this afternoon. With a little WD-40 on the bushings to persuade movement and a little work with the cutting wheel on the tool to give it more clearance on the subframe, I was able to move the eccentric bushings around.

I set them to what should be max toe-in, and get 1/4" toe-in on one side and 3/16" toe-in on the other. I’ll have to go back and work on getting it closer to an ideal amount of toe-in, but the good news is that I know for a fact that I have the adjustment range to get it where I want it, and that I have the right tool to do the adjustments.

Sweet.

#34

EDIT: Not really.

Apparently I was high on brake cleaner fumes or something. I quickly realized that I was reading the toe stick completely backwards. I’m still toed out in the rear. It’s really hard to tell by looking at the eccentric which way it’s oriented. Really freaking hard. So by the end of my garage session I figured out that by carefully watching what the arm was doing I could infer where the eccentric was positioned. I set it up with the inner rtab oriented as far back as possible, and the outer rtab oriented as far forward as possible. That SHOULD toe me in.

Best I can get is 1/8" OUT on a side.

So…

My method, while repeatable and consistent, could be flawed. I’m using string, one side at a time. String is over jackstands right at the center of the rim height. I’m orienting the string so that it is the same distance from the center of each wheel. I’m measuring from the rim using the ICM toe stick when measuring toe.

Things that could possibly be distorting my findings:

  • I didn’t fill the tires to race pressures.
  • I don’t have my weight in the car.
  • I didn’t unhook the sway bar.

That said… could they really be making THAT big of a difference that I couldn’t even get close to zero toe?

I’m at a loss here. Tomorrow I find my other tape measure and use some borrowed toe plates for a second opinion.

#35

I’ve been down the same road as you… I had a rear subframe with eccentric bolts & weld in plates that were installed by the previous owner… I could never get the rear toe to go anywhere but out. In the end I had to source a new rear subframe, weld in new toe and camber correction plates http://e30tech.com/, remove the old one and re install the new one…

#36

Lesson Learned: Don’t do this crap at 2am.

Huge thanks to JTower for coming over and giving me a hand. We found out I had one of the bushings screwed up, and were able to get some more toe-in … err… less toe out. It’s down to about 3/16 total toe out now. Still not great, but much better than it was.

#37

Unfortunately, the solution is going to be to drop the subframe and have them cut out and then re-welded in. At least now you know in which direction they need to be moved! :wink:

#38

Potentially useful info. None of the “* I didn’t…” should matter. A year or two ago I experimented with how toe might change with suspension travel. I wanted to know if suspension compression added some toe-in, which some folks say is desirable. This is discussed in detail in some old thread but the bottom line is “no, toe doesn’t change with any reasonable amount of suspension travel.”

Note that my method of measure toe multiplies the delta by 6x so if there was the tiniest amount of toe change, I’d have seen it. IIRC my conclusion was something along the lines of…“there might be a little toe in added during significant compression but it’s so tiny that I can’t be sure.” My ability to resolve absolute toe is prob 1/3 of a mm, which might as well be zero.

In a somewhat related issue, yesterday I did a quick experiment to see if camber changed due to air pressure. I think that it’s common wisdom that camber does change if you add air, but I’d have to say that I’m not sure what the physics are behind that. I figure that if you measure camber on a flat surface, and then measure it again after moving the car on to a 5mm platform, there’s no reason to expect camber to change. And shouldn’t the 5mm platform replicate putting some more air in the tires?

All I can say for sure is that if you go from 24psi to 34psi, the difference in camber is too small for my device to measure.

#39

[quote=“Ranger” post=64489][quote=“juliancates” post=64382]

Things that could possibly be distorting my findings:

  • I didn’t fill the tires to race pressures.
  • I don’t have my weight in the car.
  • I didn’t unhook the sway bar.

That said… could they really be making THAT big of a difference that I couldn’t even get close to zero toe?
[/quote]
Potentially useful info. None of the “* I didn’t…” should matter. A year or two ago I experimented with how toe might change with suspension travel. I wanted to know if suspension compression added some toe-in, which some folks say is desirable. This is discussed in detail in some old thread but the bottom line is “no, toe doesn’t change with any reasonable amount of suspension travel.”

Note that my method of measure toe multiplies the delta by 6x so if there was the tiniest amount of toe change, I’d have seen it. IIRC my conclusion was something along the lines of…“there might be a little toe in added during significant compression but it’s so tiny that I can’t be sure.” My ability to resolve absolute toe is prob 1/3 of a mm, which might as well be zero.

In a somewhat related issue, yesterday I did a quick experiment to see if camber changed due to air pressure. I think that it’s common wisdom that camber does change if you add air, but I’d have to say that I’m not sure what the physics are behind that. I figure that if you measure camber on a flat surface, and then measure it again after moving the car on to a 5mm platform, there’s no reason to expect camber to change. And shouldn’t the 5mm platform replicate putting some more air in the tires?

All I can say for sure is that if you go from 24psi to 34psi, the difference in camber is too small for my device to measure.[/quote]

I can’t see the toe staying the same unless you have solid bushings and 0 bump steer. I don’t think these cars have this with the lowered suspension, but hey I haven’t measured it yet.

Typically, I’ll just take the measurements from tie rod to tie rod, estimate a center point and take measurements from there and input to a CAD model. Then you can pretty easily tell exactly how much the toe will move given a linear amount of jounce.

Couldn’t see tire pressure making much of a difference in static camber. The difference would be the increase in stiffness of the tire and resistance to the tire rolling under given the large amount of camber gain built into a strut type suspension.

Interesting experiment though.