Maybe you shouldn't put your focus on comparing an expensive machine and the DIY method, but instead focus on the possibility to easily "check" your car setup as often as you like.
I don't say that the DIY method is the best, but it gives you an easy way to check your car whenever you have made a change on your car or if anything has happened to your car (hitting a sidewalk with the front tire for exampel)

When I changed all my bushings and shocks on my car I had a setup that was out of this world, but with the laser units I was able to make the car "drivable".
I was going to make a real machine alignment this autumn, but the machine didn't work on my car since it was too low. I will make a new attempt this spring and right after the real measurement I will drive the car back to my garage and use the laser units to see what kind of numbers I get from them.

Don't mean to hijack the thread, but it was corner balanced at the time of the suspension overhaul.

Not sure of the numbers, or weights.

Thanks guys!

I have.... in a matter of speaking.

We have a few cars that we do track prep for. Final prep is usually corner weight checks and alignments. The corner weights and alignment specs for the cars are logged and brought to the track.

During the test and tune sessions, driver comments and tire temp data are noted.. and alignment adjustments are made using toe plates, and Smart Camber tools. the adjustments are noted ( toe plates and the Smart tool are similar to "string lasers" method). This procedure is repeated until the driver is happy and tire wear/temps are good.

All changes are recorded.

Fast forward to prep for the next race.. the car is put on the alignment rack and the alignment settings are compared to what we thought we did according to our notes.

Generally our changes at the track are favorably displayed on our alignment rack. Meaning.. if we thought we reduced camber 1/2 deg the reading on the alignment rack confirms this.. Unless of course in the heat of the moment we made changes and didn't record them. or the car went agricultural for a bit

One thing someone doing DIY alignments should strive for is is a car that handles safely and predictably. Achieving that is well withing the realm of a savvy DIY'er with strings lasers or toe boards and levels.

If the car handles strangely and the tires show any odd wear.. recheck the settings, adjust as needed.

Anecdote:

I remember going to some IMSA races at Lime Rock, Watkins Glen, etc in the mid '80s when Holbery/Lowenbrau 956/962s ,the Jaguar Group 44s, Nissan, Aston Martin and even Mazda were doing battle..

It was common to see a car being aligned using strings (piano wire) set up on turntables that were leveled using linoleum tile, and seeing those meaty slicks balanced with a bubble level.

back to retirement/lurking

I shot this last year at the Glen HSR race.

http://forums.pelicanparts.com/uploa...1171504545.jpg

Tim L:

Great idea!! Following someone else's idea, I tried something like this. It involved shooting the laser attached parallel to the rim to the garage floor behind and in front for a set distance, marking the points, and measuring across under the car. He had this down pat, I gather. I never did - my floor is rough so I had to put tape down to make the marks, etc. Plus, following the other guy's lead I made a sort of three legged standoff holder, but didn't make things cleverly enough so I could bungee it to the rims. His system had merit, but your system sounds a lot simpler. Especially if, like me, you like to run zero toe. No math with that.

Normal steering geometry guarantees that when you turn the front wheels, one will turn farther than the other. One virtue of the string method is that you can pretty much insure that the wheels are pointing straight ahead when you measure - do a preliminary measurement and then set them so they are equal for the final measurement. Maybe getting the steering wheel straight, or eyeballing the wheels, gets you close enough anyway.

C2:

As to cosines and such, I found that if I taped a bubble level (the kind you hang on a string does the trick) to a chunk of old steel tape, I could get it pretty level without much difficulty and avoid this problem. I commend that to anyone using lasers or strings and measuring to rims.

I suppose I could attach one of these to a dial or digital caliper (a vernier would be a pain) as well, but it hadn’t occurred to me to try to get readings in the thousandths of an inch. Shoot, I bought depth mikes for cam chain wheel parallelism measurements - I could use those. But my instincts tell me that a millimeter rule ought to get things close enough. Haven’t done the math on that one, though. Bet you have.

Randy and others:

On the question of tire or other shop professional alignment rigs and our DIY futzing, in general I see no reason that the methods used should not produce equally accurate results. IF - things are set up right - the floor/pavement is, if not exactly level, at least all in one plane. If you don't use turn plates (and what home brew guy is going to have those), you roll the car around between attempts. I think it is probably easier for us to make mistakes than a pro, and especially than a pro with a machine.

If the Hunter and other machines use, basically, a laser distance measuring system (glorified toe plate but mounted on the rim), then they ought not to be much better than strings. But I think they work by measuring where a beam shot from one side lands on a receiver on the other side, the beam being perpendicular and the plate being parallel to the rim. Or there is only a mirror on one side, and the beam comes back and the difference is measured there. Dunlop optical systems maybe worked this way without the lasers and electronic readouts? That should have an inherent resolution better than strings I’d suspect, since you have about a wheelbase or 2xwheelbase for the radius in your equation instead of 15-18". Something like this is going on, since many of us have trouble getting an alignment shop to do our cars because they are so low these things can’t see each other.

I do wonder how stringing (properly done) compares with toe plates. By toe plate I mean those stiff flat aluminum sheets with a slot or two cut in each end. Stand the plate up against a tire on each side, run a tape measure through each slot (or move from slot to slot), and compare readings = total toe. Looks to be a two person job, but about the fastest going, so great for the track. If the sidewalls are irregular or bulgy or something, things will be off. So I wonder how well it usually compares.

For camber I sure like my digital level. Let's say I determine I want to reduce camber by X on one side. Jack up the car on that side, pull a rim, and loosen things just enough. Measure the camber (doesn't matter what it is at full droop). Adjust watching the readings change until you have changed it by X. Tighten up, put rim back on, lower away, and recheck. There might be geometric differences such that a half degree change at full droop is not quite half a degree at normal ride height, but my suspicion is that it has to be small.

I don’t have Tim T’s extensive race prep/support experience, but I know my DIY methods, even with less than perfect working surfaces and my tendency to call close enough good enough, do get my own cars to where they handle as I expect and have the tires wear reasonably (with lots of camber for the track tires, you can’t expect even wear on the street, seems to me).

Dontcha love those fishing reels in Todd’s #94 picture? But unless those guys have a centerline or other reference mark for their aluminum tubes, they have some of the setup hassles of the jack stand method (at least they know they have a parallelogram at a minimum, if not a rectangle).

I think guys with Smart Strings have some of that - I saw one used at a track and there was a fair amount of time spent measuring out from hubs, adjusting, remeasuring, etc. to get it set up. After that, piece of cake. And you can move the car.

Walt

Walt that was point of my whole post.. is that DIY alignments can be "machine" accurate

We start the car out with "laser sharp" alignments

change the settings

then in the shop note the setting for the next time out

Walt

I like the target at the same height as the laser and hub centers. If you shoot down to the garage floor the camber of the wheel comes into play.

A note on accuracy: with the laser on the wheel and shooting in front and in back of the car that’s about 20 feet in my garage. Trig tells me at that distance 1/4 inch = .06 degrees or 3.6 minutes (measuring 1/8" is easy enough)

i confirm alignment with temp probe.

Tim L - would the camber effects offset eachother for measuring toe with the spot on the floor method?

I think this guy had thought things through. He even measured camber this way - shot a spot on the floor at the contact patch area, then shot another spot on his ceiling. Dropped a plumb bob to measure difference, did the math, etc.

I like your same level system better.

Walt

Here is good link

http://home.comcast.net/~jkrane/suspension_university/susp401.html

I don't trust the "pro shops" in my area. They are in it for the money, and rush though the procedure on their expensive machines.

I take my car to a porsche specialist that works out of his garage. He uses simple tools but takes the time (4-6 hours) to do it correctly.

I thought WOW this is a great idea and I was playing with this last night.

I cut out a piece of plywood to put the level on and apply it the wheels (get the beam out beyond the fenders). Something was not working. The toe in was way off.

After thinking about it for a while I wondered if the laser came out of my $3 harbor freight level parallel to the base. I set a piece of I beam I have on the floor (parallel edges) and placed the plywood against the web and made a mark on the wall 10 feet away. I then flipped it to the other side of the I beam and made another mark on the wall. The distance between the two should have been the thickness of the I beam web + 2 * the plywood fixture + 2 * the height of the laser above the base. It was 2 inches off. I started sanding but now I don't have a square surface.

I think I'll go buy some aluminum and build an adjustable fixture.

edit: doing some geometry I am trying to adjust 100ths of inches. Maybe I'll make a calibration fixture, measure the error, and use the error in a spreadsheet.

a small tripod head could be used as an adjustable fixture

Has anyone tried this laser?

Obviously, for this method to work the laser needs to put out a plane of light not just a spot.

IMHO this laser idea is quite brilliant.

The $20k alignment machine vs. a string alignment issue always cracks me up a bit.

My 68 yr. old very tech freindly dad helped me build our pool a couple of years ago. Because I didn't want the water 2" from the coping on one end and 4" on the other, I used a water level (garden hose and 2 clear tubes at the ends). I didn't trust my 25 Euro laser's bubble level over a distance of 40'. After we had our measurements, my dad got the laser level out and remeasured "just to be sure". :rolleyes:

This is my problem with the inexpensive lasers, tho. You're relying on rather innacurate bubble levels to level the light beam - the weak link in this system. Compare the bubble levels in a good carpenter's level to a cheapo and you'll immediately see the difference. Unless this is taken car of, I'd put more faith in lower tech strings. That being said, I really like the vertical laser lines idea.

As far as accuracy goes, you don't need 100th's if you're measuring along the wheelbase of the car - tenth's is fine so multiplying the wheelbase with smoke and mirrors is not really an advantage.

Very nice work.
I think the laser is tons easier than the string.
You can do the same exact thing to square it. make sure distance of both rear wheels to laser are the same. and do the same for the front. This is how the string works.
Is this spread sheet only for 911 or can it be used for everything? (Mercedes, etc...)
Can you please share that excel sheet for calculating the camber?

Thansk

Bro this thread is 15 years old the sheet is in Swedish.

Just google "vehicle alignment spreadsheet template"

It is funny that this thread is so old.
and most DIY are still using the string approach.
I am new to this and always thought there should be something easier than the string..

There is, and it's easier than using a laser. For toe settings, just use your eyeballs to sight down the front wheel to the rear, and vice versa.

Depending on your car the rear and front tracks are wider or narrower, so account for that delta. In my case (1973 with the same 16x7 wheels on both ends) the track difference is 0.9". After I center the front wheels, I sight from the rear tires to the front. I aim to get the sight line to hit the front tires 3/4" inside the edge of the tire. That gives me a slight bit (20' or so) of rear toe in, as per the specs. Same thing for front to back, except I shoot for the sight line to fall 1-1/4" outside the rear tires, to account for the difference in track plus a little toe in. Then I push the car forward 1/2 wheel rotation and check again, to make sure the wheel isn't bent.

For camber, use a digital protractor held up against the side of the wheel, and check both the front of each wheel and the back of each wheel. They should read the same, but if they are slightly different, average the readings.

Done.

Once you get the hang of this, it's very easy to eyeball the toe alignment anytime you are down on the ground around the car, and of course the digital protractor is dirt simple to use too. The big advantage of using the full wheelbase to check the toe alignment, whether it's using the strings, laser, or eyeball, is that you have an 89" long base line for angle measurement. I believe this is substantially more accurate than the pro alignment racks can achieve using a much shorter base line. In metrology, there's a term for this decrease in accuracy with decrease in critical dimensions, it's call "geometric dilution of precision, " or GDOP.