Easy laser alignment method

[logician]

OK, so we know that we could align a 911 if we were stuck on a desert island with only some fishing line and a thumb tack. But there are other ways. So here's a different way that I find convenient for 911's with Fuchs wheels at the track. It uses $10 laser pointers and plexiglass mirrors instead of string.

Here's what you do to measure camber and toe at the front:

1) Set up two laser pointers are mounted on jack stands and at the height of the wheel caps and pointed at each other. The lasers are spaced 170" appart -- enough to drive a 911 between them and then some. Accuracy of the setup is critical, so you want to make sure that each beam hits the other laser to within 1/8" -- doable.



2) Remove the center caps from your Fuchs, and tape mirrors to the center hole. Make sure that the mirror lays flat on the hole. The center hole in Fuchs is exceedingly accurate, and a very good reference for the plane of the wheel.

3) Roll you car forward until the laser beams hit the mirrors.



4) Finally, measure how far the laser beam is reflected relative to the laser source. If the camber and toe were exactly zero, then the beam would be reflected directly back at the laser light source. But negative camber will tilt the mirror up, and deflect the beam upwards. Similarly, any toe-in would reflect the beam forward of the laser. By measuring the deflection and applying a little bit of trig, you can determine the camber and toe angles.



I set the lasers 57" from the wheel hub. At that distance, 2" of deflection is equal to 1 degree -- a convenient calibration. So stock toe-in of 15' results in a 1/2" deflection, which is an easily measurable amount. The accuracy of the mirror on the hub appears to be +/- 3' of arc, so you should be able to get +/- 6' of accuracy on the total front toe. The stock specification requires an accuracy of +/- 5'.

Once you set up the lasers, it's easy to do multiple cars with little additional effort. Also, it's easy to do the same car multiple times, which is pretty handy if you want to drive the car around to settle the suspension and then recheck. I found that you don't have to remove the mirrors if you only drive around the paddoc.

Cheap laser pointers can be had for $10-20. Try to find ones with 1/8" spot size at distance of 5'. It is convenient to have the lasers on constantly, so I tape down the on/off switch to the on position. Note that the lasers won't point exactly straight. So you can rotate the laser to raise or lower the angle of the beam to make it parallel to the ground.

I found that mirrored 1/4" plexiglass works really well for the mirrors, as it is cheap, flat, and rugged. Cheezy Team Mechanix jack stands are the perfect height for setting up the lasers. Jack stands are also good because they are heavy, so the laser less likely to get moved out of alignment. I've also seen that Harbor freight sells pretty cheap laser pointers already mounted on tripods. I haven't tried these, but they might be the best choice for laser+mount.

Some things to watch out for. First make sure that the surface that you are working on is flat. It doesn't have to be prefectly level, but it must be planar. Another point is that there will be some slop in the front suspension that will result in different toe whether the car is rolled forward or backward into position. So you should be consistant about which way you roll the car. Finally, Bilstein shocks don't settle at repeatable positions, so you may want to push down on the front and back of the car to consistantly set the suspension to it's lowest position.

Regarding measuring camber, I actually prefer to use a digital level placed against the center cap hole, as that's much easier and very accurate. The plumb line method works also.

Exercise for the reader: you can also use this setup to measure caster...

-Juan

[Chuck Moreland]

Clever.

But how do you know the fuch's cap hole is flat? That is critical.

[island911]

Roll the wheel.

[dickster]

mmmm, interesting.

your lasers dont 57" from the hubs - or is that just for the pics??

and the floor doesnt have to be level?

[logician]

Hi Chuck,

> But how do you know the fuch's cap hole is flat? That is critical.

That's a good question. I jacked up the front end, and rotated the wheel with the laser pointed at it. The reflected beam traced a circle. By measuring the size of that circle, I detetermined that the beam was deflected by only +/- 3'.

It's good to do this check, as I found one of my wheels had a raised scratch that caused the mirror not to sit flat. Fortunately, its pretty easy to know if there is a problem, as you will feel that the mirror rocks around the raised point.

-Juan

[logician]

Hi Dickster,

> your lasers don't look 57" from the hubs - or is that just for the pics??

I took these pictures in my garage, which doesn't have that much room. These pictures were taken last year, so I don't remember exactly. But I think I was using only 14" instead of 57" for these pictures, so 1 degree equals 1/2".

> and the floor doesn't have to be level?

It would be better if it is level so the suspension is not loaded sideways, but it's less critical than you might think. What is important is that the floor is planar and that the laser beams are parallel to the floor. The laser beams end up parallel to the floor as a result of pointing them at each other (providing of course that the lasers are mounted at equal heights above the floor).

-Juan

[dickster]

juan

thanks. i keep getting tempted by the convenience of doing this myself. and then changing my mind. corner balance is the other issue, which has to be done first - right?

i guess the equipment could pay for itself first time out......

[logician]

Hi Dickster,

> i keep getting tempted by the convenience of doing this myself.
> and then changing my mind. corner balance is the other issue,
> which has to be done first - right?

I think you have to iterate a bit -- 1) ride height/corner balance, 2) align, and then 3) tweek the balance again.

> i guess the equipment could pay for itself first time out......

I'd love to have the space for alignment and corner balance. Unfortunately, my garage is neither level nor planar. So I did an alignment and corner balance with a mechanic buddy of mine in his shop. I had to pay for the use of the shop, but I got it done the way I wanted, and I learned a lot.

I think most of what I want to do mess with is front toe, and the ride heights. I don't really need to change the rear alignment. So once it's aligned, I can tweek the toe at the track using my lasers, and adjust the ride heights by just turning the height adjusting screws a calibrated number of turns. I've got SAW spring plates in the rear, so adjusting ride height all round is pretty easy. The spring plates save time corner balancing too.

-Juan

[jluetjen]

Hmmm. Very clever Juan.

As far as making your garage level, the key points are that the lasers and where the tires are sitting be coplaner. I've found that scrap pieces of lenolium work fine as shims.

[Jim Richards]

Great stuff, Juan. I was thinking that the angle of the car & front wheels as you roll it into position might cause some error for the toe measurements. I imagine these can be corrected for but it might lead to mistakes.

Thanks Juan!

[billwagnon]

That is too cool!

When are the St. Louis training sessions?

[dhoward]

I've got a couple of lasers....

[cowtown]

Really neat idea, Juan. I have done the string method a couple times and find it to be tedious to the point of just paying for the alignment. This looks like an easy, cheap method.

Now how do I get it to work with C2T wheels with their semi-recessed centers?

[Tim L]

Here’s how I use the laser to align my car.

I purchased a laser level from harbor freight for $10 and got an aluminum bar that I cut to fit my rims. Then I attach the laser level to the bar and I hold the bar to the rim with a bungee cord. The first step is to make sure the car is level then set the camber front and rear. To do this I use an accurate machinist level and just hold it on the bar in the vertical position. (very easy). Then to set the toe in the rear you need a straight stick or bar of some sort as wide as your car and bar laser setup. On one end you mark a target and with the laser pointing forward from one rear wheel line the target up with the laser (I support the stick on two boxes that are the same height as the center of the wheels). Then attach the laser to the other rear wheel and aim it at the other side of the stick mark the stick at this point. Next move the stick to the rear and repeat the process. With the distance between the two marks you can calculate the total toe using trig functions (the toe of each wheel can be checked by measuring the distance from the front hubs to the laser when you have the laser pointing forward. The front is done the same as the rear and you only have to worry about total toe.

Tim

[dickster]

been thinking a bit more about this.

how do you guys get access to the rear for adjustment? do raise the car and remove the wheel each time you check/adjust?

i guess the same applies to the front for toe?

[logician]

Hi Dickster,

> do you guys get access to the rear for adjustment? do raise
> the car and remove the wheel each time you check/adjust?

I haven't done the rear using my cheezy method. But I've been told that it is a pain. When I did it in the shop with my friend, it was up on an alignment lift so access to the bolts was easy without removing wheels.

> i guess the same applies to the front for toe?

As I recall, the front toe adjusters on my Turbo tie rods were accessible by reaching underneath. Although this might be a problem if the car was lowered a lot.

Actually, if you had the number of turns vs. degrees of adjustment calibrated, then you could take a measurement, and then jack up the car and make the calibrated adjustment. That's what I do with my SAW spring plates, where I know that one turn of the adjuster changes the ride height by .2".

Does anyone know the calibration for Turbo tie rods -- turns on adjuster vs degrees of toe?

-Juan

[logician]

Hi Tim,

> Here’s how I use the laser to align my car...
>
> ...I attach the laser level to the bar and I hold the bar to
> the rim with a bungee cord...

Yes, that's the other way to do it -- lasers pointed forward and backwards, instead of side to side. A friend of mine does his similarly. He marks his garage wall instead of moving a stick around, as that is more convenient for him. He does camber by pointing the lasers up, and marking his ceiling.

Regarding convenient setups, if you have the garage space, you might mount the lasers for my technique on the wall and leave them there pointing at each other. Then all you need to do is drive your car up into position and slap on the mirrors to check your alignment any time in only a couple of minutes. This might be convenient for mechanics to reset the customer's toe after repairs that require taking appart the front end. Most shops don't have alignment rigs.

-Juan

[logician]

Hi Colin,

> Now how do I get it to work with C2T wheels with their
> semi-recessed centers?

The plexiglass used for the mirrors are pretty easy to work, so it should be pretty easy to cut a small mirrored disk to fit in the recess. Do the C2T wheels have a shelf in the recess on which the disk could sit flat? The other alternative is to do something like what Tim does and make a mirror that you and bungee cord against the wheel rim. But the more parts you add, the greater chance of misalignment.

-Juan

[Zeke]

I guess you'd have to drive the car in there pretty straight as getting in sideways would nix the whole deal. It'd be nice to be able to move the car around a bit for fine adjustment. To this end, I ask, would it be beneficial to have the car on thsoe roll around platforms? Every time you raise the car to get at the bolts, you disturb the suspension squat. On casters, the car would settle down to the correct ride height because the wheels can spread out. Just curious.

[tight as a bull's ass]

get a patent attorney....prevent others (like me) from making millions on your idea....