How important is it that the base is level when doing an alignment?

So a bit back I picked up an alignment machine from Dean. I've got a two post lift in my garage, but not a 4 post. My thought is to make 4 18-24" stands to set the car down onto when I want to align it.

I was going to make the stands out of 4x4 with Teflon/plastic cutting boards as my slide plates.

How critical is it that the stands are even? I'm assuming based on my woodworking skillz that I should be able to get all 4 stands to within 1/16" of each other, 1/8th at the worst. The fun part is that I don't knew that my floor is perfectly level everywhere, either, so although there is a layer of concrete leveler down, I haven't really measured how it's sitting.

How important is it that the top of the stands are even?

Pretty critical.

We use thin pieces of Masonite for shims then mark the ground where the stands go so we don't have to re-level all the time.

My old John Beam alignment machine would "correct" for a drunk floor when you set it up. Time consuming, but nice. Previously, doing the alignments the old-school way, I used a stack of discount vinyl floor tires as shims and I could get it certainly close enough.

For your race car - pretty critical. For the daily driver - it'll work.

In my experience, for anything this side of a F1 or Indy car, I doubt being 1/8" off will affect much. I've been doing all my "alignment" work in a crooked driveway for the past few years and I get very good results. Besides, with just a few pieces of shim stock as mentioned above, it should be fairly easy to get things darn near perfect. It helps a bunch to mark the floor and use the same stand in each position if you're going to be doing lots of alignment work. It also pretty easy to make adjustable feet for the stands. Something like the stands above work great.

I'm guessing an 1/8th or 1/16th should be okay. If you've got rubber bushings their compliance could introduce that much slop.

Are you going to put weight in the car equaling yours in drivers seat ?

Assume your floor is !/8" out of level from right to left (about 6').

You are trying to get 2.5 degrees of camber.

That's 2.5 degrees off of a line perpendicular to the floor. But the floor is not level- it's running at a .25% pitch.

You would end up with a true camber of about 2.25 degrees on one side of the car, but 2.75 degrees on the other side, even though your machine would read them equal.

I think that is fine- in my wife's mini van.

SVreX wrote: Assume your floor is !/8" out of level from right to left (about 6'). You are trying to get 2.5 degrees of camber. That's 2.5 degrees off of a line perpendicular to the floor. But the floor is not level- it's running at a .25% pitch. You would end up with a true camber of about 2.25 degrees on one side of the car, but 2.75 degrees on the other side, even though your machine would read them equal. I think that is fine- in my wife's mini van.

Makes sense if you are using a plumbob or such, but what if you "zeroed" a digital gauge relative to the floors pitch?

SkinnyG wrote: My old John Beam alignment machine would "correct" for a drunk floor when you set it up. Time consuming, but nice. Previously, doing the alignments the old-school way, I used a stack of discount vinyl floor tires as shims and I could get it certainly close enough. For your race car - pretty critical. For the daily driver - it'll work.

I wonder if this hunter digital machine does too, it requires you to calibrate the sensors before each use (spinning the around a complete revolution).. hmm..

Stan - probably, why not, right?

The nice thing is I just had my miata aligned, so that should be a good baseline.

daytonaer wrote: Makes sense if you are using a plumbob or such, but what if you "zeroed" a digital gauge relative to the floors pitch?

In theory you are correct. In practice, not so much.

First off, I wouldn't need a digital gauge to do that. I could take the average of 2 opposite readings on an incorrect bubble level and do the math to figure out perfect level, which would be much more accurate than a digital (since none of us ever calibrate our digitals). I calibrate digital levels this way- by using manual ones.

Secondly, wheel alignment tools (at least the small portable versions many of us have) don't reference the floor whether they are digital or not. They mount on the rim, and compare the rim reading to level (not the floor).

Third, you would have to remember to re-zero it every time you switched from one side of the car to the other, or you would be reading negative, and double the difference.

If you did have a unit that could zero off a reference to the floor, you'd still have trouble. Imagine the unit is 6" long, and you zeroed it to the floor. The problem is that concrete floors are neither flat nor level. The concrete could have a small pitch to it in 6" (ie: 1/8"), and yet be perfectly level from pad to pad where the car is actually sitting. You would be compensating for discrepancies that may or may not be there. You would have to set up a method of zeroing the unit at the 4 wheel contact points, and correct it every time you parked the car in a different place, or aligned a different car. Sounds like a nightmare.

It's a LOT easier to go ahead and level the pads and forget about it.

Oh, one more thing...

If you referenced the floor and zeroed the instrument, it wouldn't change the fact that the car is actually not sitting level. With the weight of the car sitting on it, the suspension on the "lower" side of the car would be more compressed than the "higher" side. Depending on the floor pitch the weight difference could be a lot, and totally screw up your alignment settings.

If you care enough to put 150 lbs of weight in the driver's seat, seems to me 2000 lbs of weight shifting (even slightly) could be a bigger deal.

Too find out, measure the camber on the uncorrected floor and after you have "leveled" it. On a strut car it can be considerable.

Toe is not so critical.

SkinnyG wrote: My old John Beam alignment machine would "correct" for a drunk floor when you set it up. Time consuming, but nice. Previously, doing the alignments the old-school way, I used a stack of discount vinyl floor tires as shims and I could get it certainly close enough. For your race car - pretty critical. For the daily driver - it'll work.

I also used floor tiles. Our floor was pretty bad so we painted four squares on the floor with the number of tiles each spot needed and always did our alignments in the same place

I used some plywood squares. Two thickness for the right front and one for the right rear.

I forget the thickness of the plywood.

I will check it the next alignment I do once I get it all set and aligned I will put a couple shims under a wheel and let it back down and see what happens.

dean1484 wrote: I will check it the next alignment I do once I get it all set and aligned I will put a couple shims under a wheel and let it back down and see what happens.

Huh, that's a surprisingly easy and logical way to check. If I get it before you, I'll do the same here.

A cool idea I remember reading about for leveling a car:

Get a clear hose and duct tape each end just a bit above and below the center cap. Left to right is more critical IMO but could be checked for front to back too.

Fill hose with water to the center cap. Check both sides. If it's level the water level will be at the same reference point on each side.

Will not be super accurate with tires worn differently left to right or if for some reason there is a MASSIVE weight difference left to right. Will get you within 1/4in level easily, within 1/8 with some careful measuring/checking/patience.

In reply to flatlander937:

Yeah, if I do need to level it, a water level it's probably what'd I'd do. That'll allow me to move the bases around so I can adjust them properly for a multitude of cars. I can't just Mark the floors for one location/one vehicle, I want the flexibility to do anything I want.

I had a 40' long water level (I call them spirit levels) to help build the foundation for my workshop. The excavators came while I was out of town, didn't know what the plastic tube was for, and they back-filled over top of it. Yay.

I have a water level- haven't used it in years, much too slow. Also prone to error if there are air bubbles in the tube, or organics.

I also have several laser levels- use them daily at work.

But a straight board and a bubble level is my tool of choice for alignments. Quick, easy, and accurate.

In reply to SkinnyG:

A spirit level is not the same as a water level.

Water levels date back to the Romans.

Spirit levels were invented around 1660. They are called "spirit levels" because the vial is filled with "spirits" (alcohol) because it's low viscosity allows the bubble to move more easily. They are sealed vial, so they do not have the problem water levels do of encouraging growth of organics in the tube (which impacts their accuracy).

Yet another bit of trivia that very few people actually need.

In reply to SkinnyG:

Oh wait...

Maybe you ARE filling your water level with spirits. I hadn't really considered THAT possibility.

I'm a bit lucky. Whoever poured the floor in my garage neglected to have any slope. You can pour a quart of water on it and it just lays there. It's great for doing alignments, but sucks with winter salt melt.

has anyone ever driven on a level road? do level roads even exist?

and i hope that you people that jack the car up, put floor tiles under the tires, and let the jack down again to get everything level either have some sort of a floating pad for it to set on or you are rolling the car back about 5 feet then back into place before measuring anything because suspension binding from setting a car straight down will throw everything WAY off..

In reply to novaderrik:

I think you're supposed to use two tiles and grease them, this allegedly leads to no bind problems.