JakeL

Hey all - I got a camber/caster gauge for my birthday, so now I am equipped to do my own alignments.

I wanted to check and see if there were any gotchas to do doing toe on a C5. I have never done my own alignments, but it doesn't seem like it's too hard, but I tried it this afternoon and had some trouble getting a result I was comfortable with it.

I bought some tubing, and ran some string through them, 78" apart, front and rear, so I have a perfect box.

So, now I have to measure the distance from the strings to the wheel centercaps. I'm running Z06 wheels, and my measurements came out showing that the front track (at least, as measured from the wheel centercap), was about 1" narrower in front than at the rear. However, carpoint.com's specs say there is hardly any difference between the C5 F/R?

Further, my last computer alignment (~2 weeks ago, post T1/Penske install) showed a that the difference in front track was 1.9" (which somehow changed to 2.3" after the alignment was done? my front toe was WAYYY off, so that might have contributed), but perhaps they are measuring track width differently?

Toe was set to zero front and rear, with the computer alignment.

My own measurements showed zero toe rear, and 3/16" toe out front (total, not per side) which seemed high, given it should have been set at zero?

I've not done any car centerline measurements, since I'm starting from a 'known good' spot, and I won't need to be changing the rear, at least for the moment, and folks have told me I can just make sure to do the same number of turns on the tie-rods to ensure I'm staying centered to the car's centerline?

Any advice is appreciated - thanks guys.

-Jake

SWCDuke

I've been doing my own alignments (including lots of experimentation with different settings on several cars) for about 20 years with just an inclinometer and tape measure.

To measure toe I make tire crayon marks on suitable tread blocks on the rear of the tread as high as possible that will allow measurement without the tape interfering with the chassis.

I measure and record the rear measurement first then roll the car forward until the distance between the marks can be measured on the front without the tape interfering with the chassis. Using the same reference points for the toe measurement eliminates any lateral tolerance in the tire. The true toe will be a little more than what you measure because you are not making the measurements at the same height as the axle centerline.

Of course, the car should be on a flat, level surface when doing alignment, and most garage slabs on relatively modern houses are suitably flat "surface plates" to align a car.

Duke

JakeL

Duke -

thanks for the response.

The method I'm using does actually take the measurement at the axle/hub center height, I just wanted to make sure I'm getting the 'box' appropriately centered, and the difference in F/R measurements from the string distance to the hub center were confusing.

Front distances were equal with eachother, and rear distances ended up equal with eachother, but it seemed odd that the front and rear numbers were different...

Thanks all,

-Jake

JakeL

FWIW, I'm using basically the technique that this fellow, 'Ausmith' is doing:
http://www.honda-tech.com/zerothread?id=267237

corvette dave

I also have aligned many corvettes at home.
I am not sure I understand you but if you have formed a perfect (side to side distances equal) box around the car and you have 1" difference from the front hub to the rear hub then that should be the difference in track.
I can't seem to find that measurement in my manual.
Dave

ConePunter

After once paying for an alignment and going back to check it myself, I have done my own alignments ever since, and I always set toe using the string method.

To your original question, almost every car has a slight variation in F/R track width. This becomes irrelevant if the strings are set up properly - more on that later.

Before ever setting up the strings to check toe, I first check that the wheels are pointed dead ahead. First, visually center the steering wheel. Then I take a very precise measurement between the inside edge of one front tire and a reference point on the chassis (or suspension). Leading or trailing edge of the tire either one is fine, but you'll need to pick a reference point that exists on both sides of the chassis. I use a short piece of string with a string level attached to take this measurement. Wherever the string touches the tire I scribe a small reference mark on the tire, and also mark the string for length. Measuring on the tire from the reference mark straight down to the floor, this tells me how far "up the tire" to measure on the other side of the car, and I repeat the same measurement. The goal would be to position the steering wheel so these measurements are exactly equal between the 2 sides of the car. Unless you're starting with a really bad alignment, at this point your steering wheel should still be reasonably centered.

To string the car, I use 4 heavy jackstands and strings about 4ft longer than the car itself. I start by positioning the jackstands so the strings are as close to the rear tires as possible without touching them. At a given end of the car, I want the strings to be positioned so the left and right measurements (wheel center to string) are equal. Once this is done at both front and rear, the strings are square to the centerline of the chassis. The way these measurements are taken, the track width difference has no effect on the strings being square to the chassis.

There's already much written about how to measure and set the toe so I'll skip most of that, but here's one thing that helped me. If the toe is going to be adjusted, and assuming you do not have a lift, it is always a pain to jack the front of the car, make the adjustment, lower and roll car to settle suspension, then reset the strings and measure toe again. So to keep from adjusting more than once or twice, I do not count flats or threads, I measure tie rod length before adjusting and set the rods to the length that will achieve the toe I want.

Hope this helps.....
Mike

SWCDuke

I understand the "box" method, now, but I think it has some potential problems and won't yield valid toe measurements for most cars.

The specified "track" of a vehicle is center of thread to center of thread. The center of tread is determined by the lateral distance of the wheel mounting plane is from the true vehicle centerline and the wheel offset. There's no guarantee that the lateral distance from the vehicle centerline to the outside edge of the wheel hubcap is the same front and rear. In fact, for most cars it will be different.

For cars with different track specs front and rear and the same wheel offset front and rear, you are guaranteed that the lateral distance from centerline to wheel hub cap is different. If different offsets are used front and rear you just don't know, but it is probably different. In cases (most cars) where the distance from centerline to the edge of the hub caps is different, you will end up with a trapezoid rather than a perfect rectangle, and you toe measurements will be off - way off in many cases

Most modern IRS cars have rear toe links, and if you carefully measure them using good repeatable reference points and make them equal length at your desired toe setting, then the toe should be equally distributed between each rear wheel.

Duke

P.S. Thought about this some more. If the two short sides of the rectangle - the pipes across the front and back - are exactly equal length and you set the strings equal distance from the center of the hub caps, front and rear, then you have a perfect rectangle.

The distance the strings are from the center of the hubcaps will likely be different, front and rear, but as long as the distances are equal on both sides on each end, then you have a good reference.

Since I like to make the front and rear toe measurements on the same tread blocks to eliminate any tire lateral runout I have to move the car forward and back. That would mean my box would have to be several feet longer, and I can see myself spending the time setting up the box, then tripping over it and screwing it all up. I think I'll stick with my "equal toe link lengths at the desired toe setting" reference. ;)





[Modified by SWCDuke, 7:57 AM 12/20/2003]

davidfarmer

String method always takes me too long to get everything setup. I can do a complete measurement in about 2 minutes, just with a straight edge and tape measure. Of course, you need either a level or camber gauge to to camber and castor.

JakeL

David -

what is your method?

-J

JakeL

OK, good, I think I'm on the right track (um...heh) then. the distance between the L/R strings is exactly 78" on both sides, and the length of them is 187" exactly. That puts the strings 3.75" from the rearwheel centercap/hubs, and 4.25" from the fronts.

I'll try the tie-rod measurement thing, that sounds interesting too.


Thanks guys.

-Jake




[Modified by JakeL, 9:33 AM 12/20/2003]

STEVEN13

Hi,

This is a prior post I posted back in Sept.

I just did a wheel alignment in my garage and I will pass along how I did it.
Please note I am not a mechanic.

Stuff you need:

6' level
2 tape measures
camber/caster gauge
abs shingles or masonry shims
toe plates(cut the bottom of each plate to clear the bulge of the tire)
2 pieces of 4x4 wood cut to about 8" each and index w/1/2" increments.
laser pointer
4 or 8 12"x12" pieces of mica

Okay, first take the 6' level and find a level place in your garage or driveway,
use the abs shingles or the shims if you have to.

You will have to set the camber/caster first. On the front add or remove the shims on the upper control arm. The rear Loosen the Bolt closest to the rear on the strud rod bar and turn the bolt to adjust (its sloted). Please note that this bar should be tighten to 185ft pounds. (My car has an aftermaket bar with 2 ends with jam nuts-not heim joints.)

After you think you have it set drive the around the block to settle the suspenion and check with the camber/caster gauge. To check the caster turn the wheel out approx 15 degrees and set the gauge to zero. Then turn the wheel 15 degrees in and read the gauge. Most gauges have the sweep angle built in so it is easy to do.

Now for the toe. Do the rear first. Now I know thier are many ways to do this I think this way might be the easiest. Take the 12" mica and use them as turn tables (2 pieces with oil in the middle) roll the car over the mica. Take the toe plates and lay them on each tire. Simply measure the front and rear of each plate. Now take the 4x4 index wood and lay them in the middle of each front tire/wheel. As you adjust your toe (by loosening the jam nut on the tie rod and rotating) take the laser and put it against the toe plate and aim to the 4x4 wood and try to get each side close (as we will do this also for the front).

When you think you have it then do the same for the front and again aim the laser now to the back tire/wheel using the same 4x4s (try to get this close as you want the rear tires to track straight.

Drive the car again and check all measurements. This will take approx 3 hours or more!

P.S. I have always done my own alignments and I always try different ways.
This method to me seems the fastest. I Also club race about 4 events a year.

Good Luck!

Steven

AZGASSER

any tips on DIY camber settings? :confused: