DIY geometery adjustment - Help please!

How'd you do in Trig class?

On my ricers, for camber, I have a metal L-angle with a matched pair of stand-off bolts. I rest the bolt heads against the rim edge (top and bottom) with a bubble level to assure it's vertical, then measure the angle with a gravity protractor.

For toe-in, I use a string hung over the front tire (one tread point) to a plumb bob, and mark the spot (front and back of tire) with a crayon. After marking front and back on both tires, I move the car back and measure between the front points and between the rear points, as well as the distance from the front to rears. For a cross-check, you can also measure right front to left rear point, and vice versa. Then it's a trig problem.

I've done better with these "rough figures" than the Toy dealership got with a Hunter machine (after mounting the mirrors wrong).

Caster, steering angle inclination, etc, are a smidge tougher. Google for DIY alignment and you'll get an education.

Follow up with an educated butt in the driver's seat.

But if you already know it's wrong, then you should probably have a Ferrari specialist shop do a four wheel full alignment -- caster, SAI, the works. The difference in handling might amaze you. And some of the alignment adjustments require an assortment of shims that you might not have on hand.

 

That is AWESOME!!! Brilliant work!

 

Here is the long answer: Especially cars that don't have solid rear axles and need rear wheel align also

On the racecars I start with 4 jackstands and kite string. Put the jackstands about 4 ft in front of the car and the other four ft behind the car on both sides. Start on one side of the car and run the string from front to back . Tie the string to one jackstand to the other front to back with the string hight equal to the center of the wheel. With the steering wheel straight move the jackstands until the strings running down each side of the car are parallel with each other and the distance from both rear hubs to the string are the same and the distance to both front hubs to the strings are the same. If you have done this correct you should have a string running from front to back with both strings parallel to each other and the car perfectly centered. At that point you can measure the toe at all four wheels in relation to the car. Again make sure the steering wheel is straight. You can measure from the string to the edge of the sidewall on the front and back of the tire or to the rim or before you start jack the wheels up one at a time and rotate the tires while someone something against the tire to scribe a line to measure to. By doing this you will know which wheel to adjust and the front and back of the car will be in the same plane.

Using a toe gauge is fine if the wheel is centered while driving and the car is very close to begin with. You can set the toe on the front and the rear and unless you put it on a 4whl machine or do the trick with the string the car could crab down the road.

Camber is easy to check with a cheap camber gauge from Longacre Racing or from any racing supplier for under $50. Caster is a little tougher since you need to know how many degrees you have turned the wheels when you are taking the measurements. Most caster/camber guages will tell you to turn the wheel x degrees and measure the camber change. To do this it helps to have turntables to set the front wheels on. Before doing any of this make sure you set tire pressures first. Also for caster and camber the floor has to be level. Front to back does not matter much but the surface the wheels are sitting on has to be level left to right.

I do this by marking with chaulk where the wheels are going to sit and then roll the car away and use 12" squares of 1/8 thick particle board. Old floor tiles also work. Put a straight edge from left to right side and check with a level and stack the shims as needed. Then do the same for the other end of the car and then roll the car up on the shims.

This is the most accurate method I have found. All the fancy machines in the shops boast how precise they are but then you go to drive the car and you can after driving a couple hundred feet it's not right.

Professional race teams use pretty much the same method only they have jigs made up that mount on the front and rear of the cars with a notch in each side to tie the string in so they don't have to take a bunch of measurements just to get the strings set up centered and parallel to the car. We also mark the spot on the floor and how much shim we need so when we go to do it again we know how many shims to use and where to put them. It's late and I'm probably not making much sense. If anyone really cares I'll try to scan in some pics of what I'm talking about.

If you just measure toe without using strings you are just measuring total toe and will not know which wheel to adjust? If the car is already pulling to one side chances are one wheel will need more adjusting than the other. If you do decide to just measure toe without setting up the strings take a 6ft or longer straight edge and have someone hold it against the side wall of the tire and eyeball down the edge then do the same on the other side of the car. Do this after you set the toe with the steering wheel straight and make sure whatever you eyeballed is the same on each side. If space is tight put the straight edge the same on each side and while having someone hold it against the sidewalls measure from the rear most end to the body and make sure it is close on each side. Not sure if that makes sense? Going to bed now.

 

Ingenious ideas guys.

For those that failed miserably at Trigonometry, i took mine to a laser alignment centre that specialises in Ferraris.

Supertyres in Maldon Essex did my 246GT and the transformation was outstanding. Drives like a new car now.

Go for the whole works, you then get to sit comfortably in there warm waiting room, sipping free coffee and biscuits. £180 and you drive home.

I think Torgue Developments (TDI) in Essex do it as well.

Sounds better to me.

Cheers

Tony

 

Here are some pics that will help make some sense out of my prevous ramblings. One shows what you are looking for to set up the strings and the other shows how to measure the toe once the strings are set up. Courtesy or Carrol Smith. Works the same if you have fenders.

 

OK...What happened to the pics? Had to resize them.
Image Unavailable, Please Login
Image Unavailable, Please Login

 

If you don't want to set up the strings and want to measure the toe some other way or just check to see if your car will track straight you can use this method. A 6ft piece of square aluminum tubing from Home Depot works great for this. Make sure steering wheel is centered! Roll car straight forward and back a couple feet after each adjustment before taking another measurement. Repeat for all 4 wheels. Let's say you check the toe on the rear of the car and it is 3mm like you wanted. Then use this method on the rear wheels. If the long end of the straight edge is close to the body on one side and you go over and try the other side and the end is 5 inches away from the body the car will crab going down the road.

This is a real fast cheap easy method to see if the shop really did a decent job on the car. With two people you can do this in under 5 minutes without getting dirty.

Again, Make sure steering wheel is centered and roll the car back a forth a bit before taking any measurements.
Image Unavailable, Please Login

 

If you want it done right you gotta do it yourself! They look great, I have a pile of old HeNe lasers laying around. I'll have to make up a set for myself. Now all you need to do is go to Harbor Frieght and pick up a couple cheap dial indicators and make a bump steer gauge.

Most people think alignment is something magic that can only be done on a $20K machine. Truth is most of the guys using the machines don't understand the basics and how simple it really is. It takes longer but I'll trust the strings more than I would most alignment machines in the shops. Can't tell you how many times I have brought a car in and drove off the lot and the car pulled and the steering wheel wasn't centered.

 

We might have to start a different thread on this one? Bump steer is the amount the toe changes as the suspension goes through it's travels. Generally it is not something that is checked on street cars or that can be adjusted with stock components. The way you check bump steer is to remove the springs and shocks and set the car up on frame with jackstands and no wheels. You then move the suspension up and down through it's travels and measure the toe changes as it travels from bump to droop. If posible you then move the steering link up or down by removing or inserting shims or washers to where you get the minimum toe change as the wheel travels up and down between bump and droop. Having too much bump steer can cuase the car to suddenly pull in one direction when hitting a dip in the road or cause the front toe to go to zero under hard braking when the nose of the car dives down. If the toe goes through zero under braking the car will tend to hunt a bit. It's cuased by the steering link not being parallel and same length as the control arms.

A lot of racers bolt a flat plate on to the hub of the car( vertical in the same plane as the rotors) and then have two dial indicators mounted on a stand on the floor. You move the suspension up and down while watching the dial indicators and see how much the toe changes. Then you try to make changes to see if you made it better or worse. On racecars it's usually easy to make changes but on street cars it involves moving the steering rack up or down or you can purchase bump steer kits for a lot of street cars that allow you to make adjustments.


There is a way to do this with one indicator as well. It involves the stand being hinged and setup parallel to the car.

Here are some pics of a couple Longacre products and a link to the site if you want to see more of the stuff they sell.

http://www.longacreracing.com/catalog/index.asp

They make some cheap toe plates that use two tape measures and I've shown the single and two indicator bump steer gauges. Also the turntables for anyone that wants to check Caster as well as toe and Camber.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Oh, yes; since nobody else mentioned it yet: on a street car, the *first* thing you need to verify is the ride height at front and rear. Even if the car isn't all that old, a sharp impact to the springs can cause them to sag, which will throw your alignment off.

(After a rim failed on the Celica, a half dozen shops couldn't get the handling back -- because none of them recognized that the front was too low, even after I pointed it out to them. I eventually had to do the work myself. With new coil-overs, the handling was better than new.)

 

Hmm, Weak spring, I probably wouldn't notice the droop most of the time. We do check ride hieghts and corner weights on the race cars but never thought too much about it on my street cars. I guess I always figured most of the time I wouldn't do anything about it anyway if a spring was getting weak. Except for the 328 I pretty much treat my street vehicles like I stole them. If anyone cares the link to Longacre racing in one of the earlier post in this thread shows various ride height tools and scales for doing corner weights. Anything you do with alignments the car has to be on a level platform left to right. Front to back is not as important unless it is really excessive.

 

First approximation is pretty easy on a US edition car -- if it's an actual "car". The insurance companies pushed through a uniform bumper height requirement back in the '70s. Unfortunately, SUVs, being "trucks", are exempt.

If your springs are sagging enough to affect ride height, you probably need new springs. That's one reason I had to opt for new coil-overs in the Celica -- none of the local shops wanted to take on the job of changing out the springs. (The odd thing is that I'd think it's pretty much the same steps as to replace the shocks, on a McPherson strut car, but the shops wanted to charge three to four times the labor.)