Front end alignment on Hertz

[deathsled]

Got tired of shops turning me away. Decided to try it myself. To be uploaded in several parts. The car tracks much better down the road but the steering wheel does not turn to center on its own. I am thinking this might be a caster issue. That is beyond my pay grade for the time being.

[deathsled]

Part 2

Re-edited to give correct information.

[KR Convertible]

Richard,

You need to have the car on the ground before taking measurements.  After you let it down, roll it back and forth a few times to allow the tires to settle on the floor.

[deathsled]

Thanks KR. I learned that after the fact. I am going to get some plates to sit the tires on and do a redo. It's still better now than it was. Thanks for the info.

[KR Convertible]

No problem.  Good luck!

[shelbydoug]

Even cars with power steering (mustangs) tend not to return to center on their own.

The total tow in is an approximation and should be 3/16" total. Lots of things can effect that.
Just getting new tires in the front can and usually does.

You need to back the car out of the driveway and then back in to set the suspension on it's normal ride height. Usually you will need help on driving onto your adjustment plates.

Now there will be an argument on whether toe should be set to the tires or the wheel rims but I use the tires. 
For that you will need two pieces of 3/4", nice and flat plywood cut to the edges of the tires. Use bundee cords to hold them in place. At this point you can take you tape measure and compare the distances between the front edge of the plywood and the back. That is where you get the distances.

You always want to end up with toe in. Never toe out. Whether that is 3/16", 1/4" or whatever, as long as it is a closer distance then the rear.


One thing that you have to consider on a Shelby is whether or not it has the 1" lowering points or just stock.

One thing rarely mentioned with the lowered mount is bump steer. With it you WILL have bump steer and depending on the tires used, the severity will vary. Mine was terrible with bias ply tires. Radials help, but the honest answer there is that you likely will NEED a bump steer elimination kit.

What bump steer is, is when the tire moves up and down in the suspension, in compression, the tire will lean out giving you TOE OUT. That is not good and really a dangerous situation.
You can reduce the bump steer by stiffening the front coils do that the suspension doesn't travel as much.

Shelby stopped doing the 1" lowering in '66 somewhere in the 600-700 range.

[deathsled]

Thanks for all that information, Doug. I am going to do a redo on the alignment as far a toe-in but caster and camber are a steeper learning curve. I saw somewhere that replacing the strut rods with adjustable ones makes doing the caster much easier. Something I am considering but need to educate myself on how it is measured and how it all goes together. 843 has a one inch drop that was added by prior long term owner so I went with it. The drop mixed with the 475 pound lowering springs with a 1 inch drop themselves makes the front end sit perfectly. I didn't calculate it that way. I was fortunate.

[KR Convertible]

You can do some fine tuning with adjustable strut rods.  If you go too crazy, it will destroy the lower control arm bushing.

[98SVT - was 06GT]

You can get cheap caster/camber gauges on FleaBay. They even have digital now. Check out some race car setup books - doing alignment at the track is the same as doing it in your driveway.

https://www.ebay.com/sch/i.html?_nkw=caster+camber+gauge&_sacat=34998&_from=R40&_trksid=p2332490.m570.l2632

[shelbydoug]

Thanks for all that information, Doug. I am going to do a redo on the alignment as far a toe-in but caster and camber are a steeper learning curve. I saw somewhere that replacing the strut rods with adjustable ones makes doing the caster much easier. Something I am considering but need to educate myself on how it is measured and how it all goes together. 843 has a one inch drop that was added by prior long term owner so I went with it. The drop mixed with the 475 pound lowering springs with a 1 inch drop themselves makes the front end sit perfectly. I didn't calculate it that way. I was fortunate.

The caster is the most complex. Camber you can do with a carpenters level IF you can get the car completely level. That isn't as simple as it sounds and why it is done on an alighment table/machine.

You want to set the camber at -1/2° on a street car. That means leaning in on the top and the -1/2° translates to 1/2" on the level.
On a race car you probably would want something like -1-1/2° camber and 2° caster but not on a street car.
Even -1/2° WILL show tire ware on the inside of the tire tread. On a race car, that matters less.

IF you are going to put on new tires, do those first since tire wear is going to effect the procedure and accuracy, and as far as accuracy goes, don't be distracted by advertisements insuring accuracy down to .001". Alignments have ALWAYS been approximate and in particular on a "Mustang". Racers are always screwing with it and don't need an alignment table to do it either.

Incidentally, the rear is set by the factory axle and has 3/16" toe in and -1/2° camber. Caster does not apply there and you wouldn't want it to since camber steers the car and you do not want the rear steering under any circumstances unless you are suicidal. Rear steer will kill you.

Your issues with steering response may be from bumpsteer and you are just noticing it now.


My '68 GT350 upper A-arms are lowered 1-1/2", uses a ball joint shim and a bump steer elimination kit.
Ride height is about 3" lower then stock and uses the Ford "Boss 302 competition" 620/inch coil springs. So it is difficult to compare it to other more stock set ups. It also uses a 1-1/8" front anti-sway bar and Delrin bushings.


The factory pretty much sets the caster at 1-1/2° and to go further you are increasing the steering effort uncomfortably. I found that by going to 2-1/2°, which you would want for very high speed stability, the tires will hit the front of the fender openings while turning.

So to go that high you are re-engineering the car to a good degree and I would not recommend that for a street driven, non-power steering assist car. All you need is 1-1/2°.


Increasing caster will tend to make the car want to go straight and does effect the return to center of the steering wheel, but at some point the caster starts to fight you and not steer from center.


Incidentally, Ford has ALWAYS limited the amount of caster that you can dial into any of their cars to basically 1-1/2°. I'm not sure why but it PROBABLY has to do with customer dissatisfaction with steering efforts.

Even the Pantera that had it's front suspension designed by Gian Dellara, a Formula 1 chassis designer,  to a F1 style specs had Ford intervene and have the upper a-arms redesigned to limit the caster to 1-1/2°. In the original design, you could get 3° by moving the shims. Ford wouldn't allow that. They were the ones that had legal liability and had to warranty the car. We always question the motives of those in power. It was Ford's game but sometimes the "Legal Department" is too involved in the design of the car?

Hope this helps?

[JFriend]

I purchased a Fastrax alignment tool, there are many similar ones. Setting the caster and camber are really not that difficult. There's lots of info on the web, and I think the Ford service manual also tells you how much change each thickness will change the setting(s). Determining the set of shims is easy for camber - do that first. Then determining the caster is done by swapping front and rear shims to keep the camber the same, but move the pivot point of the upper control arm forward or backwards. Changing the shims is pretty easy - the cleaner your suspension is the better. I loosen the upper control arm bolts, jack the car up so the wheels are hanging, that pulls the control arms out and loosens the shims, and then just reach in and remove/install shims. Set the toe last. I didn't get too crazy about this, it was easy enough that I made adjustments, drove the car a bit, remeasured and tweaked it again, until it was right on. Not a big job. My plan was to take the car to a shop and have a machine measurements done, but so far that's still a plan, lol.