Camber/Caster/Toe adjustements

Topic: Camber/Caster/Toe adjustements (Read 2282 times) previous topic - next topic

Camber/Caster/Toe adjustements

August 29, 2009, 04:24:05 PM

Camber settings are a gimme on our Fox cars. Ford put three holes in the top of the strut tower, and then pop-riveted the strut mount in the most appropriate ones on the assembly lines, right? So apparently there just isn't much camber adjustment that can be made. I would venture a guess at less than 1/2 degree by moving the top of the strut in and out to change camber. HOWEVER, a tire shop I took my old blue bird to decided to drill out the rivets, and move the strut mount anyway. So now, I have to ask, was it ever intended for the camber to be changed on these cars or not? How much variation can really be had on Camber? I found that both of my strut mounts were originally in the center holes, but the silly tire shop moved them all the way to the outside, trying to fix negative camber. Are our cars supposed to have significant negative camber? What it did do, is make a car that used to drive like a dream squirrelly as hell on the highway. Negative camber is going to be stability in curves. Not the most ideal ingredient for tire wear on the inner edges, but I never had that problem before anyway. If anything, outer edges went first. A neutral toe, or ever so slightly toed out will make it drive like it's on rails with a slight negative camber.

For the life of me, I cannot find ANY adjustment for caster. My guess is, since the bottom of the strut cylinder is firmly attached to the back of the spindle, trying to change the caster would probably be a very bad idea. So, if I wanted to raise the rear a little for more rake, I'd totally screw the caster on the front. Or is this done using shims on the LCA?

These should be one of the easiest cars to align, bearing the thought that the only real adjustment provided was toe via the tie rods. About the only adjustment on the rear is going to be setting the control arms, but I didn't see much adjustment there either. So, if we get a crabbing car, we probably have a bent frame structure. There simply doesn't seem to be many adjustments for alignment on these cars.

Bearing all this in mind, did Ford have some stock in the tire industries in 1986, or what? These things EAT front tires very quickly with city driving. They push very badly because they're so heavy in the front, and just grind hell out of the tires every time you go around a corner. It sounds really cool on a smooth parking deck surface at 5 mph, like you're drifting at 105 mph. But I can't say I like the effects on the tires, nor the very short tire life of a medium to high end performance tire or your typical passenger car tire. The OE tires on my blue one only lasted about 12500. I didn't think twice about that, because they were Firestone junk. Personally, I wouldn't put a Firestone tire on a wheelbarrow. The next set(Goodyear Eagle ST's), about 15000. Then, I put on some REALLY cheap tires, and got about 30K out of those. What's up with that? This last set, even cheaper than the previous, have about 50K on them. They're Sigma touring tires. Granted, most of that mileage was highway mileage, though. The Ex was the driver before, and most of the mileage was short hops running less than a mile in city traffic. I put the big mileage numbers on it using it for a DD for work, and doing a lot of interstate driving.

Someone wanna clue me in here? If there is an optimal setup that varies from the factory specs, I'd like to know it. I had a similar issue with my F-150 eating tires on the highway because of the Twin-I beam. I had it toed in about 1/2 degre, positive camber about 1/2 degree, and bingo, tire wear solved. The factory specs for the F-150 were apparently based on no down-force. I have a set of Michelin XCLT4's on it now with 60K on them, rotated once, and probably have that much more left in them. The problem was a combination of overhung steering and down draft on the truck causing it to toe out and camber in running at highway speeds. It's got the aerodynamics of a brick, and has a tremendous down-force on the front end. Not to mention, that's where most of the weight of the truck is anyway. It's a little funky at 30 mph on sloping pavement, but not even noticeable at 70+ highway travel.

Caster, as is my understanding will drastically affect cup wear. Front wheel drive cars typically have a negative caster, where RWD's have positive What exactly IS the caster measurement on our cars? I've never had cup wear on my Bird, and don't want any. That will RUIN an otherwise good tire very quickly. The only option to correct cup wear is to shave the tire. You just threw away a BUNCH of miles when that's done.

Camber/Caster/Toe adjustements

Reply #1 – August 29, 2009, 05:17:37 PM

I have a ford service manual that list the correct factory specs. I'll see if I can dig it out. Every cougar/bird I have ever had at front tires really bad. Maximum motorsports sells caster/camber plates that you can use to fix the issue. I have seriously looked into them a couple of times. But generally here it is cheaper to buy a new car then tires. I have held onto this bird long enough I will be putting these on in the near future. I think alot of the problem has to do with the way the suspension is set up.

Camber/Caster/Toe adjustements

Reply #2 – August 29, 2009, 06:08:32 PM

I swapped the strut mounts and the rest of the front suspension,had a professional alignment,and the tires are doing great.No abnormal wear at all.Leave the alignment to the pros.I do believe that aligning 21 year old (or older) suspensions with original parts and high mileage is a waste of time.I have seen instances where CC kits are used,and really help.I was lucky and didn't need them.

Camber/Caster/Toe adjustements

Reply #3 – August 29, 2009, 07:04:16 PM

I'm pretty sure caster isn't a tire-wearing angle. It can cause pulls if it's uneven from D/S to P/S, but that's all I know about. As far as raising the rear, you should be able to input a frame angle measurement to compensate. I'm still a bit of a n00b, so correct me if I'm wrong...

Camber/Caster/Toe adjustements

Reply #4 – August 29, 2009, 08:33:12 PM

There is NO caster adjustment stock, and there is pretty much nil in the way of positive caster built in.

One of the issues with the "push" and the lousy tire wear is the lack of positive caster. On turn, the tendency of the outside tire is to gain positive camber, or roll over on itself. This doesn't lend itself to good traction (maintaining a good contact patch). The inside tends to go negative.

The common "cure" is to add more static negative camber. This helps with counteract the camber loss on the outer wheel, but it makes the inner worse, and too much static negative camber has obvious effects on tire wear. It also lessens the contact patch when in a straight line, which reduces braking effectiveness (at least when it comes to the point of lock-up)

Adding in as much positive caster as you can (through the use of CC plates) is a better option. Adding the positive caster changes the camber gain curve on turn. At a certain point the outer wheel stops "rolling over" and the inside one begins to gain positive camber. What this does is help the tires tend to take up the "proper" attitude to help maintain a good contact patch while turning. You also need to run less static negative camber as well, which helps improve tire wear.

Adding positive caster tends to make the steering heavier (more work for the power steering system) and removes some of the "self-centering" tendency of the stock set-up. This, coupled with the fact that car makers would rather have a car push than spin the tail out when pushed, is why the stock set-up is the way it is.

On my car, I have a couple degrees more positive caster in my set-up that what is allowed by most CC plates. At the bonuses are I run maybe -1/4* of static camber, and have nil adverse tire wear. I have loads of grip while cornering as the camber gain on turn is pretty aggressive. The negatives are that the steering is heavy and the car can be cumbersome at low speeds due to the change in the scrub radius.

Anyway, on a stock set-up, the only adjustments you have are for camber and toe. Don't worry about those stupid rivets. Those are just for assembly line set-up. They serve no purpose in real-world scenarios. There are no adjustments for the rear.

Without getting CC plates, there's only so much you can do with the stock set-up, and none of them are optimal. You either give up traction or tire wear.

With CC plates, dial in as much positive caster as you can. Set camber at no more than -3/4* and total toe IN at 1/16". This is a good street set-up that improves front grip and helps maintain decent tire wear.

Camber/Caster/Toe adjustements

Reply #5 – August 30, 2009, 07:38:46 AM

Quote from: Chuck W;288863

With CC plates, dial in as much positive caster as you can. Set camber at no more than -3/4* and total toe IN at 1/16". This is a good street set-up that improves front grip and helps maintain decent tire wear.

Only 1/16" toe-in? Most of the cars I used to align called for 1/8" toe-in. This would also add more on-center feeling.

Shiny Side Up!
Bill

Camber/Caster/Toe adjustements

Reply #6 – August 30, 2009, 08:25:54 AM

Yes, 1/16" toe-in.

Camber/Caster/Toe adjustements

Reply #7 – August 30, 2009, 09:50:50 PM

Just what I figured, studying the suspension.

Of note, the strut mounts were riveted in the center hole on both towers. This means Ford makes perfect bodies with perfect strut towers. Right? (tongue firmly in cheek)

I knew caster would assist with center-return, and make the steering "heavy" if too much positive caster is used. Makes the car a might squirrelly on unlevel roads too, and if there's a level road in Alabama, I haven't found it yet. I've also always noticed the ugly negative camber on the outside wheel when turned to lock too. Sitting still, it looks like it's sitting on the sidewall as much as it is on the tread.

Now let's study this a bit. Let's say we have 1/16 toe IN, negative camber (like this \ /) and negative caster thats going to make the caster even worse at full lock (like this: | /). That's no grip at all in the front on slippery roads, which is EXACTLY what I've always noticed on these birds. They REALLY like to just go straight ahead. God help ya on a dirt road, which is what I learned to drive on. But, I learned in a 1964 Custom 100 Ford Pickup, with a solid front axle, with king-pin pivots, and the camber boost was built in by having the king-pins mounted at a pretty significant angle to the spindle, meaning off perpendicular. That thing had some SERIOUS grip on a smooth road, even dirt, and even with worn-out bald tires. But, get a little wheel hop started on one side, and you better hang on, because it wasn't going to end up well. Saturday night amusp00get was taking the Diller Killer out and find the unsuspecting armadillo making the big mistake of being on the highway. Armadillos average about 5-6 inches at the arch of their back, and the front axle of the Custom 100 had about 4.5 inches of clearance. It usually turned out badly for the armadillos.

Even my '92 F-150 has a tremendous camber boost due to the offset of the upper and lower ball joints (which puts the centerline of rotation off perpendicular). Caster/Camber adjustments are made by virtue of an eccentric lower ball joint. So, at full right lock, I get / /, and and full left lock, I get \ \ for camber. The Twin-I eliminates the problems with sympathetic wheel hop, but doesn't do much for body roll.

Do the CC plates require modifications to the tower? I.E. do I have to make a larger hole to clear the strut mount for the adjustments? Can you show me some photos Chuck?

I have no intention of trying to align it myself, just trying to make sure my deductions about the suspension are correct. I'm an electrical engineer by trade, but had to take statics/dynamics as part of my core courses in college. Aced both courses, so I'd say my understanding of steering geometry is adequate for the novice mechanic, which is all I've ever considered myself. I have tweaked the setup on my VW on occasion, but there's a big difference in a 3900 lb T-Bird, and a 950 lb VW, especially on tire wear issues.