I was curious to know if it's the nature of the cross-leaf suspension design beast that front tires wear on the inside more than the outside. I ask for several reasons:

1) I understand that when you turn, hard to the right for example, centrifugal force would naturally cause the car to want to lean to the left, thereby causing the tires to tip onto their left edges. However, in my mind I can also visualize that such a turn would put downward pressure on the cross-leaf during, causing the wheels to "splay out" for lack of a better term, thus putting more pressure on the inner edges of the tires, which might be one reason these cars corner so well.

2) I've worn down my current tires well into danger zone, to the point that the wear indicators themselves are almost gone, and that the resulting racing slick-like smoothness starts on the inside and works it way toward the outside. In other words, the outer portion of the tire still has some tread, albeit it is also very, VERY low.

3) I am very particular about how a car tracks down the road, and a tire place near me worked very closely with me to help ensure the alignment was dialed in, two or sets of tires ago, but don't recall my previous set wearing down in this manner, but I don't always drive my tires into the ground like this. Previous set was Michelin, while current set is Hankook, if that matters. I haven't noticed any alignment issues like pulling, drifting, or wandering, etc., or any loose front end components, although I am aware that it is possible that my alignment nevertheless might have gone "out" somehow, somewhere down the line.

4) My previous C4 always wore out every set of tires the same way from the beginning when I bought it off the showroom floor, although, again, I don't recall my current C5's previous 3 sets of tires wearing out in this manner, yet, again, I've never worn them down this far before.

Disclaimer: I am not an engineer, nor do I have a degree in physics, thus may be reaching a bit here potentially in denial that I may need an alignment, but I don't want to do one if I don't have to due to how well dialed in it was. Yes, I understand the keyword here may indeed be "was", hence my question of whether I'm onto something here, or merely speculating out of my proverbial a$$.

 

When I took my old Firestones off, they were definitely "done", and the inner edges were both worn more than the outside, pretty much as you describe. As were the OEM Goodyears which they had replaced. As long as you are not seeing the tires bald on the inside and plenty of tread on the outside, I don't think you are seeing anything abnormal.

 

Thanks for the reply. Glad to hear you that my experience is not that uncommon. I don't have a problem paying for an alignment, it's just that I love how it runs down the road, and don't want to risk an alignment done for nothing resulting in me not being happy.

As for condition, the tires are indeed bald on the inside with some tread on the outside, but I would venture to guess that everyone else would have replaced these tires long ago, even if the whole tire had as much tread as only the outside does. ;-)

 

The alignment specs for the car call for more camber than some people require with their driving Style. If you do not drive like an absolute all the time , then the stock alignment specs are no good.

Take your car for an alignment and have them set it to a half a degree of camber in the front and it will be great. If you like a little more steering feel, tell them to add some positive Caster as well. If the car drove well the toe was fine. Let that alone. If it tended to tramline when you hit seams in the road, then tell them to toe in slightly more.

 

Wow, how do you know all this?

 

 

Wow, is maniac a reserved word and the forum deleted it?

 

It's just basic alignment info. Each type of geometry makes the car do different things.

For instance, you're driving down the highway and go to change lanes. The tire (either one) gets to where it's passing over where the lanes meet and there's a line there. If the car lurches all over hell trying to follow or jump over that line, it needs more toe in.

Positive Caster is how far the top ball joint is behind the bottom one (forward distance). If they are plumb (top directly above the bottom), there is no force being generated in the suspension to keep the tires pointed ahead. If you imagine a line of the axle pointing out indefinitely, that line would be 13" above the ground lets say, when the wheels are pointed straight ahead. When you turn the wheel to the limits, The axle would still point parallel with the ground. That's bad.

As you move the top of the yoke rearward, the axle will still point roughly level when the tires point straight ahead. But lets say you turn the wheels hard left. Now the left axle is pointing toward the ground, and the right axle is pointing up into the air. Think of it as both wheels leaning into the turn, obviously the geometry is opposite on the two sides. So, turning left cambers the left wheel positive (top is tilted out) and the right wheel negative (top is tilted in). Besides the obvious advantage of the tires leaning the way you want to turn, this also means there's some preload in the car even when traveling forward in a straight line. The two wheels are both attempting to turn inward, which gives the car a nice "I want to go straight" center feel. I personally prefer quite a bit of positive caster, which adds some to the steering effort required to turn. IOW, you have to force it to turn, it doesn't just wander around aimlessly. This also means when you let the wheel return to center on its own, like sliding through your hands, it returns pretty quickly. Without enough caster, you'd turn the car and it'll just continue going in circles if you let go of the wheel.

Now, the amount of caster DOES affect camber. This is true when you are turning, and ever so slightly when the wheels are toed in or out. However, at no time does camber affect caster.

Camber is a way to attempt to keep the tire flat on the road at all times. How much you need depends upon how hard you take turns. If you are tracking the car, it'll really need a LOT of camber because as the car leans sideways in hard turns, the wheels lean with it. So, you put in a bunch of camber to proactively correct that. The unfortunate side effect is that now when you're just driving the car like a normal person, the wheels are tilted and riding on the inside of the tire. Not a great thing on a very wide tire such as on our cars. So, it eats the hell out of the inside of the tire.

Now here's why I say the people who advocate this are completely retarded is that yes, while the tires are brand new, they ARE going to bite a little more in turns, and the car will be twitchy and make you think it's real responsive (when in truth its really just handling like **** for the street conditions). Now, after the tires wear some, a whole bunch of that camber is now removed because the tire is worn into a cone shape instead of the cylinder it began as. So, any benefit you got, lasted a few thousand miles and is now gone. Bonus, your tires are f'ed up and will never produce that handling again. Oh, and now the forward distance traveled per rev is different on the inside of the tire as it is on the outside, making them wear even faster.

The cure is to take your brand new car to a shop and align it to street specs. If you want to go to a track, then get it done again to track specs, go have fun, come home and put it back. Now, each time you track the car, it'll actually work its best rather than eating the tires as you drive from NY to LA on I80.

You can also do your own alignments at home (how I do it generally). It's every bit as accurate as a laser alignment machine, just takes a hell of a lot longer). And it does require some tools. Camber and toe are easy as pie to do and can easily be done with just a level, tape measure and string. There's no excuse for not setting the car up properly for different situations.

$0.02

 

Outstanding explanation KSpaz! Thanks for taking the time to do the write up.

 

Thanks for those details. I can see how it might be difficult to get an alignment shop to understand what you just shared, unless they really do care, instead of just following specs in a book, if you know what I mean. Would you mind taking the time to give an overview of the self alignment process?

 

I understand you should put some weight into the car seats to get the most accurate alignment. That's what I read here a while back from a mechanic who does wheel alignment.

 

Quick as I can here cause I have to get to work...

David Farmer Racing (member here) has a (or had a) website with PDFs on alignment. It already has a lot of the math done for you so you don't need to fumble around with that stuff. C5 specs, in inches and degrees, with conversions on both and quick formulas (multipliers) for simple conversions on your own.

Began by painting squares on the floor here at work showing where the wheels will be. Leveled those 4 squares and painted a thickness on each one to show how far below the highest one it was (so as to make plywood shims to raise the floor to dead level.

Bought a digital angle cube. $20 on amazon. Best spent $20 ever.
Quickly made a gizmo with 3/4" square tubing that has a solid end with a point and a nut welded in place on the other end to take a threaded rod which also got a point put on it. (I have a machine shop, but you could do this on a grinder for as accurate as it has to be). That gizmo then gets expanded when you have it between the stems of the ball joints. Now you've got a flat surface that can rotate, giving a place to mount the angle cube to get a caster setting. There's no ferrous metal down there so finding somewhere to mount a magnet is fun.

I made 4 platforms to raise the car about a foot and placed them on each of the painted squares. Actually, jacked the car up and put them under it, on the painted squares. Each was the same height.

Grabbed a couple 1/2" square stock chunks and taped them to a 18" Stanley Level (Pro-Max ones are nice and accurate). Use that for camber by taping the steel slugs where they will contact the face of the wheel. Easy as pie, measure the amount of camber by how far one end of the level is from the wheel when showing plumb.

Paint the surface of the tire around the circumference as it spins and then scratch a line in there to show rotation path. Repeat for the other side. Use a tape measure and measure the toe that way, comparing front of tire to back of tire. Front should be closer.

Get under the car and set the caster first (if you even want to mess with that). If you've had an alignment done elsewhere, don't bother with this. You can set camber and toe in your sleep. This is a pita.

Then set camber, then set toe. I'm short on time here or I'd go into more detail but you get the idea. I used a tablet with excel on it to do the math for me when I was under the car. If someone is really interested in this, David Farmer has all the info already available and in PDF form. No sense in my reinventing the wheel.
Our cars simply don't body-roll enough to care imho. I didn't weight mine down when I aligned it here at work. I got 36K miles on a set of BFG Comp TAs on a Z51 Vert w/420whp and driven like it was intended to be. Imo, that's overrated. If you were to do that while on a alignment rack with a digital readout, you'd see the amounts it moves are about the same as what it moves when they touch the rack. There's movement in every direction (to some extent). So, wasting time trying to get dead on perfect is... well, impossible.

 

 

Moved to C5 Tech.