Alignment vs mpg

[johnmyster]

If you take a wheel from the right, and put it on the left, it's now spinning backwards - thus, it still has the same directional creep. If you mount it whitewhall in, it's now spinning backwards - thus, preserving directional creep. It has to do with how the non-radial, non-belting plies are laid, and how even the radial and belting plies are seamed. The only way they'd creep left is if you drove in reverse. Only then, reverse would be the new forward, and left would be the new right.

So even if you take a directional radial and spin it backwards, it still maintains creep. Directional tires are only directional because of tread design. Some performance tires are built with a stiffer sidewall to go outside - thus, they're not directional, but inside/outside specific.

[Bullockracing]

There are some tires that are spiral wound, but the gyroscopic effect of how the tire is constructed is offset by the balancing. No tire on your car should cause a pull in any direction, given proper mounting and balancing. That being said, the best FE alignment is zero toe (see dcb's post above). Once the car starts moving, any suspension dive will result in toe-out, and the accompanying loss of directional stability. If you have the proper front geometry, this can be negligible, but unnerving. I recommend 1/16th toe-in as a minimum for experienced drivers, 1/8th toe-in for less experienced drivers.

FTR, I run my car with zero toe...

[johnmyster]

Bull. Balancing accounts for nothing except for uneven weight distribution of the tire wheel combination. Balance has nothing to do with how a tire, deforms, twists, squashes, and otherwise interacts with the pavement.

A tire's behavior while in contact with the road, and thus under forced deformation, may not entirely be as simple as we imagine for a perfectly balanced, perfectly round tire. As a simple example, the part of the tire where cords overlap (commonly seen as radial lines in the sidewall of cheap tires) indicates a part of the tire that is stiffer. Even if perfectly round and perfectly balanced, such tires may "roll" as if that stiff spot were a "high" spot on the tire. IE, they don't roll round, but they are round. That is why certan manufacturers test their production for balance and rolling dynamics while spinning them under load against a rotating drum.

This very deformation of the tire as it rotates into and out of the contact patch is the reason that tires with diagonally laid layers will tend to have a desire to walk one direction or another under load. While radials have far less diagonal character compared to bias-ply counterparts, there are still diagonal features, such as joints in belts and cords banded at low angles.

Tire rolling dynamics are far more of a complicated subject than anybody has business getting into on this forum. Certain people, and certain people I know in the business make honest livings employing technology to explore the subject in manufacturing enviornments. Certain companies hold patents on large sections of the territory. Ever notice what tires come stock on a Honda? Cadillac? Yup, they pay extra to get those, and they have to, because certain companies put extra time and money into monitoring these things. Certain auto manufacturers are now demading that their OE tire suppliers give them tires that DO NOT REQUIRE wheel weights. However...

I was simply trying to suggest that just because your car tends to go to the right when you let go of the wheel does not necessarily mean that you need to run to the alignment shop. It may actually be designed into the equation. Certain patterns of "uneven" tire wear are actually quite normal, which is why we will always be told to rotate our tires. Every corner of the car will tend to wear differently. If you can do it every oil change, you're off to a great start. Once you can see uneven wear, it's too late.

Of course, maybe none of this applies on ecomodder. Since everyone runs infinite air pressure, infinitesimal contact patches take loaded behavior out of the question. Oh, but wait, even if the air doesn't flex, the rubber still will.

My truck calls for zero toe.

[Meph]

Im not sure if that was a rant or what, but my car is 19 years old, and pulls hard to the right, steering wheel when traveling straight is crooked and the only time it drives straight is on the wrong side of the road, Ive driving enough cars to know my alignment is off + the insides of the tires are going bald with after like 7000k, not normal. Cops run the PSI at 50 in the training cars, rising about the factory spec isn't necessarily a bad thing.

[johnmyster]

Wasn't a rant. I agree, poor tire wear indicates a tire being scrubbed. Scrubbing a tire is a waste of energy and an indication that something is causing higher rolling resistance. If you say it pulls hard, I believe you. I tend to wonder why cars go out of alignment over time. I got one airborne one time on a dirt road (dukes of hazard style) and changed my upper mcpherson pivot plate locations once, but that's pretty non typical. It's not like your a-arms or frame are bending, are they?

My theory is that lots of cars will tend to sag on their suspensions over time, which may very well be your case at 19 years. IME, sagging tends to cause excessive wear on inside edges due to camber issues typical of suspension geometry on every car I can imagine, even independent rear suspensions. Short upper arms or McPherson setups tend to go "top in" as they sag. I've seen this on most of the cars I've worked on. I don't know if coil springs tend to sag (I know leafs will) or if it's just the rubber spring seats that compress over time. Sagging will also cause your tie-rod end geometry to change, so toe will be out also.

You'll see in most of my posts - here or elsewhere - I tend to ask more questions or think of other contributors more often than I jump to the typically accepted conclusion. For instance, I know plenty of people say they need an alignment when their steering wheel is off centered. Some people (on s10forums, for instance) confuse this with "pull." While a good alignment tech will fix this, you can be perfectly aligned with a steering wheel off center. If you experience straight tracking on the left crown of the road, then I agree. You needs an alignment. I was simply throwing a word of caution and more factors into the equation before suggesting an alignment. Why? I had to have one recently on my truck and the best price in town $60 for a two wheel only - on one of the easiest to adjust setups ever. It was saw-toothing the inside edges - typically an indication of combined caster/toe issues.

I think we're all on the same page here. The first step in ecomoding is to wisely spend money on maintenance issues - but avoid spending money on things that may not help in reality.

[dcb]

Speaking of money and alignment...

I should mention that it is pretty simple to check toe and camber on all 4 wheels with a plumb bob, a small block of wood, a clean garage floor, a pencil, a tape measure and a calculator (and some basic trig).

[johnmyster]

It'll get you in the ballpark if you're out. Could be a good plan for Meph. Whole degrees are pretty reasonable, but tenths of a degree are pretty hard to come up with. Add also - make sure to scribe lines on your tread. You can't really trust that the tread blocks on your tires are axially even.

[dcb]

I put the block on the rim (assuming it isn't bent) and transfer marks from 3, 6, 9, and 12 oclock to the floor on each wheel. Bring the bob to a halt right above the floor and take care with the tape measure and your interpretation of the last digit and you can probably get close to 1/10 of a degree.

[johnmyster]

0.1 deg on my 16 inch rim is a shade under 1/32th of an inch. That's why they use lasers to project that bad boy out there.

[dcb]

Originally Posted by johnmyster

0.1 deg on my 16 inch rim is a shade under 1/32th of an inch. That's why they use lasers to project that bad boy out there.

I get more like 1/72 of an inch. My tape measure has 1/32 markings on it (0.225 degrees) Lasers not required to get accuracy below one degree though It just makes it a lot easier to do quickly in a shop.