Car Tech 101: Understanding wheel alignment
Car Tech 101: Understanding wheel alignment
5:12

Car Tech 101: Understanding wheel alignment

Auto Tech
[MUSIC] How many times have you brought your car in for a front-end alignment and weren't entirely sure what was going on? Your car came out probably driving straighter and you were told it was going to wear the tires less, but in the middle there was kind of a black box. So let's sort that out by introducing you to the big three of alignment camber, caster, and tow. [MUSIC] To help us I've enlisted the guy whose shop has done dozens of alignments on my cars Ron Vasconzelus of Dependable Tire & Break. In San Rafael, California. All right, Ron, first of all, tell us what is toe. That's what most people think of when their tires are out of alignment. Toe in, toe out, pigeon toed, duck toed. Yeah. Okay? Okay. Toe in is going to wear Where tires on the outside edge->>Yeah>>Toe out is kinda where the tires on the inside edge. So, your tires are going to toed in, pigeon toed. The outsides wear out more because they are kind of scrubbing as you drive. Exactly.>>Why do you toe wheels out in or out at all?>> You pretty much toe in because you have friction as the car rolls down the road. Friction is pulling them apart. Okay. As all the bushing move and all that kind of stuff. If it's toed in, you toe it in just a little bit and it toes out to about zero. Oh, interesting. Everything gets pulled back by all the motion. Everything gets pulled back by, somewhat by the motion. Obviously some suspension systems are tighter than others. Old front wheel drive cars, they used to toe them out because the wheels would pull them in. Oh, from the torque. From the torque pulling it in. So if you're towed out, or you aren't towed correctly you're gonna have less forward stability? You're gonna have, you'll tow out the car wants to turn. Wants to dart. Wants to dart, right. So if you're going down the freeway and the car is wandering a bit, it might have some tow-out. Negative camber, the tire is leaning in at the top. So it's squatting a little. Typically if you look at an old Volkswagen the rear wheel has negative camber. Porsches these days have a lot of negative camber. So you've got a lot of negative camber. You're getting what benefit? You're getting cornering benefit. It's gonna handle better. So when I dive into that corner, that thing's gonna plant. The tire's gonna plant instead of, if it's leaning over positive, it's gonna wanna roll the other way. So you're kinda pre-setting it for the dig it's gonna get in the road. And also, if you're not driving the car hard, you're just driving it back and forth down the freeway, well the tire's already sitting that way. Then we're on the inside edge. Okay, so there's a waste of performance if you really have an extreme negative camber. Correct. Okay. [MUSIC] So then the one that's trickiest of the big three is caster. I still have trouble with this one a little bit. How do you describe caster to someone. Caster is the angle between the upper ball joint and the lower ball joint. With the lower ball joint leading, that would be positive caster. This is the front of the car. Yep. The lower ball joint or the lower pivot. Of the steering. Of the steering. Okay. Forward is positive caster. So that's like a bicycle fork. Correct. And that is for what purpose? Why isn't that straight up and down? Stability. A straight up and down caster angle, would make for a wheel that nervously tracks left and right, at almost any whim. Input. A little positive caster for the lean back in the angle the wheel pivots along calms this down. The car will pull towards low caster so you have four degrees on the right side and three degrees on the left sie, the cars gonna wanna drift to the left. Cuz think about it, if the ball joint is going backwards, it wants to go that way. And all this stuff interacts. Car pulls towards negative caster, pulls towards positive camber. So you can have one one way and one the other and the car will drive straight. [LAUGH] But they're both off. They're both off, correct. Now of these three why do they go wrong? These are all big metal parts in here and people look at it and say how could that ever budge. Well, a lot of parts these days are made of aluminum. Yeah. Aluminum's soft. They do like aluminum because it's lighter weight. Aluminum is stronger per pound than steel. But easier to bend. Couple that That with low profile tires that transmit more road impact to those aluminum parts, and the fact that the joints and mounts that hold your suspension in place wear and then allow things to drift, and that's why you need an occasional realignment. So when someone hits a pothole, should they be concerned, and if so, why? A number of different things. You can bend a wheel. You can bend suspension parts. You can break the bead in a tire. You see a lot of people with bulge on the side of it. What's happened is they've hit something so hard that it's broken the belts in there. If I've hit something and I'm not sure if it did any damage, are there any telltale things I can look or feel for? Steering wheel was straight before when I was going straight, not the steering wheel's off. While you're going straight. While you're going straight. Okay. [LAUGH] Something got bent, right? A giveaway. Shake. Now I hit that pothole, now my car shakes as I do 60 miles an hour down the freeway. Possibly bent a wheel, something like that. Many of us only get our cars aligned when we get new tires. But notice things like polar vibration as you drive, a sign that things aren't aligned anymore. And potentially costing you some tire life, handling quality, maybe even a little fuel economy. [MUSIC] More car tech demystified right now at CNETONCars.com. Click on Car Tech 101. [MUSIC]

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