Absolutely. The ride height was carefully designed in to match the front-to-rear braking balance, weight transfer during braking, steering response, handling, and comfort. All of those things are compromised when ride height is altered. The steering and suspension geometry is also changed. That makes the wheels go through the wrong motions as the body goes up and down over bumps in the road. Even though the alignment can be reset to give the appearance of correct settings while standing still on the alignment rack, you'll still have accelerated tire wear. You'll notice your upper control arm is shorter than the lower one. That makes the tire tip in and out on top as it goes up and down. That tipping reduces the wear from sliding left and right across the road surface as the control arms go through their arcs. To achieve that best tire wear, the lower control arms are supposed to be perfectly parallel to the ground when the truck is standing still.
Related to that, you'll also notice the inner tie rod end on each side is very close to the lower control arm pivot bolts. That makes the steering linkage remain parallel to the control arms regardless of height changes as you go around a corner. One of the things we have to look at when doing an alignment is ride height. Sagged springs are very common on GM and Ford products. Those are the number one reason for customers complaining that their new tires wear out too quickly. We have to correct ride height first, then do the alignment. Every tire and alignment shop has a small book that shows where to take the measurements for each model and year, and what they should be.
As a word of caution too, lawyers and insurance investigators know all about ride height and how it affects "scrub radius" and braking balance. If you're involved in a crash when the other guy runs a red light, they will use altered ride height to convince a jury that you were partly at fault for the crash because you were less able to avoid it, and they will be right. That's why all of my vehicles, including a few '70s muscle cars, are at exactly the height specified.
You also have to look at the relationship between the steering gearbox and the spindles. Lowering the truck lowers the gearbox but not the steering arms on the spindles. That moves the gearbox closer to the left wheel more than to the right one. Again, that can be made up by readjusting the tie rod ends during the alignment, but you'll be shortening the left linkage a lot more than the right one.
The last thing to look at is the center link. During the '70s, a lot of GM vehicles had idler arms that were adjustable up and down. That center link has to be perfectly parallel to the ground, otherwise the truck will be extremely miserable to handle. It will dart in unexpected directions and be unpredictable as you hit bumps in the road. Alignment specialists know to check for this when they replace them, but people who alter ride height don't understand all the things they're messing up, so they aren't likely to know about keeping the center link level either. They typically just bolt a new one on wherever it ends up, then wonder why they have handling problems.
There are different ways of lowering a vehicle. When the springs are heated to make them sag, the flexibility of the spring metal is gone and they can break. When shorter springs are installed, few people are aware you need to loosen the control arm bolts, then retighten them while the vehicle is sitting with the tires on the ground. Failure to do that keeps the bushings clamped in a permanent twist. That leads to early failure of the rubber part.
Monday, May 4th, 2015 AT 10:41 PM
