I agree with everything except the comment about the modifications. That is absolutely not correct. I can guarantee the person who lowered the car did not change the brake hydraulic proportioning valve. Without doing that, it is physically impossible to have a shorter or equal stopping distance. Handling will falsely feel better because you're sitting lower and the car won't be able to lean as much when cornering. The lower control arms are no longer parallel to the ground. They will be going through different arcs and the wheels will tip in and out more on top with changes in suspension height when going over bumps in the road. That is why we say there is a huge difference between "aligning for the road" vs. "Aligning for the rack", (hoist). Aligning for the rack gets you good numbers on the printout and shows that everything is in specs. Aligning for the road gets you those same things, PLUS it gets you good tire wear.
When the wheels and tires tip in and out more as the suspension goes up and down, there is a smaller window where the entire tread surface meets the road surface. Couple that with wide tires and there's a more likely chance part of the tread is bouncing off the road. That might be a small amount, but it's that solid contact patch that's needed for stopping.
You also have consider "scrub radius". Half the alignment mechanics don't even know what it is or how it affects handling. If you stand in front of the car and look back at the suspension, draw an imaginary line between the upper and lower steering pivots; the lower ball joint and the upper strut mount in this case. That line must intersect the road surface right in the middle of the tire tread. As such, the half of the tread to the left of that point tries to "scrub" on the road surface and pull that wheel to the left. The right half wants to pull to the right, and the two forces offset each other. Tires with a larger outer circumference, wheels with a deeper offset, wider wheels in some cases, and changing the distance between the upper mount and ball joint all change scrub radius. Car designers know this when they carefully design it into their products.
Scrub radius is what makes both halves of the tire tread react equally when that tire hits any bump in the road. When it is altered significantly, the tire responds to every bump with a tug. That is why everyone with a raised truck knows they get very tiring to drive on long trips. You can prove this to yourself by driving at highway speed without touching the steering wheel. With proper ride height and correct alignment, the vehicle will go reasonably straight for a good half mile. With altered ride height you will be constantly reaching up to make steering corrections, first one way, then the other. That's one of many clues on a preliminary test drive that the car may have weak springs. All relatively new cars don't do that, but if the ride height is altered, they do. You may have the illusion the handling is improved but that is due to increased road feel through increased feedback in the steering system. That contributes to the tiring aspect of driving the car.
The next characteristic of scrub radius has to do with braking. If you ever drove a rear-wheel-drive car years ago with one front brake disabled, you know that applying the brakes would literally tear the steering wheel out of your hand. Almost all front-wheel-drive cars use a "split-diagonal" brake hydraulic system so if one half develops a leak, you always have one front brake working. You've had people come in with a popped brake hose, but when was the last time you heard of someone ending up on the sidewalk due to a failed brake system? The reason is scrub radius has been modified to account for that. Chrysler has this so well perfected that the only clue there's a problem is the red warning light and a lower-than-normal brake pedal. On most other cars all you'll notice is a tiny twitch of the steering wheel, but the car will still stop in a straight line. Scrub radius has been changed to move the point of contact outward beyond the center of the tire tread. When just the left front / right rear brakes are working, that left tire wants to tug to the left, but a greater percentage of it is trying to drag to the right. The two forces counteract each other perfectly, ... Until you alter the ride height and change scrub radius. Simply installing deeper offset wheels with no other alterations does the same thing. Most of the time you won't notice anything because you have two unequal forces on one wheel being offset by two unequal and opposite forces on the other wheel. That's not the case when you have a failure in one of the brake hydraulic circuits. It's not the case when you're trying to stop with one tire hydroplaning or slipping on snow, and it's not the case when a tire hits normal small bumps in the road. All manufacturers spend thousands of man-hours and dollars trying to perfect the handling and braking characteristics to make their products better than their competitors', and I'm pretty sure you and I aren't going to improve on that. If it could be done without compromising safety, all cars would handle and brake like a Viper or Corvette. The designs are already there. All they have to do is copy them.
Every car has a proportioning valve in the brake hydraulic system to limit fluid pressure to the rear brakes. That valve is carefully tailored to the weight distribution and weight transfer during braking, based on many factors including engine size and optional equipment. Trucks and minivans in particular typically use a height-sensing proportioning valve because they can have such a wide range of loading, but even those are designed specifically for the application. Cars don't use those because the engineers know how much weight is going to shift to the front tires during braking, and they calibrate the proportioning valve to that. You know there's going to be less weight transferred to the front when the car is lowered. More weight will stay on the rear wheels than expected, but there won't be more braking power going to the rear brakes. That means the front brakes will do a disproportionate amount of the stopping. With less weight transferred onto the front during a panic stop, like when that other guy runs the red light, it will be easier for those brakes to lock up. Skidding tires have no traction, so to stop faster, you have to let off the brake pedal to get the wheels spinning again. How exactly does letting off the brake pedal shorten the stopping distance?
I have to take issue with your comment too about the car possibly being a lemon. Exactly what are they going to find to indicate that? No one is going to know if that car has needed thousands of dollars in repairs, or if it has been uncommonly reliable like my 25-year-old daily driver, just by inspecting it. The only history we know is it has been altered, and it can not possibly be as safe as when it left the factory. Even if you look at a NASCAR race car, you'll see that when you remove the skirting, the suspension is stiffer than a street car but it has the same travel and the same geometry as an unaltered street car. All the inspectors care about is the profile of that skirting to the ground. If the teams could lower the chassis to improve something, don't you suppose they would do it?
Exovcds, if you referring to me that I'm afraid of what I'm not familiar with, you're dead wrong. We all know you have to weigh in on every VW question posted here, and most of the time I respect your replies and I absorb some of your knowledge, but this isn't a VW issue. It's a suspension and alignment issue related to safety. Of all the muscle cars I've ever owned and still have, I keep every one at exactly the specified height. I've done a lot of modifications including using street cars on the local race track, but as I became an experienced alignment specialist, I would never, ever suggest anyone alter the ride height or change the handling characteristics over what came from the factory. I had one student try to pull that stunt in my auto shop after he was repeatedly told not to by me, the other instructor, and my tool room attendant who used to be a tire and alignment shop manager. He did it anyway and by the time he was caught, word had already spread through another student to the very outspoken owner of the local Goodyear store. That guy tried to get me fired until he found out the entire story which his part-time employee seriously altered. It's really that big of a deal, and you should not be telling people altered ride height is okay. I can't stop you from doing that to your car, but between the two of us, if we each get hit by a guy who runs the red light, only one of us is going to have a lawyer asking us to prove our car handles and brakes better than the way it was designed. If you think I'm wrong, call your insurance agent and ask for a reduced premium because you lowered the car. While you're at it, tell them you got a speeding ticket too and see if they lower your rate. You pay an increased premium when you insure a hard-of-hearing stereo system in your car because the company is assuming greater risk. They are going to increase your premium if they know you have other alterations for the same reason. If you don't tell them, they may ask in a questionnaire every so often, and if you lie, they will typically reduce the amount they cover if there's a loss, or you'll get a letter in the mail informing you they're adding a rider to the policy, with a corresponding increased cost. They know the same things lawyers know about modifications.
You know too that every manufacturer has warranty restrictions related to modifications that affect safety, emissions, and reliability. Dodge won't warranty transmissions in trucks when a chip is installed because they know the Cummins diesels can tear them apart. GM looks for any excuse to get out of paying warranty claims, and their dealership people are good at finding things like this. Almost every manufacturer I'm aware of will not allow assemblies to be repaired under warranty. They insist those assemblies must be replaced to insure the quality of the repair. With that concern with customer satisfaction, what do they know that you and I don't that makes them nullify the warranty when their products are altered. Ask your factory trainer, if VW still has them, or your district representative what the ramifications are with these modifications. That subject came up once when a corporate trainer was making one of her frequent visits to my school. She was a REAL good instructor and very entertaining and humorous, but that comment earned a five-minute no-nonsense lecture on the ramifications of these alterations. That's where I learned, "if it could be done without compromising safety, it would have been done by the engineers", to make the marketing people happy.
Friday, January 3rd, 2014 AT 12:35 AM