SKF Hub Bearing Overview

Transcription

1 SKF Hub Bearing Overview I. What is a hub bearing? Hub bearings are an integral part of the vehicles suspension system. They provide a rigid connection between the wheels and suspension, allow the wheels to rotate with minimal friction, support the vehicle s weight, and absorb wheel forces and loads. SKF pioneered the first wheel hub unit back in the 1930 s, and has since developed every generation of hub bearing in the market. The most common type today is a Generation 3 hub bearing, which is a self contained greased and sealed for life assembly. Some may also include a wheel speed sensor as part of the ABS, Traction Control, or Stability Control system. Hub bearings are a safety related component because they provide a mounting point for the brake and wheel, serve as a structural member of the suspension, and transmit driveline torque in front wheel drive vehicles. For more information on hub bearings, see SKF publication: A technician s guide to the next generation of hub units Hub bearing safety brochure II. SKF hub bearing product line. All SKF hub bearings are premium parts that meet OE specifications for fit, form and function. On some parts, like popular GM applications, the SKF premium hub bearings exceed the OE specifications. Those parts include SKF s patented X-Tracker design that

2 features a unique double row angular contact ball bearing design that increases the overall strength of the hub for higher load carrying capacity. III. Market information A. How long does an OE hub bearing last? B. What is the vehicle age when a hub bearing is replaced? C. What percent is DIFM vs. DIY? D. Where do DIY buy their hub bearings?

3 D. Will consumers pay more for hub bearings that last longer? All market information on hub bearings from IMR, Inc. IV. What is the difference between premium and value line hubs? There are four main differences: A. Construction what is it made out of and does it fit correctly? B. Performance does it work like and will it last as long as the original OE part? C. Price how much is it? D. Warranty how long is the part guaranteed? C & D. Price and Warranty When talking about hub bearings, the conversation and focus usually centers around price and the warranty period. Value line hub bearings are typically 30% - 50% lower price than premium hubs. This lower price is a fact that usually can t be challenged. The warranty period is usually longer for premium hubs compared to value line hubs. In our case, SKF premium hub bearings have a 3 year warranty where many value line hub bearings have a 1 or 2 year warranty. Many times, especially at the point of sale, the conversation about the difference stops here. This happens because the person describing the differences is unsure of what to say next, or just doesn t know. This is where the conversation really needs to start, not stop. Construction and performance are the real differences between the two products. A. Construction On hub bearings, it s truly what s inside that counts. The saying of you get what you pay for definitely applies here. Compared to the OE or premium part, value line hub bearings are typically made from lower grade materials, manufactured with generic process controls that produce a product with less precise tolerances and finishes. Many people make the assumption that because the value line hubs come from best cost countries such as China, the real difference is the low labor costs. This is a bad assumption because on average, the labor cost is between 6% 10% of the total cost of the hub bearing. For example, on a $100 hub bearing, highest case the labor cost to produce it is $6. If the value grade part is $40 (40%) lower than the premium part, where do you think the $34 comes from? It comes from the cost of the components and the processing time in the factory. Lower grade materials can cost 20% - 50% less, and manufacturing cycle time can be reduced by up to 50% with generic process controls. This is where the big cost differences come from. B. Performance In many cases, it is very difficult to visually see the construction differences. Most value line hub bearings look just fine from the outside and will bolt up with no with problem. How they perform over the short and long term is where the real difference is. This ties back to the phrase you get what you pay for. Compared to the OE or premium part, value line hub bearings typically have a much shorter service life and a significantly higher percentage

4 of problems in the short term than OE or premium parts. Here are the most common problems with value line hub bearings: 1. Noisy out of the box. This can be caused by one or more of the following: imprecise assembly tolerances, incorrect bearing preload, improper surface finishes, low amount or quality of grease. 2. ABS issues. This means the ABS systems doesn't function properly (ABS doesn t activate when it should, or, activates when it shouldn t) and/or the ABS dash light may flicker or stay on. This can be caused by one or more of the following: lower gauge wiring, low quality copper windings and materials, generic specifications, poor assembly processes. 3. Short service life. Value line hubs typically last about 25% to 35% as long as the OE or premium part. So if the OE hub lasted about 100K miles, then the value line hub will probably last 25K to 35K miles. This can be caused by one or more of the following: lower grade materials, imprecise assembly tolerances, incorrect bearing preload, improper surface finishes, generic specifications, low amount or quality of grease. 4. NVH problems (noise, vibration, harshness). NVH issues from hub bearings are typically The problems are generated as noise or vibration Whistle, whining, howling, grinding, roaring Are heard or felt in the steering wheel, floor or pedals Sometimes they are the same as brake NVH issues. Same cause as number Material failures. This can be caused by one or more of the following: lower grade materials, imprecise assembly tolerances, incorrect bearing preload, improper surface finishes. The above common problems with value line hubs are listed in the frequency they occur. This listing is based on thousands of Installer queries / surveys about the problems they have experienced with value line hub bearings. For more information on the differences in hub bearings, see SKF publication: All replacement hub units are not created equal V. Why is the performance difference important to the Shop / Installer? The biggest asset the repair shop and professional technician has is their reputation. A shop with a good reputation is usually successful and growing. A shop with a bad reputation is usually struggling to keep the doors open. Installing value grade parts can generate comebacks, bad customer will, and can contribute to lost customers. Shops don't own the customer, so they can't assume when they get one, they have them for life. To keep customers coming back, a shop needs to do good work, at reasonable prices, delivered on time as promised, and have minimal comebacks to be successful. Installing premium quality parts minimizes the risk of parts failures. Here is an overview of the most common problems with value line hub bearings, and the issues they can cause for the shop:

5 1. Noisy out of the box. a) The Installer has to order another part that isn't noisy to repair the vehicle. Many times, this issue is diagnosed on the test drive after the part is installed, so the Installer has to do the job over again before giving the car to the customer. Twice the labor to do one job = no profit on the repair. b) The vehicle comes back after a short period of time, usually in a week or two. Now the customer is upset. The Installer has to do the job over again at no charge to the customer = no profit on the repair, and even worse, they have an upset customer who may never come back again. 2. ABS issues. a) The Installer has to order another part that allows the dash light to turn off. Most times, this issue is noticed after the part is installed and before or during the test drive, so the Installer has to do the job over again before giving the car to the customer. Again, twice the labor to do one job = no profit on the repair. b) The vehicle comes back after a short period of time, usually in a week or two. Now the customer is upset. The Installer has to do the job over again at no charge to the customer = no profit on the repair, and even worse, an upset customer who may never come back again. This is a huge problem if the customer had braking issues and felt their safety was compromised - there is a very good chance of never seeing that customer again. And, that upset customer will likely tell their friends, which will hurt the shops reputation. 3. Short service life. a) The customer comes back and complains about the short service life and needing to do the repair again. In many cases, the Installer does the job over at no cost or a reduced cost. Same results = no profit on the repair. b) The customer is upset about the short service life, feels they've been had, and goes to another shop. That customer is lost for life. And, they will very likely tell their friends, which will hurt the shops reputation. 4. NVH (noise, vibration, harshness) problems. Same effect as number Material failures. a) The vehicle comes back with a bearing failure, many times on the end of a tow truck. In the worst scenario, the wheel has come off and the vehicle was in an accident. This may then involve law suits. Even if it doesn't, the Installer has to do the job over again at no charge to the customer = no profit for the work done twice. That customer is probably lost for life, they will tell their friends, their reputation takes a hit, etc., etc., etc. The common theme here with all of these issues is that the Shop has an angry customer looking for answers and expecting a free repair. The Installer does the job over at no charge to his customer hoping to keep them happy. In most cases, the Shop is given a replacement hub by his supplier, but, the Shop has to eat the labor. In some cases, the Shop even sources a premium hub and eats the parts price difference and the labor. Either way, it cost the Shop money and they know it. What the Shop doesn t know is that if their effort to save their customer worked. Most consumers will bring their vehicle back to get it fixed under warranty, but will never go back to that same Shop again. Some will even decide to go elsewhere instead of going back for the warranty repair. Think of it this way. If you and your spouse go to a restaurant and have bad service or food, what do you do. Some times you may say something and get a credit on your bill. After that, you may or may not go back again. Other times you may not say anything, even if the server asks how everything was. You simply pay your bill, leave and decide not to go back to that restaurant again. You may even tell your friends about the bad experience, which might lead them to stay away from that restaurant too. The same thing happens to the Shop when they have a come back. VI. Quality claims and marketing propaganda? With hub bearings, there aren't very many parts that are superior to the OE part. SKF makes and sells the X-Tracker hub bearing. In the cases where these hubs were not the OE

6 part, the X-Tracker hub beraing will perform better than OE part. No other supplier in the market makes a hub bearing that performs better than the OE part. Some value line suppliers have copied the SKF X-Tracker design, but even with the X-T design, their parts do not perform as good as the OE part. See the Competitive test results section for details. The real benchmark for a premium quality hub bearing is the OE part and its unique performance characteristics per part number. A premium hub bearing is either a) made by the manufacturer who was the OE manufacturer for the specific part number, or, b) designed, engineered and made by a manufacturer who used the OE design, performance and test parameters for the specific part number, and, used the same grade of material and components that the OE manufacturer used for the specific part number. The value grade parts manufacturers use generic design, performance and test parameters, with the durability parameter usually being set to a lower performance level than the OE specification. They also use lower grade materials, manufactured with generic process controls that produces a product with less precise tolerances and finishes, as already reviewed above. Many of the value line hub suppliers have published literature with claims that include: their hubs are premium quality parts, they have OE business with the parts they offer in the aftermarket, they have re-engineered OE hubs and make them better than OE, etc. These are simply not true. Hubs are really no different than other highly engineered products that can affect vehicle drivability, such as fuel pumps or O2 sensors. If they are not made correctly, they will not perform like the OE part. Yes, they will bolt up and work, but, they will also have a much shorter service life and a much higher incidence of problems as listed above. VII. Why is it important to tell the complete story Most people really don t understand what they are getting when they buy a value line hub. Distributors have told us that they are buying hubs from a vendor they know and trust (even though the vendor has no real history with hub bearings), so they must be good. Jobber/retailers have told us that they assume these parts must be good because they are available in the aftermarket and someone had to approve them or make sure they were OK to use. Installers have said that they assume these parts must be good because their jobber, retailer, distributor or whomever they are buying from is selling these parts and they must have made sure that they were OK to use. So the general assumption from many in the industry on this product line is that there is no real difference other than the price. That is a very bad assumption. There are significant differences as described above. And what about the consumer? Most consumers don t even know what a value line hub bearing is. When their car has a problem, they take it to their favorite shop to get it fixed. Most consumers assume that the part being put on will be the same as the part that wore out. So it is very important to explain all the differences between the two products. And, the explanation can t be just the price and warranty period, it really needs to include the performance differences too. When the difference is explained with just the price and warranty period, there is an assumption that there is no real difference in quality or performance. And since just about everybody wants to save money, many will choose the cheaper repair. According to the IMR research on hub bearings, 90% of consumers will pay more for a part that lasts longer. With a premium hub bearing lasting 3 4 times longer than a value line hub bearing, it certainly makes sense to include that in the explanation. VIII. Quick difference points Many times it is difficult to tell the complete story. Here is a brief summary of the differences between premium and value line hub bearings.

7 A. Service Life Premium - OE life expectancy, usually 100,000+ miles Value line - Low life expectancy, usually only 25% - 35% of OE Premium hub bearings last 3 to 4 times longer than value line hub bearings B. Speed sensors Premium - ABS functions properly Value line - ABS may malfunction, dash light may stay on Some value line hub bearings have a sensor issues right out of the box C. NVH (noise, vibration, harshness) Premium - OE performance, smooth ride with no NVH issues Value line - Can produce wheel vibration and noise Some value line hubs develop NVH issues in a very short period of time D. Fit, form and function Premium - Proper fit, form & function with very low return rates Value line - Double digit defective return rates Premium hubs bearings perform exactly the same as the OE part E. Construction Premium - High quality materials & components Value line - Lower quality materials and components can lead to premature failure Premium hubs bearings last and perform the same as the OE part IX. Competitive test results The only way to verify the quality and performance of a hub bearing is to test it. Every vehicle platform is unique, so each one has its own performance requirements and validation (test) specifications. These are developed by the OE vehicle manufacturer when they design the vehicle. An example of a vehicle platform is the GM Epsilon II, which includes the Buick Regal & LaCrosse, Cadillac XTS, Chevrolet Malibu and others. SKF validates all of our hub bearings using the unique OE criteria. Some hub bearing manufacturers will develop generic parameters for their testing specifications. This is a common practice with value line products. The problem here is that a generic test specification may not be stringent as the OE test. Parts could pass a generic test when in fact they wouldn t pass the OE test. Think of it this way. Take a piece of 1/8 plate glass and shoot a ping pong ball at the glass at 20 mph from 3 feet away. Take another piece of 1/8 plate glass and shoot a golf ball at the glass at 20 mph from 3 feet away. Both balls are white, round and about the same size, but, the results will likely be very different. In 2011 and 2012, we conducted a major OE and competitive hub bearing test project to determine the quality level of various products in the market. In order to assure an

8 unbiased test, we used a third party company, Defiance Testing and Engineering. They participated in the test program and oversaw all testing activities. All test procedures were defined by SKF, according to the OE performance criteria. A Defiance Project Manager maintained oversight of all testing that was done to assure an unbiased result. All test samples were procured by the Defiance Project Manager. Each sample was subjected to only one of the different test types. The results, including pictures and samples of the tested parts, are featured on the SKF Automotive Technical Training Trucks. They are also included in SKF document: BR930548K-2013v1.doc