September 2019

essential in ensuring an accurate installation. If the snap ring doesn’t click into place in the hub recess, the bearing will slowly work its way out, eventually fouling against the CV joint. “It’s also important that technicians take extra care when installing bearings with active sensor rings. These must be protected from damage, as the sensitive magnetic teeth are responsible for providing the data for many safety-critical systems. Avoid laying the bearing on a workshop bench with the encoder face down, which may contaminate or damage it.” Driver at fault? If something goes wrong after a bearing has been fitted, is it necessarily the technician’s fault? “While incorrect fitting can, and most likely will, cause problems, there are other factors that can also create issues,” points out Tim, “one of which is driving style. Bearings can be damaged or wear prematurely if motorists continually fail to avoid potholes, drive their vehicle up and down kerbs, clip roundabouts or don’t drive carefully over speed-bumps. All of these avoidable scenarios can put great stress on the bearings. “Although all FAG wheel bearings undergo rigorous mud and slurry tests, no bearing can withstand contamination from deep flood water, nor are standard bearings designed for racing or rallying, which are classed as outside normal driving conditions. Technicians should warn their customers about these potential pitfalls.” Performance As we said, bearings are small, but can play an important part in the overall picture that is the motor vehicle. For example, because of Jaguar’s confidence in the bearings output of NTN-SNR, the company was chosen by the carmaker’s Special Vehicle Operation (SVO) to participate in the new XE SV Project 8. “This is a high- performance sports version of the XE saloon,” explains Mark Kidd, who is in charge of sales and customer support for NTN-SNR in the UK. “Jaguar have developed this version of the XE, so owners may drive the car on both the road and track.” To meet the Jaguar’s specifications NTN-SNR had to develop a durable lightweight bearing that still has a high rigidity when fitted, with reduced friction. “To help design this new bearing NTN-SNR drew on its expertise in aeronautics and suggested the use of ceramic balls instead of the standard steel balls, to help achieve the required specifications. It was necessary for NTN-SNR to respond to several technological challenges within a short space of time. Our wheel bearing knowledge and technical know-how allowed us to design, develop and test this new wheel bearing within the time period required.” Mark continues: “NTN-SNR used ceramic ball technology in this new wheel bearing to help achieve the required specifications for new Jaguar XE SV Project 8 bearing. This technology has already been developed and tested in single seater race cars and 24 hour Le Mans race cars. The benefits of using this technology are weight savings of 210 grams per bearing. This 840-gram overall weight saving help contribute to the performance of Jaguar XE SV. In addition, ceramic ball bearings allow for better rigidity of the bearing when it is fitted to the vehicle. “This extra rigidity helps reduce deformation of the bearing when the vehicle is being used on the race track. The ceramic balls used in the bearing also generate far less friction than a normal steel ball, allowing the bearing to rotate much easier. This lack of friction helps with both performance and fuel economy. The weight savings, extra rigidity and reduced friction all help to improve the dynamics of the chassis, this is essential for a vehicle with a top speed of nearly 200mph.” These large diameter wheel bearings are cartridge-type bearings, a.k.a Gen. 1. Mark comments: “This type of bearing is fitted using a press to push them into an aluminium knuckle. One of the main difficulties that NTN-SNR had to solve was the difference in expansion coefficients between the aluminium of the knuckle, the steel of the bearing, and the ceramic balls. The preload of the bearing was adjusted to obtain accurate compensation values and to check the integrity of the bearings under additional stresses on the test bench. “This rigorous testing has allowed NTN-SNR to be able to supply bearings with an expected lifetime of 280,000 miles, as per the strict specifications requested by Jaguar. “All the major parts of the bearing are manufactured at NTN SNR’s production facility in Annecy-France. Once the bearing is assembled final checks are carried out at the R&D centre in Annecy.” Confidence NTN-SNR has been the major supplier of wheel bearings to Jaguar Land Rover for many years. Mark comments: “Jaguar Land Rover first placed their confidence in us back in 2008 based on our supply chain, the premium quality of our products and the world leading technological and expertise we provide for our customers. NTN-SNR work very closely with Jaguar Land Rover and were the first choice when support was needed with the Jaguar XE SV 8 Project. NTN-SNR has a great technical know-how when working with sports vehicles, this know how helped Sebastien Leod win 9 World Rally championships with the Citroën race team. This exclusive project, consisting of only 300 vehicles, all happened very quickly from the start of the project in mid-2016 to the Jaguar XE SV Project 8 going on sale in September 2018. This project has been added to NTN-SNR's research plan and has helped to accelerate the development of ceramic wheel bearing technology, which will no doubt soon be used on mass- produced vehicles.” Mark concludes: “This is yet another example of NTN-SNR’s desire and determination to invest in R&D and the use of advanced technologies to continually improve the performance of its bearings. These improvements will reduce weight, and energy consumption, which in turn will help reduce CO 2 emissions.” 42 AFTERMARKET SEPTEMBER 2019 BEARINGS Below: FAG Gen.3 bearing www.aftermarketonline.net