You can find bearings on your bike in the wheels, bottom bracket, headset, jockey wheels, pedals and inside rear suspension linkages for mountain bikes. At Eurobike, the Swedish industrial bearing brand SKF presented their MTRX bearings for mountain bikes which incorporate a blue polymer coating that surrounds the ball bearings and cage. It looks nice, but my first thoughts were that it would slow the bearing down or could melt and ruin the bearing. The German brand manager, Benjamin Michael is the driving force behind MTRX and spoke to Bicycles Network Australia about the advantages of MTRX bearings.
Benjamin Michael is also an avid mountain bike and after the Eurobike show, he competed in the West Australian Cape to Cape, the 4-day MTB event which covers 205 kilometres. Two stage podium placements (mixed pairs category) amongst a competitive field of mountain bikes was a sensational start until a big nasty stick cracked the carbon fiber frame in three places (and thus ending any chances for success in the final classification).
When Benjamin Michael isn’t trying to win MTB events, he is dedicated to MTRX bearings and in this interview, explains the origins and function of the blue polymer insert along with the advantages.
Christopher Jones: You are the inventor of the MTRX bearings from SKF which differ from regular bearings as there is an additional blue polymer insert. How do the MTRX bearing differ from the Solid Oil Technology used by SKF in other industries?
Benjamin Michael: Basically it is the same technology inside the bearing. But we changed some points in the manufacturing and quality process to make the product more competitive. For example we skipped the noise control from the manufacturing process which saves a lot of costs and is not necessary for application in Mountain Biking.
Christopher Jones: MTRX bearings fill the air void with a polymer which is porus and can soak / store oil. Can you describe the advantages of this over conventional bearings?
Benjamin Michael: MTRX bearings are filled with SKF Solid Oil technology. This means an oil-saturated polymer matrix is moulded into the free space of the bearing, forming very narrow gaps around the rolling elements and raceways. This enables the bearing to rotate freely and the oil to be released during operation. MTRX bearings provide a lot of advantages due to Solid Oil, especially if bearings are mounted in dirt exposed positions in the bike. The polymer matrix contains two to four times more oil than bearings with conventional grease and so protects the bearing components. This leads to a longer bearing life, even under extreme contaminated conditions, while not requiring re-lubrication. The polymer filling physically supports integral seals, reinforcing their effectiveness while the bike is undergoing high-pressure cleaning. MTRX bearings prevent lubricant washout and ingress of contaminants more reliably than grease-filled bearings.
The advantages of the MTRX-bearings can be summarised; No lubricant washout, Lower risk of corrosion, Longer lubricant life and, Increased lubricant reservoir.
Christopher Jones: Would the polymer heat and degrade over time?
Benjamin Michael: We have the experience in other applications that the Solid Oil bearings have run more than 5 years without any maintenance. This is a life time of circa 40.000 hours as these machines are usually operating 24/7 the whole year. So we are pretty sure that there is no heat or degradation effect on the bearing life in MTB application. Especially if we consider that the average MTB rider uses their bike for 5 to 10 hour a week which is a duration of 250 to 500 hours a year.
Christopher Jones: These bearing are being applied in Mountain Biking for wet and dirty riding conditions. How do the MTRX bearing work differently in these conditions for better riding?
Benjamin Michael: The big difference is completely filling the void in the bearing and supporting of the sealing lip which can no longer be deflected because of the polymer. Standard grease filled bearings usually only fill 20 – 25 % of the free space. The bearings are, in most cases, only filled from one side with grease. That means the Standard bearings are a lot more sensitive to contamination, water ingress and to premature bearing failure. The polymer-matrix contains 3 to 4 times more base oil compared to standard bearings which increases the lubricant reservoir and provides a longer service life of the bearings.
Christopher Jones: In the technical information material about MTRX bearings, high-pressure cleaning is discussed and capillary action in which water and dirt is drawn into a regular bearing which then introduces corrosion and poor performance, wouldn’t this still be an issue with MTRX bearings as well?
Benjamin Michael: Our test results show that we nearly can avoid water ingress into the bearing. High pressure cleaning of a standard bearing can push the sealing lip into the bearing and water can pass inside the bearing. The polymer matrix of our MTRX-bearings supports this sealing lip mechanically and prevents the bearing from water ingress as the sealing lip can not be pressed (or deflected) inside the bearing. So the functionality of the contact seal is still active even during high pressure cleaning of the bike.
Christopher Jones: Does the polymer insert, along with the far higher oil content, mean that the bearing is much slower than a conventional bearing? Is there more rolling resistance?
Benjamin Michael: Theoretically we have a slight power loss in the MTRX bearing. Our test show that there is no difference in the bearing rolling resistance. We also have to think about the behaviour when contamination gets inside the standard bearings which leads to exponential power loss in standard bearings while the MTRX bearings run constant and smooth over the whole service life. So in summary we have a theoretically minor increase in power loss of the MTRX-bearing but most people not notice this on their bike while they benefit from better power transfer from the moment the standard bearings would otherwise get contaminated.
Christopher Jones: The SKF MTRX bearings can cost 3-4 times the price of a regular brand-name bearing and can even be more expensive than some brand name ceramic bearings (though nowhere near as expensive as Ceramic Speed). Will riders also expect a lifespan that is also 3-4 times as long as a regular bearing?
Benjamin Michael: The lifetime of the bearings depends on the riding conditions. For example, the load, the speed and the contamination of the bearings are the most important factors influencing bearing lifespan in MTBing. Though it can’t be said that the MTRX-bearings runs x-times longer compared to a standard bearing. Our tests show a significant improvement of the service life of our bearings compared to standard bearings. When you are looking at the costs you also have to consider about the time and expense of the bearing change itself. We want to have a lasting solution and we lend our MTRX customers the philosophy of “Don’t worry, just bike!”
Christopher Jones: The MTRX bearing are being spec’ed by Cane Creek who have a reputation for quality and reliability. Can you share any other brand / products that are using SKF bearings?
Benjamin Michael: There are some other brands that currently using the MTRX-bearings and we are also in discussions with a lot of global players in the MTB-segment. Unfortunately we are not allowed to talk about all the ongoing and existing solutions due to existing NDA’s. We will update our customers and media through our webpage and social media channels if we are allowed to share news.
SKF MTRX bearings
Photos: 1, 2, 4, 5, 6 Supplied by © SKF
Photos 3, 7 © Bicycles Network Australia