Grease-Packed Cartridge Bearings vs SKF MTRX Solid Oil Bearings: What’s Actually Different?

Here at The Grizzly Bearing Co., we provide two types of cartridge bearings; cartridge bearings that use grease to provide lubrication and cartridge bearings that use solid oil to provide lubrication.

Most cartridge bearings use grease as the lubricant, while SKF MTRX Solid Oil cartridge bearings uses a solid polymer matrix that holds oil and releases it gradually. This changes how lubrication is delivered and how it’s retained.

 

1) Lubricant type and how it reaches the raceways

 

Standard grease-packed cartridge bearings (Available Here)

In a standard cartridge bearing, the bearing is filled with grease.  Grease is made from an oil mixed with thickeners and other additives. It is, mainly, the oil that forms the lubricating film in the contact zone. The grease acts as a carrier to keep the oil in place.  

 

SKF MTRX Solid Oil bearing (Available Here)

There is very little free space within the SKF MTRX Solid Oil bearing - only fine gaps between the oil filled polymer matrix and the raceways and cage.  The matrix contains micro-pores that hold the oil and release small amounts of oil during operation to lubricate the bearing contact.  When the bearing is not in use the micro-pores allow the oil to be reabsorbed back into the matrix.

 

 

2) Lubricant loss: washout and displacement

 

Grease-packed

If water gets past the seals in a grease filled bearing, it can contaminate the grease and reduce lubrication.  This is, particularly, the case in harsh conditions (wet rides, gritty trails, pressure washing etc.) where grease can also be displaced during operation. Furthermore, once water and grit mix into grease, it can behave like an abrasive paste that can accelerate wear and corrosion. That being said, these problems can be minimised by using a good quality bearing that uses a quality grease and well-fitting seals.

 

Solid Oil Matrix

In an SKF MTRX solid oil bearing, there is no grease to churn or migrate around the bearing as the polymer matrix helps retain the lubricant in place.  However, solid oil does not prevent contamination getting in (although there is very little space for this contamination to hang around).  Its advantage is mainly reducing the risk of the bearing becoming under-lubricated due to lubricant loss.

 

3) Corrosion and contamination 

 

Neither system is fool proof. If water and grit get past the seals, grease can help form a barrier at the seal lips and slow ingress, but once contaminated it can accelerate wear.  Whereas, with Solid Oil, the matrix can continue releasing oil during operation, but it won’t prevent rust or abrasive damage if contamination is frequent - that being said the amount of free space in the SKF bearing is minimal making it difficult for the water and dirt to penetrate it. 

 

4) Maintenance 

 

With grease packed bearings, they can be maintained to a certain degree. If there is no pitting or excessive corrosion, then additional grease can be added to the bearing to negate the washout experienced.

With SKF MTRX solid oil bearings, no maintenance can be carried out as there is no wash out. The polymer matrix will operate for as long as the bearing is operational. A strong selling point as longevity of the bearing is improved. 

 

Practical Takeaway

If your main issue is lubricant getting washed out or displaced, a solid oil bearing can have a genuine advantage; especially, if you’re in a part of the world that has moderate to extreme wet and mucky conditions.

However, if you’re happy to replace or maintain your bearings often then the longevity of the SKF solid oil bearings will not do a lot for you and you may not feel that they are worth the extra investment. 

That being said, whichever choice you make, you still need to be mindful of your bearing health i.e. condition of your seals, that they’ve been installed correctly and that you’re cleaning your bike gently taking care not to allow an ingress of water and cleaning materials into your bearings.

Here at The Grizzly Bearing Co. you can be guaranteed to receive quality bearings regardless of what they're filled with.  If you need any advice as to which bearings will suit you better, then please feel free to click on the chat box below and we'll be happy to advise.  

 

Sources

1. SKF — Bearings with Solid Oil: https://www.skf.com/group/products/rolling-bearings/engineered-products/bearings-with-solid-oil

2. SKF — Solid Oil bearings (two- and three-wheelers): https://www.skf.com/group/industries/automotive/two-and-three-wheelers/wheel-end/solid-oil-bearings

3. SKF PDF — SKF bearings with Solid Oil: https://cdn.skfmediahub.skf.com/api/public/0901d196804e157c/pdf_preview_medium/0901d196804e157c_pdf_preview_medium.pdf

4. NLGI — Grease glossary/definition: https://www.nlgi.org/grease-glossary/