SKF "CONCENTRA" Axle bearings

[brian downing]

One of my suppliers was describing the SKF “Concentra” bearings.
They of course “sound great”, but I wanted to see if I could get any real world usage stories.

Last race we had a hot day with a tight sticky track and our axle came loose, slid 1/2″ to one side. I want to prevent this, and while I know nothing will replace checking set screws, how are these bearings for staying tight?
They look as though they leave the axle in a cleaner condition.

Anyone here actually use these bearings? Pros? Cons?

[Gary Lawson]

Have used same skf ceramic bearings on my kart for 4 years and never had an axle come loose. Simply clean and relube them a couple times per year. Have had soft axles come loose that were tight with standard bearings. They work particularly well on soft/thin axles that are prone to come loose if not tightened significantly but are also dented very easily if over tightened. The skf bearings keep me from worrying about either denting an axle or having it come loose during a race. The price is not an issue for me when you take into account how much longer they last.

[Brock Weiss]

I agree with Gary 100% with all his comments. I also have the SKF bearings and will never look back.  Never had an axle slide when racing and Changing axles is so much quicker and easier and my axles are super smooth because there are no set screws to file and the axle spins freely so much better.

Last year in the heat I always had an issue where the kart would bind up in the heat and the rear would have a lot of grip. This year however we have not had that issue at all.  Don’t know if it is due to the SKF bearings rolling more free or not but last year we had regular bearings in and this year we went with the SKF Ceramics and we don’t seem to have that issue.

I  have been very happy and like Gary said I will never look back either. I know they are pricey but for me I would find a way as I like them that much.

[Ron Towles]

Does anyone have a source for these in 40mm x 80mm?

[Ron Towles]

Found a source, thanks.

[pat]

where do you race that you can run ceramic bearings

[Gary Lawson]

Ceramic axle bearings are legal everywhere. I do know they are not allowed in engines by many sanctioning bodies. Comet kart sales stocks them and kartsport North America is the importer. They will be able to get them in 30,40,or 50mm.

[pat]

just because someone sells something does not mean it is legal

SKUSA 2015

20. REGULATIONS

20.2. RACE VEHICLE STANDARDS

20.2.4.8. Composite Parts: All parts made from composite material

are forbidden on the kart, except for the seat, floor pan, and the

chain guard and Stock Honda silencer.

to me that is cut and dry  no ceramic  am i wrong

[Mark Traylor]

Pat,

I do think from an engineering perspective that your definition of composite is flawed.  The bearings are certainly hybrid but that is not the same as composite, nor is the ceramic silicon nitride a composite.   First a composite material are two different materials that are combined to provide a material property different than the two (or more) materials individually.  Typicaly thought of as fiber and a resin in todays day and age (rags and glue).  It does not need to be this way it can be concrete, a mixtrue of portland cement, gravel and sand, or a natural composite of wood.  the ceramic balls and stell races do not interact this way, they are merely a mechanical system.  The silicon nitride also on its own is not a composite material, it is silicon nitride that is formed into blanks by a sintering process of applying  heat and extreme and pressure as the agent, no matrix or “glue”.  Funny enough I have heard in technical papers carburized steel referred to as a “self assembling nano composite” (bearing steels are carburized).  This is actually a more accurate definition of composite that silicon nitride as you have iron as the matrix material.

All that being said no one is going to be beating you due to ceramic bearings.  Most karts I have encountered have atrociously dirty bearings, keeping your bearings clean will result in longer life and better performance where ceramics have the real improvement is in product life.  I am sure many will argue this and I don’t really care.

[Gary Lawson]

That skusa rule is clearly targeting making parts on the kart out of carbon fiber etc. Neither skusa or any other national organization in the U.S. have ever checked axle bearings in pre or post tech. That includes skusa, wka, uspks, and rotax. Let’s get this thread back on topic.

[JT TT]

Have you guys ever had a bearing get destroyed by dirt or debris entering the unit?  I didn’t think the concentra’s were sealed.

[Gary Lawson]

No issues. They have removable seals

[Mark Traylor]

dirt is the biggest enemy of bearings.   seals are worth it.  From an engineering perspective the concentra design is great.  I cant say it is worth the expense but i love the collet design.

[brian downing]

I ordered the ConCentra bearings, but they don’t fit (out of the box) into my cassettes. The collar that tightens adds too much width such that one cannot insert the bearings perpendicular to the cassette.

One either needs different cassettes or there’s a trick to removing the collar.
I’ve sifted through the SKF docs on the ConCentra and can’t find any trick to remove the collar.

Do I have to order new/different cassettes?

[Rodney Ebersole]

Take out the set screws Then squeeze the collet and push it out over the ribbed inner race. Reinsert the collect once the bearing is in the cassette.

[brian downing]

That did it!
Thanks for the quick reply.

Squeezing the collet lets the entire inner insert come out.
Then I could insert the bearing into the cassette and replace all the inner bits.

[Steve Libretto]

I put these on my chassis recently and I’m very happy with them. I found out the hard way that you have to install them all facing the same direction! Does anyone have a trick to easily release the collet without having to give the axle a shunt with a dead blow hammer?

[Gary Lawson]

I use an extension for a 3/8″ ratchet to smack it with. Or if I have a drift punch available I’ll use that. There’s no problem using this method.

[brian downing]

Here are the release instructions from the SKF ConCentra PDF (easily found via search engine).

Lightly tap the sleeve edge on the mounting collar side of the bearing until the locking system releases the shaft. As an alternative, tap on the bearing inner ring side face on the side opposite the collar.

I’ve just installed mine and have not yet needed to either re-grease or release/remove, but when I do, I’ll use a plastic hammer or a piece of PVC with a steel hammer to protect the bearings. “Lightly tap” means these should free easily.

[Gary Lawson]

I would say it’s a more firm tap but you’ll just have to try your way and see.

[Ron Towles]

Steve, could you describe the direction you had to install the bearings and why you had to install them that way? Gary, what direction do you install yours on your Arrow chassis. We have an Eagle on order and ordered a set of SKF bearings to install vice the stock bearings. Which direction do the collet lock screws point on each side?

[brian downing]

Each bearing is independent of the other and they don’t have to be pointing the same direction. However if you need to loosen and change an axle one would certainly want the left side (brake side) to point out towards the tire to make access to the set screws easier. If you have the set screws pointed from the cassette towards the rotor it’ll give you very little room to work.
Conversely, if you CAN make that work, then you might want the removable seals facing such that they are easily removed so you can more easily clean and regrease the bearings.
Whatever works for you.
Think about maintenance, go through a mental dry run of tightening, changing axle and regreasing, then decide what you want to do

[Gary Lawson]

Both set screws point inward on mine

[Ron Towles]

We installed ours with the set screws facing outward. Glad we did because they did not release easily. Found a good way to release them if they are installed like ours. Found an old 40mm hub and removed the studs. Slide it on backwards and it pushes uniformly on the collet when you tap the hub with a hammer. This releases the bearing without marring the collet.

[brian downing]

One other, minor factor, is having them facing inward or outward can stiffen or loosen the axle. It’s a very minor tuning aid, and I haven’t met a driver yet that could feel the difference, but it will change the axle’s deflection.
Facing in will stiffen the axle a tad compared to facing out which loosens the axle.

Just an update to this, I was speaking with someone who’s been using these for quite a while and he said to ensure both collets point in the same direction. Since the collars pull the axle during tightening, having the collars pointing inward would cause a lateral tension and the collars both outward would cause a lateral stretch. Having them both in the same direction will also cause the axle to shift 1mm in that direction after tightening the collars.

If there are any racerz here that believe they can notice this, or have this effect their lap times by any measurable amount, Torro Rosso has a car with your name on it!

[Dave Ahrens]

What is the best lube to use on these bearings? Do you just use break clean and air hose to clean them?

[brian downing]

SKF sells a grease for these, it is on their website.

Is just a pasty white lithium soap based grease.

I would also consider 3M Molikote, which I bought on Amazon

[Dave Ahrens]

Thanks Brian.

[Author]

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