Motorsports tapered roller bearing

W

wd6681

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Jul 6, 2009
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I will be taking over a set of tapered roller bearing hubs to run on an endurance racing mazda Miata from a teammate. These hubs never really worked well for them and were constantly eating bearings. They tried running mobile shc220 and a fancy motorsports grease. Disassembling the most recent set I found one pair to be acceptable but with hazy scoring. The other pair of tapered roller bearings on the left front (most racetracks in USA have more right handers and therefore hammer left fronts) had what looked like bruising to me which would indicate cleanliness or lack there of. However with the number of failures they have had (many of which under 20hrs) I am interested in trying something new. The bearings are same inside and outside, 28x68x19.75 and are quality units from nsk or koyo. I would say peak speed is about 1900rpm (reflecting 130mph). If I understand speed factor correctly, could bumping up to a NLGI #3 be in order?
Your thoughts and input are all greatly appreciated.
 
The other crazy thing is looking at the size of the bearings. I thought maybe they were undersized however they are far larger in ID and OD than any tapered roller used on vintage Porsches including 928s!
 
Maybe try a polyurea grease.

I have a truck that has been hard on front wheel bearings. I could only get about two years at most out of a set of bearing before they needed to be replaced. Since switching to polyurea I have not had to replace bearings and the set that is in the truck is 3 or 4 years old now.
 
CDX825 said:
Maybe try a polyurea grease.

I have a truck that has been hard on front wheel bearings. I could only get about two years at most out of a set of bearing before they needed to be replaced. Since switching to polyurea I have not had to replace bearings and the set that is in the truck is 3 or 4 years old now.
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Any specific suggestions? Such as polyrex?
 
You can calculate the requirements as long as you have the information. Once you know the requirements you can select a grease that is likely to improve bearing performance.

Dn and NDm are not very high, 53200 and 91200, respectively. Operating temperature is an important factor calculating minimum and optimized base oil viscosity requirements. Range of racing rpm is also important. Lower rpm require higher at temperature base oil viscosity. For example, at 1900 rpm at 158-185°F, the minimum base oil recommendation is 17.3 cst. At 1250 rpm it is 23.3 cst. If you add in a high load factor, the optimized BOVs are 52-86.5 and 70-116.6 cst at operating temperature.

It might not be easy to find greases with these viscosities. An approach might be to find a higher base oil viscosity grease than you have worked with so far with EP properties. Loads must be high going into curves. I think the Mobilgrease SHC 220 has a 250 kgf D2596 weld point. You might want to boost that to 400 kgf minimum and ≥500 kgf preferred.

Do you know the range of bearing temperature or can you accurately estimate it?

Do you know the actual range of bearing rpm on the straight and in a curve? You mentioned 1900 rpm. I assume this is on a straight. What are the rpm in a curve?
 
RDMgr said:
You can calculate the requirements as long as you have the information. Once you know the requirements you can select a grease that is likely to improve bearing performance.

Dn and NDm are not very high, 53200 and 91200, respectively. Operating temperature is an important factor calculating minimum and optimized base oil viscosity requirements. Range of racing rpm is also important. Lower rpm require higher at temperature base oil viscosity. For example, at 1900 rpm at 158-185°F, the minimum base oil recommendation is 17.3 cst. At 1250 rpm it is 23.3 cst. If you add in a high load factor, the optimized BOVs are 52-86.5 and 70-116.6 cst at operating temperature.

It might not be easy to find greases with these viscosities. An approach might be to find a higher base oil viscosity grease than you have worked with so far with EP properties. Loads must be high going into curves. I think the Mobilgrease SHC 220 has a 250 kgf D2596 weld point. You might want to boost that to 400 kgf minimum and ≥500 kgf preferred.

Do you know the range of bearing temperature or can you accurately estimate it?

Do you know the actual range of bearing rpm on the straight and in a curve? You mentioned 1900 rpm. I assume this is on a straight. What are the rpm in a curve?
Click to expand...
Thank-You, based on average speed over a lap I would say the average rpm is 1200-1300 with peak loads (cornering g loading) happening around 1000rpm. (Total speed range of 1000-1900 rpm). Operating temperature I do not have a measurement at the hub but because of the long duration of the races combined with the high heat from the rotors heat soak is inevitable. I would venture a guess of somewhere in the 200 degree range. I know my teamate did shoot the hub at pitstops with a temp laser but I do not have those measurements. They were using for the purposes to identify a failing bearing.
Those cst values you were quoting were at 40, 100c or at the 158-185 operating temp?
Many thanks
 
Chris142 said:
Probably an adjustment problem and not a grease problem.
Click to expand...

I was thinking the same. It has to be worth experimenting with a different adjustment or checking the adjustment when the bearings are hot. taper roller bearings have the longest life with a small amount of pre-load but the life falls off a cliff if the pre-load is too high.
 
barryh said:
I was thinking the same. It has to be worth experimenting with a different adjustment or checking the adjustment when the bearings are hot. taper roller bearings have the longest life with a small amount of pre-load but the life falls off a cliff if the pre-load is too high.
Click to expand...
Previous versions had a traditional manually set preload with the axle nut. Updated versions add a few internal parts and go to a torqued axle nut to set preload like a cassette bearing. Both versions have experienced failure, but I do not disagree with this line of thinking. Perhaps under torquing the axle nut, putting some heat in the bearings with a few laps then torquing to the final spec would be in order. I have also decided to try and 'overkill' bomb and jump to an iso 1000 grease in Valvoline cobalt. I understand it is not GC LB rated, your comments are greatly appreciated as I could be persuaded to swallow the $9 loss of its purchase.
 
proper bearing preloading should be checked and set to spec ,, and if too hot temp you may be over packing them,is any excess grease being forced out of the seal lips? if so, try a little less grease in the cavity,
 
Just wanted to update all on this. Ended up running these hubs with new koyo bearings. Setting them up I found that one side was too tight after torquing and the other too loose. Machinist friend pointed out the prospect of using arbor shims to get the torque and free play right. Following a timken procedure I ended up getting both sides to .06" play at proper torque. Ran Valvoline cobalt grease in a race weekend and put approximately 14 hours of racing on the hubs. No issues, no noise.
Inspecting the car post race: front wheels have increased in play to what I would typically deem excessive. In the coming weeks I will pull the wheels off and get a dial measurement of free play, disassemble the hubs and report back with pictures.
This is likely not going to be a problem grease can solve
Likely possibilities are:
The Motorsports hubs were poorly designed and the wrong bearings were chosen for the job (look to be used mostly in transmissions).
The NSK and Koyo bearing are both low quality?

All ideas and opinions welcome!
Thankyou
 
My original recommendations were based on the original parameters provided. I actually did a search to get some typical values for an endurance Miata running up to 130 mph, Parameters include typical tire diameter, gear ratio, bearing temperature etc. After doing the calculations for grease selection with the new “typical” parameters, I’m not surprised that the Valvoline Cobalt performed well. It has excellent EP properties and its base oil viscosity is right in the range for a tapered roller bearing operating at 150-200°F.
 
Vexorg said:
Have you checked the alignment of the bearings in the hub and then on the stub axle? It almost sounds like something is bent.
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I have not checked this however it has been experienced on several other knuckles (that successfully have run standard stock ball bearing hubs). Theoretically the bores for the races could be not perfectly centered to the center or more importantly on another (two bearings). I am doubtful of this as the wear does not show miss alignment in the cups. I will get everything torn down after Christmas and report back. Something I listed to today that was interesting is that the metric Koyo tapered rollers are 5210 steel and the inch series are a different, low carbon steel that is then case hardened making the bearing more forgiving.
Below are what I expect are the most torturous things the bearings see
-axial loading from cornering
-axial and radial shock from running over curbs
-occasional rapid acceleration/deceleration from lock ups/partial lockups
 
Now this is a big surprise. I put the dial on the hub and got a reading of about .008", maybe less. Its cold so I did not take my time to get the best perch/setup for the magnetic mount so the numbers are probably +-.004" but the play was clearly less than I thought it would be based on what it felt with the wheel.
The greatest shock was that the outer bearing looks MINT. Too cold to investigate the inner bearing but these guys look good to be repacked and slammed back in.
The bleeding on the cap shows how I feel this grease was not up to snuff for the temperature. Discussing with my friend, he remembers hub temps with a laser (on aluminum cap) being over 200 degrees, which to me would mean that the steel not getting any air will be hotter.
I think the adjustments and setup were a win but a more thermally stable grease will be needed.
I am curious about trying a clay/bentone thickener. I felt a much more viscous base oil was needed but this is leading me to believe that greater thermal stability of the grease, particularly the thickener is more needed.
The slight increase in play at the hub is I believe to the bearings loosing their grease pack.

Let me know your thoughts

Thankyou
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I'm still trying to understand what the failure (or damage) mode is for your bearings. The photos suggest there may be debris denting, so cleanliness may be an issue.

As far as setting clearance, aim for 0.010 mm, or as close to 0 as possible. Err on the side of clearance, not preload.
 
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