Motorsports tapered roller bearing

W

wd6681

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Jul 6, 2009
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13
Location
NY
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.
Click to expand...
Any specific suggestions? Such as polyrex?
 
Royal Purple Ultra Performance grease would be a better choice.
 
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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,
 
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