Race car wheel bearing grease

[200mph]

I road race a C-4 Corvette. They are notorious for poor wheel bearing life. I'm attempting to find a way to extend the life a little longer.

I currently use NTN modular roller bearing assemblies in the rear hubs. Those bearings have a poorly designed seal. When the assembly gets hot from heavy braking, the grease becomes too viscous for the seals to retain.

I believe I can mitigate the problem by inserting a grease fitting and pump grease between the two roller bearings before each race. I wondered if one of the experts here could recommend a grease that will tolerate 500 degrees F. and high bearing loads.

Thank you!

 

[oliver88]

NEO or Redline. Krytox if those two don't do the trick.

 

[Kestas]

What do you mean by "poor bearing life?" What is the failure mode?

Grease purge can also come from overfilling the cavity with grease. I believe the rule of thumb is to fill no more than 30% of the cavity volume with grease to prevent purge.

Or, as you said, the seals can't handle the pressure from the heat developed inside the bearing cavity. How many lips are sealing the bearing? I've seen up to four lips seal a bearing, but the downside is drag from the bearing during your application.

Check Kluber or Mobil to see what they have to offer. You need a Grade 2 grease with EP additives that has a higher temperature rating than conventional wheel bearing gerase.

 

[Ken2]

You can get grease that will take temperatures that still take the temper out of the bearings. Your best course of action will be high temp grease plus frequently renew these bearings. 300°F is too hot for the temper in the steel.

This shows a bit about grease thickeners and the temperatures:
http://www.schaefferoil.com/greases.html
Note that you'll need to completely remove one type of grease before putting in a grease with another type of thickener. Do not mix the greases, unless you know in advance that the base thickeners are compatible. Trying to flush out the old grease is probably not adequate. Your best solution is probably to buy bearing assemblies by the case ($100 each for Timkens from Rockauto--ouch).
http://www.machinerylubrication.com/Read/1865/grease-compatibility

 

[Kestas]

300°F will not take out the temper from bearing steel. High temperatures will affect the grease and seals long before temper is affected.

 

[200mph]

Poor bearing life to me means 20 laps on a 2 mile road course. I'm not certain what the "failure mode" is, but I believe the bearing gets hot, the grease becomes to viscous for the (one lip) seal to hold, grease escapes and they burn up.

The bearings are sealed from the factory. I plan to dissassemble them, drill a hole in the housing and race between the two bearings and inject new grease after each race. I know the new grease will probably escape as well but hopefully not before the race is complete.

I will check your recommendations - thank you sir.

 

[Kestas]

So the wheel bearings don't fail, per se. You're just worried about what we call in the industry "grease purge". This is not a serious issue; you may even learn to live with it if you can't control it.

I used to own a 66 Corvette. If the rear hub design hasn't changed, they were known to be problematic because it was incredibly difficult to access and maintain these bearings. Back then the fix was to drill passages for a zerk fittings, in order to replenish grease to the bearings.

Unfortunately, I don't see how this can work without having grease purge. After all, all that grease has to go somewhere. It may work for you since you're already experiencing grease purge.

 

[200mph]

Correct, the bearings don't completely fail. The get loose and must be replaced.

The original '91 Corvette bearings which are now hard to find were far better than replacement bearings available now. Those bearings had much better seals. The bigger problem is the geometry of these bearings is poor and that compounds the problem. With zerk fittings I can replace the grease that blows out of the seals. I'm sure that will be helpful in extending the life. I can remove the grease used during assembly and replace it with a Shaeffer product like 197 Moly Pure Synthetic.

Thanks for all your help and words of wisdom!

 

[Kestas]

If the bearings get loose, then the bearings aren't mounted correctly. During assembly, bearings must be torqued down with a lot of axial force to properly seat the bearings. Only then do you back off the axial nut and set the proper axial clearance. The bearing should move none to very little after that.

How do you figure the geometry is poor? Bearing assemblies are finely designed from calculations optimized for the application and torture-tested for proper function.

 

[Ducati996]

Perhaps venting the assembly will elimnate pressure from pushing the grease out.

 

[Kiwi_ME]

From an engineering perspective it sounds to me like there's too much grease installed, or if a sealed assembly then it's not being run-in at lower speeds when new to spread the grease around without overheating it first.

If it's a tapered roller pair or an angular contact pair and has adjustable preload, it's needs to be preloaded enough such that they run without clearance under full load.

 

[dailydriver]

Let me guess, you're running Hoosier R6es (or something even stickier) on this beast??

Everyone on frrax.com has the same problems with front wheel bearing assemblies when running very wide (315/30-17), gumball/super glue race compounds on their road racing f-bodies.

THIS is a case where the exorbitantly priced NEO wheel bearing grease IS justified!

 

[mkIIIman089]

Originally Posted By: Kestas
Check Kluber or Mobil to see what they have to offer.
As far as which grease to choose for a racing wheel bearing, this is the only thing that needed to be said.

 

[Michael_P]

I have never seen a new bearing unit in a box that had too much grease. Sometimes for heavy equipment, but never auto.

 

[tdi-rick]

Neo HP800.

 

[Kestas]

For automotive wheel bearings, the grease fill is measured and controlled at the factory so it gets just the right amount of grease.