Rear wheel bearing re-build project
07-23-2011, 12:14 AM
#22
Race Director
I ran the car last weekend with the new bearings. I machined the stock retainers flat and installed new hardened washers before the race. I ran two twenty minute practice sessions on the east track at Miller Motorsports Park. I checked the axle nut torque between runs and they lost about 5 pounds of torque during the first session. ( Used 190 ft pounds initally) I took the car home and inspected the rear wheel bearing assemblies. The bearings themselves appear to be fine, but as I suspected, the bearing retainers were starting to fail again. They had compressed a few thousands where the retainer contacts the inner bearing race. The new hardened washers were starting to fail as well.
I purchased new 6820 steel to machine new retainers from and will have them hardened. The stock retainers rockwell tested at 20 HRC. I'm going to shoot for 40 HRC with the new retainers and eliminate the hardened washers and see how that works. Next test is August 5th - stay tuned.
I purchased new 6820 steel to machine new retainers from and will have them hardened. The stock retainers rockwell tested at 20 HRC. I'm going to shoot for 40 HRC with the new retainers and eliminate the hardened washers and see how that works. Next test is August 5th - stay tuned.
07-27-2011, 05:19 PM
#23
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I have considered ways to stop the heat from soaking from the brake rotors into the hubs, but haven't determined a good way to do that. Perhaps a heat coating would do the trick. I think heat is a big factor in bearing life and will keep working toward a solution. Thanks.
07-27-2011, 06:08 PM
#24
I have brake cooling ducts for the front wheels which cool the hubs too but not for the back brakes / hubs.
I have considered ways to stop the heat from soaking from the brake rotors into the hubs, but haven't determined a good way to do that. Perhaps a heat coating would do the trick. I think heat is a big factor in bearing life and will keep working toward a solution. Thanks.
I have considered ways to stop the heat from soaking from the brake rotors into the hubs, but haven't determined a good way to do that. Perhaps a heat coating would do the trick. I think heat is a big factor in bearing life and will keep working toward a solution. Thanks.
heck guys use similar things to spray intercoolers.
07-27-2011, 10:42 PM
#25
Tech Contributor
No doubt heat is detrimental. However in my opinion it's far down the list of why these bearings fail so quickly. As evidence I'll offer the number of failures people report after one day of auto-x. 6 to 8 one minute runs certainly don't generate enough sustained heat to kill the bearings.
So what causes the failures? The guys that report the failures are typically on sticky tires...ie Hoosiers or equivalent. On my car, when I was running the Hoosier R6 during track days and time trials, I was going thru right front hubs within 2 to 3 twenty five minute sessions. Left front hubs lasted about twice as long. Since my decision to scale things back and run Nitto NT01s, less sticky than the R6s, hub life has increased by a factor of 4 even though my braking philosophy is still "count to 3, brake when you see God!".
Given the above, my opinion is that the failures are almost exclusively driven by side-loading of a design not suitable for the track. Harder metals and a better bearing cage are what is required, and I hope the OP is successful in this endeavor
FWIW
So what causes the failures? The guys that report the failures are typically on sticky tires...ie Hoosiers or equivalent. On my car, when I was running the Hoosier R6 during track days and time trials, I was going thru right front hubs within 2 to 3 twenty five minute sessions. Left front hubs lasted about twice as long. Since my decision to scale things back and run Nitto NT01s, less sticky than the R6s, hub life has increased by a factor of 4 even though my braking philosophy is still "count to 3, brake when you see God!".
Given the above, my opinion is that the failures are almost exclusively driven by side-loading of a design not suitable for the track. Harder metals and a better bearing cage are what is required, and I hope the OP is successful in this endeavor
FWIW
07-28-2011, 12:14 PM
#26
Team Owner
Pro Mechanic
Good post^
Seems like a reasonable conclusion based on good, solid evidence.
Seems like a reasonable conclusion based on good, solid evidence.
08-02-2011, 12:52 PM
#29
I have a '92 Vette and as I see it the front bearing itself can't be replaced, you have to buy the complete hub etc..
enclosed a picture of my front disassembled bearing.
The rear bearing can be replaced, you only have to get yourself, just as I did, a NTN or SKF bearing... see picture
Can anyone confirm what I wrote or is just my '92 front hub/bearing not rebuildable and the earlier years can be rebuilt???
enclosed a picture of my front disassembled bearing.
The rear bearing can be replaced, you only have to get yourself, just as I did, a NTN or SKF bearing... see picture
Can anyone confirm what I wrote or is just my '92 front hub/bearing not rebuildable and the earlier years can be rebuilt???
09-13-2011, 10:49 PM
#30
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I have a '92 Vette and as I see it the front bearing itself can't be replaced, you have to buy the complete hub etc..
enclosed a picture of my front disassembled bearing.
The rear bearing can be replaced, you only have to get yourself, just as I did, a NTN or SKF bearing... see picture
Can anyone confirm what I wrote or is just my '92 front hub/bearing not rebuildable and the earlier years can be rebuilt???
enclosed a picture of my front disassembled bearing.
The rear bearing can be replaced, you only have to get yourself, just as I did, a NTN or SKF bearing... see picture
Can anyone confirm what I wrote or is just my '92 front hub/bearing not rebuildable and the earlier years can be rebuilt???
I'm in the midst of testing the replacement bearings. I damaged my transmission last month which delayed the process but I'm going to the track this coming weekend to test.
I found that the bearing retainers are too soft so I've machined new retainers and had them hardered to rockwell 60 which is 3 times harder than the retainers the bearings come with. I also eliminated the thin washer because every time I use them they get crushed.
If you have any questions send a PM and I'll tell you what I know.
09-14-2011, 02:40 PM
#33
Team Owner
Pro Mechanic
Me too.
09-14-2011, 10:48 PM
#34
Burning Brakes
im seriously looking into making a spacer for the front spindle that will allow me to run c5 bearings on the front taking measurements now iv run the crap out of my c5 for years. and the bearings are still rock solid amasing to me!! it looks pretty simple a thick billet aluminum cylender mabe 6 or 7 inches in diameter that bolts to the c4s 4 bolts then mill a 4 1/4 by inch and a half deep recess with 3 studs to accept the c5 bearings drill oult the treads on the c5 bearings and secure with lock nuts....
Last edited by TRACKMAN2; 09-14-2011 at 10:52 PM.
09-15-2011, 07:24 AM
#35
Race Director
This is why I stopped running track events. So, if you guys figure out a way to fix this bearing problem, then maybe I'll get back into it. I like the C5 up grade idea. Once the prototype is finished maybe it can be produced and sold.
09-15-2011, 10:24 AM
#38
The C4 Challenge era used bearings made by AC Delco with Mobil 1 synthetic grease, and then of course air ducts to the bearing/hub assembly.
The C5 used tottaly different bearings made of unobtanium. I think LG sells them though, seriously.
The C5 used tottaly different bearings made of unobtanium. I think LG sells them though, seriously.
09-20-2011, 11:01 PM
#39
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rear wheel bearing update
I raced the car last weekend, however I destroyed a half shaft (new denny's nitrous ready shafts ordered today) and only made about 10 laps on the bearings. For what it's worth, the rear bearings are still perfect, no grease leakage and the hardened bearing retainer was just like I installed it.
I run again Oct 7-8 and will update the forum with the results, but at this point I'm confident the rear bearings are going to last long enough to stick with the rebuilding program. I can rebuild them for about $35 a side and two hours of work. The hardered bearing retainers were $50 each but that is a one time expense. Stand by for more updates.
I run again Oct 7-8 and will update the forum with the results, but at this point I'm confident the rear bearings are going to last long enough to stick with the rebuilding program. I can rebuild them for about $35 a side and two hours of work. The hardered bearing retainers were $50 each but that is a one time expense. Stand by for more updates.