UstaB-GS549

I was at a MCSCC timetrial event at Blackhawk Farms this weekend. At the end of my third practice session, I heard a ping and then brake scraping noise just after tracking out of turn 7. We diagnosed the scraping as a severely warped front left rotor and replaced it. I did one more lap with the same exact noise and brought the car in. The second rotor had massive amounts of warpage too. Duh! You can't warp a rotor so that it has an 1/8" of runout... the flange on the hub was cracked. I missed it in my haste to get the rotor changed out before the next session.



Three weeks ago I detected play in the right front bearing and ordered a replacement. When I got around to replacing it, I discovered that the top 2 bolts were loose and the bearing was fine.

Because I didn't want the new bearing laying around in the humid garage, I brought it into the house.... it would have been nice to have it along as a spare....

I ended up limping home at about 60 MPH and riding the brakes in every corner to support the hub with the caliper. The sound of the pads hitting the high spot on the rotor for two hours on the drive home was a bit unnerving and comforting at the same time. I also packed 4 spare rotors, my tool box, and all the heavy stuff in the right rear corner to take load off the front left.

imp zog

Welcome to the sub-standard Timken hubs (who make the AC Delco replacements), I've had three crack just like that (all fronts) and almost come off. I've since switched to the SKF race bearings and haven't seen any problems yet, even after turning my fastest lap times to date this weekend.

Bimota Guy

Just had same failure in my last T1 race. I had a set of the SKFs sitting in the trailer. Just had not gotten around to installing them. They are installed now!

varkwso

Welcome to the club - our FRC effectively lost the LF wheel at T1 at Roebling when ours failed - no warning at all....

Jason

Damn yall are going to make me spend some money.

ghoffman

Well, Steve, since you had them, you can kick yourself in the butt! For the rest of you, we use and sell the SKF bearings that have a much thicker flange (about .4 versus .3 inch).




http://hardbarusa.com/hardbar/produc...roducts_id=136

Make sure you get the made in USA 12 point bearing fastener kit as well which eliminates the PITA Torx bolts. The kit also includes Nordlocks for the bearing fasteners and a new nut with a Nordlock for the lower ball joint.



http://hardbarusa.com/hardbar/produc...roducts_id=115

imp zog

It's the economies of racing; the cost of a couple of hubs are rounding error compared to the cost of repairs to the car (and your body!) when a wheel comes off! And I say "when", not "if" with those Timkin hubs, they are junk. Do what I do, just close your eyes and give them your credit card. And don't let your wife see the statement when it comes in!

UstaB-GS549

Update:

I put my 17x11 with 315's on the front and drove to work on Monday. It was to check steering feel and clearances, as I thought I had a deal going on two more 11" rims.

Immediately I noticed bearing humming at 45 MPH. The extra overhang of the 11" rims may have loaded the bearings a little more than normal and allowed me to hear the bearing hum.

Tonight I checked and it was the right front bearing. Seems that I needed one there anyway. It's original to the car and has survived 6 years of DE & time trials events. Not too bad for an OEM bearing. The left front went 4 years. The replacement Timken unit was only on the car for about two seasons.

I'm going to compare the machining on the OEM with the replacement Timken hubs. The machining grooves at the fillet between the flange and hub are kind of coarse looking on the replacement bearing. You can see this in the above picture. Like 32 threads per inch? This is a notch (stress riser) at the area of highest bending moment in the flange. Not to mention that this is a reversed bending situation, that will result in a fatigue fracture if the stress level and number of cycles is high enough.

ryan0

yeah.. you got lucky you caught it.. usually the wheel just falls off.

varkwso

The caliper bracket kept the wheel on long enough to come to a stop. The caliper itself works OK as a bearing on the inside of the wheel until the car comes to a stop.

According to Jake, once it failed, you could only really encourage the car in the direction you wished to go...

It did destroy the bracket though....was not too nice to the caliper and wheel either

TJM

I am a naturally suspiscious person, anyway BUT!

This seems all to common? Recently. It's a rash all over. We had a a guy in Norway lose one?

This is ugly, but I wonder if the boxes are the only thing SKF / Timken / AC-Delco????

Cheap Chinese bearings are $50. Good ones.... well more.

That leaves a lot of room for someone to make a serious profit with a lousy box?

Has anyone looked at the bearings to see the MFG marks.

TJM

UstaB-GS549

The box says Made in USA. Timken used to be in Canton, OH and known for their tapered roller bearings.

I just gave the flange 3 heavy hits with a 3 lb sledge hammer. I was not able to break it off. Further, I cannot see where the crack goes thru to the inside of the flange. I may have to cut it apart and do an autopsy later.

UstaB-GS549

This may be due to my stock exhaust. It's relatively quiet and you can hear a lot. With a loud exhaust you may not hear the brake pads hitting a huge high spot and effectively have no warning.

TJM

Gary

Since your the nearest thing to a resident expert, has this been a long term problem, since 1984?

Also notice you don't sell C4 front units. Any input there?

TJM

ghoffman

Well, I don't know about that, but Thanks!
If you think what the requirements were in 1984 or in this context, 1997 for the first year of C5's, you had 345HP with 245 runflats (front) with slide rail brakes with low friction pads. Now, the power is at least 2x or more, and people are running Hoosiers at 295-345 widths with monster NASCAR or German Touring car brakes that are better than what NASCAR had then. It is simply that the original bearing design was (I think) well done, nice work, but is seeing loads that were never envisioned by the original designers. An updated design is long overdue and the new bearings are really from the CTS-V and ZR1 programs.

davidfarmer

just curious, SKF=OEM ZR1 bearings right???

Also, does using your hardware kit make it possible to get the lower bolt our without breaking the ball joint loose??? Fortunately I haven't had to change one in a while, and I can't visualize if their is room to get a wrench/ratchet wrench down in there and get any leverage.

THANKS

Jason

there's room for a wrench, but I think the bolt would still be too long to get out.

drivinhard

jason's so talented he can break the lower ball joint loose while driving.

Jason

The things I can break while driving never ceases to amaze.

ghoffman

Yes, and you do have to separate the lower ball joint, hence the other nut and Nordlock.