Why are my plastic bearings melting

JOEAMSTADT

MEMBER
1998 CHEVROLET S-10
150,000 MILES

I changed my upper and lower ball joints and then packed the bearings and reinserted them into a new rotor. After everything was reassembled and properly torqued I took it for a test drive and I hadn't made it more than a mile when I heard a pop. I turned around and went to investigate in the garage. I took off the hub cap and found the dust cap popped off and the front bearing(PLASTIC) was melted and greese had poured out a bit. It now seems nearly impossible to remove the rotor without doing damage to the knuckle etc. I double checked the parts I got from the store to make sure they were the correct ones and they are and I know I packed the bearings and inside the rotor really well, but I cant figure out why this happened. I did the other side a little while ago and it's fine.
Any thoughts?

7 Replies

HMAC300

MECHANIC
48,601 POSTS

If you cleaned the bearings with mineral spirits and then used lithium grease to pack them the mineral spirits weren't dried out engouh and it eitehr ate the grease up or you didn't pack them right. In my professional career I NEVER used plastic wheel bearings because people who did had the same problems. Get steel ones. Also properly torqued means to torque to 50' lbs and back off to first hole on nut on a chevrolet. You may have tightened it to much.

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Tuesday, January 3rd, 2012 AT 6:07 PM

JOEAMSTADT

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4 POSTS

Thanks for the tips. I will definitely never use the plastic bearings again and I was a little hesitant when I got it at the parts store, but it matched the one I took out so I figured it would be fine. I didn't use any cleaner and I am pretty sure I packed them really well and filled the inside of the Rotor hub with plenty of grease as well. I did find a couple guides online that said to torque it to 180' lb to 240'lb and not 50. That did seem a little tight, but when I got it there, the hole for the cotter pin was lined up perfectly so I went with it. Once I get it off, I will be getting a new metal bearing.

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Wednesday, January 4th, 2012 AT 12:07 AM

HMAC300

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48,601 POSTS

Ok my mistake ont eh torque but you have to back it off 1 notch for the cotter pin.

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Wednesday, January 4th, 2012 AT 12:12 AM

CARADIODOC

MECHANIC
33,916 POSTS

180 to 240 foot pounds is for the axle nut on the one-piece bearing and hub assembly on a 4wd truck or front-wheel-drive car. That torque is critical in preventing the bearing from becoming noisy.

I never used a torque wrench on tapered bearings but 50 foot pounds would seem to be about the same as "common sense". Failing to back the nut off to the nearest cotter pin hole can leave the rollers too tight so they squeeze the grease out rather than let it run in between the axle and rollers. I've run into a few people who think tight is good and tighter is better.

Hi guys. I've been following this to learn what is meant by "plastic" bearing. If you mean the outer cage is plastic, that is common. It just holds the rollers in position. Are you saying that causes problems or am I missing something else?

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Wednesday, January 4th, 2012 AT 1:36 AM

JOEAMSTADT

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4 POSTS

Yes, plastic cage that holds the rollers.
Looking again, I think you may be right about the torque. It's not a 4X4, but just a rear wheel drive and therefore it shouldn't need the full torque. And thinking back to the first time I took the nut off, I did it with my hand(no socket).