depami

I was considering repacking the front bearings on my 86.5. I don’t know if they’ve ever been off or not.

But, then I read this:

Wally, what were his concerns? Improper packing? Improper tightening?

Grabbing the wheel top and bottom does not allow movement. I will at least slide the calipers off and check the “feel”. What else should I check?

Any comments are greatly appreciated.

Thanks

Denny

Rich9928p

Unless a bearing is sealed, I don't agree that they shouldn't be repacked. Grease as improved over the years so the interval can be longer, but repacking the bearings is one of the factory stated service items.

mark kibort

top and bottom of the wheel is all you need to grab. you dont need to pull the calipers off, its not rocket science. if the washer can be moved with some resistance between the tightening nut and wheel bearing, its fine. (some resistance is the only subjective factor).

often, you can confuse wheel bearing slop with upper ball joint wear, or front to rear grabbing movement can be confused with tie rod slop. If you are really concerned with the pads not giving the right "feel" for adjustement, just pull the pads back in the calipers slightly.

repacking is a good idea, as they can get dried out over 20 years.

when they go bad, usually the bad side will howel when loaded. (outside tire in a turn)

mk

dr bob

In my limited experience, most front wheel bearing failures seem to happen when they are "adjusted" to correct a wear problem. If you find that you need to tighten the adjustment well into the life of the bearing, it's really time for replacement. If your bearings are holding adjustment well and you are doing a repack as PM, by all means go for it. Inspect them carefully when you have them out and clean, and if there are any signs of wear or damage, go ahead and replace them.

Common mistakes include overtightening the bearings. Roller bearings are designed to have a film of lubrication between the rollers and the cup face, so adjustment must allow for that space. The WSM instruction is to adjust until it's snug, then check to make sure that you can move the washer behind the nut using s screwdriver. No prying with that screwdriver, just gentle pressure; you MUST be able to slide the washer around some. If you get it too tight, loosen the nut, roll the hub around a few times to re-establish the film, and try again. I can generally use a flat-blade screwdriver to do the adjustment and get it pretty darn close. This is a twisting adjustment with the screwdriver sticking straight out, parallel to the spindle axis. Three fingers only on the screwdriver. It's that light. Then verify that the washer moves OK. With the wheel mounted, you can verify with the push-pull test.

Another common mistake is packing the hub in between the bearings with grease. This is generally not a good idea, mostly because it will cause water to get drawn in past the seal. Unless you are working on the boat trailer with the bearing-buddies on it, don't pack the hubs. A little is OK smeared on the installed bearing, but no more is needed.

Last but not least, the Mobil-1 synthetic grease in the tube is the same color as the factory grease and is readily available. I use that, and also like the Redline CV-1 grease for wheel bearing service.


Oh-- don't forget to replace the seal and inspect the spindle where the bearing races sit for wear. The wear will be on the bottom of the spindle. A spindle that doesn't hold the cup squarely and snugly will cause problems. If it's loose to where you can feel the cone doesn't fit snug, you probably need to replace that spindle.

Leon Speed

I'm in the camp that says if it ain't broke, don't fix it. Mainly because I'm afraid to repack either too tight or too loose.

Edit: what dr bob says

WallyP

Earl Tuttle, deceased, was a long-time mechanic, engineer, SAE (Society of Automotive Engineers) member, and bearing application specialist. He gave an SAE presentation on wheel bearings at one of our meetings years ago. Some points from that presentation:

Bearing Life:
- A properly-spec'ed, properly adjusted, properly used bearing will have unlimited life if properly lubricated and not abused. Most wheel bearing failures are the result of dirt, maladjustment, or extreme offset.
- In most cases, failure is caused by dirt introduced during servicing, or maladjustment during servicing.
- Earl's recommendation was to clean, clean, clean and repack bearings only when they have been removed for some other reason, such as brake or hub service. He did NOT like bearing packers, as most people don't keep them clean enough. He liked hand packing with clean hands or new gloves.
Seals:
- Never reuse a grease seal.
- Never install any lip-type seal dry. Never. Lubricate the seal lips and the sealing surface with a good grease (this includes oil seals).
- The proper sealing surface is NOT mirror polished. The best sealing surface is pretty much what you will get by sanding the surface lightly with 400-grit wet-or-dry paper at a 22 degree angle. This is not quite sanding around the shaft, but at a slight angle. You want to see light scratches. A polished surface drys the seal lips, with quick failure.
Grease:
- The old "wheel bearing grease", which is not sold much any more, was a thick fibrous grease, and was a terrible lubricant for wheel bearings. We had lubricant application engineers from two different oil companies (Shell and Texaco) there who could get any of their company's products for free, and both of them, and Earl, agreed that the sticky black moly grease that Sears sold was the best wheel bearing lube that they knew of, and was what all three of them used in their cars. (There are now specialized high-temp greases sold for wheel bearing use that are probably as good or better.)
- You don't want a super-grease in bearings, and you don't want a thick grease. If the grease is too slippery (Teflon, silicone, etc.) or too thick, the rollers or ***** will slide instead of rolling, leading to failure.
Adjustment: The proper adjustment for a wheel bearing is zero preload and zero end play. Earl liked the method used on the production lines.
- Install the hub. Use pliers or a wrench to tighten the bearing nut firmly, but not tightly - perhaps 20 lb/ft - as you rotate the hub. This takes any play from the bearings.
- Stop rotating and loosen the nut.
- Without rotating, tighten the bearing nut as tight as you can get it with your fingers only - no tools.
- Check the hub for any sign of looseness. If you can detect any end play, repeat the process.

I hope that this helps. I realize that other people will have their own opinions on the subject...

mark kibort

Dont use Redline syn. grease, as it will liquify and come out the seal cap. this might not happen with daily driving, but when you get stuff hot down there, it doesnt hold up. the good ole high temp wheel bearing grease seems to work best.

dr bob

Great write-up and explanation. Wally.

I never gave much thought to the smooth sealing surfaces. 22º angle is almost identical to what you want in hone marks in a steel bore to seat piston rings and hold just the right oil film. Coincidence? No such thing...

WallyP

Earl also explained something that had puzzled me...

If you tighten a front wheel bearing nut to perhaps 20 lb/ft, the bearing will quickly fail.
If you don't torque a visually identical tapered roller bearing in the differential to 90 lb/ft, it will quickly fail.

It turns out that the difference is just a few degrees of taper in the rollers - but that few degrees makes the bearing behave very differently.

I miss Earl...

dr bob

I have an idea that a splash-fed or immersed-in-oil differential carrier bearing can take some preload that a non-pressure-greased wheel bearing can't. I suspect that the normal radial 'load' on a wheel bearing squeezes the lubricating film quite a bit more than 15 lbs/ft of preload on the nut will, but the pressure point is dynamic as the wheel rolls. That radial load allows the unloaded rollers to rebuild the lubricating film of grease before they are loaded again, I continue to suspect.

WallyP

There actually is a physical difference in the bearings. If you substituted a differential bearing for a wheel bearing, it might last for a while. If you substituted a wheel bearing for a differential bearing, it would fail very quickly.

smiffypr

[QUOTE=WallyP;7338216]the sticky black moly grease that Sears sold was the best wheel bearing lube that they knew

I see you are still recommending "moly" grease. I have had a wheel bearing fail after one track day, and the damage was diagnosed as being from molybdenum grease. (I had run out of the other grease, so only the one wheel bearing had the moly "chassis" grease.

Looking at grease maker's web-sites, I found that the do not recommend moly grease for wheel bearings:
http://mclube.com/products/80 says
"Do not use with high speed ball or roller bearings."
http://www.opieoils.co.uk/p-6315-cas...ly-grease.aspx says "It is not recommended for use in small, high speed ball and roller bearings."

Maybe the particular sears grease is a grease with a small amount of moly rather than a "moly grease" containing a large enough amount to damage roller bearings, but people need to know.

I would advise everyone to look on the tin and see if the grease they have is recommended for car wheel bearings or not.

Smiffy

WallyP

A front wheel bearing will never meet anyone's definition of a small, high-speed bearing. They turn at about 1000 rpm at highway speeds, perhaps 3000 max on a top-speed run. A high-speed bearing is three to ten times that.

I was reporting the recommendations of a skilled, experienced bearing engineer, as vetted by a room full of other SAE members...

blown 87

Just a thought from a poor old country mechanic that has done thousands of front Timken style bearings on cars, when set up per the factory recommendation, the 928 front wheel bearings are set up with clearance, not preloaded or set up with zero clearance like many others manufactures recommend.

Maybe it is because of the high speed nature of the car, I do know this much, it is far cheaper to replace a set of Timken style wheel bearings than it is to do a hub.

Just one more instance of replace, instead of repair, it takes far less skill to do a hub than it does to set clearance or preload, so that may have had some bearing on the "Why".

smiffypr

Re: A front wheel bearing will never meet anyone's definition of a small, high-speed bearing. They turn at about 1000 rpm at highway speeds, perhaps 3000 max on a top-speed run.

High speed and small are both relative terms, so to a ship builder anything smaller than a foot would be small and anything faster than 1000rpm would be fast.

Re: A high-speed bearing is three to ten times that.

A high speed bearing is a bearing designed and toleranced for high speed. Even when it is not turning, it is still a high speed bearing.

re: I was reporting the recommendations of a skilled, experienced bearing engineer, as vetted by a room full of other SAE members.

I am reporting my actual experience, plus the recommendations of grease makers, and one bearing expert. I don't believe any experience or qualifications are required to join the SAE.

Smiffy