LMAO, yeah I did miss that.

Seems funny that 500 different vehicle manufactures could have 700 different ways of doing the same job, with the EXACT same bearings.

Tapered front wheel bearings of rear wheel drive vehicles are almost universally the same general size, there are maybe only two or three different specific sizes used from Audi to VW and beyond, dating back over 70 years. And only a handful of Bearing manufactures which are all 100% compatible to each other over that entire span.

Some manufactures want a lil play in the bearings, some, like MB, look at end play. Others look at runout. Others still, want not only zero play, but actual preload, where you physically measure the amount of torque required to rotate the hub. Some are real finicky, others are real technical. Yet all of them are using the same darn bearings.

Whether its a trailer hub on your boat, or the front bearings on a Ferrari, the same basic principles and practices apply. Whether the nut was snugged to give a lil drag and zero play, or loose enough to give .003" play, neither one would be perceptible to feel and neither one would offer greater or lesser wear, all things considered.

Its really not anything so technical it needs to take up three pages.

Me, I snug, turn, loosen, turn, snug again, loosen a bit, turn, snug again but hard while turning, then back off a bit while turning. I get the nut just loose enough to turn by hand, and tighten to the next cotter hole. On vehicles that use a clamp nut (MB, Ferrari and some others), I do the same and just clamp it 1/16 to 1/8 tighter and lock it down and "feel" for play.

On new bearings and races, I snug them down tight and rap the hub real hard a few times with a leather faced mallet while turning the hub to seat the races. Loosen, tighten, more raps, keep doing it until there is no change.

Afterwards, I like to feel the hubs with my hand after a drive just to be sure they are running cool. The only bearing failures I have ever seen came almost immediately "after" a repack.

Actually, it's far more technical than typically understood by most mechanics. The tapered roller bearing would run perfectly well for a long period of time if it ran with zero clearance under all conditions. However, the installation of a bearing at zero does not assure that it will remain at zero under all temperature conditions. If the bearing warms slightly due to the heat from the brakes, the clearance could drop below zero.

In the condition where there is preload (below zero clearance), the bearing wear is significantly increased. They really do not like preload under any condition. Any manufacturer that suggests that they run with preload is doomed to an early bearing failure.

In my business, we balance jet engines and we strive for .0005" clearance in cylindrical roller bearings. If the clearance is lost for any reason, the life of the bearing is compromised.

I presume the cylindrical bearings are straight rollers not tapered like in the wheel bearing? If so how do you preload them?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Should we bow to the superior intellect?

Curious. Have you ever rebuilt or worked on a differential, or set up pinion or differential bearings? All of them preload the pinion and side bearings, but depending on manufacturer and application, some are assembled with quite significant amounts of preload.

That some of these differentials (as well as other assembies with preloaded bearings) operate for decades or as much as a million miles or more without failure, that they will somehow rapidly self destruct with significant preload is simply not believable. Early lathes used to have large ball bearings behind the chuck, but because they had no real preload, simply would not allow machine tolerances under .001". They went to preloaded double ball bearings which allowed tolerances to fall below .0005", and some lathes from the late 50's are still in use every day spitting out parts.

Most bearing wear comes from heat and dirt. Keep those two out and many will run amazing distances. The bearings in my old 75 MCI tour Bus are likely original, and likely have several million miles on them. But they run in oil, not grease.

Yes, I agree that they are assembled with preload under certain conditions.

Why cause undue loading on the bearing if it can be avoided? The life of a bearing is dependent on loading and running time. If the load can be minimized, the life of the bearing is increased significantly.

Many of the cited examples can survive with preload due to a splash oil feed that can remove any heat generated. This is not the situation with a typical automotive wheel bearing.

We can preload a cylindrical roller bearing if we end up in a condition where the inner race grows slightly due to heat while the engine is rotating on the balancing machine. We start with .0005" and it slowly gets to zero, or below zero when running.

It's highly undesirable because the temperature then climbs dramatically and the bearings are not running with any oil for coolant.

A wheel bearing on a vehicle is similar. It can suffer far more internal force due to temperature increases in operation with no way to remove the heat.

Who would "we" be?

I didn't realize you knew anybody?

This statement is telling, although you don't realize it.

If you preload a bearing and have no way to remove the heat generated from the preload and the operating load (a typical automotive wheel bearing), you can expect an early failure due to heat. Several folks on this forum have suffered wheel bearing failure...........most likely due to the application of a "random" preload following your practices.

If you have a way to remove the heat (the example of the bus) via oil, the bearing can last quite a long time.

This is an interesting case. We also manufacture spindles that must locate the engine component to a tolerance of .000030". We definitely must preload the angular contact ball bearings that are utilized in such a spindle, and they must survive without any coolant.

The reason they survive is that the bearings are 10" diameter and can handle a load of over 100K lb. So, if we put a 2K lb. preload on the rather large balls in such a bearing, it's effectively meaningless as far as durability.

Your example of the lathe is similar. A very large bearing that has a fairly low (relative to the maximum load of the bearing) preload.

Contrast this with a wheel bearing on an automobile that is only 2" in diameter with much less load carrying capability and the potential to build quite a bit of heat. A completely different environment.

What is missing in the above analysis is that the Metal Alloys the Axles are made of is different and one Alloy will have different a expansion chiastic and different rigidity from other Alloys if they are made in the same Shape.

The other issue is if the part is made in a manner that will transfer heat away from the Axle or not; the heat transfer ability is going to change the expansion rate.

More generic a Bearing might have a range that allows it to be operated safely with a Preload, with no preload and zero end play or with some End Play.

Here is a question. If I was an Aircraft Mechanic and I was replacing bearings on an Air Plane would you want Me to do it exactly by the Air Plane Makers Instructions or would you want Me to do it the way I felt was Best?
Which ever one you pick give an answer.

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84 300D, 82 Volvo 244Gl Diesel

If you do it the way "you think is best" and you have an A & P license, you can be criminally liable for anything that happens to that aircraft due to your negligence.

Fortunately for our friend, it doesn't really matter with an automobile.

My understanding of Bearing Preloads is when you set the Preload you sort of looking a head or sort of compensating for what the Bearing Clearances are actually going to be when everything is up to the normal range of operating temperatures and loads and the parts have expanded due to heat.

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84 300D, 82 Volvo 244Gl Diesel

No one is saying to put "excessive" loading on the wheel bearing. The point I was simply trying to make is that more than 100 different vehicle manufactures, over a more than 50 year span, covering 1000's of various models, have used specs from rather well preloaded, out to over .001" runout, and all of them fall between the bearing manufactures specs, and none have been prone to early failure.

You can make rocket science out of it all you want, but its not, and I wont. There are a lot greater things to make a big to do about, but wheel bearing adjustment shouldnt be one of them. I learned it at 12 years old, and a lot of guys learned it in high school auto mechanics.

In all reality, bearing quality the last 20 years has been so high, and lubricant quality so good, that its possible to put half a million miles on them and never even touch them. When you do, its often more cost effective to just replace them and start over new. The days of repacking them every 10K miles, as my Dad taught me, are far behind us.

Many dont know this, but most cities have bearing suppliers who can match just about anything you can bring through their door, often at great savings over parts stores and dealers. Just look in your local yellow pages under "bearings". I dont buy bearings or seals anywhere else unless I they cant get them, and in 40 years ive only stumped them once.