Front wheel bearings question

[madjack4]

Well it would need to be very worn ive worked for myself in the motor trade for 50 years ive seen some very bad repairs and some very worn parts over the years in a scale of 1 to 10 i would say a slightly worn stub axle rates as a 1 . No disrespect to people who are on forum but most of them have no experience in the repair of motor cars .Everything you strip down on a car is worn to some extent experience tells u what to replace and what not to replace ,so a normal man on the street has not got that experience .Anyway ive said my bit now i will leave it at that

[angelw]

madjack4 Wrote"

If jaguar had a design flaw all early fords like cortina escort anglia all early vauxhalls had the same flaw it was the done thing in the day.

The bearings and the Stub Axle dimensions are exactly the same as used on a Box Trailer; nothing exotic about the front wheel bearing system of a Jaguar.

The reason for the running fit of the bearings on the axle is to make it easier for the mechanic servicing the vehicle. If inner bearings were an interference fit, or bearing retainer was used to secure the bearing, any time the hub had to be removed, for whatever reason, the bearings and the seal would be left on the axle. This would then require a further operation to remove the bearing and seal.

Using a spacer and adjusting the bearing pre-load or end float with shims was used on many cars of that era, and the best solution in my opinion.

Regards,

Bill

[jp928]

I worked in a brake workshop in another life, and when we found signs of inner race rotation was advised to apply a couple of dimples to the area with a centre punch, just enough to require tapping the inner race home on the axle. Timken's web site shows a steep decline in bearing life when a pre load is applied cold - end float needs to take account of operating temperature to avoid pre-load. Some british cars of the 40s-50s called for .003-.005 float, and provided means to adjust this finely - eg Rover used a round hub nut with 4 holes and a keyed washer with 13 holes to provide a 52 step vernier.
Roller bearings dont like heat, hence hot bearing detectors along railway lines.
jp

[angelw]

jp Wrote:

I worked in a brake workshop in another life, and when we found signs of inner race rotation was advised to apply a couple of dimples to the area with a centre punch, just enough to require tapping the inner race home on the axle.

Hmm. I suspect that company was called "Rough Nuts Are Us Inc".

The main reason the fit of the bearings on the journals is a running fit, is for the benefit of servicing. An interference fit for the inner bearing would leave both the Cone of the inner bearing and the seal being left on the shaft. when, for whatever reason, the hub is required to be removed. Even mutilating the journal with a centre punch would probably result in enough localized interference to have the same result.

The following graph, is quite typical for Taper Roller and Angular Contact Bearings. You can see that the life expectancy of the bearing peaks in the Preload Zone.



For many years, I rebuilt precision spindles of CNC machine tools and without exception, the bearings are arranged in Preload. Often, Machining Centers working on large dies with small diameter tools to get into small corner radii, may run 24/7 at revs in excess of 20,000, and will exceed in a few months, the revs of an E Type wheel bearing in more than a typical life time for the car.

For those bearing systems of machine tools that are greased once for live, the amount of grease used is typically only 10% of the available air space between the balls in the bearing. Accordingly, when I fit new wheel bearings, the amount of grease used in only what can be pressed into the bearing and compared to a machine tool bearing, is an overkill.

To preload the front bearings of an E Type (the same bearings and axle dimensions of a small box trailer), without some form of restraint, will ensure that the bearings spin on the shaft. So truth be known, its probably the running fit of the bearings on the shaft that led to having an End Float specification. There are many cars today that use Angular Contact Bearing with split center races, so that when the retaining nut is torqued up tight, the bearings achieve the preload to the extent built into the bearing.

I manufacture a Stub Axle where the bearings are an interference fit on the shaft, but the better system that I also manufacture, is a spacer that sits between the two bearings that allows the bearing retaining nut to be torqued up tight, thus preventing the bearings from spinning.

Regards,

Bill

[rfs1957]

Timken's web site shows a steep decline in bearing life when a pre load is applied cold - end float needs to take account of operating temperature to avoid pre-load

Could you substantiate this statement with an example, as it appears to be the complete opposite of Bill Angel's experience, and his research.

Frankly Bill, I admire your perseverance in replying to this kind of nonsense.

As Christopher Storey is no longer with us, we shall need to step up our own vigilance.

[angelw]

Following is but a small extract from a paper on the design and operation of Taper Roller bearings.

Wheel end tapered roller bearings are designed to be set to preload. They are not designed to be "loose" or have endplay.

In a preload condition, all clearances (endplay) between components in the wheel end assembly are completely eliminated and the bearings are slightly compressed. Keeping a light preload force on the bearings keeps the tapered rollers lined up so they roll the way they should.

This point about the alignment of the rollers prompts me to mention the misconception regarding Drawn Cup, Needle Roller Bearings, of which there are two distinct designs, Cage Guided and Full Compliment.

As the name implies, the Full Compliment version has a Full Complement of Needle Rollers, where its not possible for further rollers to be inserted in the Drawn Cup. The Cage Guided version, also as the name implies, employs a cage inside the Drawn Cup to hold each Needle Roller separated from each other and in precise axial alignment.

Many believe that the Full Complement version is superior to the Cage Guided types and at least some of the Jaguar Parts suppliers, offer the Drawn Cup, Needle Roller bearing for the Jaguar Manual Gearbox First Motion Shaft, in both versions, with the Full Complement version being described as Uprated, where in fact, they should be described as a Down Rated Bearing.

Its true that in certain applications, the Full Complement bearings has a slightly greater load bearing capacity, but where its used in the Jaguar Gearbox is not one of them. where the revs that the bearing can run at is more important. Although all of the rollers are rotating in the same direction, CW or CCW, the circumference of each adjacent roller, 3 o'clock on one and 9o'clock on the other, pass each other in the opposite direction. As there is nothing to separate the rollers, the Full Complement Needle Roller bearing is prone to overheating due to friction between the rollers and therefore, have a much lower speed rating than the Cage Guided version. The other condition that the Full Complement Needle Roller Bearing suffers, is skewing of the rollers, due to the absence of a precise guiding apparatus. This skewing of the rollers results in more rapid wear of the journal on which they run.

The Cage Guided, Drawn Cup, Needle Roller Bearing has either a metal or composite cage that keeps the rollers separated and precisely aligned axially. Accordingly, they have a much greater speed rating than the Full Complement type.

Regards

Bill