Steering, Suspension, & Brakes

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302GT
Larry Shimp

(226 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

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Worn front hub
Posted by: 302GT
Date: April 03, 2022 03:09PM

I had some slight noise from a front wheel bearing so I decided to remove and inspect all of the front wheel bearings even though there was no noticeable play or binding in any of them. I removed both the outer races as well as the bearings themselves. In the first hub the outer race was a tight fit and took some effort (with a punch) to remove. The inner race come out with a light tap. In the second hub, the outer race was again tight, but the inner race was only held in by congealed grease. When I cleaned it up I found that the hub bore was worn at least 1/16 of an inch larger than the bearing race. The bearing was well lubricated and showed no sign of seizing. In fact, all of the bearings were well lubricated and in good condition since I checked and lubricated them every 5 years or so. Anyway, I bought two used hubs and rebuilt them. In both hubs the inner and outer bearing races were a nice tight fit. It is obvious that the one hub has been bad for a while, but with no obvious symptoms. Over the last few years I noticed the steering was less precise and the brake pedal dropped after driving a while. Both can be symptoms of loose wheel bearings but the bearings were shimmed properly such that even the bad hub showed no play when tested manually. However, it was obviously moving under the forces of driving. With the new hubs, the steering and brakes are back to normal.

Since it is virtually impossible to know the detailed history of an old MGB, I suggest, at least once, removing all the front wheel bearings and checking their fit. You might be surprised. Keep in mind it will probably be necessary to replace the inner grease seals since they will most likely be ruined by removal.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6261 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: Worn front hub
Posted by: BlownMGB-V8
Date: April 05, 2022 10:57AM

So this old chestnut then, Larry when you set up your bearings do you set them up with clearance or with preload?

Jim


302GT
Larry Shimp

(226 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

authors avatar
Re: Worn front hub
Posted by: 302GT
Date: April 08, 2022 05:34PM

I set them up with, as close as possible, about 0.002 to 0.003 inch end play. My procedure is to first clean the bearings of as much grease as possible, assemble the bearings and spacer with shims, then slowly tighten the retaining nut while checking for play. Once I get the shim pack to the point where all play seems to go away in the last quarter turn of the nut (at about 60 ft pounds) I put in a 0.003 inch shim. I then check to make sure that there is a slight amount of play with that shim in the shim pack with the nut fully tightened. After that I take everything apart again and grease the bearings before final assembly. Note: when I reach no end play with the last quarter turn of the nut, there is also a noticeable rotational drag. With the final 0.003 inch shim in place, there is no increase in drag with the nut fully tightened.

Play (end float) of 0.002 to 0.003 inches is recommended in a video by John Twist:
[www.youtube.com]


Moderator
Curtis Jacobson
Portland Oregon
(4533 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Worn front hub
Posted by: Moderator
Date: April 08, 2022 07:39PM

Yep. That's my preferred technique too. Good thread.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6261 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Worn front hub
Posted by: BlownMGB-V8
Date: April 09, 2022 11:15AM

OK first off,

YOU'RE DOING IT WRONG!

(flame suit mode: ON)

These are NOT ball bearings. They do not require end play. The practice of setting them with end play was a carry-over from the old days of ball bearings before tapered bearings were widely adopted. That practice was mistakenly continued in the wrong belief that what was good for one was good for the other, and a refusal to believe that a bearing could operate without clearance. The maintenance procedures are stuck in the far distant past and never caught up. John Twist is mistaken, and not for the first time.

In fact the tapered bearing was designed from the very start to operate not only without clearance, but with something called "preload" which is a small amount of crush or negative clearance. There are many, many proofs of this but one very common one is the axle differential. Would you EVER set up your differential side bearings with clearance? If you do the axle as a whole will not last long and the exact same principles directly apply to your spindles (and front brakes).

The tapered bearing evolved from the straight roller bearing but the issue with the roller bearing is radial clearance. Even the most precise roller bearing has no way to compensate for break-in wear except to get loose which means that the load becomes concentrated on a few rollers on one side of the bearing. Ball bearings are even worse. This means that the bearing has to be made overly large because the load is not evenly distributed. in many cases the ENTIRE load is concentrated on one roller or ball, meaning on one very small contact point. Think what this means about the point contact load. It can be exteme. This flaw was remedied by making the rollers tapered, that way play can be taken out by pushing the races towards each other and once all rollers contact both races the load becomes evenly distributed and the size of the bearing can be reduced.

This is important because if you run these bearings without preload in effect you are fitting a functionally smaller and weaker bearing.

Now as mentioned the bearing was designed this way from the very start. The geometry of the parts means that there is no roller wipe as it rotates. The taper of the rollers and races is precisely matched so that the same exact line of contact between roller and race runs straight and true from initial contact to release, meaning that the tapered bearing is as close as we can get to a true frictionless bearing with actual contact.

Now the preload: Please accept the proposition that all materials are plastic to some degree. No matter how hard or brittle something is, were you able to measure accurately enough any material will deform slightly before it shatters. Bearing steel is no different and you can prove it by setting a bearing race on edge and striking it with a hammer. It will bounce. The only way it can bounce is if it deforms, therefore it is plastic.

When preload is applied to a tapered bearing this plastic deformation, though very slight, is enough to allow all of the rollers to take up slack and make full contact with both races simultaneously. Again you can test this by taking a fresh, clean and dry bearing, the larger the better, assemble it and hold it between both palms while rotating it. You will find that as pressure is applied the bearing smooths out, runs true, and exhibits the accuracy and precision these bearings are renowned for. Release all pressure and the bearing soon shows signs of more erratic and rough rotation. This, more than anything else should convince you.

The range of acceptable preload is small and too much can be as damaging as not enough, but standard practices allow even the most ham fisted mechanic a way of assembling in an acceptable manner. ALL TAPERED BEARINGS OPERATE ON THESE EXACT SAME PRINCIPLES. Therefore all tapered bearings are designed to run with preload. It doesn't take much, but if they are run with clearance, like a ball bearing MUST be installed, then you get a phenomenon called "roller skip" which is when a roller loses contact with one race and skids along that surface until positive pressure is re-established. This, not surprisingly causes wear and it's much like when you lock up your brakes and flat spot your tires. It isn't immediately noticeable but over time it will get worse and worse as the roller begins to find the flat sport more consistently and it will make the bearing rough and eventually cause it to fail. Once this process begins there is no way to fix it except to install fresh bearings and preload them correctly.

So now you have the full story. If you continue to insist on installing your bearings wrong that's up to you, the very fortunate thing is that they are a bit oversized for the application and will not immediately become unsafe. You will need to replace them more frequently (Installed correctly they will last the lifetime of the car) but they are inexpensive for what they are. So you do have the choice in persisting in your delusions that the factory manuals and John Twist have it right. You have the freedom to believe what you like no matter how misguided. That, and the earth is a flat platter stacked on the back of turtles that go all the way down.

Jim


40indianss
don foote

(83 posts)

Registered:
08/01/2013 04:35PM

Main British Car:


Re: Worn front hub
Posted by: 40indianss
Date: April 09, 2022 12:12PM

I was taught that you set the tapered bearing then slightly back off the castellated nut ever so slightly to insert the cotter pin in the appropriate opening. It has worked for me for many years with nary a failed front wheel bearing. I may need to borrow Jim bs flame suit now


88v8
Ivor Duarte
Gloucestershire UK
(1001 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Worn front hub
Posted by: 88v8
Date: April 10, 2022 05:11AM

YOU'RE DOING IT WRONG!

Jim, never saw that thesis propounded before.

Last week I was into the front bearings of my 74 Land Rover. Taper roller. Factory spec 2-4 thou end float. The car (if that's what it is) had come back from a garage where they were doing some work I didn't want to do.. getting old... and they'd set the bearings with zero clearance.
I indignantly got out my dial gauge and set them to 2-3 thou as I've always done, using the double lock nuts.

Rear hubs are the same spec.

Situation is as you say; oversized bearings, low mileage. I might have to adjust them occasionally.

My 63 Rambler in contrast has iddy biddy bearings for a fairly heavy car. Same idea, tighten and back off a flat. No way to set it accurately. In this case, one hub had over 25 (twenty five) thou end float, that I took out with a shim to leave the magic 2-4 thou. That noticeably improved the tendency to weave under braking.

I had an MGC back in the day. There the end float was set with shims.

On my TR6 I used the Revington hub strengthening kit where the end float was set with shims rather than back off one flat.

In all cases there was an end float.

You're propounding revolution here. But I don't say you're wrong.

Ivor



Edited 1 time(s). Last edit at 04/10/2022 05:12AM by 88v8.



MGBV8
Carl Floyd
Kingsport, TN
(4319 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: Worn front hub
Posted by: MGBV8
Date: April 10, 2022 09:46AM

Who's making the popcorn? ;)

There are million & million & millions of American cars that use spindles that do not have spacers between the bearings. They use the tried & true method of snugging up the nut (12-25 ft-lbs or thereabouts) to set the bearing, then backing of the nut until the wheel just spins freely. Millions & millions over many years.

Disclaimer: I have used the above method for over 40 years on my Camaro, Chevelle, EL Camino, & Ranchero. I use the spacer on my MGB & set the end play at .002". Both methods work.

From Timken:

Generally, the ideal operating bearing setting is near- zero to
maximize bearing life. Most bearings are set with a cold setting
of end play at assembly. This comes as close as possible to the
desired near-zero setting when the unit reaches its stabilized
operating temperature.

The ideal operating setting that will maximize bearing system
life is generally near-zero to slight preload.

[www.timken.com]






Edited 1 time(s). Last edit at 04/10/2022 09:48AM by MGBV8.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6261 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Worn front hub
Posted by: BlownMGB-V8
Date: April 10, 2022 11:46AM

Unfortunately Timkin's public face is now managed by marketing types and is therefore subject to public opinion rather than being based purely on Engineering Standards as it was in the past. As a result, where they used to offer a very accurate but technical treatise on the proper setting of bearing preload (there IS a very narrow ideal loading but all tapered bearings will function adequately outside that ideal if not using the minimum acceptable bearing size), their literature now fudges the issue in an attempt to both limit liability from improper installation while broadening the definitions of what correct installation entails. Since these two goals are mutually incompatible the end result has been a bit of a muddled mess, allowing researchers to draw whatever conclusions they like and say it is supported. But even so their instructions do contain a kernel of truth, note they say from zero clearance to a slight preload, an acceptable if somewhat less than ideal range since most people have no idea what either zero or slight preload mean, particularly in this context.

If you want to do it right, just give a few moments of serious thought to what you are doing. Do you want your rollers to skid? No. This would be analogous to saying you want your tires to skid, or claiming that they will last longer if they do. Everyone knows that is not true. Same for your rollers. If they skid they wear. If they wear they develop flat spots. With flat spots they wear ever faster. The fact that they are hard does nothing to alter this dynamic, though it is a tribute to their design that they will generally outlast your tires regardless. So you do not want any clearance as clearance allows roller skid. Also you do not want either heavy or even medium preload as both will result in heat which is very damaging. If you run aluminum hubs you might want lighter preload than with steel as the differences in expansion can pinch the outer races a bit. The goal here is to use the lightest preload that still ensures full contact while using enough that you aren't constantly having to readjust to keep the rollers from getting loose from wear or being loose when cold.

There is enough give in the ideal range of preload to meet the bearing's requirements within an average mechanic's abilities, and in fact as Carl says domestic use here has an admirable track record of doing so, and there is little to fear. In all my years of setting bearings by feel I have only ever had one failure from excessive preload, back in my very early days as an inexperienced 18 year old when I admittedly cranked down too hard on the spindle nut thinking in an all too human way that if a little was good then more would be better. In this case it is not. A little is good. More is worse and less is worse. Do yourself a favor and listen to the voice of experience. I have researched this topic extensively and I know what I am talking about. Rather than setting end float at .002" of free play I would recommend shooting for .002" of crush if you feel more comfortable with keeping the spacers. More would be acceptable but that setting should be well within your comfort zone and if you find on subsequent disassembly that any play has developed you can increase it accordingly.

And, just to be clear, this is decidedly NOT a revolutionary idea. What WAS revolutionary was the concept of a tapered roller bearing, patented by Timken in 1898. Here it is 124 years later and we still don't understand how to use it, which can only be seen as a tribute to human stupidity. The concept is not that difficult.

BTW the video Carl shared above on the proper setting of wheel bearing preload is really quite good. Certainly the best I've run across in a practical sense.

Jim



Edited 2 time(s). Last edit at 04/10/2022 12:53PM by BlownMGB-V8.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1158 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Worn front hub
Posted by: ex-tyke
Date: April 11, 2022 08:23AM

Quote:
Rather than setting end float at .002" of free play I would recommend shooting for .002" of crush..

I, like Carl and the others, aim for about .002 end float, as dictated by the cotter pin hole/flat insertion - I have gone away from the 'addition of shims' to set end the float method outlined in the BMC/MG manual
. Any attempt at bearing "crush" renders the wheel unable to rotate by hand - surely that can't be right!



Edited 1 time(s). Last edit at 04/11/2022 08:54AM by MGBV8.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6261 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Worn front hub
Posted by: BlownMGB-V8
Date: April 11, 2022 09:28AM

>Any attempt at bearing "crush" renders the wheel unable to rotate by hand - surely that can't be right!

Graham, as a professional Engineer I expect better of you. The term "crush" was used to denote negative clearance or preload and no, it certainly does not render the wheel unable to rotate by hand. If that were the case not a single one of our rear axles would be able to function, as the typical preload on the side bearings is usually .010", or five times the above figure and those are quite easily rotated by hand.

Jim


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1158 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Worn front hub
Posted by: ex-tyke
Date: April 11, 2022 11:25AM

Quote:
The term "crush" was used to denote negative clearance or preload and no, it certainly does not render the wheel unable to rotate by hand.
Jim, Im not disputing, theoretically, what youre saying, but in practice with the bearing/spindle/castellated nut design of our cars, any attempt at the above negative clearance will not allow free wheel rotation....at least, it doesn't work for me!


DiDueColpi
Fred Key
West coast - Canada
(1336 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Worn front hub
Posted by: DiDueColpi
Date: April 11, 2022 01:51PM

I was getting ready to ramble on about wheel bearings and clearance.
But I can't put it any better than Jim did.
So I'll make some burgers, put on the nomex and go visit Jim's camp.

Cheers
Fred


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1158 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Worn front hub
Posted by: ex-tyke
Date: April 11, 2022 03:24PM

Quote:
So I'll make some burgers, put on the nomex and go visit Jim's camp.
..You forgot the scotchy scotch!


88v8
Ivor Duarte
Gloucestershire UK
(1001 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Worn front hub
Posted by: 88v8
Date: April 12, 2022 04:52AM

I suppose what was implied in Jim's initial comment, and picked up by Carl, is the difference between hot and cold.
The traditional theory, or vague hope if you want to call it that, is that a small cold clearance will disappear when hot.

Worst problem I ever had with a wheel bearing was on my 34 Lanchester, where one of the fronts had the outer race rotating on the spindle. Back in my teens I had no idea how to fix it, and it intermittently schreeched around like that for over a year before I sold the car.

Edit; just watched the video. The retaining cap allows a precision of adjustment that is impossible with ye old castle nut. It would still be possible to shim the castle to a much lower clearance, 1 thou maybe, if one wanted to.

Ivor



Edited 1 time(s). Last edit at 04/12/2022 04:58AM by 88v8.



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6261 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Worn front hub
Posted by: BlownMGB-V8
Date: April 12, 2022 12:11PM

Graham I understand what you are getting at but it does not take into account the geometry of the bearing. You aren't pushing the parts into a hard stop like you would be with a thrust bearing or even a ball bearing. Rather, the taper generates a "soft stop" if you will where distance traveled by the races is translated by the taper into radial forces, much like a Morse taper in a machine spindle. Therefore the travel distance is multiplied by a factor of 5 to 10 or so for any given amount of force. And since the bearing is a frictionless design it take a very great deal of pressure indeed to lock it up. Having tried this exact exercise with wheel spindle bearings a very long time ago I can say with assurance that if you spin the wheel and then crank down hard on the nut it takes a very hard twist of the wrench to force a braking effect on the wheel and tire, something on the order of 50 to 75 ft/lbs of torque IIRC. (At the time I was attempting to "make sure" the races were properly seated.) Try it and you will see that I'm right about this. (And why are differential side bearings only preloaded to .010" when a heavier preload would make them more resistant to gear pressure? It's a practical matter. At .010 you can assemble the carrier to the case without resorting to a case stretcher. Any more and it gets increasingly difficult but you could double that number without any serious risk to the bearings. Couldn't even begin to do that with a ball bearing.) And this is exactly the reason why lathe spindle accuracy went way up with the switch to tapered bearings. How well do you think that would work if they weren't preloaded, hmm?

Now the spindle nut thread is 20 tpi so each revolution is .050" and each flat is about .008" and most spindles are double cross drilled so you can go vertical or horizontal with the cotter, cutting that down to .004" of adjustment, say from .002 to .006" which is a very satisfactory range, or zero to 4 if you are more conservative. The new castellated washer design makes it even more accurate but the old style does work just fine and we have trillions of road miles to back it up.

Jim



Edited 1 time(s). Last edit at 04/12/2022 12:14PM by BlownMGB-V8.


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