Front axle nut - How tight?

Earle

Earle

Senior Member
I've had the front brake drums off and on dozens of times in 25 years and was just informed that I have been doing it wrong! (by my very-trusted mechanic - who shall remain nameless - to protect the innocent). Now I am the proud recipient of "authoritative" but conflicting advice on how tight to make the spindle nut before installing the cotter pin:

Technique #1: (per various owners, and "A" restoration books, etc.) - "Finger-tighten" the spindle nut against the bearing retainer washer while spinning the brake drum to insure the bearings are well in place and most of the grease is squeezed out from the roller-race contact surfaces. Then back the nut off to the next nearest slot in the nut. Install the cotter pin. After the wheel is istalled, pull in and out at the top of the wheel. No looseness or a VERY SLIGHT amount of looseness is OK. This insures that some grease can circulate throught the bearing rolling surfaces while running, keeping the bearing cool and not over stressed. "Any tighter on the nut will cause accelerated bearing failure."

Technique #2: (recently per a "very-trusted & experienced 'A' mechanic") - Same procedure as #1 EXCEPT after the nut is "finger-tight", turn the nut TIGHTER to the next slot in the nut using a wrench if necessary. Then install the cotter pin. "The bearings must be preloaded. ANY looseness at all will cause accelerated bearing failure." There NO looseness in the wheel, of course, after it's installed.


HELP! what do you experienced Barners do? I have always used Technique #1 and never had a bearing problem. I DON'T like the idea of having the bearings clamped up tight and beyond. Intuition, mechanical sense, and engineering experience tells me that this forces all the lube out from the roller-race running surfaces, causes a hot-runnung bearing and increases fatigue loading and brinelling-failure of the race.

Since there may be more time-tested Model A "art" than science here, I'd like to hear how you guys approach this "simple" task!

Getting this "simple" task wrong could lead to bearing failure which could mean loss of control on the road. This critical task should probably get more attention and discussion than it typically does.

Earle
 
I'm with you, Earle. I've always used technique #1(except I tighten with a wrench a castle past finger tight then back of a castle or two) and never had a bearing failure.
 
In the past few months this was kicked around a bit. Someone remarked that the current castellated slots are are not as accurate as the original so it's difficult to get a good cinch,then back off and have the slot line up as per original nuts. Urban legend?.............darned if I know.
 
A little pre-load on brand new bearing and race might be fine in in./pounds, but then how can you calibrate it? I tighten with a wrench till the bearing starts to drag and back off for the cotter pin.
 
The method I use is similar to your #1, I tioghten with wrench, or pliers while spinning the hub, (to seat bearings) then back the nut off, then with 2 fingers I tighten as much as I can, then back off to closest cotter pin hole.

Later cars have fancy torque specs for wheel bearing adjustment, the final tightening works out to about as tight as 2 fingers can tighten (as long as the threads do not drag any)--maybe if I can just almost get the cotter pin in I will go tighter--like if 1/2 of the cotter pin would fit.

Ideally there would be no preload, and no play, but slight play is better than slight preload, some cars call for .001,.002 end play which would translate to some play felt at the tire.

If you have wear in your spindles there will always be play ---even if the nut is so tight that it could burn up the bearings.
 
ok heres my method, tighten the bearing till it has a fair amout of drag, spin wheel around a few times, this centers the bearing in the race, then back off nut till its loose, spin wheel again, then tighten till a small amount of drag is felt, a loose bearing will start to let the bearings slip a little crooked in the race and destroy them selfs, a small amount of drag on the bearing is 100% better than a loose bearing, there should be no play in the wheel if the bearings are adjusted right, heres a hint on getting the bearing a little more looseness if need because of the caselated nut, use a thinner cotter key so you have a little more room to back of the nut, there is very very little pressure put on the nut, not near enough to shear it, now here is where the argument starts, bend the long leg of the cotter pin up and over the the nut, cut off the short lrg next to the net, this makes it it a heck of a lot easier to remove it the next time you have to, your only straightening one leg to pull it out of the spindle, only need one leg bent to keep it from falling out
 
Yes, I still like the concept of getting the nut "two-finger-tight" - enough to get all looseness out of the bearing but not tight enough to drag the spinning drum to a fast stop. THEN - if this "perfect" nut position happens to put a castle over the cotter hole, put another washer under the nut and shave its thickness until the above set-up allows a slot to fall exactly over the hole. Or try a different nut! - "Luck of the draw".

It seems that the consensus so far is that a pre-loaded bearing with a tight nut is worse than a VERY-slightly loose bearing. That's what I've always heard.

The whole bloomin' problem is the width of the castle when it ends up directly over the hole at the "perfect" bearing tightness (and it always does!!). Going the next slot tighter is too tight and going the next slot looser is too loose! Stupid castle nuts!

I'm gonna try the shaved, added washer and nut-swapping techniques.

I'm trusting that Henry, as with other A detail designs, over-designed (sized) the outer wheel bearing to take the abuse no matter if it's too tight OR too loose!

Thanks for all the good input, Gents. Keep 'em comin"!
 
HI
Going to put my 2cents worth in. All the weel bearings I put in were snug but free!!
Tighten the nut up with wrench then back off to nearest slot. Wheel should turn
SNUG BUT FREE
Works for me
 
If you want to double the adjustment points drill another cotter pin hole in the spindle-usually 90 degrees from the original hole---or whatever angle allows a 1/2 way between adjustment.
 
i tighten the nut with a wrench while spinning the wheel untill the wheel drags, then back off the nut and tighten the nut with my finger's, if i cant tighten it enough with my fingers to the next castle [hole] i back up to the next hole. "agin" as said above slightly loose is better then slightly tight. you should never use a wrench to get the carter pin to line up. JMO.
 
I vote for technicque number 1. HOWEVER be sure to use the castle nut with the correct number of cotter pin slots.

I forget what the number is but I remember on the coupe last year that some replacement castle nuts for the front wheel bearings have FEWER slots than the original and thus not as "FINE" an adjustment.

There was a reason that Ford used the number of slots that they did.

Over tightening the bearing will cause premature bearing failure from many causes.

Heat, stress, more heat, more stress....repeat....crunch...grind....stop.

Dennis L Oberer
Green Bay WI
 
Earle said:
I've had the front brake drums off and on dozens of times in 25 years and was just informed that I have been doing it wrong! (by my very-trusted mechanic - who shall remain nameless - to protect the innocent). Now I am the proud recipient of "authoritative" but conflicting advice on how tight to make the spindle nut before installing the cotter pin:

Technique #1: (per various owners, and "A" restoration books, etc.) - "Finger-tighten" the spindle nut against the bearing retainer washer while spinning the brake drum to insure the bearings are well in place and most of the grease is squeezed out from the roller-race contact surfaces. Then back the nut off to the next nearest slot in the nut. Install the cotter pin. After the wheel is istalled, pull in and out at the top of the wheel. No looseness or a VERY SLIGHT amount of looseness is OK. This insures that some grease can circulate throught the bearing rolling surfaces while running, keeping the bearing cool and not over stressed. "Any tighter on the nut will cause accelerated bearing failure."

Technique #2: (recently per a "very-trusted & experienced 'A' mechanic") - Same procedure as #1 EXCEPT after the nut is "finger-tight", turn the nut TIGHTER to the next slot in the nut using a wrench if necessary. Then install the cotter pin. "The bearings must be preloaded. ANY looseness at all will cause accelerated bearing failure." There NO looseness in the wheel, of course, after it's installed.


HELP! what do you experienced Barners do? I have always used Technique #1 and never had a bearing problem. I DON'T like the idea of having the bearings clamped up tight and beyond. Intuition, mechanical sense, and engineering experience tells me that this forces all the lube out from the roller-race running surfaces, causes a hot-runnung bearing and increases fatigue loading and brinelling-failure of the race.

Since there may be more time-tested Model A "art" than science here, I'd like to hear how you guys approach this "simple" task!

Getting this "simple" task wrong could lead to bearing failure which could mean loss of control on the road. This critical task should probably get more attention and discussion than it typically does.

Earle
Click to expand...
Just repacked a bearing tonight and had the same question! Logged on to ask it and your question was at the very top! Small world!
 
I'm strictly a number 1 person. For reference the July 1932 Service Bulletin says the nut should be run up tight and then backed off 1 quarter turn. Since 32 used the same bearings it would seem to apply.
 
Thanks, Gents. Hey, Jerry, I saw that Service Bulletin and I thought it was really vague. What is "tight"? And backing off as much as a 1/4 turn could really result in a loose, wheel and bearing!

After I mentioned my "added washer" idea above, I thought - Duuhhh - All I have to do to get a teeny weeny more turn on the nut is to LIGHTLY touch the surface of the nut on a belt sander or the flat side of a grinding wheel! Forget the extra washer.

'Giving it a try tomorrow. --- "Two-fingers tight" while spinning the drum - BARELY dragging. Then trial-and-error grinding/sanding of the nut face so the nut slot matches the hole EXACTLY at that tightness.

Off to the garage tomorrow morning.

Thanks again for all the good added input.

Earle
 
Tapered roller bearings, as used in front hubs, should NOT be pre-loaded.

Doing so almost guarantees a burned bearing.

Turning-up snug , then back-off one slot has been the instruction I've seen in almost every shop manual printed between 1935 and 1970.

I err on the side of "one slot loose" rather than "one slot tight"; the weight of the car and the taper of the bearings forces the bearings outwards, against the spindle and the nut & washer.

Pre-1955 Chevrolets used ball-bearings up front; these ARE supposed to get a "pre-load".
 
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