I have a 86 300sdl with 226k on it. I am going to attack this over the week end. Lokking at front end with the wheel off it looks like i only need a large pair of channel locks too work the cap off...

Is that correct or do i need to do something else to access the Bearings

Channel locks or a screwdriver & hammer.
allen keys & make sure you have a new seal.

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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The removal of the cap and the clamp will allow you to remove the rotor and the outer bearing will fall out in your hand.

However, the inner bearing is trapped behind the grease seal. Removal of that seal without damage to the bearing is a bit of a trick. You'll also need a new grease seal when you're finished repacking that inner bearing because you destroy it with the removal process. So, be sure to purchase same prior to starting the job.

On 123s the FSM calls for a Dial Indicator and Magnetic Base to adjust the front Bearing Clearance.
I tried to do it by "feel" as I had done on all of my other vehicles; got it too tight and ended up overheating the Grease and having to remove the hub and re-grease it.

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84 300D, 82 Volvo 244Gl Diesel

W124 Front Wheel Bearings NEED Dial Gauge (AND Magnetic Holder) to properly
"set" the "Axle Nut" Torque.

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'84 300SD sold
124.128

I suspect the FSM has a typo. I just recently reread mine, and it calls for 0.01 - 0.02 of play. It doesn't specify units, but neither inches nor mm make sense. Inches, and it's too loose, mm and it seems way too tight to handle thermal contraction summer -> winter.

YMMV of course

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

maximum limit 0.05mm

Adjust to between 0.01 and 0.02 mm, tighten and Re-Check.

Fine German Tolerances.

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'84 300SD sold
124.128

Here is a nice site to convert measurements quickly.

http://www.worldwidemetric.com/metcal.htm

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84 300D, 82 Volvo 244Gl Diesel

the clearance is not only to compensate for thermal expansion... a film of lubricant must remain at a minimum thickness.

Don't forget there are two entirely separate items expanding at very similar rates despite differences in volume.

TCE for steel 0.343 E^-6 ; with delta T = 27* K there is no issue with the specs proposed by the manual even if the spindle was the only piece expanding (for seasonal difference).

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I'd think the hub will expand more than the spindle because it is in contact with the brake rotor. The hub could possible reach close to 200F after some very spirited braking. The spindle will likely always run cooler than the hub. This will lead to a (slight) tightening of the bearing. There is no issue on the lube film thickness. Rolling element bearings operate with microscopic film thicknesses... "elastohydrodynamic lubrication" is the term for it. This means that the film is thin enough that the asperities (microscopic high spots) on the bearings elastically deform under load, and the lube film pressure in the contact zone rises very high to provide a very slight separation of the bearing elements. The reason rolling element bearings have a finite life (as opposed to plain bearings that can theoretically last forever) is because this cyclic elastic deformation of the metal ultimately leads to fatigue and spalling of material from the surfaces. Improper tightening (tight or loose) will cause the rollers to be unevenly loaded -- more towards one end or the other, rather than the middle. The uneven loading will cause premature failure.

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1987 W201 190D

I'd have to agree with the hub expanding more than the spindle.. but the bearing is just as isolated from the hub as it is from the spindle. The rims 'suck' thermal energy away from the bearing instead of transferring it to the knuckle / spindle via the bearing.

If we are to imagine thermal expansion only in the linear sense, which is how we make the tolerance measurements, we can assume the same metal, despite volume, will expand at the same rate, correct?

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and... if the hub was indeed, expanding more than any other part, and indeed transferring enough thermal energy to the bearings.... this expansion could possibly CREATE clearance b/w the spindle and the bearing.

what happens when a solid ring of metal is expanded? I.D? O.D?

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Well, I'd have to study the geometry. The fit of the races in the hub will get tighter, but the inside diameters of the races will get larger. This will create more bearing clearance. The length between the two bearing outer races will increase (hub side) while the length between the inner races (spindle side) will not increase as much. This will create less bearing clearance. Both effects are influenced by the characteristic lengths in question... the race diameters of the inner and outer wheel bearings, and the lengths between the respective races along the spindle axis. The taper angle will also affect how much of the linear and radial expansion translates into actual bearing clearance changes. It's not a difficult analysis, but it would require some measurements and more work than I could do at this hour after a couple of glasses of wine.

My offhand guess is that worst case situation... hard use of brakes right after starting off on a frigid day... would not change the bearing clearance by as much as the adjustment tolerance they give. Still an interesting question to ponder.

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1987 W201 190D

I'm not really thinking about the rollers in the bearing expanding. They're so small the expansion isn't worth thinking about. The races, however, will expand enough to influence things and they are in intimate contact with either the hub or the spindle.

As far as the expansion... of course... it's dependent upon material, temperature, and linear dimension only. The volume only comes into play in transient conditions... when a greater mass will take longer to change temperature given the same heat input as to a lesser mass. Take a piece of steel 1 x 1 x 10 and a piece of steel 4 x 4 x 10 and put them in a hot oven at the same time. the 1 x 1 x 10 will expand faster than the 4 x 4 x 10, but they'll ultimately reach the same length.

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1987 W201 190D

I think you nailed it with mention of the angle of the rollers. That's critical.

Lets imagine the races are the same thickness, therefore they expand the same amount and have a negligible effect here. We assume they are the same material as the hub too.

The angle (@) is then determined by axial linear expansion, and radial linear expansion only, right?

We'll call the rollers the Hyp.(H) and axial is cos(@), radial = sin(@).

On the w123 / w126 cos(@) is greater than sin(@). This makes sense b/c it how the car is supported, it needs a greater surface area.

The spindle is also much greater in length than width.


uhh... where was I going with this?

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