Rear Main Bearings

[squeak]

I have heard it said that moisture plus periods of inactivity promotes rust and pitting in the rear main. Could a fully sealed bearing minimize this  by virtue of it being coated in grease not used engine oil? Would the bearing run hotter not being flushed in engine oil? In other words are sealed rear mains a good idea?

[Ruairidh Dunford]

Tony is right they are Hard to fit.

Colin
NZ

I have no experience of fitting such but I imagine you would need to employ similar strategies to those used when installing the centre cam rollers Colin, does that sound correct?

I am also interested to know if the extra rollers in this bearing add longevity?

[David Stepney]

Thank you all for your advice and comments.to answer Bob Culver's comment, the outer race is a reasonably good fit in the housing, but the inner race is only a little tighter than a good push fit on the crank. I can't turn it on the crank though, and neither the old bearing nor the crank shows any sign of rubbing. Both the old bearing and the new bearing are about the same fit.

I shall speak to Jamie this morning and possibly ring Hoffmann Precision Bearings at Huddersfield to seek advice. The extra rollers may extend the bearing's life. The old one is probably about 50 to 60 years old, but the car did very little mileage during that time and was laid up in a warm garage for 25 years prior to me buying it.I have some Loctite 641 bearing fit, so I may coat the crank with this prior to fitting the bearing if that is what I decide to do.

I think I have worked out how to fit it. Put a cable tie round the rollers whilst I tap it into position making sure that it all goes into the outer race without jamming.

I will post again when I have decided what I am going to do.

[Colin Reed]

HI Ruairidh,
As tony said they will take a higher loading so I would assume they will have a longer life.
Regarding a sealed Bearing have not seen a cylindrical roller bearing with seals .

Colin
NZ

[Ruairidh Dunford]

Tony,

Would these bearings last longer do you think?

I was discussing with another Forum member a few weeks back how the bearing here needs regular change, unlike the front two that hardly ever wear out. Any help at the back seems a good idea in theory, do extra rollers provide that in practice?

[Chris KC]

David,
Think very, very carefully before securing crankshaft bearings with Loctite.
If there is no sign the bearing has been spinning, I'd leave the shaft alone.
Otherwise I would look at having it built up and reground a thou or two tighter.
It's hard to get a proper purchase on a rear main to remove it if it has a death-grip on the shaft.

[Zetomagneto]

Hopefully not for the rear main! You definitely don't want a sealed bearing there.

[Bob Culver]

Normally if run in clean conditons, wear of rolling bearings is neglegible. Life is determined by spalling fatigue failure. I have asked before but as far as I know tha latter is never the problem with Seven mains. Wear seems more a corrosion problem; cars in regular hot running give good service and I am surprised with modern oils it still seen as a problem. Just an additonal .001 clearance is apparent whereas in a plain bearing car never notice. I dunno if the rear wears more or if the flywheel just accentuates what wear there is. One argument for a.c preload is that it is decades before it disappears, assuming the lip does not break off in the meantime.
More rollers would reduce fatigue. As the tracks wear most where load is greates presumably would also reduce other wear. The commencing clearance has huge influence.
Any building up of the shaft has to be done carefully as most process' accelerate fatigue, esp heating.

[Zetomagneto]

           
Not with this baby they don't stand a chance, it fits round the web and engages the inner track only.
I have a bigger one for the 1 and 5/16 crank

[Tom the Blacksmith]

Now that's what I call a tool!