Lotus Elan

wheel bearing grease in hub

PostPost by: rdssdi » Sun Mar 03, 2013 12:08 am

The workshop manual says to fill the bottom portion of the interior of the front wheel hubs with grease. This is in addition to the traditional packing the wheel bearings with grease. I did one side the way described in the workshop manual and a mechanic who works with me did the other side and did not fill the hub with grease. He said he never does it. He believes the added grease has no way of entering the bearings so it is not necessary.

I have not given it much thought but I side with the workshop manual.
What is the general consensus?

Bob
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PostPost by: StressCraxx » Sun Mar 03, 2013 2:50 am

rdssdi wrote:..... He believes the added grease has no way of entering the bearings so it is not necessary.

I have not given it much thought but I side with the workshop manual.
What is the general consensus?

Bob


I agree with your mechanic. The grease in the hub will not flow into the bearing unless its really cheap grease and the oil separates from the thickener and runs out.

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Dan Wise
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PostPost by: rdssdi » Sun Mar 03, 2013 6:06 pm

Unless my recollection is incorrect the manual instructs to fill the bottom interior of the hub with grease. I have a difficult time believing that it was added in error or is entirely superfluous.

Bob
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PostPost by: stevebroad » Sun Mar 03, 2013 6:16 pm

My racing guru, Graham Hatherway, says that there is no point in putting additional grease into the hub as there is no way it can be used. Centrifugal forces will throw it away from the bearings so all you are doing is adding weight :-)
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PostPost by: Bill » Sun Mar 03, 2013 6:55 pm

Bob and all

Years ago I got an explanation for this - filling the hub carrier cavity with grease deminished the intrusion of water thus decreasing / eliminating / minimising the possibility of corrsion of the components. That made scence to me at the time due to the climate of our wet coast here on the Island.

One of the (silly) tips of that time was to stuff the cavity with styrofoam packing 'peanuts' with the grease to save unsprung wieght and to lower the quantity of grease required.
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PostPost by: stevebroad » Sun Mar 03, 2013 9:47 pm

How does the water get into the cavity? Via the oil seals and bearings? The rear wheel bearings are sealed units and the front bearings are packed with grease so they would have to be running dry and the oil seals very worn for water to get through, or am I missing something?
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PostPost by: Bill » Mon Mar 04, 2013 3:16 am

Simple. The strut, and its cavity warms up from the small bearing frition heat, the warm air in the cavity expands and expells thru the inevitable small spaces of fitment due to pressure and apon cooling thus creates a small vacume that may then draw in moisture - it would take a loooong time but it could well happen. That is what I was told was the reason although I dont get my cad wet these days anyway.

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PostPost by: rgh0 » Mon Mar 04, 2013 6:43 am

The recomendation around packing the hub with grease also in the Lotus manual appears in most car and other machinery manuals that use back to back taper roller bearings like the Lotus front hub. Either they all have it wrong or there is a basis to it.

While the grease may not be able to enter the bearing directly grease lubricates bearings by releasing small quantities off oil from the soap emulsion it is trapped in within the greases structure. This oil then does the actual lubrication. It is released by heat and pressure and motion. The grease in the hub provides some sort of oil reserve where heat and motion can release it and the oil can find its way into the bearings in the general agitated state the bearings and hub are in. This may just be as an oil mist - its not all smooth rotation but lots of starts stops and bumps to stir up the oil released and get it into the bearing.

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PostPost by: worzel » Mon Mar 04, 2013 9:10 am

Hi

As a "fix" - something others have no doubt also done- I removed the inner seals from each bearing, drilled a "relief" hole in the uppermost part of the alloy hub (fitted with a small split pin to prevent dirt entering) and drilled and tapped the side of the alloy housing for a grease nipple. Twice a year re-grease. Did this 18 years ago to both sides as a fit and forget measure. Has worked so far.

John
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PostPost by: rgh0 » Mon Mar 04, 2013 10:52 am

Putting grease in the rear strut housing is a different topic to the one raised originally around the front hubs. Its usefulness with sealed bearings would be limited and is not normal practice with this sort of assembly. Of course changing the assembly by removing the inner seals and then providing a grease reservoir inside the rear strut housing that can be topped up may work but there is little heat or agitation in the strut housing compared to the rotating front hub and brake disk to help separate the oil out from the grease sitting in the bearing housing bottom.

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