tolsen

Front Wheel Bearing Modification - One Good Out Of Two Bad!

36 posts in this topic

I noticed my driver side front bearing had a wee bit of rumble. Mandatory vehicle annual inspection (MOT) is due soon so had to engineer a fix. Dug out my old front bearings and dismantled both, cleaned all parts and carried out a thorough inspection.

Inner inboard race rings were worn due to ingress of water. Outer inboard race rings were still fine. All outboard race rings looked like new.

The plan:

Make one good bearing out of the two knackered bearings. There are two inner race rings in the front bearing, an inboard ring and an outboard ring. These are identical so all I needed do was this:

[*]Decide which of the two outer bearing units to use.

[*]Scrap the inboard inner race ring. Use the two good outboard inner race rings complete with balls and ball retaining rings in the rebuilt bearing.

[*]Additionally, modify the bearing for oil lubrication as opposed to grease.

Internals of the bearing have been cleaned and are ready for reassembly:

DSC02154.jpg

This is how the outer bearing unit looks like inside when internals are removed:

DSC02158.jpg

DSC02157.jpg

Bearing has been assembled. It is important to add grease between the two lips on the elastomer seal on inboard side. The grease prevents the environmental lip running dry. Note that I have not fitted the steel dust seal. This is not required as the bearing is modified for oil lubrication:

DSC02165.jpg

Bearing caps are modified with assistance of the Queen. The coins are silver brazed to the caps. Caps are later centre bored and tapped M4. These are "modern" two pence coins made out of steel with very thin external copper plating:

DSC02150.jpg

Bearing has been fitted on driver side of Smart. Note the machine screw in centre of bearing cap. The hole where the screw sits is used for filling oil into the bearing. I used EP90 GL5 gear oil. Filled to bottom of filler hole:

DSC02168.jpg

The rebuilt bearing spins without any noise or rumble. Oil can be added with ease at any time. My initial plan was to fit a grease nipple in the bearing cap but the grease nipple interfered with the centre cap in the wheel and there was a risk that the high pressure of the grease gun would push the elastomer seal off the bearing. Gear oil is a much better lubricant and having a filler hole and level makes servicing a lot easier.

Only time will tell whether this oil lube modification was worthwhile. I did the other side as well when I was at it.

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Another amazing TK solution!With this installation as described, do I understand correctly that the bearings in motion will always submerged in oil? I wonder how long it might take to leak out the gear oil - as opposed to grease - and whether it might then run dry and fail?What lubricant does MB/smart use for the bearings?And do you know if ceramic ball bearings need special races or would they work in this application?Bil :senile:

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The gear oil is rather thick and sticks to the bearings and wets the surfaces just like in a gear box. Got them filled to the centre so half full. No leaks so far and I doubt there will be much. The seal is a double lip seal. Pressure energized on bearing side - that's why a grease nipple won't work safely. The seal won't pass grease under pressure and popped out when I did some tests.Standard bearing grease is what they all use - just EP litium grease.I have no experience with ceramic balls. Are they not prone to sudden disintegration if impact loaded?Marine prop shaft gear oil is probably better as it contains more corrosion preventive additives.

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I like that! I've spent some time trying to source replacement bearings & gave up, I'm not throwing my old front hubs out when mine need replacing.

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Posted (edited) · Report post

It may take a while before I can report on inservice performance of the bearings. I think the modified bearings will outlast my Smart as long as the seals don't fail.

Seal maintenence is important for bearing life. The seal is a double lip seal. Inner lip prevents grease from escaping and outer lip is an environmental seal that prevents water and grit entering the bearing. Packing the cavity between the two lips with grease will substantially increase bearing life. Motor home owners beware: Transporting the Smart on a trailer will reduce bearing life. The bearings will fail due to false brinelling caused by vibration.

Coming soon: How to fit grease nipples on rear bearings.

Edited by tolsen

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I believe the modified bearings will, I never thought much of bearings or ball joints that couldn't be greased with a gun."lubed for life" means just that...the life of the part ;)

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Posted (edited) · Report post

I'm fitting new front bearings today so I'm going to modify my dustcaps to take a sheetmetal screw and pump gear oil in,can't hurt!Edited to add that removing the disc brake rotor from the bearing hub proved to be so much work given the fact that the t30 set screw holding it to the hub was so corroded that it stripped out so I had to remove the disc & hub as one unit. It was a good thing they both needed replacement....I'm going to use antiseize on that t30 screw as these new discs will probably need replacing before the hub, now.

Edited by strawboss

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tolsen said:

I noticed my driver side front bearing had a wee bit of rumble. Mandatory vehicle annual inspection (MOT) is due soon so had to engineer a fix. Dug out my old front bearings and dismantled both, cleaned all parts and carried out a thorough inspection.

Inner inboard race rings were worn due to ingress of water. Outer inboard race rings were still fine. All outboard race rings looked like new.

The plan:

Make one good bearing out of the two knackered bearings. There are two inner race rings in the front bearing, an inboard ring and an outboard ring. These are identical so all I needed do was this:

Bearing caps are modified with assistance of the Queen. The coins are silver brazed to the caps. Caps are later centre bored and tapped M4. These are "modern" two pence coins made out of steel with very thin external copper plating:

DSC02150.jpg

Just an FYI TK....defacing a coin of the realm is an offense, at least here in the colonies.... ;)

So don't be surprised if there's a knock on your door late one night.....just sayin.... :lol:

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Another great mod Tolsen.The front wheel bearings on transport trucks on this side of the ocean, are oil filled, exactly like Tolsens mod. And they last for millions of kilometers.Canman

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what seal is used in this? i went to a belt and bearing shop an they said they couldnt get a seal for it

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Got everything done up with the modified dust caps,smooth....now that the bearings are tight I notice a bit of play in the ball joints, . :rolleyes: a mechanic told me I needed new ones 2 years ago, guess that's next.

Edited by strawboss

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Great fix! But just a friendly advisement you may want to periodically check that rear seal fir weeping or sweating, as grease seals and oil seals are different Other than that,good job!!

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Great fix! But just a friendly advisement you may want to periodically check that rear seal fir weeping or sweating, as grease seals and oil seals are different Other than that,good job!!

Some oil on the rotors arrests rust and make both rotors and pads last longer. No serious leaks so far. I'm using an oil/ grease mix.

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LOL say what??

My gear oil was a wee bit too thin for this application. There was some minor sweating on one side so I thickened the gear oil by injecting lithium grease using an Oregon chainsaw grease gun. Two years on and my modified front bearings are still rolling without any noise or rumble.

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Your oil leak could happen because you dont have breather vent. When the oil is warm, a pressure is create! It's the reason why heavy truck with front brearing oil lubrication have a vent hole on center of front hub cap. A vent hole could be the solution?

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LOL say what??

Two years on and my modified front bearings are still rolling without any noise or rumble.

Four years later and front bearings are still fine.

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The kms are uncountable. Front bearing failure is due to ingress of water and dirt. By keeping water and dirt out, these bearing will last uncountable millimeters.

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Yes I agree infiltration is a problem but mileage is the ultimate wear and tear. It doesnt sand paper itself to bits if it doesnt move. . .

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More miles is more wear of seal.

Injection of grease, if done right, will wipe bearing seal clean of dirt so less wear of seal. Water and dirt is kept out as long as seal in intact. Of course with missing or disintegrated splash guard, seal area becomes directly exposed to the elements hence very short bearing life.

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My first smart's bearings went to 250K km and were still fine after 8 years. Too bad that car was written off.

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My first smart's bearings went to 250K km and were still fine after 8 years. Too bad that car was written off.

Not much salt and grit on your roads Mike?

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