Trailing Arm Bearings --- Outer Race Extraction Tip

BX Tech talk
ellevie
Forum Treasurer
Posts: 657
Joined: Sat Jan 21, 2006 9:10 pm
Location: Southampton

Trailing Arm Bearings --- Outer Race Extraction Tip

Post by ellevie » Sun Jun 11, 2006 11:12 am

Trailing Arm Bearings --- Outer Race Extraction Tip

Jon Wood describes how to go about changing your trailing arm bearings in the DIY section --- http://www.bxclub.co.uk/diy/armbearings/. As you will see from his description and by browsing elsewhere on the forum, the most difficult part is generally held to be the extraction of the cup or outer race of the bearing. When the plastic dumbbell shaped dust protector has been removed, there is only about a millimetre of the cup’s inner diameter exposed to work with. I recently managed to replace the bearings on both sides without using very much equipment --- not even a vice. The trick is to use the old inner metal tube to tap out the cup by putting your finger in the tube at the bottom to guide and hold it against the exposed rim of the cup, and then tapping away on the top of the tube with a hammer. You can easily guide it around the rim to balance the movement of the cup.

So, there is no excuse ! Anyone can change their bearings with hardly any special equipment.
David

BX19TRS 118K E Reg 1992-2008
BX19TRS auto abs 96k F Reg
BX19TXD 150k K Reg

Stewart (oily!)
1K Away
1K Away
Posts: 1604
Joined: Wed May 18, 2005 6:23 pm
Location: North Wales

Post by Stewart (oily!) » Sun Jun 11, 2006 6:34 pm

When I did mine I had to grind the head off one of the long throughbolts to get it out, this flat cut end made a superb drift for the outer tracks once the plastic tube was out of the way, it took seconds to tap those tracks out.
Stewart
TZD 19 TD one of the few
Xantia Td estate, going soft

User avatar
Vanny
Merseyside resident
Merseyside resident
Posts: 3422
Joined: Tue May 17, 2005 11:48 pm
Location: BX Pub
My Cars: BX 16v Ph2
x 11

Post by Vanny » Sun Jun 11, 2006 6:54 pm

i always aim to shatter the race with a good thumb, its generally very difficult to get them out whole (and a little boring!). I use a masonry pointing chisel sharpened to fit the lip, always works well!

ellevie
Forum Treasurer
Posts: 657
Joined: Sat Jan 21, 2006 9:10 pm
Location: Southampton

Post by ellevie » Sun Jun 11, 2006 7:08 pm

That's a good use for the bolt --- shame to see them going to waste.

I wonder if many people just replace the bearings themselves rather than buying a complete kit --- you seem to end up with redundant long bolts and metal tubes which would have been perfectly reusable in my case. But it's difficult to see how you could get the outer race out without destroying the plastic dust protectors. I wonder if these plastic protectors are really necessary ?

Vanny, you must have an extremely powerful thumb :D
Most of mine shattered --- no point in saving them really.
David

BX19TRS 118K E Reg 1992-2008
BX19TRS auto abs 96k F Reg
BX19TXD 150k K Reg

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Sun Jun 11, 2006 11:55 pm

Common trick out here is to hit them with a welder and just run a bit of weld off a MIG around the inside of the outer race or alternatively if really jammed in, weld a flat washer in the guts of it and just a tap then usually sees them fall out.
As regards kits versus just bearings; we can get the kits but they cost about as much as you guys pay for a whole car so there's a tendency to just go the bearings only route wherever possible. Reusing the old seals or alternatively using CX set ups is the usual option. This is one reason the grease nipple option is proving popular and successful as an occasional pump with the grease gun sends the grease contaminents out of harms way and keeps it smooth all the time.
I suppose the fact that with us, we might drive in the wet a couple of times a year means we can be a bit more lenient with the condition of the seals, but the fact that when we do, it's usually in conditions you guys only have nightmares about means we have to be more diligent in servicing the bearings once they've been replaced.


Alan S
By the time you're old enough to know it all, you can't remember why you were learning.

ellevie
Forum Treasurer
Posts: 657
Joined: Sat Jan 21, 2006 9:10 pm
Location: Southampton

Post by ellevie » Mon Jun 12, 2006 12:53 am

I had forgotten about the seals --- mine were mostly chewed up. A more economical kit might consist of news seals, bearings and a Nylock nut. My tip is really aimed at people like myself who don't have very much equipment or welding experience, etc.

The bearings were well overdue for replacement. Two of them were almost nonexistent and the other two were in very bad condition. Fortunately there was very little damage to the arm housing --- just some marks where the needles had embedded themselves into the metal.
David

BX19TRS 118K E Reg 1992-2008
BX19TRS auto abs 96k F Reg
BX19TXD 150k K Reg

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Mon Jun 12, 2006 1:56 am

I agree; I think there needs to be 2 schools of thought on doing this job.
One for those with workshops and equipment to do the job a certain way and the alternative way for those like yourself who don't have that luxury.
The system I spoke of with the modification works particularly well, so much so that there are owners doing it before the bearings fail so as to be a long term solution as it has been a proven mod from back GS days, so anything that lasts 30+ years has to be OK, but there's still some who can't comprehend how it works unfortunately, but I feel as these kits and bearings become more expensive and harder to buy, they'll see the light.



Alan S
By the time you're old enough to know it all, you can't remember why you were learning.

User avatar
Vanny
Merseyside resident
Merseyside resident
Posts: 3422
Joined: Tue May 17, 2005 11:48 pm
Location: BX Pub
My Cars: BX 16v Ph2
x 11

Post by Vanny » Mon Jun 12, 2006 8:42 am

ellevie wrote:I wonder if these plastic protectors are really necessary ?
the inner tubes are not just there to stop dust getting in, they're there to hold the grease in! If you look at it logically the plastic tube seals up the inner edges of the bearings and the outer seals seal the outer edge of the bearings, these then seal onto the center metal tube so what you end up with is a totally sealed unit with the bearings inside.

This is the reason why you need to make sure you put plenty of grease into the cavity before you put the rest of it together and onto the car, its also the reason why grease nipples dont work. Drilled bolt types inject oil between the bolt and the metal tube and the tap into the arm simply fills the arm with oil.



As i under stand it the correct way to do it is with a large metal washer the same size at the outer diameter of the bearing race, two opposing sides of the washer are trimmed flat so the washer can fit through the hole in the race , then pulled flat behind the inner race. Threaded bar, nuts and a second top plate and you can supposedly wind the inner race back out, but where is the fun in that?

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Mon Jun 12, 2006 10:48 am

As I said.......

AlanS wrote: The system I spoke of with the modification works particularly well, so much so that there are owners doing it before the bearings fail so as to be a long term solution as it has been a proven mod from back GS days, so anything that lasts 30+ years has to be OK, but there's still some who can't comprehend how it works unfortunately, but I feel as these kits and bearings become more expensive and harder to buy, they'll see the light.
Alan S
By the time you're old enough to know it all, you can't remember why you were learning.

ellevie
Forum Treasurer
Posts: 657
Joined: Sat Jan 21, 2006 9:10 pm
Location: Southampton

Post by ellevie » Mon Jun 12, 2006 5:44 pm

I wonder if it would make sense to "service" the bearings say once a year or so, by stripping them down and washing everything with solvent to remove any grit that may have accumulated in the grease. I see from browsing the Timken bearing site that the really expensive bearings in heavy duty machinery are serviced periodically like this.

Interestingly, I notice that the seal rotates with the arm housing about the metal thrust bush which itself is fixed via the metal tube to the chassis, but that it makes a really tight fit when dry --- so I made sure to put a good dollop of grease on their mating surfaces.

I really like the idea of the "sawn-off" washer --- a very neat trick. I wonder if there is a way of getting the cup or outer race out without damaging the protector ? Perhaps by shattering it from the outside with a chisel or something else.
David

BX19TRS 118K E Reg 1992-2008
BX19TRS auto abs 96k F Reg
BX19TXD 150k K Reg

ellevie
Forum Treasurer
Posts: 657
Joined: Sat Jan 21, 2006 9:10 pm
Location: Southampton

Post by ellevie » Mon Jun 12, 2006 6:03 pm

Sorry, I should have said "the thrust bush is fixed with the metal tube to the chassis". So I made sure to grease the surface between the bush and seal.
David

BX19TRS 118K E Reg 1992-2008
BX19TRS auto abs 96k F Reg
BX19TXD 150k K Reg

User avatar
Vanny
Merseyside resident
Merseyside resident
Posts: 3422
Joined: Tue May 17, 2005 11:48 pm
Location: BX Pub
My Cars: BX 16v Ph2
x 11

Post by Vanny » Mon Jun 12, 2006 9:51 pm

AlanS wrote: but there's still some who can't comprehend how it works unfortunately
Well there must be something rather key the your not explaining if there are people who cant comprehend?

Unless the bearings are refitted witout the plastic tube, a nipple in the arm wont get anything near the bearings. However if the bearings where to be fitted without the plastic dust tube, then oil/grease would reach the back of the bearings and keep them lubed, however you would have to make sure that the arms are seriously clean on the insides first!

Bleed nipples in the bolts will only ever lube the surface between the bolt and the metal tube, which isn't where it's needed.

I've looked at this time and time again and if the plastic tube is fitted then from the engineering side of things, it wont make any difference how much lube you through at them if its not going into the right place.

Now i've started building racers from scratch i've done a lot more research into the problem, the best solution is to replace the bearings for totally different units! The problem for these bearings is that they are rotational bearings, there designed to go round and round and they dont. The problem with roller bearings is that they're designed to go round and not under a lot of load, in the case of the rear arm bearings they only ever travel round by +/- 90degrees (ish) they dont actually go round, and most of the load is ALWAYS in one specific point. once the rollers start to wear, they gain play and one day when your least expecting it they turn side ways. At this point the wheels straighten back up, so you wont notice, but then they start to cut through the arm its self (NOT good once it gets to this point), when they start to really creak and crack, this is why!

Whats really needed is a twin ring ball race bearing, these should be able to withstand the loads and minimal rotation that is present at the arms. Only huge problem, it's impossible to get good quality twin ball bearings of exactly the same size! So realistically the opening into the arm needs to be enlarged to fit bigger bearings, but then the load on the thinner metal of the arms is greater and on and on!

I'm hoping i can get a spare rear arm into the 3d scanner and see just how good they are with FEA, then change them for the better! I suspect it should be possible to make reinforced alloy rear arms with much better bearings! But we will see!

ellevie
Forum Treasurer
Posts: 657
Joined: Sat Jan 21, 2006 9:10 pm
Location: Southampton

Post by ellevie » Mon Jun 12, 2006 11:12 pm

That’s a good point about the wear not being spread evenly amongst the needles. To spread the wear more evenly, you could make sure to rotate the bearing by 90 degrees each time you strip them down for cleaning. The needles themselves are tapered as well so I expect they would need to be really well worn in order to turn sideways. I like your idea of scanning the arms into a simulator --- wouldn't it be great to see the whole BX suspension on a simulator.
David

BX19TRS 118K E Reg 1992-2008
BX19TRS auto abs 96k F Reg
BX19TXD 150k K Reg