Replacing Rear Arm Bearings

Frequently asked technical questions and common modifications/improvements
User avatar
white exec
BXpert
Posts: 682
Joined: Sat Sep 12, 2020 4:04 pm
Location: Sayalonga, Malaga
My Cars: 1992 BX19D Millesime
- LHD, NA, AC, RP_5800
1996 XM 2.5TD Exclusive
x 70

Re: Replacing Rear Arm Bearings

Post by white exec »

One of the problems with the bearings is that they don't fully rotate, and only operate over a small arc, so have to put up with the loading being repeatedly taken by a small part of the track and likely only a very few of the rollers. (The small needle rollers used on the Mini, would be an even worse case, and the toll taken by water ingress/rust on these would be quite serious.)

I think you're right: given 'open' bearings, and if some added lubricant could be 'mobile' (eg oil+grease, or very heavy oil), some regular Citrobics would help move the rollers around a bit more than usual, and hopefully move some of the lubricant around.
Chris

User avatar
Vanny
Merseyside resident
Posts: 3544
Joined: Tue May 17, 2005 11:48 pm
Location: BXProject
My Cars: BX 16v Ph2 - Jazz
BX 16v Ph2 - XPO
x 53

Re: Replacing Rear Arm Bearings

Post by Vanny »

The bearings don't need lubrication. They only ever rotate through what, 30 degrees? The point of greasing is to keep moisture out.

Every fully shagged arm I've ever taken apart has had the rollers rusted to hell. This rust, coupled with standing, is what eventually causes a roller to bind, twist and start eating the housing. So the lube/grease is to keep the moisture out rather than some how minimise friction like a normal rotating bearing.

I've strong views on the idea of needing continual lubrication, most are previously documented in the forum. There are some frankly Ill thought 'solutions'. I don't see the point. Fitting them correctly in the first place, and regularly using the car, keeps the bearings in final fettle for a long long time. I think my current ones have been in around 20 years, not showing any issues yet.

User avatar
white exec
BXpert
Posts: 682
Joined: Sat Sep 12, 2020 4:04 pm
Location: Sayalonga, Malaga
My Cars: 1992 BX19D Millesime
- LHD, NA, AC, RP_5800
1996 XM 2.5TD Exclusive
x 70

Re: Replacing Rear Arm Bearings

Post by white exec »

Agree about the rusting. When ours failed on our previous '89 19D (failure occurred around 1995), the OE bearings were found to be rusty and dry. This was despite the car being used more or less daily for its entire life.

I think you're right about the principal need is to keep water and off the bearings.
Sealed ones would be nice, but not sure whether anyone has managed to identify any.
Does anyone have a new set available, which they could provide exact dimensions for?
Chris

User avatar
Vanny
Merseyside resident
Posts: 3544
Joined: Tue May 17, 2005 11:48 pm
Location: BXProject
My Cars: BX 16v Ph2 - Jazz
BX 16v Ph2 - XPO
x 53

Re: Replacing Rear Arm Bearings

Post by Vanny »

I've many sets, and planned to measure and upgrade next time I'm doing rear arm bearings. Just hasn't happened yet 😂

If I find an SKF kit while I'm tidying the garage, I'll dig the part numbers out