CSB question

[E30_fiend]

I have been thinking more and more lately about my support bearing. I replace a lot of bearings at my work on anything from a ford to an International tymco sweeper truck. Now I am talking about external bearings here. I doubt anyone one here has the same career as I do but these bearings are tough. These work non stop for hours on end and they will last for 2 or 3 years without replacement, just a good lube every so often. So I am pretty sure that I can find a bearing that has the same inner diameter as our support bearings do. I mean fafnir makes a lot of different bearings so there is one for this application as well.

So here's the question:
Has anyone ever thought of making the center support bearing solid rather than a floating design? You know, delete the rubber part and we have solve the problem with the support bearing rubber going bad.

Just thinking out loud, let me know what you guys think. Let me know of any problems that would arise from doing this.


E30Fiend

[jw 325ic]

i feel like a dick for not having an answer on whether this would affect the attachment to the driveshaft or the guibo (flexibility wise) but ive thought about this also after replacing two e30's CSBs. kinda a pain in the ass and i wish i would only have to do it once.

[E30_fiend]

That's exactly why I am asking this question. Its royal pain in the ass to replace it and if this was possible, all you would have to do is service it every once in a while.

Someone please chime in.


E30Fiend

[jlevie]

Seems to me that this would be a fix for something that isn't broken. The CSB will normally last as long as the drive shaft. Once the u-joints in the drive shaft start binding the rubber mount for the CSB will fail. When that happens replacement of both is required and after doing so the combination is good for at least another 100k.

[Farbin Kaiber]

In a perfect car, in a solid mounted race car, yes. On a street car, with rubber/flexy mounts on the rest of the drivetrain, I'd think solid mounting may cause increased vibration and/or long term damage to other components. Just from my experience/opinion.

[DarkWing6]

In a perfect car, in a solid mounted race car, yes. On a street car, with rubber/flexy mounts on the rest of the drivetrain, I'd think solid mounting may cause increased vibration and/or long term damage to other components. Just from my experience/opinion.

Basically yes. I was actually talking through this at work with a couple guys the other day. You could solidify it, but it will just cause other (more expensive) parts to wear much faster. This isn't a huge deal in purpose built race cars cause they tear them apart after every race anyways. If you want to aviod replacing things making a solid CSB is not your solution. CSBs last a long time and are not that tough to replace.

[E30_fiend]

Seems to me that this would be a fix for something that isn't broken. The CSB will normally last as long as the drive shaft. Once the u-joints in the drive shaft start binding the rubber mount for the CSB will fail. When that happens replacement of both is required and after doing so the combination is good for at least another 100k.

Failure of the CSB is rarely due to the drive shaft. This is my point, our drive shafts can go through many changes of the CSB without actually changing the entire shaft. Failure can be cause if the car sits for a while and the rubber dries out, it can break due to heavy constant acceleration. With a solid mount, there are no worries about the mount failin h and even if it does begin to fail, it won't be nearly as annoying as the thumping on the body.

This to me would be more intented for a more spirited driver rather than a DD.

Farbin,
Yes it would make the drive line more rigid and may cause some extra vibration but in auto x and drifting and road racing, the vibration is the last thing that's worried about. I don't see why it would do damage to other components seeing that the bearing would be in the same position as it is now. The shaft will be doing the same thing, just no rubber.

Thanks for the replies.


E30Fiend

[E30_fiend]

Basically yes. I was actually talking through this at work with a couple guys the other day. You could solidify it, but it will just cause other (more expensive) parts to wear much faster. This isn't a huge deal in purpose built race cars cause they tear them apart after every race anyways. If you want to aviod replacing things making a solid CSB is not your solution. CSBs last a long time and are not that tough to replace.

I see what you mean but to people that don't have a shop and or the correct tools, this would be a one time replacement so the hassle of finding a shop and finding the time is a one time thing.

What I was also thinking was what about having a rubber bushing where the bearing mount to the car? This would help absorb the vibration a bit more.


E30Fiend

[Farbin Kaiber]

I just think what driving on steel tires would be like, then apply that concept to my driveshaft support.

[E30_fiend]

I just think what driving on steel tires would be like, then apply that concept to my driveshaft support.

Ah, I see what you mean. I was just thinking out loud because mine needs to be replaced and I have done it before and it just seemed so much easier to have one that doesn't need to be replaced.

Anyone else wanna chime in?


E30Fiend

[jlevie]

Failure of the CSB is rarely due to the drive shaft.

I think you'll find that asking experienced BMW techs about this will yield information contrary to that statement. I've yet to see a failure of the rubber mount for a CSB that wasn't also accompanied by binding u-joints in the drive shaft. In a like manner I've yet to see early failure of a replacement CSB when the drive shaft and CSB were replaced at the same time.

[E30_fiend]

I think you'll find that asking experienced BMW techs about this will yield information contrary to that statement. I've yet to see a failure of the rubber mount for a CSB that wasn't also accompanied by binding u-joints in the drive shaft. In a like manner I've yet to see early failure of a replacement CSB when the drive shaft and CSB were replaced at the same time.

I took my entire driveshaft to a driveline service shop to have it tested. They spun the shaft, it needed no balance and they tested my u-joints and everything checked out. Same thing with a friend of mine. The u-joints were fine in both cases with the support bearing completely thrashed. My other friends went bad also and he just replaced the bearing and he has driven on the new one for 2 years now with not one vibration.

Not a very educated asimption on your part. The BMW techs are taught to upsell upsell upsell. So of course if a support bearing comes in messed up, they tell the service advisor and they sell the whole job rather than just the CSB. That's how all shops works because all shops want to make money.

What sounds better to a service department, 70 bearing and 2 1/2 hours labor at 85 an hour, or 70 for the bearing, 60 for the flex disc, and 600 for the driveshaft?


E30Fiend