Mangled pivot bearing

[robc]

For those of you following my RT and GS breakdown sagas you'll know that to keep me on the road I put my GS's final drive into my RT.

Last Saturday I got the RT's final drive back fro the menders so I was refitted. When I removed the GS's final drive I saw that both pivot bearings had split across the outer race and on the right side the bearing cage was completely mangles and the pins had fallen out. They certainly weren't like that 4 days earlier when I put it into the RT. They were only 12 months and 20,000 miles old.

Fortunately I had a spare set handy so they were replaced immediately. Oddly, they just slipped into place without the need for a gentle tap like the old ones needed.

When fitting I used the correct torque for the bolts and nut and nothing was out of place. I rode only about 650 miles that week so the failure happened pretty quickly.
I didn't have cause to check during the week but I didn't feel any movement in the pivot bearings when removing the wheel and bolts on Saturday. I felt nothing when riding either.

So, question time: Is this kind of failure common for pivit bearings?

Maybe I'm just special to have all of these bearing and gearbox failures in recent weeks.

Regards

Rob C

 

[dancata]

To all the friend's bikes that I replaced the needle bearings, had some marks of the inner race moving on the bearing, instead of moving on the needels. Some had like half the wear, some had the pivot wear all around it.

That's why bushings are 0.13 mm smaller than 17 mm bearing. You heat them and then they enter nicely on the pivot.

 

[davegs]

For those of you following my RT and GS breakdown sagas you'll know that to keep me on the road I put my GS's final drive into my RT.

Last Saturday I got the RT's final drive back fro the menders so I was refitted. When I removed the GS's final drive I saw that both pivot bearings had split across the outer race and on the right side the bearing cage was completely mangles and the pins had fallen out. They certainly weren't like that 4 days earlier when I put it into the RT. They were only 12 months and 20,000 miles old.

Fortunately I had a spare set handy so they were replaced immediately. Oddly, they just slipped into place without the need for a gentle tap like the old ones needed.

When fitting I used the correct torque for the bolts and nut and nothing was out of place. I rode only about 650 miles that week so the failure happened pretty quickly.
I didn't have cause to check during the week but I didn't feel any movement in the pivot bearings when removing the wheel and bolts on Saturday. I felt nothing when riding either.

So, question time: Is this kind of failure common for pivit bearings?

Maybe I'm just special to have all of these bearing and gearbox failures in recent weeks.

Regards

Rob C

Sounds like wrong touque settings to me, much too tight.

 

[monkeyboy]

For those of you following my RT and GS breakdown sagas you'll know that to keep me on the road I put my GS's final drive into my RT.

Last Saturday I got the RT's final drive back fro the menders so I was refitted. When I removed the GS's final drive I saw that both pivot bearings had split across the outer race and on the right side the bearing cage was completely mangles and the pins had fallen out. They certainly weren't like that 4 days earlier when I put it into the RT. They were only 12 months and 20,000 miles old.

Fortunately I had a spare set handy so they were replaced immediately. Oddly, they just slipped into place without the need for a gentle tap like the old ones needed.

When fitting I used the correct torque for the bolts and nut and nothing was out of place. I rode only about 650 miles that week so the failure happened pretty quickly.
I didn't have cause to check during the week but I didn't feel any movement in the pivot bearings when removing the wheel and bolts on Saturday. I felt nothing when riding either.

So, question time: Is this kind of failure common for pivit bearings?

Maybe I'm just special to have all of these bearing and gearbox failures in recent weeks.

Regards

Rob C

Alright Rob

I've certainly had the needle bearings just fall out of their cage on taking them out without showing signs of play beforehand. Weird they should go in a week though. Maybe the range of movement they encountered on the RT was not the same as the GS and their wear pattern was disrupted. Dunno. I think I'm going for the solid ones next cos the needles never look up to the job to me.

I think you've just had an unlucky streak mate. Maybe it's keeping that lone magpie as a pet

 

[robc]

I believe the torque settings were correct:

Left pivot bolt = 8nm (wrench doesn't go down to 7)
Left pivot nut = 160nm
Right pivot bolt = 160nm

I'll remove the bolts from time to time from now on to check.

Yes, I'll release the magpie and stop breaking mirrors.

Regards

Rob C

 

[davegs]

Bearings

That probably did it that extra bit of pressure these are highly stressed parts and that extra tension will have done the taper bearings no good at all. So, do hire or borrow or buy a low range wrench and do the job correctly these things last for years only a few come up on here but there must be thousands about that last for ever, so good luck in your efforts at least new bearings are cheap and easy to fit, when your moving the b/box about tie the bearings in place with a cable tie as they can fall out on the floor and get covered in shite as I found out!.
Dave GS

 

[davegs]

Bearings

That probably did it, that extra bit of pressure, these are highly stressed parts and that extra tension will have done the taper bearings no good at all. So, do hire or borrow or buy a low range wrench and do the job correctly these things last for years only a few come up on here but there must be thousands about that last for ever, so good luck in your efforts at least new bearings are cheap and easy to fit, when your moving the b/box about tie the bearings in place with a cable tie as they can fall out on the floor and get covered in shite as I found out!.
Dave GS. PS, Also make sure the bearing pivot dosent move when the lock nut is tightend, mark it with a pencil and check it, if it moves it will of course
tighten and increase the pressure on the bearings.

 

[robc]

I don't think 1nm would be a problem. Either way, it was the other side that was mangled. Races were split on both though.

I found that 7nm is little more than finger tight. I had to look in two different manuals because I originally though Haynes had got it wrong. 7nm is very low but I guess those guys at BMW know what they're doing.

Regards

Rob C

 

[robc]

Oh yeah, I've dropped the bearings on the floor more than once. Will I ever learn? Probably not.

Regards

Rob C

 

[ebbo]

When you tighten the lock nut it’s very easy for the center bolt to tighten a little with it, and that can really pile the Nm on. Make sure it stays exactly where you set it when tightening the lock nut.

 

[khpossum]

I just did my pivot bearings as well (installed the bronze aftermarket bearings instead). I had a problem with my torque wrench at 7 NM as well. I can easily see how this torque could be critical in this application. I would not trust many torque wrenches at such a low setting regardless (is the quoted +/-4% accuracy 4% of full span, or +/- 4NM??).

I did want to do it only once and do it right, so instead I measured the length of my wrench, converted the 7 NM to FT-Lb and hung a milkbottle on the end of the wrench with the right amount of water weight. More accurate and trustworthy then any torque wrench. Certainly a whole lot cheaper then buying a low range torque wrench that I will (hopefully)never use again. I locktited the inner bolt with blue to make sure it would not move with tightening up the locknut.

KP

 

[davegs]

Clever git

Whats a milk bottle? all we get are plastic containers.

 

[Wrigsby1]

The bearings are a bit fragile but I don't think 1Nm is going to do it. I have replaced these bearings without the aid of a torque wrench before without any probs (I have wrenches now before anyone faints).

It sounds more like a variation in the exact size of the two arms or similar for total collapse like this.

Spose I'd better get the 2' wrench fitted in the tool kit then

 

[khpossum]

Whats a milk bottle? all we get are plastic containers.

same thing, we call some things a bit different from what you call it there. plastic is even better than a glass bottle because it does not weigh anything and all I had to do is get the right volume of water. Did not even need a scale, just a measuring cup.

Wrigsby1: I don't use my torque wrench all that often. For this bearing I can see how the right pre-tension could be important. Bolts I can get pretty close by feel, this one I was not all that confident.

KP

 

[Wrigsby1]

same thing, we call some things a bit different from what you call it there. plastic is even better than a glass bottle because it does not weigh anything and all I had to do is get the right volume of water. Did not even need a scale, just a measuring cup.

Wrigsby1: I don't use my torque wrench all that often. For this bearing I can see how the right pre-tension could be important. Bolts I can get pretty close by feel, this one I was not all that confident.

KP

I read a simple guide for no torque wrench fitment of this bolt. It said finger tight until you can feel a bit of stiction and then back 1/4 to 1/2 a turn where it usually dissapears. I have seen the low torque wrenches and they are usually for medical techs and I can't remember seeing a motorcycle tech wielding one! Plenty of big 'ammers though

 

[Womble]

Plenty of big 'ammers though

They're not hammers, they're screwdrivers. The spindly things with the pointy ends are screw REMOVERS

 

[Wrigsby1]

Thats what a farmer once told me "hammer 'em in, screw 'em out"