Catastrophic rear wheel bearing failure (pics)

[dark_knight]

Had to ride home 30 kms through the bush with a failed bearing:foul:

I just installed new bearings approx 2000km ago when rebuilding the wheel after the rim developed a crack.

Now I may need a new hub. And obviously a new spacer and bearing ?

Any thoughts?

[donny662]

That sucks, especially with the pretty new rim.

[rcifs]

That sucks. Definitely need a new hub.

[motothump]

What was the brand of bearing?

[Scoutin Wyo]

I think it will buff out. ?

Bummer!

[jimmyhoffa]

Nothing that can't be fixed by handing it off to a really good welder, who will then hand it off to a really good machinist, who will then hand it off to a really knowledgeable metallurgist. Erm... new hub.

[Noble]

Looks like the single bearing on the brake side that gave up. The seal bore is all chewed up but the bearing bore may be OK. Have to get the outer race out and take a look.

[jimmyhoffa]

Why does the brake side always give up the ghost? My friend's DR350 brake side bearing tanked too. I'd think it would be the opposite.

P.S. You're not being trolled. I seriously don't know.

[dark_knight]

Yeah. Sucks is what I thought too. OEM hub plus bearings, spacers, seals comes to $500 plus!

I managed to get a second hand set of E rims complete for $600.

Now I just have to relace my 'pretty' rim to the hub again! ?

I guess on the positive side, now I'll have a spare front wheel.

Perhaps I overtightened the axle after the last tyre change but I'll sure tighten it to spec now.

I think I'll put it down to 'just one of those things' and move on.

[jimmyhoffa]

You really have to go down to crank-on-it town to cause a wild failure like that by overtightening. That collar in between the bearings should be doing its thing unless you wrenched so hard it started deforming stuff. Either way, good call on torquing to spec.

[Hatchet]

gnarly.

was there any significant warning sounds to listen out for?

I just changed my rear bearings too.

[obrianmcc]

Brand of bearing? Install procedure? Lots of water crossings?

Either way that sucks!....anymore I replace the bearings when spooning on new tires...needed or not.

[ohgood]

unless you poured sand on the bearing while it was horizontal, with missin

g seals, it wouldn't fail that early.

I'm voting for a failure during installation.

what did you use to seat the bearings ? what did you torque the axle to ?

was the hub scarred before the new bearings were installed ?

we'll all learn from this when you answer. :-)

[Mr-Adventure]

Why does the brake side always give up the ghost? My friend's DR350 brake side bearing tanked too. I'd think it would be the opposite.

P.S. You're not being trolled. I seriously don't know.

Heat from the disc transfers to the bearing, melts the grease, dry bearing = failure.

[ohgood]

Heat from the disc transfers to the bearing, melts the grease, dry bearing = failure.

id have thought if any heat made it to the hub it would dissapate very qquickly... going to testt the heat transfer theory on the way home today. ill betcha a beer there is little/none.

*********update- tested *********

seat-o-the-pants-o-meter said it's a big effing hill, dragged the rear brake to the bottom.

finger-no-burn-off-o-meter said the rotor was effing HAWWWT ! caliper was warmish. didn't dare the pads. a spit smudge on the rotor went away instantly.

hub wasn't even warm, let alone ready to fry bacon on.

completely unscientific, only tried 3 times (for heat soak/build up).

that being said, i guess it makes a bit of sense that if getting the disc hot could fry the grease in the bearings, causing them to fail, we'd all have failing bearings every 2k miles.

what really surprised me was how fast the rotor dissapates ALL the heat into the air. it was managably warm in 4-5 minutes, then operating warm (just a machine that's happy) in less than 10.

liiiiiike it was designed that way or something ? ? cool

Edited May 7, 2011 by ohgood

[Mr-Adventure]

id have thought if any heat made it to the hub it would dissapate very qquickly... going to testt the heat transfer theory on the way home today. ill betcha a beer there is little/none.

*********update- tested *********

seat-o-the-pants-o-meter said it's a big effing hill, dragged the rear brake to the bottom.

finger-no-burn-off-o-meter said the rotor was effing HAWWWT ! caliper was warmish. didn't dare the pads. a spit smudge on the rotor went away instantly.

hub wasn't even warm, let alone ready to fry bacon on.

completely unscientific, only tried 3 times (for heat soak/build up).

that being said, i guess it makes a bit of sense that if getting the disc hot could fry the grease in the bearings, causing them to fail, we'd all have failing bearings every 2k miles.

what really surprised me was how fast the rotor dissapates ALL the heat into the air. it was managably warm in 4-5 minutes, then operating warm (just a machine that's happy) in less than 10.

liiiiiike it was designed that way or something ? ? cool

Don't want to question your sophisticated test procedure but it is quite common on aggressively ridden motorcycles to have disc brake side rear wheel bearing failure, although it is more common on road bikes.

The reason being is that the back brake is used for more than just slowing down.

A good rider will use the rear brake as a traction/wheely control device letting them use full throttle without any nasty surprises, along with trail braking and being on the power at the same time.

The technique of trail braking and powering on at the same time can be applied in tight single track.

I don't know if the OEM wheel bearing's on bikes have grease applicable to their application or just any old grease but when I have repacked car wheel bearing's I use a disc brake hub grease and it's resilience to heat for the very reason of heat transfer.

Do a little research and you will find it can be an issue in not just bikes but cars, trucks and even trains.

No doubt hub design has evolved but the fact remains it has restricted air flow and is joined to something which can get extremely hot.

[dark_knight]

unless you poured sand on the bearing while it was horizontal, with missin

g seals, it wouldn't fail that early.

I'm voting for a failure during installation.

what did you use to seat the bearings ? what did you torque the axle to ?

was the hub scarred before the new bearings were installed ?

Good point.

I didn't notice any difficulty with installation although the bearing (Nachi Japanese-made) slipped in very easily (no need for a press - just tapped it in by using the old bearing like I have many times before). I actually put a drop of loctite in the hub for peace of mind and so it would stay seated.

I torqued the axle to 80 ftlbs (isn't 74 ftlbs recommended?) like always.

There was a fair bit of sand and gunk in behind the seal when I pulled the old one out so maybe some did get into the new one after some beach rides.

I think I will pop the dust seals out each time I take the wheel off and give it a good clean and inspection from now on.?

I still haven't got the outer race out of the old hub. Might have to cut through it with a mini grinder.

[ohgood]

Don't want to question your sophisticated test procedure but it is quite common on aggressively ridden motorcycles to have disc brake side rear wheel bearing failure, although it is more common on road bikes.

The reason being is that the back brake is used for more than just slowing down.

A good rider will use the rear brake as a traction/wheely control device letting them use full throttle without any nasty surprises, along with trail braking and being on the power at the same time.

The technique of trail braking and powering on at the same time can be applied in tight single track.

I don't know if the OEM wheel bearing's on bikes have grease applicable to their application or just any old grease but when I have repacked car wheel bearing's I use a disc brake hub grease and it's resilience to heat for the very reason of heat transfer.

Do a little research and you will find it can be an issue in not just bikes but cars, trucks and even trains.

No doubt hub design has evolved but the fact remains it has restricted air flow and is joined to something which can get extremely hot.

yep yep on the re-pack with higher temp good stuff. if there was a weirder finger-feeling-test-method result, i was planning on getting the laser thermometer out and really checking out the heat spread. after a few runs and no noticable heat soak ,i was satisfied. i also pack the entire hub with grease, so maybe it was traveling through (and disappearing) the entire assembly. makes sense that if any heat moves, it's going to have to go through the bearings to be released in the hub. kinda like why welding without a ground on a shaft with bearings always ends up killing them. (apprentices, god love em cause no one else does!)

can't see it happening with a non-racing application on a drz. i mean, if it was common on drz's, we'd all be changing our pads, disks, and bearings every month.

****

op updated-

the slack on the bearing fit may have contributed the failure. if the hole was egg shaped or misaligned with the rest of the bore( s ) it will certainly help wear things out fast. bearings love to be in line, and will moan n groan if they aren't. the green (don't know the numbers off hand) loctite does a good job of helping out with looser fits, but if it's too far out of alignment... see above.

also, the question about why it's always the brake side that fails... i'd imagine that huge bearing on the drive side is helping out a good bit. the chain tends to sling things everywhere to the outer circumference, whereas the brake just sheds dirt, mud, sand and has to drop somewhere. oh look, a bearing to land on, yayyyy !

[Mr-Adventure]

There was a fair bit of sand and gunk in behind the seal when I pulled the old one out so maybe some did get into the new one after some beach rides.?

I think you have just answered your question of why the bearing failed.

I'm not a fan of repacking bike wheel bearing's and disturbing the dust seal, I check for smooth operation when the wheel is out and if there is any doubt replace them.

[nhess81]

And with this, I am now ordering some Pivot Works bearing kits front and rear! Eff bearing failures!