Ducati.ms - The Ultimate Ducati Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!

1 - 16 of 16 Posts

·
Still needs a life.
Joined
·
12,619 Posts
Discussion Starter · #1 ·
From the ST owners' Yahoo group: two ST4s's have had a rear wheel bearing go out this past week. I was with one of them, Mark Turbo, when his went out outside a small town in Eastern Washington. Anyone know how long these bearings should last?
 

·
Registered
Joined
·
882 Posts
In LT's guide he recommends replacing them every 20k miles. Some people say they grease them but I don't know how they pull that one off. Mine are sealed bearings, same as every other motorcycle I've ever owned.
 

·
Member
Joined
·
7,733 Posts
Regularly inspecting them when changing tires is always good. These are sealed units yes, and if they make any clicking or gritty sounds, or don't turn easily, and smoothly, it's probably a good time to replace them. Sealed units can be good for ?, who knows, miles. HD states 100K for their sealed units. Also, who knows if the wheel nuts were torqued too much even if the bearings passed visual/audial inspection. Too much preload can also cause catastrophic bearing failure.
 

·
Registered
Joined
·
722 Posts
I am not sure about the st bearings but often they are single sealed and the back side (inside) is open so they can be repacked. i for one never repack mine as it is too much of a PITA to remove than and I worry that they will be damaged by the removal anyhow. So, what i do is to feel them each time I change tires. I do not recommend replacement as a mater of course. The way bearings tent to fail is that 10% of them may die in a short time, the other 90% can last 10 times longer. I would think 50K miles is no big deal. If they feel rough, replace the bearing with a new one. That is what I do, anyhow.
 

·
Registered
Joined
·
23 Posts
Bill,
I would tend to question proper torque or installation after Mark had his tire replaced Sat. Who replaced it? Did he go to Post Falls or did someone in Lewiston do it? I try to always properly torqe the axle nuts when replacing rear tires on my SS. Thanks, Scott.
 

·
Premium Member
Joined
·
1,956 Posts
96ssportsp said:
Bill,
I would tend to question proper torque or installation after Mark had his tire replaced Sat. Who replaced it? Did he go to Post Falls or did someone in Lewiston do it? I try to always properly torqe the axle nuts when replacing rear tires on my SS. Thanks, Scott.
The tire was replaced at Mac's Cycles in Clarkston, WA, by their chief mechanic, Ivan. He's a very experienced guy and I know he put the wheel on properly and torqued the nut down to 83nm. I spoke with him at the shop as he disassembled the remains and I'm confident he didn't do anything wrong.

The bearing was 48,000 miles old when it failed. It didn't just fail. It grenaded and sent fragments tumbling around in the wheel hub! The fragments destroyed the wheel! I checked with my service manager and the bearings have been checked at every recommended service interval. There was no obvious sign that this was going to happen!

The end result is that I need a new wheel, hub sleeve, both bearings, axle, axle nut and rear brake caliper bracket (the spacer on the bracket was ground down to slivers by the broken shards of bearing!). It's about $1,700 in parts (the Marchesini wheel costs over $1,200 alone!). Luckily, my 3rd party extended warranty/service contract covers everything except the axle and axle nut (about $130 that I'll have to pay myself).
 

·
Member
Joined
·
7,733 Posts
That's some *serious* damage. Thank goodness you have the third party warranty. Best part is you are physically unscathed. Scary scenario to say the least. How'd the seat hold up? :)
 

·
Registered
Joined
·
23 Posts
Mark,
Great to here the warranty will pick up most of the bill. It just seemed ironic that the bearings would fail just after the tire was replaced. Sounds like everything was done properly. Good luck with getting it back together. Scott.
 

·
Registered
Joined
·
887 Posts
Turbo said:
The tire was replaced at Mac's Cycles in Clarkston, WA, by their chief mechanic, Ivan. He's a very experienced guy and I know he put the wheel on properly and torqued the nut down to 83nm. I spoke with him at the shop as he disassembled the remains and I'm confident he didn't do anything wrong.
Impossible to know for sure but it would not be at all uncommon for his torque wrench to be way out of spec. Most fasteners on Ducati's have a +/- 10% tolerance but the rear wheel nut is one of the few with a +/- 5% tolerance. It is not that uncommon for torque wrenches to be out of spec by 10%-20% or even more. That could possibly have contributed to the failure but there is not much you could do about it, particularly since your warrantee provider has agreed to be so generous.
 

·
Registered
Joined
·
406 Posts
What do nuts have to do with it?

I'm no engineer... But it seems to me the axle/nuts torque have little or nothing to do with the bearing and bearing failure.

Along the axle there are a series of componets stacked together. For example, adjuster, spacer, inner race, spacer ect. All of these components stack along the axle. The axle keeps them aligned with each other.

So here's where I'm confused; The wheel spins on bearings that are pressed into the wheel. The outer bearing and rollers are not "pinched/compressed" by the axle stack assemly. IE.. over torquing of the axle would merely compress the inner race. Not the bearing assebly itself. Unless one believes this inner race compression would cause some sort of race deflection which would inturn lead to failure?

I don't know... This kind of stuff reminds me to have a beer when I get home!
 

·
Registered
Joined
·
882 Posts
You're correct. The torque on that axle nut is meaningless. With 48,000 miles I'd hazard a guess that the bearing simply reached the end of its useful life.
 

·
Member
Joined
·
7,733 Posts
pazzoduc said:
I'm no engineer... But it seems to me the axle/nuts torque have little or nothing to do with the bearing and bearing failure.

Along the axle there are a series of componets stacked together. For example, adjuster, spacer, inner race, spacer ect. All of these components stack along the axle. The axle keeps them aligned with each other.

So here's where I'm confused; The wheel spins on bearings that are pressed into the wheel. The outer bearing and rollers are not "pinched/compressed" by the axle stack assemly. IE.. over torquing of the axle would merely compress the inner race. Not the bearing assebly itself. Unless one believes this inner race compression would cause some sort of race deflection which would inturn lead to failure?

I don't know... This kind of stuff reminds me to have a beer when I get home!
I'm no engineer either but if torque didn't matter in terms of bearing performance, then why have a specific setting which varies between models rather than just stating to torque them down "good and tight"? Seems to me the races are aligned and if the inner is shifted from too much pre-load, ie compressing the spacer, then my guess is catastrophic destruction within short order considering the loads and rpms involved. And what about the effect of not enough torque on the nuts on bearings when the wheel wobbles? But like I said, I'm no engineer, but IMO axle nut torque and bearing longevity and rider safety are intertwined. YMMV.
 

·
Registered
Joined
·
406 Posts
well there you have it...

but I'm still not convinced. :think: I believe the axle torque is relative to two things. First and most importanly is to secure the wheel from shifting under load. It is quite possible that a 5% range limit has been set to ensure the product liability insurance watchdogs would trim some of the premium. Secondly, it is to prevent catastrophic failure of the axle adjusting plates at the end of the swing arm. Without enough torque on the axle, load is transferred to the plate which is the only device then holding the wheel in place. Too much throttle here would cause the plate to "suck in" or the bolt will penetrate the plate. I think bearing failure would then take second seat.
 

·
Registered
Joined
·
887 Posts
stryder said:
Seems to me the races are aligned and if the inner is shifted from too much pre-load, ie compressing the spacer, then my guess is catastrophic destruction within short order considering the loads and rpms involved. And what about the effect of not enough torque on the nuts on bearings when the wheel wobbles? But like I said, I'm no engineer, but IMO axle nut torque and bearing longevity and rider safety are intertwined. YMMV.
I agree, the bearing spacer is made of soft aluminum and does not have much bearing surface. Correct torque will avoid deforming this spacer and insure there is not too much side load on the bearing. In all liklihood there are a number of factors including age of the bearing and the possibility of the Simple Green Mark said he used creeping into the bearing, rendering the grease useless and causing corrosion which is the beginning stages of bearing failure.

Probably never know what factor or combination of factors caused it. One thing I do that may or may not catch such bearing failure in time is to always center-stand my bike when fueling. I generally take a quick look at the chain/rear wheel components and feel the rear wheel for side play. It should feel hard as a solid board if you give it a little whack with your palm. Also, never hesitate to pull over and check the chassis if it starts to feel a little loose. Might avoid the chain reaction of destruction or even bodily harm that such a failure can cause.

Off on a ride, cheers!
 

·
Registered
Joined
·
406 Posts
Not green with envy

Agreed agreed. And I've got gallons of simple green!

All in all, I'm glad he came out OK.

Years ago, while stopped at a restaraunt, my buddy noticed my swing arm nut had fallen off...
 

·
Registered
Joined
·
882 Posts
pazzoduc said:
Years ago, while stopped at a restaraunt, my buddy noticed my swing arm nut had fallen off...
That's why there's a specific torque value for the axle nuts. I had a buddy who rode for hours after installing the rear wheel (Kawasaki 500H2), without ever installing the nut! He said it felt a little loose in the back, but that's it.
 
1 - 16 of 16 Posts
Top