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 - 11 of 11 Posts

·
Just Visiting Your Planet
Joined
·
10,236 Posts
Discussion Starter #1
I'm in the middle of tearing down the ST3 for maintenance. I've removed the belts and took a look at things. Everything is visually good, but I'm wondering about the movement of the idler and tension bearings.

They feel "packed." When I go to spin the bearings, they don't spin effortlessly. It feels like they're all packed full of grease and take just a bit of effort to get moving. Once they're moving, however, it's nice and smooth. They all feel about the same.

The bike has 25,000 miles on the original bearings. I'm just wondering if I should replace them or if this is how good bearings will feel. IIRC, they felt this way at the last service, too, but it's been a couple of years. Nothing is bound up. It just feels "sticky" to start them turning.
 

·
The days are getting longer!
Joined
·
8,278 Posts
Mine felt the same way, I replaced them with 35,000 miles on the clock and the new ones felt the same way. Maybe someone else will chime in and let us know differently. I did it for my own piece of mind.
 

·
Premium Member
Joined
·
5,656 Posts
Probably fine.

Last time I had the 916 apart I had the opposite problem. The grease was coating the inside lip of the pulley and the bearing was loose. Unfortunate part was this was a bearing I had replaced the time before, so only 6K miles old. It was a SKF brand bearing, but not one made in France. It was made in India or someplace like that. There was a thread some time ago, maybe by DavyJ, that warned about some poor quality SKFs made elsewhere. Probably not relevant to this thread, but if buying bearings from someplace like Amazon or eBay, you're taking a risk even if they are a known brand. VXB.com and Nachi for me from now on!
 

·
Premium Member
Joined
·
876 Posts
I've written about this before. A properly working bearing is better than the unknown of a new bearing. That said, how do you determine if the bearing is indeed working properly without obvious wear issues. The bearing and the seals are both critical. The biggest problem with buying a replacement bearing by visiting a bearing shop and getting a size equivalent is that the quality of the bearing or seal will be different from what the factory has determined to work. This is a critical application where bearing are known to fail and result in catastrophic damage.

There is a whole slew of failure modes for a bearing. Without a post mortem inspection with very expensive equipment, there is only one way I know to overcome this challenge. That is to have the bearing in hand and spend at least 20-30 minutes rotating it in every conceivable way you can. If you ever sense the slightest hitch, don't talk yourself into thinking that it was just you. It takes that long, IMO, to run the bearing through every combination of each ball or roller with the race to see if a pit can be noticed. You may not encounter it again for a very long time. If there is a single pit, you no longer have a bearing with a predictable life. If the pit is on the race, it won't take so long to find it. Personally, I think this can result in a bearing that I am more confident in than a new one that may have a flaw or be a knock off.

Bearings have a number of specifications. Every character or digit in the part number means something and if you take a bearing that is 90% of the same number and it looks and measures outright identically, there is something different about it, which could affect the mission or service life of the bearing. Beyond that a crappy bearing may have the identical number and be made in a cheaper way or dirtier factory in order to achieve a lower price or higher profit. Buying a name brand and not a knock off is important no matter where you get it. NASA and the military and commercial and private aviation have all had catastrophic failures attributed to knock offs that made it through commercial inspections. Examine the box as carefully as you examine the bearing for signs of errors such a misspellings and logo differences. Ever the wrapper inside the box will usually have the manufacturers logo on it. Unfortunately, and no stereotype implied, there are places in the world where integrity is not important and everything that can be copied in a cheaper fashion is. I personally will inspect closely even if I bought the bearing from a Ducati dealer because somewhere along the line they could have had clones injected into their purchasing system.

I am not a conspiracy theorist that sees things that don't exist in everything I see. I normally am pretty trusting in my purchases. It's just that if you have a failure in this application and a resulting belt jump or break, it will significantly alter the value of your bike and in many cases, essentially total it.
 

·
Registered
Joined
·
1,272 Posts
I did my streetfighter's at 37,500, they rolled smoothly but had a side to side wobble. Cheap insurance, on my bike kind of a bitch to get the rear vertical bearing out.
 

·
Registered
Joined
·
7,104 Posts
Any movement in any direction other than spinning smoothly is a sign of wear and the bearing should be replaced immediately. Any difference in the resistance as you spin the bearing and the bearing should be replaced. Keep a new replacement around to compare the used one to if you're unsure. It simply isn't worth the risk.
 

·
Registered
Joined
·
36 Posts
A good bearing should have no play up/down left/right. They should also have a slight bit of friction as you start to rotate them, once moving they should be smooth as silk, That bit of friction is just the dust seal on the outside providing a hint of resistance :)

Yours sound okay, But yes, as above - if you replace them make sure they are the specified brand and type.
 

·
Registered
Joined
·
104 Posts
bearings

Hi
I have a M 900 with a little over 101,000 miles on it and ,and have always check the roller bears each time i have R&R the timing belts mine still fell fine , .although i would replace them now if i wear not parting the machine out
 

·
Registered
Joined
·
7,104 Posts
At that mileage I’d change them “ Just Cause “. If the bearing feels good you can always pop a seal and repack them with good grease.
 

·
Registered
Joined
·
104 Posts
.although i would replace them now if i wear not parting the machine out.

and i got something modern last spring , 05 Multi 1000
 
1 - 11 of 11 Posts
Top