Bearing question

[ssevy]

Quick summary - while pulling out the oil seal on the main output shaft, I broke the plastic rail on the output shaft bearing.
Bought a pair of tranny shafts on eBay for $75, mint condition and same 95 year as mine.
Now the question:
The output shaft bearing in my bike is an open roller bearing with plastic spacers. The one on the shaft from eBay is a sealed bearing.
I had a dealer look at the one listed as the current replacement, and it is also sealed on both sides.
Several mechanics here at the rally in Oley have said they don't understand why Triumph would use a sealed bearing in a location that gets plenty of oil? Some suggest removing the inner seal to expose the bearing to the oil supply.
My thought is to call Triumph NA and see what they say?
Anyone want to add an opinion?
By the way, this bearing part number is still used, for example, in the new Scramblers, so Triumph must have a reason?
Thanks for any advice!

[Britcyclerider]

Interesting and familiar dilemma- I had a similar situation with my XT500. The OEM supplier shaft bearing was sealed, which I thought was illogical for a bearing receiving a filtered supply of oil. Therefore,  I carefully removed the inner seal and have had no problems since, happy that the bearing is properly lubricated. However, the situation on your Tiger may be different, although I too see no logical reason why it should be sealed both sides.

I'm not really helping here so would suggest, as you say, that you talk to a mechanic familiar with that engine.

[ssevy]

Thanks for sharing your experience. I would really like to hear from a Triumph engineer why they made the change. Hope to speak to someone at Triumph directly. If I am able to do so, I will share his/her answer.

[ssevy]

I did some research on the web about using sealed bearings in the presence of an oil bath and found some interesting stuff. In some applications, the seals keep small metal chips out of the bearing so they don't ruin the bearing. Someone mentioned BMW bikes having used sealed bearings in trannys, as well as some automobile manufacturers.
There was also a suggestion that oil might still work its way into sealed bearings, and the consensus was to go ahead and use them without worry.
Interestingly, someone mentioned an unsealed bearing is more expensive than the identical bearing with seals, so that may also be a factor?

[threepot]

Wasn't there an issue with part sealed bearings being put in the wrong way on the output shaft on early Rocket 3's? Lack of engine oil as a lubricant resulting in early failure,or something on those lines?

[ssevy]

If you put a part sealed bearing in backwards, with no oil supply getting into it, it would certainly fail!
Have not heard the rocket story, but an assembly line worker who did not understand a semi-sealed bearing's function could certainly put one in backwards and it would still work okay on initial inspection. After some time running at cruising speed, however...😳

[ssevy]

Called Triumph NA today to ask about the bearing, was on hold nearly forever, and the customer service guy I finally spoke with could not have cared less. Helpful as tits on a bull.

[Sin_Tiger]

OK I'll throw my hat in the ring here and take from it what you will.

Years ago I was in a position where the fleetwide stocking of parts was partly my responsibility. I discovered that we were stocking essentially the same bearing on the vessels and in warehouses, in three different guises, ?000 series as std, metal shielded (Z/ZZ) and rubber sealed (RS/2RS). I had a dialogue with a few major bearing suppliers (SKF, FAG, Toyo & NSK)engineers who confirmed my suspicions that the internal components and dynamic specs for nearly all standard ?000 series type ball bearings were the same for load, speed, hardness, MTF  and that only 2RS spec had a lifetime lubricant added. It was the general opinion that a bearing with 2RS (double rubber seals) could be used in all other applications, there was only a few cents difference in price for us. If an std open bearing was required for lubricant flow such as gearboxes etc. the 2RS could simply have the seals popped out, where a greased shielded bearing was recommended for dusty environments such as electrical motors, fans or extended transmission shafts was required one seal could be removed on the lubrication entry side. So instead of carrying all the variants we could carry a fewer number of 2RS bearings adapted as required. Another benefit was that, engineers being try it and see types, where an open bearing in a sealed pack might be opened and returned to the shelf where it was prone to corrosion and dust now that the package seal was broken, this became less of an issue as a 2RS bearing was still well protected even if the protection of the packaging had been breached.

The bearing you are referring to I have only seen on three engines, all were std / open type, it's possible that the one you got from ebay had been replaced at some stage since it's unlikely you'd know the mileage of the machine it was taken from.

Other than inadvertantly damaging the plastic carrier, I'm guessing that the bearing would probably be in good condition. Personally I'd be inclined to use a std / open bearing but I very much doubt you'd see any issues by using a 2RS bearing in it's place.

[ssevy]

Thanks Sin! Based upon the used tranny shafts having a sealed bearing in place, and the fact that Triumph currently uses a sealed bearing on the output shafts of many current models, I will just go with what they provide. Since any opening that would allow the heavier grease to leak out would also let the thinner oil inside, there should be plenty of lubrication with no danger of a dry bearing.
That's my theory anyways, and I'm sticking to it