Greg's FD bearings deconstructed

[Steptoe]

C3

That's quite an important part of the bearing ID.

 

[Slipperyeel]

The bearing fitted to the final drive is a:-
61917C3
Open type, Thin wall, Deep grooved, Ball type
(I/d 85mm X o/d 120mm X 18mm)

You can buy this bearing from any bearing supplier or independent motorcycle parts supplier. Prices may vary.

You can also buy:-
61917
or
61917NSE,
or
61917DU,RS,SH,RSR,LU,2NSE,DDU,2RS,2RSH,PP,RSR,LLU,ZZE,ZZ,2Z,KDD,DD,FF,2ZR......etc

If you want, you can buy any old bearing and stuff it it, open, metal shielded, rubber shielded, Who cares? Tolerances, what the fuck are they? why care! Stick it in and rock on! Your back wheel spins at roughly 1000rpm at 75mph. The bearing will get warm and expand. If it doesn't get adequate lubricated, because of shielding. Then it will just get a little warmer and expand a bit more. But hey what do you care right! A bearing is a bearing is a bearing. It was the right size often all.

My point being:-
You may think that because these bearings have the same dimension, they are all the same.

They are Not.

Buy the bearing of the correct type and spec and fit it correctly, and you will reduce your chances of failure.

I wondered what you were on about cos your point is obvious. But then i clicked on the link. Now i understand

 

[Ian J Hartley]

I wondered what you were on about cos your point is obvious. But then i clicked on the link. Now i understand

Actually, I was referring to the OP's post, of modifying a 61917Z bearing by removing the shield, thinking that that would be enough to turn it into a 61917C3. Ignoring all the other stuff associated with bearings like tolerance etc.

I wasn't referring to Kenny Rodkiss link. My apologise to him if he thought I was having a pop at him, because I wasn't. He posted a link to demonstrate the availability of bearings.

I was maybe being a we bit sarcastic in my response, but there are a lot of people who use this forum expecting to get hard facts. The OP is perfectly entitled to fit what ever he wants to his bike. But just because one member chooses to fit a bearing of a particular type to his bike, should not imply that others should take it as a recommendation, and follow suit.

 

[Slipperyeel]

Ah! I did misunderstand then! So worth clarifying

And I agree whole heartedly with your point!

 

[DrFarkoff]

In saying that the changes to clearances are very very slight according to what I found earlier on

for a bearing between 80 and 100 mm diameter

C0 or CN clearance was like 18 - 36 micron and the C3 was 32 -50 micron

I think it would be an okay fit, especially if you take out the outer shield to allow better oil access and leave the inner in place

but I'd need an 1150 and a lot of money for fuel to ruggedly test this theory

In all seriousness I would give it a go on my own bike If I had an Oilhead The only time I "think" that there would be an issue is if your back brake was jammed on and the disc was red hot

At that time I think that the bearing might get tight but very much doubt it would heat seize the Alloy FD casing is an astonishing heat sink

But you'd be noticing something wrong way before that methinks

 

[Nin]

Oh shite what have I started?

Just to be clear - I bought the bearing and thought I'd have a good look at it. I'm more concerned about it getting the right lubrication. I'd be happy to fit it as I've modified it. I don't recommend you follow my lead. Make up your own mind.

Nin


Sent from my iPhone using Tapatalk

 

[Greg Masters]

These are the only bearings in this size I can get. They are made to C0 standard although, as has been noted, there is some overlap with the looser C3 standard. The bearings come with a pair of metal shields. I really don't think that that's an issue but, if it is, and as Nin has shown, they are easily removable.

I bought a batch of these bearings so as to be able to offer them out at a really decent price - just as I do with the other stuff I stock and sell.

But if you only ever fit OEM stuff - brake pads, bearings, tyres etc - then my stuff is not for you. I'm really not that bothered.

 

[PhaedrusMC]

I've zero experience with the GS FD, so this may be a dumb question, but if the FD bearing is effectively immersed permanently in gear oil (which AFAIU thins when heated, as it presumably is when the bike is being ridden?), then isn't the heated (thinner) gear oil easily going to make its way past the metal shield anyway?

I may be misunderstanding things, and my interest is just curiosity.

 

[Ian J Hartley]

I've zero experience with the GS FD, so this may be a dumb question, but if the FD bearing is effectively immersed permanently in gear oil (which AFAIU thins when heated, as it presumably is when the bike is being ridden?), then isn't the heated (thinner) gear oil easily going to make its way past the metal shield anyway?

I may be misunderstanding things, and my interest is just curiosity.

Only about the bottom third of the bearing is immersed in gear oil, and only when static. The oil level drops under dynamic conditions as the crown and pinion gears pick the oil up and centrifuge it around the inside of the casing.

 

[Greg Masters]

I've zero experience with the GS FD, so this may be a dumb question, but if the FD bearing is effectively immersed permanently in gear oil (which AFAIU thins when heated, as it presumably is when the bike is being ridden?), then isn't the heated (thinner) gear oil easily going to make its way past the metal shield anyway?

I may be misunderstanding things, and my interest is just curiosity.

My lifetime experience of dealing with motor oil says it gets fecking everywhere! In particular places that you don't want it - my hands; my clothes; my drive etc

It really shouldn't have any problem getting where it ought to be .....