Rear wheel and its bearings and seals

[Marqus]

Hi there,

I tried to spend some new bearings and oil seals for my 85 rear wheel. This is a question for anyone who knows how things look in this area.

Lets start with the brake disc side of the rear wheel. This looks ok and I think I did not mess up the orientation (see attached pic1). There is a new 6304 bearing (red), a new oil seal and this collar that I am holding between my fingers in the picture.

Now the part where the chain kit is mounted. You have the larger bearing, the two-sided tube/collar sitting in that bearing and on top the oil seal 42-62-8. In this seal the large ring shaped collar has to be installed. The before mentioned two-sided tube touches the inner ring of the 6304 bearing (red) seei n in the picture with the rubber dampers. Between the two 6304 bearings there is this long spacer (No. 2 in explosion pic).

Question: Does this spacer has to be SQUEEZED in between the two bearings or is it loose with gaps to both sides?

Question2: Is grease mandatory in this whole axle area? Do I need to grease everything? If so, then why is there no oil seal between the rim and the cast wheel? The only seal would be No 13 in explosion pic. But what about the whole damping area? When you place the cast wheel to the rim there is no seal before bearing No.4. So grease could be everywhere on the rubber dampers.

Am I totally wrong here? Any help?

:-)

Thanks

[fj1289]

The spacer #2 between the 6304 bearings is CRITICAL!!!  DO NOT even bolt the wheel onto place without it - it will side load the inner bearing races and deform the bearing elements and WILL fail at some point (if it doesn't bind up so tight you can't even rotate the rim). 

Unfortunately you are going to have to remove one of the bearings to install the spacer #2 - this will also damage that bearing so you will have to replace that one too (as far as I know the only way to remove it is by driving it out or pulling it out by the center race which will damage the bearing elements the same as not using the spacer #2.

Sorry for the bad news 

[Marqus]

Hi,

Thanks. Spacer No 2 is installed but it is not tightly pressed in between the two bearings. I can move the spacer towards each bearing. There's a gap approximately 1-2mm.

I tried to hammer in the two bearings as deep as possible. But still there's a gap.

[fj1289]

Hi,

Thanks. Spacer No 2 is installed but it is not tightly pressed in between the two bearings. I can move the spacer towards each bearing. There's a gap approximately 1-2mm.

I tried to hammer in the two bearings as deep as possible. But still there's a gap.

Something is not correct then - sounds like one or both bearings are not fully seated.  That gap will still cause a bad side load on the bearings.  How are you hammering in the bearings?  Using a large socket the almost the same size as the outside of the bearing?  You can also use the old bearing as a driver to hammer in the bearing.  Make sure they go in straight and not crooked.  

Also, when they are in all the way the sound of driving them in changes - you hear s more solid "thunk" sound.

[Millietant]

These days I ALWAYS put my bearings in the freezer for an hour before fitting them (still in in their plastic wrappers) and I use my heat gun (basically a high heat hairdryer) to heat up gently the area where the bearing goes in. The slight contraction in the bearing diameter and expansion in the bearing seat area mean I haven't had to "hammer" a bearing into place for a long time - with a suitably sized drift they can be "tapped" in until they "ring" when I tap them and they get properly seated.

As Chris also says, you must use a drift/driver/socket, that matches with the outer race diameter, otherwise you'll damage the bearings - sorry if this is a bit of a "teaching granny to suck eggs" comment, but it's always worth covering the basics.