Installing drive-side rear wheel bearings

[jdosher]

I have a question about the proper way to install new bearings in the rear wheel. My question has to do with the gap that exists between the outer races of the two bearings and the bearing spacer.

If the design is such that a gap exists between the outer races and the bearing spacer, what provides the stop when installing the outer bearing? Typically you seat a bearing's outer race firmly against the bearing pocket (just like the smaller, inner bearings). But in the case of the larger bearing you can't (and wouldn't want to) tap or press it in until the outer race was firmly seated; to do so would mean you'd somehow managed to press the outer race in far enough to pinch the bearing spacer between the outer races of the two bearings. Which of course would result in significantly side-loading the inner races of the two bearings and even transferring force via the internal spacer to the brake-side bearing.

Obviously to do this you'd really have to "go to town" wailing on that outer bearing's outer race. But the question still stands: what provides the stopping point when seating the outer bearing? If you luck out and drop a cold outer bearing into a hot hub and it comes to gently rest against the bearing spacer, great. But you're not guaranteed that's always going to magically happen.

[adv rider]

I am a bit confused by your description. The bearings should "sandwich" the spacer in the center of the hub, to prevent bearing failure when you tighten the axle. If it is loose when bearings are in, you need a new spacer if it is loose.

What year and model are you working on? I have not replaced the bearings in my Gasser, but on other models with dual bearings. They would just butt up against each other. Install 1 side, drop in the spacer. Then install the opposite side.

[Jakobi]

http://www.gasgasrider.org/html/rear..._bearings.html

Pretty sure they have different ODs. I'd have to check my spares to confirm.

[jdosher]

Originally Posted by adv rider

I am a bit confused by your description. The bearings should "sandwich" the spacer in the center of the hub, to prevent bearing failure when you tighten the axle. If it is loose when bearings are in, you need a new spacer if it is loose.

What year and model are you working on? I have not replaced the bearings in my Gasser, but on other models with dual bearings. They would just butt up against each other. Install 1 side, drop in the spacer. Then install the opposite side.

Starting sometime mid-2000's the GG EC's have three bearings in the rear - one on the brake side, two on the drive side, with a flanged spacer/washer between the drive-side bearings (see the link I posted below). My bike is an '09 EC300, but I purchased it new, in crate, not that long ago, so this is its first bearing change.

[jdosher]

Originally Posted by Jakobi

http://www.gasgasrider.org/html/rear..._bearings.html

Pretty sure they have different ODs. I'd have to check my spares to confirm.

My '09 has a different setup. The above procedure is for an earlier model and doesn't show or discuss the washer/spacer that lives between the two drive-side bearings. I'm not sure what year this was added. That spacer can be seen in this post:

http://www.gasgasrider.org/forum/showthread.php?t=2566

Note how there is a gap between the outer races of each bearing and the outer (thinner) part of the bearing spacer/washer.

It's part number 58 in the rear wheel parts diagrams. GG calls it the "INTERIOR HUB WASHER".

https://www.dropbox.com/s/665yypem51...wheel.jpg?dl=0

[Jakobi]

Checked the parts fiche from 2010.

Sprocket side still uses 2 different OD bearings, and the spacer.
BEARING 6204 2RSR
6005-25R1 C3 / WHEEL BEARING

I see the point you are making about if there was no step essentially you could load the inner race against the spacer (which is what would still happen when torquing without a spacer in there). The stepped lip is what the outer races seat against.

[jdosher]

Originally Posted by Jakobi

Checked the parts fiche from 2010.

Sprocket side still uses 2 different OD bearings, and the spacer.
BEARING 6204 2RSR
6005-25R1 C3 / WHEEL BEARING

I see the point you are making about if there was no step essentially you could load the inner race against the spacer (which is what would still happen when torquing without a spacer in there). The stepped lip is what the outer races seat against.

The INNER, not the outer race of the larger bearing seats against the wider (inner), stepped surface of the spacer. The spacer is thicker in the middle, and thinner at the outer edge. There is supposed to be a gap between the OUTER race of the bearings and the spacer. So there's nothing that the outer race of the large bearing rests against. The spacer is contacting the INNER races of both bearings and isn't touching the outer race of either beings. So my question still stands: How does one tap in the larger bearing when there's no solid surface for the outer race to rest against?

The problem I see is that as force is applied to the large bearing (while tapping it in around its outer race), its inner race will start to apply force to the bearing spacer, this then applies force to the inner race of the smaller bearing, this then applies force to the axle tube, which then applies force to the inner race of the brake side bearing. This is obviously bad, since now you're side-loading the bearings.

It seems like a design flaw, but I KNOW the GG engineers know more than me, so I'm obviously not understanding the design. The problem still stands though; I don't understand what surface stops the larger bearing from being tapped in too far.

[Jakobi]

Take your bearings out of the hub and look at it. Both bearings have different OD's. Shown in the parts fiche, the images you posted, and the link I posted. The hub is reccessed to allow the bearings to seat into the hub. The spacer is just that. A spacer that sits between them so that when you crank the axle nut up the inner races don't get pulled together. Essentially the same as the crush tube.

If the stepped spacer goes in the wrong way it can bind against the outer race/face of the bearing which obviously causes drag and resistance. I get where you are coming from, but you're assuming that the only thing that holds the bearings apart is the spacer/washer. This is not the case.

Granted this is only what I make of it by looking at the diagrams. In the 2 Gassers I've owned and collectively put over 400 engine hours on, I've changed more front wheel bearings than rears. I can't recall last time I had to change the rears. The 2 bearing drive side design is solid.

[jdosher]

Ah, okay, I see what you're saying; the larger bearing does indeed seat against the hub. I see it now.

I'm still a bit confused over the spacer in my hub, though. When I removed my old bearings this weekend I very carefully held the two bearings and the spacer together with the spacer flipped one way, then the other, and there was an identical gap between the spacer and the outer races of both bearings. I kept thinking "no, one way is the wrong way and I'll see that because the gap will be wrong". But I could never get the wrong orientation to determine the right orientation. It really confused me. I totally understand that the inner races of the two bearings are different diameters, hence the spacer is supposed to have raised ridges at two different diameters to accommodate that.

I wonder if the spacer was redesigned so that it can now be properly installed either way? I don't really want to press out a new set of bearings to look at it again. I just didn't like how much the rear wheel started to bind up as the axle was torqued down.

I did note that the rear wheel on my wife's KDX was stiffer after putting in bearings this weekend, but nothing like my GG. (We ride in a very wet area, so wheel bearings get water in them no matter how much grease they have. The KDX bearings were full of grease and water - there's just no way to keep it out.)

[bkwdc]

Hold the bearings in your hand with the spacer between. Then turn the spacer over. Feel the difference?