Why do my front wheel bearings only have a seal on one side?

[m511y]

I removed the bearings from my front wheel off of my 79XS750 and one of the sealed bearings was only sealed on one side. At first I thought I lost the seal, but it is meant to be that way. Why? Wouldn't it be better for a bearing to be sealed on both sides even if it is inside the hub?

The real reason I'm asking is because I'm attempting to swap the 19" XS750 front wheel with a smaller 18" XS400 front wheel and the only bearings I can find that will work are only sealed on one side. I want to be sure I don't use bearings that could seize at some point because they weren’t sealed on both sides.

 

[Tim]

Lots of wheel bearings are like this. Chances are high though that there is a '2RS' version of the bearing which if I recall refers to there being 2 seals.

What is the ID / OD / width of the stock bearing? What bearing are you looking at?

 

[m511y]

I'm looking for a 17/42/13. Stock outer and thickness of the xs400 is 42 and 13. My XS750 front axle and inner OD of the bearing are 17mm.

The only bearing (In the US) I can find is for the front wheel of an 87 GSX750 or 1100. I have two on order. I'll see if they can work. I think the actual bearings I ordered are KOYO DG1742RSC3.

 

[Hoofhearted]

Why/ Pretty straight forward. The seal is on the outside to prevent dirt and crap from getting in. With a bearing on each side with a seal on the outside of each no dirt can get to the inside. So an inside seal would be redundant. In addition the factory is saving a buck or two by not having to buy bearings with two seals.

 

[Tim]

The DG1742RSC3 reads like it has both seals. Some sizes are really odd and come in limited options in terms of seals or even width. Count yourself lucky that you found the right ID/OD/Width combo.

 

[m511y]

Great new, they arrived and have seals on both sides. They are in my freezer now and will be going in the hub tomorrow. Front wheel conversion almost finished.

 

[Tim]

Don't forget the internal spacer

 

[DrJ]

Maybe there's an external seal where the axle enters the hub?

 

[m511y]

Don't forget the internal spacer

I have the spacer. I had to shave 4mm off of it. I should have a rolling chaise by tonight.

 

[crazypj]

Apart from the cost difference when your buying bearings by the million, although it's miniscule, there is a measurable drag with dual seals.
I tend to remove the inner one so I can change bearing grease

 

[Tim]

When you do have open bearings on the inside of the hub, does it need to be packed with grease to keep the grease from migrating out of the bearings?

 

[lingo]

it will help keeping water out if a seal fails

 

[crazypj]

Nope, you put a thin smear of grease around the inside of hub to prevent corrosion or any loose dust flying around then just pack the bearing only.
Packing the hub will make grease come out when it warms up

 

[m511y]

So I have the bearings sorted out. Now I have to make the wheel 5mm wider because the wheel and forks on the XS400 are 5mm closer together than on the XS750. Can I just put 2.5mm washers on each side of the axle where it meets with the forks?

My first thought is that this would be fine. I just want to be certain that I won't be doing anything to make the front wheel fail and lock up while on the road. That’s one of my biggest fears. Xpo Streetfighter Bos Bro crash keeps coming to mind.

 

[4eyes]

Yes, but make sure that the spacers only contact the smaller diameter part of the bearing.

 

[m511y]

Yes, but make sure that the spacers only contact the smaller diameter part of the bearing.

The spacers won't be touching the bearing at all. In fact, on the left side the bearing contacts the speedo gear and then the speedo gear touches one of the 2.5mm washers and then the forks. On the right side the bearing contacts the stock spacer and dust seal and then that spacer will contact the 2.5mm washer and then the fork leg. In between the two bearing is the long internal spacer.

I should be able to mock all of this up tomorrow for final measurements. Maybe even take some pictures.

 

[rocxylemmon]

Apart from the cost difference when your buying bearings by the million, although it's miniscule, there is a measurable drag with dual seals.
I tend to remove the inner one so I can change bearing grease

You're comment is what helped me get my front tire spinning again after torque the front axle nut, thank you for this big piece of information sir.

 

[rocxylemmon]

If you need any information on bearings that you could be experiencing then just watch this video.

Bearings and stuff