Front disk hub axle direction
 

I disassembled the front hub, to clean cones and bearings. Of course I forgot to remember the direction of the axle when I pulled it out. Now I am not sure is there a direction? Cones and screw nuts are the same on both sides, no marking I can see on the outside to identify direction. But there is a groove on the outer ring on both sides which seems like it has a direction? Hub is some Joytech from the Cube Nuroad 2021 bike.

some pictures : https://imgur.com/a/5E8qp9T

Assuming you're talking about the hub spindle and not the through axle: You're good to go.

what’s a hub spindle? He’s talking about the axle - the non-rotating shaft around which the hub rotates on the bearings

The pictures clearly show a hub for a through-axle, These hubs have a hollow outer tube that I called a spindle, for want of a better term (Shimano apparently calls it an axle pipe). This is indeed an axle; however these hubs use something called a through-axle in place of a QR skewer to lock the hub to the fork. The OP's question was about the direction of the axle. If he/she were asking about a through-axle then the direction would be important.

I didn't invent, nor do I support ambiguity in part names. It's something we all have to keep in mind when we post questions here.

What is that loop of stuff that is sticking out from the non-brake side? Also on the brake side. Part of the seal? I'd try to fix it if possible.

The thru-axle goes into the brake rotor side of the hub and screws into the drive side fork leg.

Before you do that, check your work. Looks like there's a seal peeking out from under the endcap/locknut assembly:


https://cimg9.ibsrv.net/gimg/bikefor...f46c14c116.png
https://cimg0.ibsrv.net/gimg/bikefor...c50224250a.png

I absolutely agree with you about not supporting ambiguity - that’s why I called it an axle, because there isn’t a better term for it, nor a more correct term for it.

1. Sorry if I was not clear, I am not asking about the actual axle which holds the wheel into the fork, obviously it has only one direction and the fork dictates that. I am asking about the direction of the tube (whatever its called) in the hub itself which holds the cones, as you disassemble the hub, you can pull it out both sides. So not sure if this has a direction.

2. I am aware of the seal rubber, its tiny, already stretched out and does not sit tightly in the incut its suppose to be, and as I screw cone nuts back, the grease just keep pushing this rubber out.

you should probably replace that oring then. its clearly "swollen" and no longer going to work.

On the front it shouldn’t make a difference. On the rear, it probably will. The gear cluster will probably make a difference in cone spacing.

One way to avoid this kind of problem is to pick a side that you always work on. Since the rear is usually worked on on the left side (Coaster brakes are different), work on that side on both the front and rear. That way you avoid any confusion.

The o-ring is likely swollen from the grease. Replace the o-ring to fix the problem.

You were plenty clear. The axle - as in the threaded tube which holds the bearing cones - is usually symmetrical on a rim-braked wheel (I've never disassembled an asymmetrical disk front hub, so I don't know if the innards are also asymmetrical). In your case, it doesn't matter which way around you install the axle, as long as you center it in the wheel (protrudes the same amount on each side). As someone else said, the easiest way to ensure this is to leave one cone and locknut in place when disassembling.

What you refer to as the "actual axle which holds the wheel into the fork" isn't an axle - it's either a quick-release skewer, which can be installed either way but usually with the lever on the left, or a "thru-axle", which can only be installed in one direction as it screws into the fork end on one side. Both are clamping devices, neither are axles, despite the name.

My lbs says this rubber o ring cannot be ordered. Where to buy alternative?

Try your local hardware store. Smaller ones might be better than a Big Box. At least they will be more helpful and knowledgeable. If you know the size…ask the shop or the hub manufacturer…you can order one from several suppliers on-line, although you will probably have to order them in anything up to 100 lots.

Mcmaster-Carr is a good source. O-rings are spec'd by diameter, thickness, and material (Buna-N is the standard for oil/grease). You should use the groove in the hub to determine the diameter and use a caliper on the ring for the thickness. Price is reasonable even for a bag of 50-100, though shipping may be more than the product price. I have a lot of various o-rings so if you post the size you need, I'll take a look.