Rear casette alignment - Bent Axle?

Schobiedoo

Apologies if this has been covered before, but I couldn't find anything on the search.

Just spent the weekend bashing around Afan on my pride and joy and on return I noticed that the rear wheel was not running true, I intially thought that I had buckled the wheel but on closer inspection I saw that as I span the rear wheel it wasn't just the rim that was running untrue as the cassette also had a bit of wobble on it (around 1mm movement forward and backward when looking at the wheel along the axle). It doesn't sound a lot but it was noticable. I'm now wondering whether this is normal or whether I've bent the axle/hub instead. The wheel is solid, i.e. it can't be wobbled side to side by hand and the discs run between the pads with no problem.

Questions:
1. When the cassette is put on does it go on totally square to the axle or is there chance of mis-alignment?
2. If this amount of wobble is not normal, should I be checking out the axle first or are there any other suggestions?
3. How far can a wheel run out of alignment before I need to get it down to the LBS for repair (e.g. is a couple of mm OK, or is it liable to collapse next time I go out riding)?

The rear hub is a Shimano hub if that makes any difference (bike is a GT Avalanche).

Sorry if they are stupid questions but I'm new to this game.

-liam-

The cassette aligns true to the freehub. The spindle could be bent. Take it out and roll it along a flat surface to check.

nicklouse

cassette wobble is quite common on some hubs.

a bent axle would not case this as most freehubs are bolted to the hub body and spin on there own axle. shimano included.

IE remove the wheel axle and the cassette will still be attached to the hub and will still spin.

timpop

This is a very common question with lots of opinions as you no doubt will hear. Basically this is normal and nothing to worry about. I'm efficient (some say lazy) so here's a techy bit I borrowed from Martin to help explain:

The hub rotates on an axis defined by the spindle and it's bearings. When the drive is on (you're pedalling) the freehub/freewheel is locked to the hub and rotates with it around this same axis.

When the the wheel is still and the sprockets are rotating (freewheeling) the freehub/freewheel is rotating about an axis defined by it's own bearings not the wheel bearings.

In theory this axis is concentric with the wheel spindle. There are manufacturing tolerances in the bearing races and the threads cut on the hub and the freehub/freewheel to fix them together. This means that the hub axis and the freehub/freewheel axis may not be concentric - not parallel and/or not centred in the same place. The difference may be small but you'll see in movement (run out) between the sprockets and the adjacent spokes.

It's normal and expected. It will vary from hub to hub as the inaccuracies involved may add up or cancel each other out. It doesn't necessarily indicate any wear and it won't cause any transmission problems.

If any bearings are worn you'll feel the play in the cones or in the freewheel bearings by rocking the wheel or sprockets with your hand. If the spindle is bent the sprockets will run out of line but won't appear to wobble.

Ride on!

Schobiedoo

Thanks all, that helps me a lot.