MTB Rear Axel Question

Vitrox

Hi folks,

Great site. Some interesting reads on here.

I have a question that may seem a bit lame to some more experienced cyclists, but it's been bugging me; despite searching on the net I can't find much information on it.

Basically, I removed the rear wheel of an adult mountain bike to replace the old 26in tyre. The bike uses a threaded axel similar to below, with nuts at each end holding it in place.



When I was removing and replacing the trye I noticed the lock nut on the free side of the axel roates with the axel both ways, making the axel protrude more either on the chain side or the free side, if you get what I mean.



The lock locknut and axle moved quite a lot, and I toyed with it trying to figure out how the whole thing works. I wondered if the axel thread movement has any effect on the centering of the wheel and therefore the centering of the chain in relation to the front mech. I don't know if it does, or whether the axel movement serves no purpose other than to all room for add-ons on either side. It's got me a bit confused and I am worried I may be altered something I shouldn't.

If anyone can explain how this type of works and why the axel moves like this I would be most grateful.

Thanks a lot for any help you can give.

supersonic

DO you have any cone spanners to hold the cone in place as you tighten the locknut agianst it?

Vitrox

Hi supersonic,

I don't have the tools for that at the moment. The axel only rotates if I loosen the (correction: nuts) at each end. Also before tightening the nuts if I turn the locknut on the free side, the whole axel moves instead of just the locknut. The locknut seems tight against the spacers.

supersonic

If the lockut rotates on the threads then you need a cone spanner hold the cone as you nip the locknut up.

Park Tools website has a guide on how to do this.

Vitrox

Sorry if I was unclear I am a not very good with mechanical stuff and have made a couple of corrections. Sorry about that.

The locknut moves with the thread, making the axle protrude through the nut (or recede), unless the nut is tight.

supersonic

I am not quite sure I follow lol.

This is happening when you try and tighten the wheel nuts up against the frame?

Vitrox

It happens when the nuts are loose. I just wondered what the reason was for the whole axle bolt moving left or right through the wheel nuts, whether it is for centering of the wheel and rear mech.

I figured that the if locknuts stay in the same place with only the axle thread moving, the wheel nuts will always tighten to the same set distance and keep the rear mech in line with the front mech. I am not 100% sure I am right on that, however; I can't see anywhere that says why the threaded axle bolt allows it to be screwed more through one wheel bolt, and less through the other depending on the direction of turn, and whether this movement does affect centering.

gbrnole

Yes it will affect centering, you should keep equal amount of thread either side of the locknuts.

The cone and locknut should be tightened onto each other when the correct bearing preload has been set to prevent movement.

See this link for good reassembly info:

http://steveukmtb.wordpress.com/shimano-hub-overhaul-cup-and-cone/

supersonic

As gnrnole says, and as I have hopefully said, once the bearing adjustment is locked with the apropriate tools, it will stay put. The axle will not move so...

I am unsure what you are actually doing! Can you confirm the bearing adjustment has no play? If the bearings are smooth, no play, with the wheel OUT of the bike, with equal amounts of axle protruding, and the wheel actually fits your frame then...?