assistance pls: shimano rear hub rebuild problem

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assistance pls: shimano rear hub rebuild problem

Postby stardotstar » Sat Mar 07, 2009 10:02 pm

Hi,

I have tackled a pull down, service and rebuild of the rear cassette, and cup and ball hub on my GT Avalanche 1.0 '06.

I followed the Zinn(and the art of MTB maint) instructions meticulously and had all the right tools and took great care cleaning and reassembling the components.

All appeared to be in place but when I remounted the rear wheel to the frame it wouldn't turn due to the brake rotor fouling on the caliper.

On closer investigation the whole wheel assembly appears to be mounted further to the left of its original position with respect to the caliper. I also found that the gears wouldn't climb all the way up to the biggest cog and had a spare click on the outboard end... So, that confirms that the wheel is not centered as it was before.

But, I did not miss any components. The build is from left to right (disc side to drive side - facing forward from behind the bike:

disc rotor/skewer-lever-nut/spring (apex in) -> lock nut (correct orientation)/dust-cover/spacer/cone [nb this side locknut/spacer/cone was not disassembled) -> 9 balls in cup/race -> hub shell -> balls in cup/race -> cone/spacer/dust-cover/locknut -> spring/skewer quick release nut.

(AT)?}#(|>*][-----][*<|)#{&

There were no shims lost or spacers assembled in different positions.
I ensured there was some free play in the axle when adjusting the lock nut against the cone.

Since I didn't disassemble the disc side of the axle I don't see how I could have moved the location of the wheel on the axle relative to the frame of the bike and therefore the rear derailleur/brake caliper/housing.

Have I done something obvious - is there a step in setting the locknuts to the cones that I have failed to finesse or what?

Any ideas guys? I hope this is enough of an explanation (don't have time to get photos and what not right now)

TIA
Will
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by BNA » Sun Mar 08, 2009 7:27 am

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Postby herzog » Sun Mar 08, 2009 7:27 am

That's odd. Only thing I can think of is it possible that the rear brake lever got squeezed when the wheel was off?

A travel spacer between the pads can help prevent this.

Doesn't explain the cassette not lining up though.

Sometimes just taking it apart again and reassembling does the trick.
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Postby stardotstar » Sun Mar 08, 2009 8:48 am

Hmmm, thanks for the reply! It's been bugging me overnight.

The brake lever is not to blame since the piston is still fully retracted and the rotor is fouling on the caliper casing itself.

I can't see how it isn't something I have left out that would cause the whole assembly to sit further to the right of its current position.

For example the first thing I thought I had to do was remove the shims between the frame and the brake caliper - which I have occasion to adjust when switching between my two sets of wheels. This didn't help much at all - just meant that the rotor wasn't being warped to fit in!??!

So... I will mount my other wheel this morning and confirm that it is the wheel not the frame (somehow).

Then I'll pull the hub and cassette down again and take some photos - someone may be able to see something I have missed.

It's frustrating since despite this being the first time I have broken down a bicycle hub I have done it on my 4 wheel drives several times and trailers and so forth so I am not being caught out by not having any experience, tools or a methodical approach.

Is it possible that in tightening the lock nut against the spacer/cone the whole assembly can be pressed over? That would be witnessed by crunching/grinding/tight rotation in the bearing race on the axle wouldn't it - there is a few thou of end play and rotation is super smooth...
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Postby stardotstar » Sun Mar 08, 2009 9:21 am

Getting some pics now... Then gotta run,
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Postby stardotstar » Sun Mar 08, 2009 9:22 am

(Sorry for double posting - above was my 9th post so I can link to pics!)
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Postby stardotstar » Sun Mar 08, 2009 9:22 am

OK here is a quick photo - got to go to park with the kids - so I thought I'd snap the current state of affairs:

Image
Here you can see the drive side with the balls sitting in the grease directly on the cup. - there is no dust cover or other assembly undertaken below this point. ie I took the balls out and cleaned them, cleaned the cup and re inserted the bearings (on each side).

Image
This is the axle - the left/disc side remains unchanged from the original pull down - therefore the axle length on the left of the locknut/spacer/cone is exactly what it was before the rebuild. The dust cover remains on the disc side of the wheel because the axle can be removed through it. On the drive side I have loosely threaded the components on in the order they are assembled. Note the cone, the spacer, then the dust cover - since it is captured by the locknut - but not, as far as I know, interfere with the seating of the locknut/spacer/cone - they are all hard up against each other.

Anyway thats what I have so far.

Looking forward to any thoughts.

Will
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Postby Kalgrm » Sun Mar 08, 2009 2:04 pm

I really have only one idea on this one, but it's a slim chance ...

You can move the LHS cone inwards during the tightening phase if the lock-nut was not doing its job properly, but it's not easy to do. Even harder if you never undid it. However, all that would do is move the threaded axle across - not change the spacing on the internal workings.

Now my only idea is a real long shot, because you've done everything I would have done to make it work. Have you compared the size of the new ball bearings with the old ones? Those look pretty big, and if they are bigger than the original bearings, they'll move the whole assembly across to the right (since the LHS cone didn't move ...).

I've found in bikes (and indeed in life) that if you're balls are too big, you can find yourself maladjusted in all sorts of ways.

Cheers,
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Postby stardotstar » Sun Mar 08, 2009 3:09 pm

:lol:

Thank you for the thoughtful advice.

I have only just given up after another couple of hours trying to get it to work the way it did only two days ago!

I did not replace the balls, and I have just done several adjustment cycles with moving the fixed side locknut assembly inboard by as much as 1mm and found that the clearance is not changed enough to warrant another adjustment given that there would be only 3mm of axle on the disc side and as much as 7 on drive (when the original setup had 5/5) - I am stumped - unless I can identify some spacer missing or something - but it would have to have come from the disc side and since that was still in one piece I am left completely confounded.

I have just set the bike up with my alternate rim set and so I am able to ride in the morning but this has been a frustrating experience.

I will put the offending rim aside with its counterpart and continue to build experience mechanically before reconsidering it.

Thought it was going to be fiddly but straightforward - silly me.

Here are the final shots - the caliper setup and drive side of the GT Av with the alternate rims fitted - note clearance and shims on calipers to match the alternate rim build - brakes could be further fine tuned but are pretty spot on here now.

Other shots are disc and drive side of the offending wheel. There is about 6mm axle on the cassette side and 4 on the disc side as mentioned above.

Image
Image
Image
Image

I'm not holding out much hope on this one - I must have stuffed up somewhere but I can't fathom it.


Cheers,
Will
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Postby stardotstar » Mon Mar 09, 2009 6:35 pm

Final analysis

There is something majorly wrong with the hub after I serviced it - a quite noticeable amount - I must have dropped a spacer or some sort of component and would appreciate any mechanics advice on how to set the hub up to make it serviceable again.

These photos show the error - the first is the clearance between the rotor and the outside locknut on the alternate set I am riding now...

The second is the space on the reassembled hub. Note that no amount of moving the axle through the cone/locknut assembly will change this measurement!

Image
Image

As I say I must have lost a piece at some stage but since I didn't disassemble the disc side until after complete rebuild and finding it didn't fit I am completely stumped... Voodo.
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Postby Mulger bill » Tue Mar 10, 2009 4:06 pm

You and me both Will, I've looked at the pics for a while and they all look good, maybe time to rope in a pro?

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Postby stardotstar » Tue Mar 10, 2009 4:54 pm

yep thats what I am thinking; just got to find a shop mech who will chat with me about it... I must understand.
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Postby glawrence2000 » Tue Mar 17, 2009 1:37 pm

MAte,
Are you sure you haven't got the axle in ass about?
Failing that are the bearings in the right side of the hub? Some have smaller bearings on one side to the other.
Else pretty hard to get that part of a rebuild wrong.

Hope you can sort it out. Let us know.
Thanks heaps.
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Postby familyguy » Tue Mar 17, 2009 2:42 pm

glawrence2000 wrote:Failing that are the bearings in the right side of the hub? Some have smaller bearings on one side to the other.


Shimano tech docs on their website show all Deore hubs have 9 x 1/4" balls per side (18 total).

It does look like the long spacer could be in the wrong side, but that wouldnt give you a 2mm differential. It might account for the mis-aligned brake disc though. I'd go with glawrence's a*se-about call, cant hurt to try.

Jim
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Postby stardotstar » Tue Mar 17, 2009 8:52 pm

Good points guys; and yes the balls are the original 18 - 9 a side; and all the same size.

I will try to sus out a possibility of a reversal but it shouldn't have been - I mean the problem originally surfaced upon reassembling after servicing the hubs bearing-races and balls but NOT disassembling the disc/non-drive side cone and lock nut (as per the instructions!) so that is one of the reasons I am baffled. The axle could only orient one way and furthermore couldn't have changed its disc side position by the amount witnessed.

The spacer couldn't get mixed either in this case since it must reside between the lock nut and the cone!

And I wasn't even drink wrenching!!

Thanks heaps for the suggestions guys - appreciated. I will be returning to this rim periodically looking for inspiration :L)
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Postby stardotstar » Wed Mar 18, 2009 7:26 pm

Of course there is a part missing - a spacer in fact - despite all my protestations to the contrary it simply must have got lost somewhere in the process - although I am absolutely confounded as to how - and if so where the bloody hell is it ??? my work space is not messy,...

anyway - the exploded diagram of the hub calls for spacers on both sides:
http://techdocs.shimano.com/media/techd ... 608924.pdf

and so there it is.

I'll have to find one (or THE one) or source one somehow.

Regards,
Will
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