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Rear Wheel Issues - What Do You Think?

June 10, 2018, 8:31 p.m.
Posts: 1405
Joined: Aug. 6, 2009

Issue #1

On my last few rides, usually after a drop, I've heard what sounds like a stick pinging in my rear spokes. The first few times I'd stop to take a look, but find nothing to explain the sound. I'd get back on the bike, and the sound would be gone, but it might come back again later after another drop. Today, I had the wheel off to re-grease the bearings (see Issue #2) and found some pretty beat up spokes when I took off the cassette:

When descending, I usually have the chain on my biggest ring and my biggest cog so it isn't slapping around so much. I assume the spoke damage is from my chain falling between the cassette and the spokes before it somehow jumps back onto the biggest cog. Is this happening because the shock compression is adding enough slack that the chain is falling behind the cog? Would keeping the chain on the second to last cog be the solution to prevent this, or is there something else (shorter chain) I should be looking at? I checked the limit screw on the derailleur, and I wasn't able to shift the chain past the big cog.

Related to this, should there be only two rivets on the back of the cassette, or have one or more been pulled out?

Issue #2

While cleaning my drivetrain, I noticed an unusual noise coming out of the rear hub. I assumed it was the bearings, so took everything apart and re-greased. While the bearings were out, I discovered that the noise (which seems very bearing-like) is coming from the freehub. Could whatever this is be related to Issue #1? You can see above that there was enough force at some point to bend one of the spokes. Could it have also damaged the freehub? Can I ride until I get the freehub repaired/replaced, or do I need to worry about it suddenly locking up when whatever is making the noise fully fails?

The bike is a Norco Fluid 7.3 with two summers (just over 100 hours) of riding on it, mostly on Seymour. Wanting to figure out if I can prevent these issues from reoccurring before I do some catastrophic damage.

I'll be taking it to BicycleHub ASAP, but thought I'd seek some input from the collective first.

Thanks!


 Last edited by: PaulB on June 10, 2018, 8:33 p.m., edited 1 time in total.
June 10, 2018, 8:44 p.m.
Posts: 10418
Joined: June 4, 2008

You definitely want a rivet in that third empty whole.

I'd have a look at your derailleur L limit setting.  Looks like it's let the change go further than it should...

Do you have any pics of your freehub?

June 10, 2018, 8:57 p.m.
Posts: 1405
Joined: Aug. 6, 2009

No pics of the freehub, but it seemed normal on the outside, no noticeable damage to any of the splines.  I've never removed a freehub before, so I didn't go that extra step to see what might be happening inside.

June 10, 2018, 9:02 p.m.
Posts: 10418
Joined: June 4, 2008

It's easy-peasy.  Just make sure you do it in a completely whited-out room so when the springs go flying you'll be able to find them again...

June 10, 2018, 11:23 p.m.
Posts: 28
Joined: May 11, 2018

For issue no 1. As you have already figured out your chain is falling between your spokes and cassette. As indicated above, it is due to a limit screw not being adjusted tight enough. When you put your derailleur into the largest cog and then push on the shifter there should be no wiggle in the derailleur. As you are in the easiest gear the limit screw keeps the derailleur from being able to allow the chain to move beyond the biggest cog. It is usually not due to chain slap etc.

For issue no 2. Most free hubs are disposable and cannot be rebuilt. The way you know your free hub is failing is if it fails to freewheel (chain would acculumate between the cog and chainring). Or it would fail to engage. You should be able to feel this stuff going on when you ratchet the frrehub by hand. The splines rarely have issues unless you are a heavy rider on a alloy free hub like a Chris king. 

The sound you are hearing could be spokes rubbing against each other. Are any of the spokes loose? Also, those spokes that got chewed up by your chain are now at risk of breaking. If you break one of them, it's probably worth while to rebuild or replace all the damaged ones as when one spoke goes the rest are likely equally fatigued.

Hope that helps

June 11, 2018, 9:11 a.m.
Posts: 2079
Joined: Sept. 5, 2012

Spoke damage looks to be from over shifting the chain . 1st thing any biker should learn to do is adjust the limit screws to prevent this. Ask the mechanic if he can show you this procedure or check out youtube . You will be great full to know this adjustment , should you need to do it after tweaking a derailleur on the trail.

What is your brand rear derailleur ?? I am confused as to why you would decent on the biggest rear cog , put the chain in the middle of the cassette.

Also reading through , you mention descending Big on Big , this could be your issue. If you are dropping with the chain on both the biggest sprockets , you more than likely do not have enough chain growth during the travel of the suspension.

June 11, 2018, 10:31 a.m.
Posts: 14144
Joined: Nov. 20, 2002

when the der on a mtnbike hits something the hanger most likely will bend inwards towards the wheel

which also knocks out the low limit adjustment allows overshifting and the chain goes between spokes & cassette

Riding behind people looking at chain lines it looks to me like a lot of mtnbikes have bent hangers

edit: if you take drops on big/big maybe you are getting a flexing/ticking noise from that big cog with no rivet I had a difficult to diagnose ticking noise from a sloppy cogset on a new touring bike back in the day solved by shimming the cogset

try jumps using a different combo to see if you still get noise, that bike came with a triple chain ring setup, personaly on a triple or dual chain ring setup with big ring removed I would mostly be staying on the middle (or what was the middle) front ring and somewhere mid rear cog

as for those spokes I supose YMMV but usually I see them break at the J bend or at the nipple not where the chain drops and scuffs them


 Last edited by: XXX_er on June 11, 2018, 10:53 a.m., edited 3 times in total.
June 11, 2018, 10:59 a.m.
Posts: 1405
Joined: Aug. 6, 2009

I took another look at the L limit screw and it was tight enough to prevent over shifting, with no noticeable movement of the derailleur once on the big cog and pushing on the shifter. However, I was able to tighten it a half turn or so without it affecting the final shift, so maybe that was enough to cause problems once bumping around on the trail.

Derailleur is a Shimano Deore 9-spd, no clutch.

If the chain was too short, wouldn't it want to rip apart when I reached full compression? I did shorten the chain when I replaced my third chain-ring with a bash guard last summer. If anything, I think I left it a link longer than the various setup guides I read said was necessary, just to make sure that wouldn't happen.

I'll stop putting the chain on the big cog when descending, and order up a new freehub to have on standby.  Eventually, I'm going to convert to 1x11.


 Last edited by: PaulB on June 11, 2018, 11:05 a.m., edited 2 times in total.
June 11, 2018, 11:20 a.m.
Posts: 14144
Joined: Nov. 20, 2002

I would crouch down 3" behind the bike and site down the chain/der to see if the der looks straight OR is the hanger/der bent inwards

If  a chain is too short the soft aluminum  der hanger is usually  the first thing to give and bend inwards  when the suspension goes full compression,

I think the formula for chain length is put it on the  big/big without going thru the der then add 2 links

June 11, 2018, 12:36 p.m.
Posts: 1036
Joined: May 30, 2004

One thing to note is that you really need to have those spokes replaced or better yet, have the wheel rebuilt. If you decided to rebuild it, why not get a new hub instead of just replacing the freehub?

June 11, 2018, 12:52 p.m.
Posts: 2079
Joined: Sept. 5, 2012

also how big of a drop are you doing ???

June 11, 2018, 1:49 p.m.
Posts: 28
Joined: May 11, 2018

Sounds like you are doing everything I would do. If your big ring is really a middle ring, there is no issue in my mind running "big" front and big rear unless you didn't leave enough chain. If you have a single pivot, the chain stretches on compression, easiest way to judge is take all the air out of your shock. Put the gears in big/big and see what happens to the rear derailleur as you go through the travel. If there is not enough chain your rear mech will be stretched out so far that the chain is running straight from cog to chainring without doing the little zig zag.

As for the worn out stuff. There are a few camps. I used to run my stuff until it broke (snapped spokes, skipping chains etc) but now that I am not so poor, I just keep everything fresh. One trick a mech in squamish shared is that he runs a few chains at the same time and swaps them out every two weeks or so. With Sram chains and power links it is easy to do and makes sure you keep your drive train clean as I always clean it before removing.  With $400 cassettes, you better bet I pay attention to chain wear.

Good luck getting your rig all tuned up. If you have some spare $, Wheels with chris king or hope hubs are worth their weight in gold!!!!

June 11, 2018, 3:32 p.m.
Posts: 1405
Joined: Aug. 6, 2009

The derailleur looks to be hanging straight. One of the first things I checked the other day was that the hanger bolts hadn't come loose, as that had happened to me before.

The biggest drop I've done is the gap on Lower Oilcan (which I realize isn't huge in the bigger picture). Otherwise, it's just the small ones on John Deer, Severed, Floppy Bunny, that sort of stuff. Until this spring, I would have rolled them where possible, or rode/walked around, but I've discovered its more fun to get airborne.

I did the "no air in the shock, big-big test" when I shortened the chain last summer. I'm pretty sure I left at least one extra link in to be on the safe side. I do use a quick link on my chain as it makes cleaning everything so much easier.

I went for a quick lunch ride across Bridle, up Good Sir Martin and down Asian Adonis and Lower Severed. Shifting was good, kept the chain off the big cog on the descent, no funny noises and nothing blew up.

I'll keep an eye on the spokes and monitor the noisy freehub. I don't see a new hub and rebuilt wheel in my future unless something really goes sideways. A Chris King hub costs more than half of what I paid for the entire bike! Going to mid-level 1x11 is the only major upgrade this bike will get.

Thanks for all the input.

June 11, 2018, 4:19 p.m.
Posts: 219
Joined: Nov. 25, 2013

PaulB - I've got an ebay-special 12x142 10sp hub that is brand new and looking for a new home. PM me if you are interested in a discounted rebuild option.

June 12, 2018, 10:53 p.m.
Posts: 28
Joined: May 11, 2018

If your bike only cost you 2 x Chris king hub then it is supposed to make all those funny noises. ;)

And if ever you did invest in a really expensive hub the outrageously loud freewheeling sound would drown out any other noises your bike was making.

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