Hi there!

I know the collective pool of knowledge on the singletrack forum knows no limits, so I thought I’d try my luck at getting a solution to a problem that has been annoying me for a while.

I have a Cannondale Trail2 hardtail. Recently it was converted to a 1×11 setup, using XT single ring cranks, XT 11-42 cassette, XT shifter, and an XTR trigger. I am running a KMC x93 chain. Overall, I have been very happy with the setup, but there is one thing that really toads my sprocket. When I am on the second largest cog (37 teeth), I get a lot of noise from the chain, especially when under a lot of power. It is a sort of rumbling noise, and there is no skipping or jumping gears. No noise at all on all the other cogs.

I have tried adjusting the barrel adjuster. I have measured hanger alignment. I have visually inspected all parts, nothing seems to be bent or warped.

I have only done about 250 kilometers on the setup so far, so I am not inclined to toss the cassette and try another one, even though I suspect that it could be the culprit.

Any ideas to where I should look for a solution?

[Thinks out loud] Freehub clean,good bearings and no cracks in FH body? Cassette lockring done up tight? Could the chain be rubbing on an adjacent sprocket. IE it’s not 2nd that’s causing the problem. [/Thinks out loud]

B screw adjustment?

I fitted 1×11 this weekend (11-46 casette) and have had to spend time adjusting the B screw to get rid of the rumbling noise, there was still a slight amount on the first ride but this went away after the first few climbs.

All good suggestions!

The thing that is really wierd is, why only on the second largest cog? The freehub is looking good, b screw seems to be alright… I haven’t tried tightening the lockring, so I will be trying that.

From what I can see, the chain does not rub on the adjacent cogs.

The noise does not seem to have any impact on performance, but once you hear it, you can’t unhear it!

Besides, I’m getting pretty tired of having my riding buddies asking me if I can’t adjust a rear derailleur properly! 🙂

Well, I think i might have an idea of what the problem is.

There is a slight wobble in the freehub, not much when you just grab the hub, but enough to make the cassette move a couple mm at the outer edges. I think Davesport hit the nail on the head when he suggested that the chain was rubbing on the bigger sprocket under load.

Now… better contact Cannondale and ask what kind of freehub I need to fix the problem.

Thanks, all!

Sorry but there’s no way it’s going to be rubbing on the largest sprocket, the angle of the chain prevents this.

And tons of freehubs have a bit of play in them, not going to be that.

I’d play with B-tension.

The chain and cassette were new at the same time yes?

Yes, the chain, crankset, derailleur, and cassette were replaced at the same time.

Top pulley wheel was about 12 mm from the largest cog, moved it in to about 5 mm, it didn’t solve the problem. Maybe the gap should be even smaller?

Hmmm… might have to do a little more digging.

on my 11-42, i had the same issue. its a big leap from the 42 down to the next one and a bit of B screw tweaking during a ride sorted it out. Silky silence now!

Another vote for b-tension. Confused me because I’d never had a situation before I went 1×11 where adjusting it in the biggest sprocket didn’t mean every other sprocket was then fine.

Of course it’s never a bad idea to check hanger alignment too.

Right!

B tension tweaking it is! The hanger is straight…

By the way, the chain might be a tad long. Anyone think thats a problem? Its not too long, but I reckon that one less link wouldn’t hurt.

Too-long chain really only affects the littlest sprocket.

Yeah, I thought as much regarding the chain length…

So, if anyone needs med, I’ll be in the shed, playing with my B-screw.

I think too-long chain might contribute. A shorter chain would pull the mech forwards/away a bit when you’re in the bigger sprockets, wouldn’t it ?

That, and maybe B screw is what I’d be looking at

I’d bin your chain if I were you. Get an 11spd Shimano or SRAM one. The KMCs are noisy on 11 speed in my experience.

Hmmm… never had problems with KMC chains before, but it is worth a shot if the B screw does not yield a result.

Sorry but there’s no way it’s going to be rubbing on the largest sprocket, the angle of the chain prevents this.

My XT cassette has ghost marks of the shape of the links on the side of the 42T cog from the chain doing this, mainly from dirt filling the tiny gap but it does do it. I don’t have any noise when it’s clean but after a few bits of dirt it makes a slight tinging noise. If you put a clean chain on the 37 cog and push it towards the 42 there’s very little room, if any. Guessing it’s down to Shimano fitting 11 cogs in the space of 10.

I’d bin your chain if I were you. Get an 11spd Shimano or SRAM one. The KMCs are noisy on 11 speed in my experience.

+1, had a KMC originally and it was noisy and slightly rough until it bedded in after a few big rides. The XT chain that replaced it worked 100% from the off.

Guessing it’s down to Shimano fitting 11 cogs in the space of 10.

They’ve not actually done that though.

Gentlemen, I stand corrected.

I have been using KMC chains for years, no problems at all, until this crunching noise started.

I took a chance, and slapped on a cheap SRAM chain… The noise is gone, I can even back pedal on the 42 cog without dropping the chain!

Amazing.