Help me troubleshoot this mtb, please

I don’t get stumped often, but I’m stuck here.

2018 Giant Trance, Sram Eagle GX.

Under load, the chain “pops” on the cassette, as if it comes misaligned and then snaps back into place on the cog. Not quite as heavy as when the chain almost shifts to next cog, but definitely sounds and feels as if the chain is coming un-meshed from the teeth and then popping back into place. This happens in most of the cassette, so I don’t think it’s the “teeth tolerance” issue I’ve seen people discuss regarding a specific cog.

Bike pedals and shifts flawlessly in the workstand.

So far I have checked/confirmed:
New chain
Cassette does not appear worn
Hangar is straight
Torqued all suspension pivot bolts
Torqued rear through-axle

I’m stumped and it is keeping me from riding in beautiful weather because I can’t stand a noisy bike.

If it only happens under load it is most likely a worn cassette…how many miles on the previous chain and how many miles on the cassette?

Don’t know about the mileage, this bike doesn’t do too many miles. I replace when stretched. This cassette has seen 3 chains, I believe.

I’ve had similar things when the cogs got worn, I’d second that theory. It can be really hard to tell just by looking at the cogs if they are worn. If it seemed to start with the new chain, I’d bet that’s the culprit.

Agreed about the cassette, but also check your indexing. Maybe change the cable/housing if possible.


I’m gonna put a cassette on it (ouch); I think I don’t consider cassette wear often because I don’t keep bikes long enough and I stretch chains so quickly that they don’t ride on the cassette too long

Chains are relatively cheap compared to cassettes. I will change the chain every three or four hundred miles on the MTB(way before it shows stretch on a gauge) which seems to really prolong the life of a cassette.

Well, back to the drawing board. New cassette, same issue.

Shifts beautifully in the work stand, cassette pops under load when riding.

Try new cables.
12 speed doesn’t tolerate much slack in the lines.

I had your problem with my Spark. The shop mechanic swapped all the cables over free of charge during the first service and the problem went away.

Hadn’t thought of that. Slight stretch In the cable under load could do this.

Im gonna give that a shot.

I think I’ve got it, finally.

Tested it in the yard today and got the sound to repeat enough that it sounded like it might be in the rear wheel.

Took the whee off to inspect cassette installation and check for play in the hub and found a comically-loose spoke.

Hopefully having the wheel trued quiets it up.


Swapped a rear wheel and the noise disappeared, so I’m pretty confident it’s in the rear hub.

Time to upgrade!

Have you tried pulling off the freehub body and checking the pawls/ratchet?

Might be one or more is stuck with rust/dirt/grease. If never been off it can be quiet a shock to see inside a freehub.

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That’s the final thing on my list; it’s never been opened and has been ridden very hard for two years.

Well, there’s damage to every pawl that looks indicative to “almost” engaging and then being forced backwards. There was also a flake of something on the tip of one pawl.

They all spring back freely but are pretty chewed up and some now have tips that are curved in the wrong direction at the very end.

New wheel it is!

What wheel is it? Might not be an expensive fix (but could be!)

Novatec hub laced to a WTB rim; the wheelset was $125 2 years ago, I’m not sure I want to spend any more on it.

Have you checked the B limit? Not sure about whether the Trance is full suspension, but as Sram GX wears it becomes more susceptible to b-limit adjustments.

As I understand it, you have to set this limit while the bike is under load (ie sag is engaged) for maximum performance.

Good luck!

Yeah at $125 replace for sure