Help! Grinding sound from rear hub when peddling under high torque (video)

[Stupak]

Hi all,

A while ago my chain snapped ripping the derailleur and quite tightly wrapping the chain between the cassette and Freehub. Following this I replaced the full drive train (derailleurs, cassette, chain, front chainring as it was also time to replace). 2 spokes also got replaced that were slightly damaged.

However, when accelerating under relatively high torque I get this sort of crunchy/grinding sound. 

What is odd is that it’s pretty much perfectly silent in the middle gears, but makes the noise in the further out gears. From the video I first accelerate in the middle gears where it’s silent, then when I change further out you immediately hear it in part 17-21 seconds and later. When freewheeling it is also silent. 

Gears are indexed perfectly, The cassette is properly torqued and it’s not the cassette itself as I’ve tried three different ones, all brand new.

I can only imagine that the hub is somehow damaged?

 

Edited March 27, 2023 by Stupak

[kingalton]

check the B screw adjustment.. there are tutorials to do so without the tool if you dont have one.

 

[openmind]

5 minutes ago, kingalton said:

check the B screw adjustment.. there are tutorials to do so without the tool if you dont have one.

 

I second that - sounds like the upper pulley wheel of the derailleur is grinding against the underside of the cogs. It might work ok on the bike stand but then get pulled up a bit under torque. It makes sense that this would only happen on the larger cogs when you see how the derailleur moves as it goes up the cassette. 

Edited March 27, 2023 by openmind

[kingalton]

 

[TheoG]

That sound like a AXS derailleur?  You get a tool with it to set the B-Screw.  Chain must be on the second largest gear and then you use the "tool/template" on the largest gear to adjust the b screw correctly.

Its really easy, google for a video if in doubt.

Edit:  

 

Edited March 27, 2023 by TheoG

[Stupak]

Thanks for the feedback. It is the AXS, I did also use the included b-gap adjustment tool with the bike under sag and chain the correct length. I’ll recheck tomorrow morning as soon as I can (hopefully is just something this simple). 

Edited March 27, 2023 by Stupak

[Stupak]

Checked this morning and it wasn’t the B-Adjustment screw unfortunately. Then took it to my LBS today who did a complete service this afternoon of the hub as there was a tiny amount of play. Unfortunately also didn’t fix it. On an indoor trainer it’s also silent in all gears. So they confirmed it’s definitely the wheel somehow. Gone for the last resort option which is a complete wheel rebuild.
 

Should take about a week as they’re busy, but will keep this thread updated until it’s resolved incase anyone comes across this same issue. 

 

[Murrob]

I struggle to believe that a complete rebuild is necessary if all hub, freebody  bearing are good and there is no play. Looks like a Dt Swiss hub, have you checked that is not the star ratchet? In the freebody?I know there were manufacturing defects there causing weird non engagement issues.

Sometimes though, it’s the simplest explanations for things. I had a phantom scratching gearing type noise a while ago on my mtb, spent the whole ride trying to figure it out and coming up with all sorts of explanations and eventually managed to also recreate the noise consistently when turning right and under load. Finally when I got home and got a closer look, turns out it was it was the bike shield frame protector adhesive film that had come off the frame in the rear stay BB area and when pedalling under load the frame flexed and the lose film caught the outside knobs on the tyre. So maybe look out for something like that also?

[Stupak]

Resolved

They first did a full hub service but the noise was still there. Bike shop said it must then be the spokes, but a Santa Cruz mechanic said it’s definitely still the Freehub. So considering it needed rebuilding to see if it was the spokes I just replaced the hub at the same time incase it was the hub. Fixed the issue. So ultimately it was either the spokes or hub.

Edited April 17, 2023 by Stupak

[AkwA]

On 4/17/2023 at 6:16 PM, Stupak said:

Resolved

They first did a full hub service but the noise was still there. Bike shop said it must then be the spokes, but a Santa Cruz mechanic said it’s definitely still the Freehub. So considering it needed rebuilding to see if it was the spokes I just replaced the hub at the same time incase it was the hub. Fixed the issue. So ultimately it was either the spokes or hub.

Have you opened up the hub? Had a similar issue and turned out i snapped the axle inside of the hub and that shaving against my thru axle was the problem