Shimano 10sp cassette uneven spacing and shifting issues

[wafter]

Shifting issues prompted me to check the sprocket spacing on a problematic 10sp cassette; which in places looked wonky.

The plain shanks of 0.1mm increment drill bits were used as go / no go gauges around the circumference of the gap that separates each sprocket.

The short is that pitch ranged from between 3.8 and 4.3mm, with the average coming in at 3.97mm which correlates well with Bike Gremlin's published value of 3.95mm.

This seems like an enormous variation; and unsurprisingly the shifting issues correspond with sprocket subject to the most erroneous spacings - I can't get a clean shift in both directions across those with the largest spacing; only in one direction at a time as cable tension is manipulated.

This seems like a really weird fault - has anyone else experienced similar? One pair of affected sprockets are fairly large so I can see how one could perhaps be warped / dished; however the other problem area is between the two smallest sprokects and I'm at a loss to see how this could have happened..

 

[88robb]

That's a huge variation and definitely the cause of your shifting issues. I've seen it from a bent spider, a warped sprocket, or a bad spacer. You can't fix that much error; you need a new cassette.

 

[wafter]

That's a huge variation and definitely the cause of your shifting issues. I've seen it from a bent spider, a warped sprocket, or a bad spacer. You can't fix that much error; you need a new cassette.

Thanks - really appreciate the validation as it was driving me a bit mental and now after measuring seems so obvious yet unlikely.

Potentially weird that it occurs at opposite ends of the cassette.. I was musing on this last night and I don't think it's due to warped sprockets as the problem seems to exist at their root / next to the spacers. While I could conceivibly replace the smallest sprocket - as this has no seprate spacer so the issue must lie with the sprocket itself - the issue at the other end lies between sprockets 2&3 (counting from the largest) which according to the Shimano docs are all riveted together..

I wonder if there were some QC issues during Covid, as this would have been produced around then and tbh the rest of the bike is a bit of a shitheap

 

[Dadam]

Oh God not another weird thing that can go wrong with a bike! 😱