Rear mech jockey cage clipping spokes

[Sturat0]

On one of my bikes, when in bottom gear, the inside of the jockey wheel cage catches on some of the spokes. It only does this when I'm riding the bike, it doesn't do it when the bike is on the workstand. I assume that's because of the extra stress on the wheel or rear mech when I'm riding. It's the top end of the cage that catches. When I've checked the gap between the cage and the spokes it's probably about 1-2mm but it's not all the spokes that it's this close to. I've checked two of my other bikes and the gap is a lot more and I don't have this problem. Is it something to do with the way the wheel has been built with either too much or not enough dish? It's a 10 speed Shimano cassette on a Shimano 105 hub. Admittedly it's been like this for a long time, probably since the bike was new. I'm going to have the wheel rebuilt at some point in the near future because the rim is getting pretty worn so that may resolve it. If not, would it just require a spacer on the freehub body to push the cassette further out? Grateful for any advice! Thanks.

[Cyclothesist]

A photo or 2 would help to understand what might be the cause. Apart from issues with the wheel possibilities include:
Bent derailleur hanger
Bent rear derailleur cage
Missing 1.85mm cassette spacer (e.g. for 10sp MTB cassette on 11 sp road hub)

[NickJP]

You don't say if the 105 hub is 9-speed, but 10-speed cassettes are slightly narrower than 9-speed ones, and frequently came with a 1mm spacer for installation on 9-speed hubs. This was to ensure that the lockring tightened down on the cassette and not on the freehub body.

However, if your cassette doesn't have the 1mm spacer behind it, you could fit one and then adjust the derailleur stops and derailleur cable, which would give you an extra 1mm clearance between the derailleur cage and spokes.

[drossall]

Or just that the limit screws need adjusting. The sideways travel of the derailleur is limited by two screws on its body, H (high) for how far right and L (left) for how far left it can move (when seen from behind the bike). If the bike goes easily into bottom gear, locate the L screw and turn it in maybe half a turn. See whether that makes a difference. You're looking for the maximum amount you can screw it in and still have the bike go into bottom gear just as well.

[Sturat0]

A photo or 2 would help to understand what might be the cause. Apart from issues with the wheel possibilities include:
Bent derailleur hanger
Bent rear derailleur cage
Missing 1.85mm cassette spacer (e.g. for 10sp MTB cassette on 11 sp road hub)

Have added a couple of pictures, not sure if they'll help much though!

[drossall]

In the upper picture, the chain is bent to the left, because it and the cage are travelling too far towards the wheel. In the lower picture, you can see the H and L screws marked. Do what I said to the L screw, with the objective I stated.

Let us know whether that helps.

[Brucey]

remember that shimano have carefully made the cable pull abnormally long for the 2-1 shift, just to be sure that the mech always pulls into the'L' screw. Unfortunately, this causes wear on the 'L' screw itself as well as the part the screw bears against. The upshot of this is that the mech invariably, inexorably, heads for the spokes, unless the 'L' screw is re-adjusted from time to time. I too am suspicious that there perhaps should be another thin spacer but it is missing. This is very easily done with a 10s setup. Unfortunately I think you can't see anything; the spaces between the cogs appear to be full of crud. If so, some dismantling/cleaning would be in order anyway, which would be a good time to check/adjust the spacers.

[atoz]

Jockey cages can vary. The Acera on my ancient CB Dalesman has about 2 mm of protrusion facing the spokes from the upper jockey axle. This is normal with Acera cages. With other models eg Deore, 105, Tiagra, there is no protrusion, it's flush with the jockey cage.

Also whether it's an issue can depend on your hub and flange size. Definitely not an issue with old large flange hubs like Campag Tipo. It can be with modern small flange cassette hubs which can have less spacing between the cassette and the hub flanges. Brucey is dead right on the spacer issue.

[DurableAce]

In my opinion, you will find the derailleur hanger is bent slightly inwards, causing the issue. It explains why the clipping happens when not on a trainer. I've had the same issue after a crash. I thought everything was ok, but when pedalling hard in the largest sprocket the cage tickled the spokes. A new hanger (or straightened one) sorted the problem.

[peetee]

On the top photo it does appear there are two things going on.
First is that the L screw needs adjusting inward. The mech cage has over shifted (see Bruceys post) causing the jockey wheels to twist slightly
Secondly, get your derailleur hanger angle checked. It appears to be leaning inwards below and possibly to the front - although this may just be the wonky jockey wheels.
What could also be contributing to the issue is slack spokes. There is greater tension in driveside spokes so as the overall tension reduces the wheel rim can move to the right reducing the inward lean of the spokes on the driveside and bringing them closer to the cassette and mech.