105 Cassette has trouble shifting from 3rd to 4th gear

[DareDemon666]

So recently I bought a new set of wheels for the bike. Thought I'd upgrade to a bit of deep section for the summer. I bought a new cassette to go with them so I can change back to the winter wheels no worries once the wind and rain are more prominent again.

Only issue is that ever since there's a real issue shifting from 3rd to 4th on the back. It shifts as slick as ever in the 1-2-3 range and also in the 4-11 range, but to get into 4th I more often than not have to push the lever two clicks to jump 3rd to 5th, and then back down to 4th. Additional strangeness is that shifting from 5 to 4 is very slick, as is 4 to 3 - no issues. It's only when i try to shift up into 4 that there's a problem and it really just doesn't want to go. Maybe 4 or 5 full revolutions of the cranks before it admits defeat and shifts.

It's really frustrating because when I'm cruising around town with lots of stop start I'm usually in the 3-6 range, and especially at red lights and such i like to shift 3-4-5 as I go from stopped to riding again.

I was dead sure to install the cassette correctly and made sure there are no gaps or anything, torqued the lock-ring to the right spec, everything. With the exception of the Cassette, the rest of the group-set is untouched - all 105. The cassette itself is an identical 11 speed to the one on the winter wheels, so the fact I had no issues with the old one suggests the new cassette is at fault. The fact that the shifting either side is flawless seems to suggest that's not the issue though - unless the 4th gear is flawed or something?. Just wondered if anybody had any ideas what the problem might be?

Thanks in advance!

[tatanab]

I think firstly we have to understand what you mean by 3 and 4 etc. Which end are you counting from.? it was easy in the good old days when people changed down in gear which meant to a larger sprocket, but so many people these days talk about changing up the cassette to a larger sprocket. Logically, the lowest gear (gear 1) is the largest sprocket

As I read it, you have fitted a new wheel with a new cassette. I suspect that all you have to do is tweak the indexing a little to account for a very small difference in alignment of freehub/hub/cassette. Although if you did not change the chain at the same time, then that might be a problem since it has worn to the old cassette. Quick solution - put the old cassette on and see if the problem remains.

[Eyebrox]

When I change cassettes or derailleurs and find the gears work perfectly except when the chain drops to the bottom two or three gears (second largest/third largest cogs) and only in that area I suspect the fault is a bent hanger. Alignment tool is usually the answer.

[NickJP]

1. The cassette may not be in the exact same lateral position on the two wheels. Check that the top jockey pulley on the derailleur is correctly centred on the cassette cog. If it's slightly off one side or the other, it can affect the shifting - more so in one direction than the other.

2. Check the alignment of the derailleur hanger. If the hanger alignment is out, that can also affect the shifting.

[jb]

Sometimes there are a couple of sprockets that just don't get on with each other, They will work on a brand new system but when a bit of age sets in they refuse to work despite renewing everything that its possible to renew without buying a complete new derailleur and shifter.
You can either go mad trying to fix it or just accept that you'll have to push the lever a bit further to coax it over. Its more a problem with wide range cassettes than a close ratio set I think.

A new chain obviously has less flex and will be forced to change more easily than a used one but its not very desirable to keep changing half worn chains - ditto with the top jockey wheel.

[DareDemon666]

Hello everyone,

Thanks so much for the insights. Hopefully I can clear some things up that you've pointed out.

So first up, When I say 3rd or 4th or 5th gear, I mean in terms of difficulty/speed/size. 3rd largest, 3rd most teeth, 3rd easiest, 3rd from the hub, whatever. In my experience and thus my parlance, a higher number means a faster gear. So the smallest on the cassette is 11, the biggest is 1.

The chain is not new, so as you say that may be the issue, but I don't think so - I'll explain why in a sec.

The hanger looks as good as it's ever done, I can see no signs that it's bent, misaligned, or damaged in any way. Just to be super sure I changed the winter wheel on and it shifts like silk all through the range. So unless I miraculously bent the hanger back by the perfect amount during the change, and then bent it again to the same point changing back again to the summer wheels, I doubt that's the issue

I think NickJP has got the winning ticket. I've had a look at the top jockey wheel and rear mech as a whole, and it is definitely biased to the inside edge of the cassette. That is to say, when I set it to be in the 4th gear, the chain is actually tracking like the derailleur is between 3 and 4. Or in other words, the chain isn't centred on the gear, but rather is off to one side towards the wheel and centre of the bike. It seems like this persists throughout the cassette's range from 4 to 11, but below that it is barely noticeable. It does explain why shifting to 4th is tricky, but it doesn't explain why only 4th is the tricky gear, while 5-11 shift as expected.

In any case I guess it's a case of adjusting limit screws and/or the indexing - so could I ask some further advice there. What do I need to do exactly? Seems like I need to open up the top/high end (towards 11) of the range slightly and then slightly increase the size of the increments on the indexing?

Thanks all for some top tips and in speedy fashion. Happy riding!

[Eyebrox]

You shouldn't need to adjust the limit screws if the RD is reaching the first and last cog without the chain coming off the cassette. If the tensioning on the cable is suspect loosen the cable at the anchor bolt on the derailleur, clean and lube round about that area particularly at the adjuster screw. Make sure the adjuster is screwed in almost fully (leave a few turns for fine tuning) - it often comes out and doesn't work properly although you can't detect that because the taut cable is holding it in place. Reattach the cable taking up any slack with the chain on the smallest cog and the shifter in its most relaxed position (work the inner paddle fully to the end of its range). Then change gears up and down the cassette, adjusting the tensioning as you go. There are videos on line that will show you some extra tweaks. Pay close attention to the RD movement either side of the problem area. Again fine tuning with the adjuster could help you identify the sweet spot you're looking for.

[peetee]

The last time I came across this issue the rear mech wasn’t tight to the frame.

[RideToWorky]

The last time I came across this issue the rear mech wasn’t tight to the frame.

Hi Peetee,

Good call on something to check!

I had exactly this, but as a clicking noise as riding, when shifted into the middle gear.

Mind you, this was when I first I finally pulled the bike out to ride after a long lay off. (2 plus years, just shoved the bike into the shed when covid kicked off in the UK, and full lock down etc.)

The clicking now noise has gone down now, since I've been riding though.

Regards
Martin

[flat tyre]

Depending what 11 speed cassette you are using you may or may not need a spacer ring on the freehub. If you haven't fitted one and one is required (or vice versa), this could make the gears difficult to index correctly.
Some more information in this thread - viewtopic.php?p=1474807#p1474807