RD Adjustment Screws

[Dogtrousers]

Last weekend I broke a spoke in my back wheel, so on Saturday I transferred the cassette (Shimano 11S) over to my spare back wheel. The same cassette has worked perfectly well on that wheel before, but now it wouldn't engage the bottom 34t sprocket. It was as if I'd forgotten the spacer, which I hadn't (I took the cassette off again to double check). So on Sunday I tried again and had to slacken off the LO end stop a bit and fiddle with (tighten) the back-and-forth adjuster (is that the B screw?) til I could get it going. HI stop seemed fine, it's not over-throwing past the small sprocket.

Now, I'm paranoid about fiddling with the end stops. To my mind they are to be set once on installation and don't need changing. I'm especially paranoid about the LO end stop because of the danger of putting the mech into the spokes, so it felt very wrong to be doing this. As a precaution, at the end of my bodging session I re-tightened the LO screw until it didn't work any more then slowly slackened it until it just worked.

What's bugging me is whether I've been bodging beyond my abilities. I know my limitations when it comes to bike bodging. Why should this have been necessary? The bike has a steel frame with integral hanger, so the immediate response of "your hanger is bent" does not apply. As far as I know the mech has not been bashed. The mount bolt, which came loose about 18 months ago and needed re-tightening, was still rock solid.

Mech is RD-r7000-GS. About 4 years old. Stops were last adjusted when it was installed (by someone who actually knew what they were doing).

Any thoughts on what might have been going on?

 

[Paulus]

I have had a similar thing happen to me. Swapped cassette onto a new wheel and the changing was out.
I did exactly the same as you and have had no problems. I guess that the dishing on the different rear wheel put the hub a couple of millimetres out from the original. I may be very wrong on that though.
I wouldn't overly fuss about it, just remember that when you put the original wheel back on, the limit screw may need to be tightened slightly

 

[bikingdad90]

Have you changed your chain since last fitting your wheel? A shorter chain could be putting the mech in the wrong position and it’s not catching the 34t cassette ring?

Unless you have thru axles you can always expect to have to play with indexing when swapping wheels so I wouldn’t worry too much about it.

 

[Dogtrousers]

I have changed the chain, but I always try to keep the same number of links. I have QRs not thru axles.

I had to work on Sunday afternoon, so the bike is still only "on the stand" adjusted. I'll take it for a couple of careful test rides before doing anything proper on it.

 

[Ming the Merciless]

Different hub may mean the cassette is a few mm or so further left.

 

[Alex321]

I have changed the chain, but I always try to keep the same number of links. I have QRs not thru axles.

I had to work on Sunday afternoon, so the bike is still only "on the stand" adjusted. I'll take it for a couple of careful test rides before doing anything proper on it.

QRs are inherently slightly "moveable", because of the way they screw together.

 

[fossyant]

You may need to adjust them with different cassettes/hubs so just do it. Recently had a case of overshift twice on a ride and there was a bit too much overshift available on the stop, not adjusted it for years, but it had possibly been knocked.

 

[Dogtrousers]

Thanks all, for the reassurance that is is normal.

I just find it a bit odd that I've used probably three different back wheels, plus direct drive turbo with this bike and gears but I've never had to fiddle with the screws before.

 

[Ajax Bay]

The bike has a steel frame with integral hanger, so the immediate response of "your hanger is bent" does not apply.

Agree with all those above: the lateral positioning of the cassette will vary from wheel to wheel (hub and dishing).
However just to comment on the 'don't tell me it's a bent hanger' line (and I don't think it is), the dropout/virtual hanger of a steel frame can be bent too. Don't assume it's vertical: check. Acknowledge much less liable to be out because steel needs more stress to bend than an aluminium hanger.
Checking and getting it (back to) vertical on a steel frame made, for me, a difference to the RD shifting accuracy across the cassette.