Hi, My bike has 105 mechanical and is set up with an 11-34t cassette. I have just got a second/better set of wheels, stock wheels for winter/commutes and better wheels for longer summer rides. I have an 11-28t cassette spare, if I put this on one of the wheelsets can I use the wheelsets interchangeably without adjustments to indexing of rear derailleur and length of chain?

I have many times in the past without issues.

Thanks, wasn't sure about it

Ideally, but I'd try it to make sure. Disc or rim brake?

Disc brake, thought I'd check first before I tried it, in case I was gonna do damage!

Might work, though you may have to adjust the B screw when swapping.

I'd be more concerned if you were going the other direction: using a chain sized for the 28t max and then sticking in a cassette with a 34t; that could end badly.

It shouldn't do damage, but it's possible there might be a very slight misalignment which would lead to brake rub. Do you know the business card trick for aligning brake calipers?

The other thing is if the rotors are worn on one wheelset and new on the other, the pads will be less tolerant of misalignment on the latter. Maybe use those wheels to set the caliper alignment, which - again, IDEALLY - should work fine with the other wheels.

Caveat: My experience with this is limited to one bike with two wheelsets, but it was successful, and yeah, the pads rubbed a little on the new rotors till I realigned them.

I’ve done this with 30 & 34 no problem.

Ah, I hadn't even thought about that. Yeah, OP might have to realign brake calipers with each swap...When I got tired of doing that, I bought these and solved the issue.

You can shim your rotors so the more inboard one takes the position of the other wheel. We used to stock special shims for that, but I would try a beer can and scissors.

What they are not telling you is that it won’t do too much damage.

I see a slopppy chain on that 28t cassette if you use the 11t cog. Good luck

Why would the 11t cog on one cassette be any sloppier than the 11t cog on the first cassette? Magic?

I have a checkpoint with 2 wheelset of the same make and model, but I had to run a shim on the rear wheel of one set to ensure the disc did not rub. That beats having to adjust the calipers around when you want to swap wheels. I would also think the B screw adjustment would be advisable, and while it should work, that is probably at least 1 or 2 link difference in proper chain length, so if you are running something other than 12 speed, I would pick up a Wipperman Connex link and have a 28T chain and a 34T chain. I do that for when I want to run my 44T cassette versus the 36T cassette, takes all of a min to swap out.

Think about it for a second. Kontact is clearly right. The chai is the same length and the number of teeth the same in 11, regardless of whether the largest cassette is 28 or 34. If the chain is sized to work well with the 11-34, it will work with the 11-28.

you could shorten it a few links for the11- 28, bu then you couldn’t use it for the 11-.
34

In my experience, it’s unlikely you’ll need to adjust the B screw. A textbook set up would likely include adjusting the b screw for the smaller cassette, and it might wrap just a touch better, but it’s like to shift acceptably without bothering.

I would add, How old is the chain? Sometimes you can have an old worn chain that works acceptably on the cassette that it’s been used with which has also worn, but it will skip with a new cassette, or at least hasten the wear of the new cassette.

I’d measure the chain for wear before adding the new cassette, or if the chain has a fair number of miles in it, just start with a new chain.

If you do replace the chain, and are going to use it with both cassettes size it for the 11-34.

The difference in chain wrap, since the chain only engages have the cog, (34-28)/2=3t. 3t is a link pair and a half. I wouldn't bother for one link pair, and on modern cogs a bit of a chain gap doesn't usually cause a problem, so you could probably ignore the B screw as well.

Lots of people do this and it works fine.

There are several concerns but all are manageable.
1 cassette placement...are both cassettes equidistant? if both line up exactly with the rear derailleur you are fine but if one doesn't and you have to adjust the rear der then you have to shim one of the cassettes in order to equal the alignment...easy task
2 rotor alignment...are both wheel sets rotors equally aligned with the caliper if so fine if not some work may have to be done or if the misalignment is minor it is of no concern...long as they are not rubbing
3 chain wrap, when using the 28 cassette the chain will be a bit longer than necessary but not a big deal, just stay away from gears that magnify the loose chain

You're right. The DR is already taking up the slack. My bad. I'll take a timeout now

As I mentioned earlier, it should not be an issue with a newer quality setup. I have four 11-speed disc brake Shimano bikes with five interchangeable wheelsets, all with different hubs, cassettes, and disc brake rotors. Except for the Dura-Ace bike, which has limited capacity, all are interchangeable, with no disc rub or indexing problems. I have ordered a set of Nobl Wheels with King hubs and have no concerns with them working without issue. Think about all the teams with large quantities of wheelsets that are regularly interchanged without all this fuss.

It has nothing to do with quality. There just end up being dimensional differences between hub brands.

This is the internet; you're not supposed to EVER admit to a mistake. Damned rookie.

That is the point. Better quality components are built to tighter tolerances, thus avoiding issues. It is just typical of these forums where people are looking for issues which, in reality, are not common. Just follow this thread with all the bizarre potential problems; most of the time, the person does not even have any experience with the topic or recall a narrative from 30 years ago.

I largely agree, especially regarding the necessity for rear derailer adjustment: usually this sort of thing will work well enough that no adjustment is necessary. The disc brake thing is pretty common when swapping wheel sets, though.