utoner34

Obviously its better to have matching components but if you end up with spare wheel with speed incompatilbity you have to use spacers.

Does having spacers make this system more prone to some issues / more acceptable to damage / makes it shorten its (cassette / freehub) lifespan etc... or it doesnt matter?

Duragrouch

I don't see inherent issues, provided:
- No chainline issues with front chainrings; Probably not as that is a small spacer. But, not only can you also space out the right side external bottom bracket bearing, I discovered the spacer is the exact same one as for the cassette (at least a standard 7/8/9 cassette), the inner and outer diameters are the same. I kid you not. However this can reduce the left crank arm clamp length on the shaft (assuming hollowtech II style), unless your crank can accommodate a 70/73mm shell and the existing BB shell is only 68mm, so plenty of room for spacer(s).
- Cassette should not be excessively close to right dropout, as its outward position is limited by the lockring, the spacers are to accommodate that.
- Inboard, there is a bigger gap into which a chain can drop between the large cog and the spokes, chewing up the latter; I am reformed and have begun reinstalling spoke protector discs on all my bikes (tasteful clear plastic ones, just large enough for the largest cog).

Kontact 

No, there are no issues with having spacers. The gap created is smaller than the gap freewheels had, and that gap should never be an issue because your rear derailleur low stop prevents the chain from falling into the spokes.

Not having enough spacers causes all sorts of problems and damage.

utoner34

In any case, I will have to re-index he rear gears after adding spacer?

zacster

Definitely.

utoner34

What about limit screws?

zacster

Yes. You've moved the cassette over 1mm, you'll need to set the limits over by 1mm.

tFUnK

Try it and it should be obvious (in that it either matters or it does not matter). Not being facetious, just how I approach it every time (all my bikes are on 10sp still and I mix and match cogs to build custom cassettes so how many spacers and in which order can vary).

tFUnK

Ah the good old first gen Shimano road 10 speed. Only took 105, Ultegra, and Dura Ace cassettes, so the 28t is the biggest cog you'll ever fit without filing down the ridges.

Kontact 

It's just the Dura Ace wheel.

zacster

The other day I put my bike back on the trainer after riding outside in the nice weather, and I noticed this small u-shaped part on the trainer mat. I figured it came off the trainer somewhere and put it on my trainer table and forgot about it because everything was working. It couldn't have been more than .2mm thick. Yesterday was another nice day so I put the wheel back on and went on a 20 mile ride, but it was really frustrating because I couldn't get my derailleur to go into the largest cog. I thought to stop and maybe adjust, but I didn't want to bother with it as the next largest cog was the same as I had as the largest for years, 13-29 currently vs. 13-26 Campy. And besides, in NYC there are no hills that even require going onto the small chainring. As I'm riding it dawned on me where it came from, the frame's dropout, not the trainer. When I get home I take the wheel off and look, and sure enough that's what it was. I glued it back onto the frame, put the wheel on and clamped it with the QR for good contact, and took it for a quick spin to see if it worked. Bingo! That was exactly it. It now shifted perfectly again.

I tell the story just to show how little it takes to get shifting perfect, or to throw it off. Every spacer means something. When I thought about it I realized shifting on the trainer was slightly off, but I attributed it to the Shimagnolo cassette I built up. But even that cassette had shifted perfectly in the 5 years or so I've used it that way. I haven't put it back on the trainer to try it there because I expect to go outside again today.

tFUnK

Ultegra as well.