Nose4it

I currently have an 11 speed with the 11-32 cassette and Ultegra 6800 medium cage derailleur. Living in the flat part of Florida, I would like to change to the 11-25 cassette. Will I need to change to a short cage derailleur and will I need to remove any chain links?

HerrKaLeun

Since you go down in largest rear teeth, no need to change RD. You may need to shorten the chain, but depends on how much slack you have now. if you ever change RD, you may consider a shorter one.

cny-bikeman

You do not have to change either chain or derailleur. They both currently work on the 25 cog, after all. You can choose to shorten the chain or get a small cage derailleur, but if you travel with your bike to a hillier region you will no longer have the option of a larger cassette.

DrIsotope

<anxiously awaiting someone to show up and tell the OP to change his RD because it will "shift faster.">

Just take out a few links and you're good to go.

HerrKaLeun

And the shifters also need to be changed along with the cable. And needs to be 105 at minimum - everything else will ruin your Strava times. Just to be sure, also change the frame because frame expansion and contraction could stretch the cable and prevent crisp shifting. Must be a steel frame, definitely, nothing lese will work. After all the shifter cable is steel. Unless the RD has CF parts, then it must be a carbon frame - nothing lese will do.

Bill Kapaun

No need to shorten the chain since both cassettes have the same smallest cog and thus the same "slack" as before.
Leaving as is would allow a quick swap back to the original cassette (if desired) without having to lengthen the chain.
One might make a case that having a few extra links could spread the wear out.

HerrKaLeun

Of course no NEED to shorten it and you make a good point with future swap. On the other hand, whenever you change cassette for wear, you change the chain anyway. Unless you really swap cassettes just for the sake of different cogs. I assume the time to change a chain or cassette due to wear, is the time to make drivetrain ratio changes.

If you go by the Park rule (1 link longer than having chain over large front and large rear) would require shortening the chain. but of course, also works with a bit longer chain.

I don't think a longer chain wears slower. After all rollers still get friction - now just more rollers getting friction. You may get more drivetrain losses. But we are talking academics here. I'd bet a properly adjusted chain causes less overall drive train wear than a too long or too short one.

I noticed on my brand new bike the chain was at least 2" too long according to the Park-tool rule. And the B-screw also was by far not adjusted to what Park recommends. I took 1" out (to meet in the middle?). I guess my suggestion was more once you get your hands dirty replacing cassette - a good time to verify all other adjustments.

Nose4it

That's a good point. I do travel to Wisconsin in August so I may want to use the larger cassette.

shelbyfv

The best way would be to use a new properly sized chain with the new cassette, save the old cassette and chain for your trip. Easy swap out and no possible chain vs cassette wear issues.