How to convert 9 spd to 10 or 11 spd

If my tt bike were, say, a 9 speed…all I would have to do is replace my:
right shifterrear derailleurcassette
Correct?

chain too
.

If my tt bike were, say, a 9 speed…all I would have to do is replace my:
right shifterrear derailleurcassette
Correct?

Chain.

If my tt bike were, say, a 9 speed…all I would have to do is replace my:
right shifterrear derailleurcassette
Correct?

I’m 99% sure that you don’t need a different rear derailleur, just the rear shifter, cassette and chain.

Hugh

I just did this and left my Dura ace 7700 rear derailleur on. I did have to change my front derailleur to a 7800 series because I couldn’t get the darn thing tuned right with the skinnier chain. If you have Shimano Barend shifters with friction enabled, you don’t even have to change the shifter which is great! Otherwise for me I needed:

Chain
Cassette
Front Derailleur

Well that would depend on what the rear derailleur was. If it is a 9 speed derailleur then he certainly does.

If you have Shimano, you need the shifter, the narrower 10sp chain, and a cassette. You might need the inner chain ring on your crank but I can’t remember. You do not need the rear derailleur as the 9 and 10 have the same parallelogram and the 10 is simply lighter. In fact all Shimano rear derailleurs from 8sp to the present should work except the 8sp Dura Ace which had a different parallelogram.

If your shifter can switch to friction mode (as opposed to index shifting a.k.a. click shifting) then all you need is a 10 speed chain + 10 speed cassette. On the 9 speed Shimano shifters twist the silver ring on the outside of the shifter. There is no need to change the chainrings or derailleur(s).

For shimano there isn’t a “9 speed derailleur” The RD moves a certain amount with each click. For shimano the shifters 8,9, or10 determine how far the RD moves. You can use any RD with any Shifter and it will work. The only exception, maybe, is that the newest 10 speed shifters, the ones with both cables under the tape only work with there own shifters and vice versa. Some say you can mix them also, some say its not precise if you mix.

Styrrell

I guess for some combination the jockey wheel width becomes an issue?
Not sure if that affects Shimano 9 to 10 though.

For shimano there isn’t a “9 speed derailleur” The RD moves a certain amount with each click. For shimano the shifters 8,9, or10 determine how far the RD moves. You can use any RD with any Shifter and it will work. The only exception, maybe, is that the newest 10 speed shifters, the ones with both cables under the tape only work with there own shifters and vice versa. Some say you can mix them also, some say its not precise if you mix.

Styrrell

I think the jockey wheels on 8/9/10 are different to deal with different chains, but in the real world it makes no actual difference.
I changed from 8sp to 10sp a few years ago, and I even managed to get along with not changing my front deraillieur for a while when I was budget limited. Wasn’t ideal, but it did work. I went with new chain and friction shifting with the 8sp shifter, then finally changed to new shifters and got a 10sp FD later on when I got the cash

What if I have Campy?