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RD-6800 vs R8000 vs R7000

lukasamdvLJ27cA7lukasamdvLJ27cA7 Posts: 51
edited August 2018 in Workshop
Hello,
I have Ultegra 6800 SS rear derailleur. Want to exchange all housing, and maybe also derailleur - I used my bike as road bike / gravel / CX bike with 50/34 + 11-28.
Don't want to use bigger cassetes - 28T is enough, so don't need medium cage. But I consider new derailleur beacuse few advantages on R8000/R7000:

- Shadow - may be more secure in forest, gravel commuting
- better (?) cable routing than on 6800/5800 (ending on the derailleur) - is it true?
- better tension - (I read about that in some reviews) - the chain has never fallen, but it's important in gravel riding... - I also use frame "cover" and it isn't big issue
- available to use 30T cassete (but as I wrote before, it isn't necessary, also 6800 SS should be ok with 30/32T)

So my question is - is it worth to upgrade and also sell 6800? 
If yes, what will be better option - Ultegra R8000 or 105 R7000? Weight difference is not important - but I looking for better quality.

And yes, I know there is also RX800 - but only with medium cage, I must then buy new chains. Price is also higher.

Posts

  • timothywtimothyw Posts: 2,482
    You don't need to buy a new chain to go from short cage to medium cage.

    Length of chain required is determined by cassette and chainring size, not derailleur cage.
  • lukasamdvLJ27cA7lukasamdvLJ27cA7 Posts: 51
    Hm... I think derailleur cage also matter - short cage vs medium cage is about 2-3 chain links longer.
  • timothywtimothyw Posts: 2,482
    Nope.

    Consider, what is the standard method to set chain length?

    Wrap the chain round the big chainring and the biggest gear in the cassette, see where they meet then add two links. Cage size doesn't come into it.

    On an otherwise identical setup, the medium cage will sit a bit further back than the short cage for a given gear, and the short cage will run out of capacity sooner when it can't go back any further.

    A medium cage has the capacity to carry more excess chain, but that doesn't mean doing so is desirable.
  • lukasamdvLJ27cA7lukasamdvLJ27cA7 Posts: 51
    Hm... yes, your right. Standard method doesn't use derailleur, maybe it doesn't matter because other "angle" with medium cage.

    Ok, so it wasn't problem but... what about choice between stay with 6800 or replace to R8000, R7000 or RX800?
  • timothywtimothyw Posts: 2,482
    Stay with the 6800. If you do start riding off road more and find you are throwing the chain you could consider changing the derailleur to the higher tension spring setting - I've never done it but it is explained in the park tools overhaul guide:
    https://www.parktool.com/blog/repair-he ... r-overhaul

    Look for "As cage is removed from body, make note of the spring hole in the derailleur cage and body. There are commonly two or more hole choices. New derailleurs are typically assembled with the spring in the hole that allows the most relaxed position of the spring. If more cage tension is desired, the spring end can be installed in the other hole."
  • lukasamdvLJ27cA7lukasamdvLJ27cA7 Posts: 51
    Whoow, I didn't know about that.
    Thanks! Replacing has no sense now.
  • bjlbjl Posts: 353
    Interested in this thread, just bought a Giant TCR advanced SL frameset and am going to fit my R8000 groupset from my Giant TCR advanced pro. I have never had a problem with the shifting or chain dropping, however , seeing as this is a nee frame I have been lusting after for a while I am considering fitting a chain catcher, just in case. Is this overkill just for general road riding, use 50/34 and 11-32 ?
  • lukasamdvLJ27cA7lukasamdvLJ27cA7 Posts: 51
    I think, all depends on your strength and terrain.
    For mountains, 32 may be good option - lighter, better for knees.
    For flat - not very, if you can ride on smaller cogs with good cadence.

    Also, a wider range in cassete = worse gradation and more noticeable changes on shifting.
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