Page 1 of 3

Pushing R8000 limits/capacity

Posted: Fri Oct 12, 2018 9:17 am
by JScycle
Hi,
I am going to change my derailleurs from 6800 to r8000 (rear derailleur for bigger cassettes, front derailleur for the built-in barrel adjuster so I can run jagwire elite link cables).

I currently run 11-28 with a 52/36 and occasionally do some really hilly races or riding. I can't decide whether to buy a GS (11-34 max) or SS (11-30) rear derailleur. Most of the year I will be using the 11-28 with the correct sized chain. Could I possible push the SS to an 11-32 or 11-34 with a new chain? This would keep crisper shifting with a short cage for the majority of the year.

Cheers,
J

Pushing R8000 limits/capacity

Posted: Fri Oct 12, 2018 9:17 am
by Weenie

Re: Pushing R8000 limits/capacity

Posted: Fri Oct 12, 2018 9:33 am
by pdlpsher1
I have two bikes with the 8000 GS. On one bike I run a 11-40 and on another bike I run a 11-34. I imagine you can 'push' the SS to a 11-34 but what makes you think you'll get crisper shifting with the SS on a 11-28? A longer cage doesn't mean worse or slower shifting. On a rear derailler the upper pulley is the one doing the shifting while the bottom one is called the T-pulley, with the 'T' for tension. The distance between the two pulleys has no bearing on shift quality. For optimal performance on a 11-32 or 11-34 the answer is the GS. And you will get crisp shifting with a GS on a 11-28.

Re: Pushing R8000 limits/capacity

Posted: Fri Oct 12, 2018 9:46 am
by fa63
Yeah, just get the GS; I doubt you would notice a difference in shift quality in a double blind test. I have been running a 6800 GS RD for a couple years now, and it shifts great with 11-28, 11-32 and 11-34 cassettes (I also briefly used a 11-40 cassette with a Wolftooth Roadlink; also worked great).

Re: Pushing R8000 limits/capacity

Posted: Fri Oct 12, 2018 9:56 am
by alcatraz
6800gs will work fine up to 34-36t, on my friends domane he could have also gone 38t without a hanger extender. Depends on the bike.

I still recommend you stay around 34t. Thats about the size the derailleur was designed for. You'll get better shifting with mid cage on 34 than a short cage on 32. It's because the geometry of the derailleur suits a certain slope on the cassette. This slope angle can't be adjusted. If you clear a big cog barely on an undersized derailleur you will have poor shifting on the small cogs because of the huge clearance there. That's why hanger extenders don't really work except for amateur level riding, and also why mid cage derailleurs don't work well with small cassettes or vice versa.

Re: Pushing R8000 limits/capacity

Posted: Fri Oct 12, 2018 6:02 pm
by Hexsense
And for 11-30, short cage (at max stated capacity) or long cage would work better?

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 10:13 am
by JScycle
Thanks everyone. So just to clarify if I buy a mid-cage and run two chains it will work awesome with both 11-28 and 11-34?

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 10:23 am
by bm0p700f
11-28 to 11-32t us what the mid cage is meant for. The mid cage mech can't maintain good chain tension in all gears with an 11-34t.

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 12:13 pm
by LiquidCooled
bm0p700f wrote:11-28 to 11-32t us what the mid cage is meant for. The mid cage mech can't maintain good chain tension in all gears with an 11-34t.
The r8000 mid-cage is meant for 11-28 to 11-34. It's only the previous-generation r6800 which is meant for 11-28 to 11-32.

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 12:14 pm
by LiquidCooled
JScycle wrote:Thanks everyone. So just to clarify if I buy a mid-cage and run two chains it will work awesome with both 11-28 and 11-34?
Yes.

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 8:27 pm
by TheKaiser
So wait, are y'all referring to the SS or GS when you say "mid cage"? Do you consider SS and GS to be Short and Mid, respectively, or do you consider them to be Mid and Long? Just wanted to be sure, as the terminology changed from letters to sizes midway through the thread.

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 8:40 pm
by LiquidCooled
SS = short cage.
GS = medium cage.

Shimano does not have any long cage road derailleurs.

Re: Pushing R8000 limits/capacity

Posted: Sat Oct 13, 2018 11:42 pm
by bm0p700f
I was getting confused for a moment with the capacitues on the new mech.

Pushing R8000 limits/capacity

Posted: Sun Oct 14, 2018 12:00 am
by pdlpsher1
JScycle wrote:Thanks everyone. So just to clarify if I buy a mid-cage and run two chains it will work awesome with both 11-28 and 11-34?
To be clear, the cage length determines the chain wrap capacity. If you use a RD and pair it with a cassette that is not recommended by Shimano, you will not have sufficient chain tension for all of the gear combinations regardless whether you use a different chain or not. Using a longer chain will let you run a big-big gear combo but the derailleur won’t be able to take up the extra chain slack on a small-small combination if the RD lacks sufficient chain wrap capacity. There’s a very good reason why Shimano makes two different versions of the RD.


Sent from my iPhone using Tapatalk

Re: Pushing R8000 limits/capacity

Posted: Sun Oct 14, 2018 12:35 am
by 2lo8
Pretty sure nowadays the GS/SS versions have different geometries to better track different size cassettes.

Re: Pushing R8000 limits/capacity

Posted: Sun Oct 14, 2018 12:35 am
by Weenie

Re: Pushing R8000 limits/capacity

Posted: Sun Oct 14, 2018 3:21 am
by alcatraz
2lo8 wrote:
Sun Oct 14, 2018 12:35 am
Pretty sure nowadays the GS/SS versions have different geometries to better track different size cassettes.
<---- This, is what many people don't realise.

It's confusing to call derailleurs short/medium/long cage when the geometry is also different.

A triple road crank would need a small derailleur with long cage.

A 1x mtb would need a big derailleur with a small cage.