Sram Force/Red mechanical - difficult to get it to shift to the smallest cog.

[alcatraz]

Hey wws

I'm still on sram mechanical and apart from it not wanting to shift to the last 11t cog, it works fine.

I'm running:
red 28t cassette
red derailleur
force shifters
kmc chain (i have three chains that I rotate)

The b-screw is set so the derailleur sits super close to the cassette.

I have a veeeery long housing before the derailleur and the cable is nice and smooth. (shimano sp41+sus cable+shimano cable grease) I always grind the housing ends flat and use plastic ferrules wherever possible. I also use an inner liner for the entire portion of the cable that runs internally.

The derailleur hanger is perfectly aligned with a tool.

The limit screws are not holding back the shift.

I can't adjust indexing more to aid the shift, without messing up all the other gears.

After using the shifter to start the shift onto the 11t cog I notice that the derailleur doesn't quite pull the cable all the way. I can with my hand give it a gentle tug and then it shifts immediately.

So is the spring in the derailleur too weak? Is there anything that can be done about that? I just oiled all the linkages in the derailleur but still. Seems the spring is too weak.

[alcatraz]

I'm tempted to try and compress one loop of the spring together with a ziptie or something. Is that just crazy or what?

[Marin]

Lower stop set too high?

Just had a similar issue with Rival 1 but there the derailleur gap was too big and there was friction.

As you said, friction would be the first thing to check - how's the run from the lever to the 1st cable stop?

[nikospeed]

May sound stupid but I had a similar issue with a friend's 105 just last week....
RU sure your indexing is right and when you are on cog 28 you can't shift further? Unless that is the issue and you are "one off" then I would also suggest to losen the Hi limit screw just a little more to see what happens. Remember, on 11th cog your pulley wheel is not supposed to sit directly under the cog but slightly right (see manual).
Note: I am a Sram user (and adjuster )

[Nickldn]

Cable tension set too high?

If so the RD may not be able to move the the smallest cog.

[Mr.Gib]

Just dealt with this issue with one of my wife's Sram Red equipped bikes after I swapped from a Shimano to a Red cassette. I fixed it by turning in the b-screw. Yes, moving the cage further from the cassette. Wierd I know. Maybe it had something to do with using a wifli RD on an 11-28 cassette.

[grover]

Agree that it can be B-tension too close to the 11 cog. Increase the B-tension to move derailleur away from cassette and then readjust limits and indexing. Also consider your cable routing could be too long and pushing the derailleur forward.

That said, I've seen exactly this scenario a number of times. SRAM have warrantied the derailleur and replaced with a new one on occasion. You are correct in that the spring is not pulling the derailleur far enough. Anoth fix is to put a washer (one of the pedal washers that come with all SRAM cranks works) between the derailleur hanger and derailleur. It means the spring is on a little more stretch for each gear so will reach the 11 cog better.

[js]

I ran into this when running SRAM 22 on a bike previously (Tarmac SL4 I think?) I had the cable tension and limit screw set correctly, and even tried setting it wide open, but it was still a poor shift down to the 11t cog. My assessment was that the spring was simply too limited in its tension at that extreme to make the shift. I ended up putting a pedal washer between the derailleur and the hanger and reset everything for that new / slightly adjusted spacing. It shifted like a dream from that point onward.

[Gary71]

grover and js thank you I never knew this trick - that is genius.

[alcatraz]

Brilliant idea to put the washer. I'll try that today.

I was thinking to try and get the cassette farther left, but this is obviously much smarter.

[Lucendi]

Is the pulley cage loose? Often the Sram rear derailleur pulley cage axle and security screw wear and it creates play before it fails.

Also, if you have a bike with long cable housing sometimes they s-curve under tension if they are of the lightweight variety, negatively affecting the indexing.

[alcatraz]

It is true that twisty internally routed frames aggravate the issue but really after observing that it's only the last millimeter of travel that is impeded (where the spring is the weakest), it makes sense just to avoid going there and just use a washer. The rest of the cassette shifts fine as the spring is under proper tension everywhere else.

[NiFTY]

Could just be friction. Frame liner adds it. And shimano runs a 1.2mm shift cable sram is designed for 1.1mm, so this will increase friction within the ahifter itself.