Stormy Archer

I recently switched from a single speed crankset with a 39 tooth ring to Ultegra 6800 52/36 cranks. Everything else is Ultegra 6800 except for the cassette which is Sram.

Now I'm getting "clunky" downshifting on a few of the cogs, with both chainrings. What I mean by clunky is it takes a split second longer to shift and seems like it hang on the cogs for just a tiny bit too long and then when it shifts and then when it does there's a big chunk of crank rotation before it engages. No amount of indexing seems to have any effect on this problem.

I'm confused about it because the only things that have changed are the chain length and the chainline, which I can't really imagine causing this problem... chainline maybe, but I have the problem in both chainrings. I lubed my chain and I have a new one on the way to try.

Any ideas?

redlude97

did you change the b-screw setting? If you turn in the tension screw a significant amount such that upshifts become a problem and it still has problems on downshifts then cable friction or a kink would be my next guess, possibly a frayed cable head

Troul 

Is the chain alignment good?

Bigbus

I'm going with chain line and cable drag for these reasons: Chain alignment might have shifted just a smidgen from adding the new dual front sprockets and Cable drag usually is associated with clunky down shifting as the poor DR spring is being overworked. It still manages to do the job, but it's struggling against the drag created by either dirt, grunge, or splayed cable. 'B' screw setting might be a factor, but I kinda doubt it. They have so little effect on things, at least on my bikes. Good luck and keep us posted, that's how we all learn. Thanks

Troul 

how many links were added to support the dual containing more teeth count?

Stormy Archer

No cable drag, I just got new cables.

Didn't add any links to the chain. Do I really need to? With the b screw unscrewed, it actually has a little bit of slack if I shift to 36x11 which would imply its a little bit big?

Chainline is good and problem isn't affected much by which chainring I'm in...

Troul 

You cant base the chain length off the small small cross chaining. You need to measure the big big for length.

redlude97

if you changed the cables and housing and the chain was sized correctly(ie you can use big+big) then I'd check hanger alignment next

Bigbus

Try this formulae and double check it against the big-big sprockets for chain length. I always do the math first, mark the link, and then dry run it over the big to big sprockets before sizing the chain.

Chain Length= 2(C) + (F/4 + R/4 + 1)
C=axle to BB distance (inches)
F= Front Chainring (#teeth) largest
R= Rear sprocket (#teeth) largest

Double check all that and see what you come up with. Let us know, please.

squirtdad

yes

cny-bikeman

New cables does not mean there is not a friction problem, which can be caused by excess cable length, ferrule problems or cable stop issues. Also, it might be helpful if you specified shifting to larger or smaller cogs being the problem. Some people mistakenly call shifting to smaller cogs in the rear as "downshifting".

02Giant 

The chain is too short.

Stormy Archer

I checked my chain yesterday, it's sized correctly. There are 2 bends in the chain on each deraileur pulley while going big to big.

OK, I mean upshifting. God is such confusing lingo. I checked the cables by pulling it through without the cable clamped down on the derailleur.

deacon mark

cny-bikeman

The OP has clarified that the problem is shifting to the smaller cogs (upshifting). That is what is typically caused by cable drag, and the easiest way to diagnose is to disconnect the cable completely and then see if the derailleur shifts to the small cog (outer limit correctly set) when you push it in manually to the next cog and then release.

ctbiker

cny-bikeman,

You have a tent for sale but multiple messages remain unanswered -- ????

Stormy Archer

I'm 99.999% sure cable drag is not the problem.... already checked cables. Also, there was a bit of cable drag before I got new cables, and I didn't have this problem??? With my 39t single chainring? And now the new ones have like zero drag.

I need more ideas.

cny-bikeman

Check your inbox again - two messages sent to you - 8/30 and 9/02. If BF messages somehow not working PM me with your email.

cny-bikeman

If you have not tried the procedure I listed above you have not eliminated cable/housing as the issue. Actually, there is a small chance that the shifter could cause lag as well. You'd have to check that by holding onto the cable at the shifter to check that. There is absolutely no reason that a chainwheel change would in itself lead to slower shifts to the smaller cogs, especially when your small chainring is not that different from the original and in fact is smaller. That leaves out a "chain too short" cause.

Stormy Archer

I'm not really understanding what good this test will do me, because my problem is not whether or not it shifts into the small cog. My problem is that upshifting is clunky.

squirtdad

seems like there is still a terminology issue.

If problem is shifting from a smaller cog to larger cog (using the combined brake/shift lever) it is probably an adjustment issue, very likely not enough tension, try turning the barrel adjuster counter clockwise to increase tension.

If problem is shifting from a larger cog to a smaller cog then it is very likely too much friction some place or again an adjustment issue.....which I would start from scratch on

I had this issue on a 9 speed ultegra set up and loosened everything and then followed the park instructions to adjust the rear derailler. B screw setting can also make a difference.

RocThrower

This test will help determine whether the cables are causing any drag when shifting to smaller cogs (upshifting). If the chain drops down to the smallest cog without any clunkiness or hanging with the cable disconnected, then it's a pretty good indicator that cable drag (which would have been eliminated by disconnecting it) is causing the shifting issues. As he mentioned, you'll want to make sure the limit screw is adjusted correctly so the chain doesn't jump of the small cog and get wedged between it and your frame.

I'd also second redlude97's suggestion of checking the hanger alignment. Sometimes an misaligned derailleur hanger can cause the bike to shift gears perfectly in one direction, but shift poorly in the other. I had symptoms like this on an old bike and after having the derailleur aligned it shifted correctly in both directions.

reptilezs

are you using a shimano chain? they are asymmetrical. what is the cassette range? what derailer?

Troul 

detached the main cable goin to the der. take a small section of spare cable & set the der with the small section of cable to a fixed tension. You will need to loop the what was the adjustment end over & around to the pinching plate in order to "fix" the tension.

If the ghost shifting persists, then you have an issue unrelated to the cabling. If this is not what you're experiencing, then it's likely a component within the hub or possibly the shifter mech or even still the cable/housing.