Page 1 of 1

SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Fri Jun 22, 2018 8:43 pm
by mike001100
Hi,

this is a continuation from my previous thread (here: https://weightweenies.starbike.com/foru ... 3574d8a10e), where the problem has now crystallized into one essential form: chain drops when shifting from large to small.

I gave up in my previous thread and took the bike to an LBS. I picked up the bike today and the technician (apparently a very experienced one at that) said he adjusted everything (he had to, as he clearly shortened some of the cable housings) and that the bike shifts fine. "Great" I think. Only to bring the bike home, do the first 100m down the road and shift small-big (OK) and then big-small to drop the chain (on the first shift!!!!!). I figure "bummer", put the chain back and ride another 100m... to drop the chain again.

After adjusting nothing but the low limit screw (to the point where on the 25 cog it rubs) I can get it to "work" slightly better than before, i.e. it will only drop the chain say one out of 4 times - but to me, this is still unacceptable.

A chain catcher is not the solution for me. A chain catcher is an aid when riding cobbles etc, but not when riding on flat perfect tarmac imo...

Setup is - with everything being new:
- SRAM RED levers, SRAM RED FD, SRAM RED RD, SRAM RED casette
- KMC X11SL DLC chain
- Cannondale Hollowgram cranks, the 2016 version

So, I'm starting to thing that componentry is at play here:
- will SRAM RED (mechanical) work with Cannondale Hollowgram cranks?
- will SRAM RED work with a KMC chain?

I am thinking about switching the chain to an OEM RED one, and if that doesn't work... then I'll ditch the whole thing and switch to Dura Ace.

Any input (except "watch the SRAM video") welcome.

Thank you.

SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Fri Jun 22, 2018 8:43 pm
by Weenie

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Sat Jun 23, 2018 6:40 am
by 2lo8
There's a reason SRAM ships their FDs with chain catchers even if you don't like them. They're not a solution for cobbles, they're a solution for SRAM FDs.

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Sat Jun 23, 2018 7:58 am
by Beaver
I am/was running SRAM RED on several bikes (without chain spotter ;) ) and always needed some time to adjust the front derailleur.

It's no general problem for sure and works as well as Shimano - without the trim step and also a possible crossed chain (which one should avoid though).

Even if your mechanic is experienced, it's all a little different with the YAW derailleur. Just follow the setup as described here:

https://www.youtube.com/watch?v=ZTOyxOPHoGc

https://www.youtube.com/watch?v=jKzA-QVyBWo

And your derailleur is just too far inwards, so you need to increase cable tension or turn the inwards screw half a turn clockwise (or more if needed).

You could also upload pictures from the side and top on the big and small ring.

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Sun Jun 24, 2018 1:05 am
by Hexsense
Indeed the Sram FD potentially have higher chance of dropping chain compare to Shimano set-up.
Shimano have 4 settings, when you drop from big ring it'll be in Low setting, which is not the inner most position. That position leave very little chance of dropping chain. You have to press down shift again to go into low trim which is the inner most position to clear chainline using small ring+big cog in the back.

While on Sram, there are only 2 settings and when you drop from big ring the cage will go all the way inward in a quick single action. That position leave enough gap for cross chaining without chain rub, which also increase space for chain to drop. Chain-catcher is recommended to catch the case when the FD kick the chain too hard and it fall too far inward. So it is included with Sram FD.
However, it is not impossible to set up reliably without one. Good luck with that.

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Sun Jun 24, 2018 8:57 pm
by mike001100
Ok so I messed about with it some more today...

First, I lowered the cage approximately 1 mm, which lessened chaindrops alot (same as before = say once every 5 shifts or so)...

Further, I nudged the tail out a tad...

Then I noticed one thing when shifting... I can shift the cage "slower" if I hold on to the lever... so, I tried this, and it seems like I haven't dropped a chain since... is this a good way to go about it? When downshifting, I hold the paddle after the click and drive the cage down slowly...

Ho ho, lo lo... going to ride it now with midcompact and then see if I want full compact for the climbs and mess around with the whole thing again...

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Sun Jun 24, 2018 9:14 pm
by bm0p700f
While the issue maybe the inner cage is sitting too far inboard and a Catcher may help, have you tried different rings. There was a campag equipped bike that came in with an odd chain skip. I tried everything, jockey wheels, chain but it turned out to be a worn inner ring even though the ring looked fine. So don't rule out the inner ring. Wear can lead to dropped chains.

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Mon Jun 25, 2018 2:10 am
by alcatraz
Are you using OPI spiderrings? What is the condition of your inner ring?

Is the bike frame very small perhaps? Chain angles are a bit more extreme then.

Are you running a wide bottom bracket shell like 73 or more millimeters? It's relevant to the chainline. Combined with a small frame and hollowtech crank could be the issue.

Is your FD mounted so low that it basically touches the big teeth of the large chaimring?

Have you checked if your chainrings run perfectly straight? What of bent teeth?

If you put your thumb on the FD can you make it go further in than after the lever releases it? Sometimes the friction in the cables and fd joints cause it to drop shorter than it should. This means you'll be fighting between limit screw/chainrub and chain drops because it's unpredictable.

Are you experiencing the same frequency of chain drops when you are to the right of the cassette as when you are to the left?

/a

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Mon Jun 25, 2018 3:49 am
by Hexsense
Sram likes quick and snappy shift movement. But as you can see, sometime the shifting in the front can be too violent and can benefit from slowing it down.
(Or just use chain catcher, and don't worry about it, it's only ~10grams and included in the weight spec of Sram's FD.)

Shimano, in the other hand, incorporate overly complex mechanism into their shifters to slow down shifting action which also make their shifters heavy.
Sram moves all the cable at once.
Shimano, not only they have 4 settings which you have to push small lever twice to move FD into the inner most position. But in their movement on each lever click is also split into two halves. It moves cable half way when it click. And another half way as the lever return to the position.
This video at the time i linked demonstrate that, Shimano's half way cable movement at a time.
https://youtu.be/YmhJpj4M64c?t=3m7s

No wonder Shimano's shifting is smoother and Sram's shifting is faster.

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Tue Jun 26, 2018 10:21 am
by mike001100
Thank you all for the input.

I rode the bike yesterday and didn't drop the chain once - however, I do get massive rub in the largest cog at the back. Even so, out of the say 20 big/small shifts, I could see that at least 3 or 4 times the chain was about to land "inwards" on the teeth, and then slip off..

The bike is size 52, 405 mm chainstays, and yes, the chainline when in the biggest cog seems very "bent". The bike seems to throw the chain most when in the second largest cog - the FD does not rub on the chain and leaves a gap for the chain to fall. BB is cannondale's BB30A.

Inner ring - OPI chainrings - have about 500 km on them and shifted fine on the previous Ultegra setup.

I believe I could get the FD a tad lower...

There is now no movement when trying to push the FD further in by hand.

I experience many more chaindrops when on the left side of the casette (big cogs) than on the right...

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Tue Jun 26, 2018 11:55 am
by alcatraz
I'd play with the angle of the FD a bit and make sure it's as low as possible.

There are two lines on the fd when looking from above. The manual specifies that they should be in line with the big chainring when the cage crosses over. Verify that you got that right.

When crosschaining small/small or big/big, if one of these two gears have a steeper chain angle than the other I'd try to angle the fd cage a tiny bit to compensate. I'd only do this if I run out of options.

Lets say your chainrings/spider are designed for 68mm axle lengths but you are running them at 73mm. It means that the big/big combo will have a more extreme chain angle. The fd cage would benefit from being angled with the tail inward a tiny bit so that the inner plate is more parallell to the chain and gives better support.

Just a theory... I'm not a super experienced mechanic but I like to think about problems and solutions.

Re: SRAM RED + Cannondale Hollowgram dropping chain?

Posted: Tue Jun 26, 2018 11:55 am
by Weenie