Sram etap chain length

Discuss light weight issues concerning road bikes & parts.
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Det55
Posts: 9
Joined: Mon Apr 09, 2018 7:28 am

by Det55

Solving my chaindrop issues by micro adjusting the fd and shifting carefully another thing came up during the first 1000 km.
My setup 52/36 mid compact and 11-32 wifli cassette.
Shifting the rear cog with the 36 crank went smooth but rattling noise came up using the 28 and 32 cog. Using the 52 crank rattling noise came up from the 19th cog upwards. Ok, it is not recommended to cross the chain to much but running 52- 22 should be possible.
After checking everything I used a 2 links longer chain than before ( Sram method). Now I have +4 links (two more than recommended) The noise has been reduced compared to the SRAM method and the chain tension is still good, even if slightly loose at small-small which I do not use.
Adding three instead of two or three chain links would be the optimum. Unfortunately the SRAM chain always needs two inner links to be connected.
Thus a Dura Ace Chain would be a possible solution, connected by a bolt.

What is your experience regarding noise and chain length using etap Wifli?




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alcatraz
Posts: 1298
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Your derailleur hanger needs to be extra straight when using larger derailleurs as a small misalignment gets amplified by the longer derailleur.

Clamp your skewer tight like it should be and eyeball the upper pulley wheel if it's parallell with the cassette in both planes. (Put the gear somewhere in the middle of the cassette). Don't focus on the cage, but only the pulley and try to look really carefully.

If you think chain tension has to do with the problem you can simulate a low/high chain tension by simply screwing the B-screw in/out fully. (Note that if you screw it out fully you might have a slack chain in smal+small gear combo. Avoid that gear for the test.)

Are you sure your rattle is coming from the rear derailleur?

Are you running a very small frame? What crank are you running? (chainline issue? too short chainstay issue?)

/a

by Weenie


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MayhemSWE
Posts: 225
Joined: Thu Mar 12, 2015 12:44 pm
Location: Stockholm, Sweden

by MayhemSWE

Det55 wrote:
Tue May 08, 2018 1:03 pm
Adding three instead of two or three chain links would be the optimum. Unfortunately the SRAM chain always needs two inner links to be connected.
Thus a Dura Ace Chain would be a possible solution, connected by a bolt.
Umm, no a Shimano chain would not make any difference. You still cannot directly join an inner to another inner or outer to outer. AFAIK half-links are only available for single-speed chains.

Det55
Posts: 9
Joined: Mon Apr 09, 2018 7:28 am

by Det55

alcatraz wrote:Your derailleur hanger needs to be extra straight when using larger derailleurs as a small misalignment gets amplified by the longer derailleur.

Clamp your skewer tight like it should be and eyeball the upper pulley wheel if it's parallell with the cassette in both planes. (Put the gear somewhere in the middle of the cassette). Don't focus on the cage, but only the pulley and try to look really carefully.

If you think chain tension has to do with the problem you can simulate a low/high chain tension by simply screwing the B-screw in/out fully. (Note that if you screw it out fully you might have a slack chain in smal+small gear combo. Avoid that gear for the test.)

Are you sure your rattle is coming from the rear derailleur?

Are you running a very small frame? What crank are you running? (chainline issue? too short chainstay issue?)

/a
I ride the comlete SRAM setup, including bearing, my frame is a Colnago 54s, somewhere in between 57/58 traditional. The chainstay is 411mm, not to short. The frame is new everything aligned. As said with the longer chain the the drivetrain runs smoother in the bigger cogs and I can ride 52-22 (4/11) without any noise. Before with the shorter chain it starts rattling. 25,28 and 32 will not work with 52 due to the crossed chain, even with the longer one.
It seems to me that the Sram chain length manual is more focussed on the short cage RD?
Calculating online the chain has to be 112 links, my has now 113 including the lock, following Sram instructions the chain should have 111 links incl. lock.




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Det55
Posts: 9
Joined: Mon Apr 09, 2018 7:28 am

by Det55

MayhemSWE wrote:
Det55 wrote:
Tue May 08, 2018 1:03 pm
Adding three instead of two or three chain links would be the optimum. Unfortunately the SRAM chain always needs two inner links to be connected.
Thus a Dura Ace Chain would be a possible solution, connected by a bolt.
Umm, no a Shimano chain would not make any difference. You still cannot directly join an inner to another inner or outer to outer. AFAIK half-links are only available for single-speed chains.
Using a bolt (not a lock) can fix an inner and outer link together.


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alcatraz
Posts: 1298
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Is it possible your wheel isn't straight in the dropout or that your crank is sticking out too far on the drive side?

Does your front derailleur extend further out than you see on other bikes to go big ring? That could be a clue. If it is then any spacer you have on your crank axle could be moved to the left side and see if it helps.

Either this or derailleur hanger alignment issue is my guess. Although I don't have any experience with etap. Maybe there is a software setting to help with this.

Getting your chain the right length +/- one link is not a big deal for shifting I think. Just get it into the ballpark. If the chain is too tight it will influence shifting but with tight I mean big+big with derailleur cage pointing 4-5 o clock. As long as it's not completely slack in small+small it's correct and maintains good chain efficiency.

/a

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MayhemSWE
Posts: 225
Joined: Thu Mar 12, 2015 12:44 pm
Location: Stockholm, Sweden

by MayhemSWE

Det55 wrote:
Tue May 08, 2018 3:38 pm
Using a bolt (not a lock) can fix an inner and outer link together.
Well, duh. That still does not change the fact that the total sum of inner and outer links must be even. Just like a chain from Sram or any other brand joined with a quick link.

Det55
Posts: 9
Joined: Mon Apr 09, 2018 7:28 am

by Det55

alcatraz wrote:Your derailleur hanger needs to be extra straight when using larger derailleurs as a small misalignment gets amplified by the longer derailleur.

Clamp your skewer tight like it should be and eyeball the upper pulley wheel if it's parallell with the cassette in both planes. (Put the gear somewhere in the middle of the cassette). Don't focus on the cage, but only the pulley and try to look really carefully.

If you think chain tension has to do with the problem you can simulate a low/high chain tension by simply screwing the B-screw in/out fully. (Note that if you screw it out fully you might have a slack chain in smal+small gear combo. Avoid that gear for the test.)

Are you sure your rattle is coming from the rear derailleur?

Are you running a very small frame? What crank are you running? (chainline issue? too short chainstay issue?)

/a
Thanks for your advice. Next week I‘ll be at a race where SRAM and Colnago offer some support. I‘ll show my bike to the guys. Maybe they have an idea. Maybe the frame has a specific chainline. On the driveside is only one wave washer as written in the SRAM manual for GXP.

TobinHatesYou
Posts: 1881
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

4 additional half-links with 52/36x11-32 creates some very loose small-ring combinations and will result in chainstay slap over bumpy terrain. Not recommended unless you’re planning on squeezing an 11-34t or 11-36t in back with the same chain later.
Last edited by TobinHatesYou on Wed May 09, 2018 2:41 am, edited 1 time in total.

Det55
Posts: 9
Joined: Mon Apr 09, 2018 7:28 am

by Det55

TobinHatesYou wrote:4 additional half-links with 52/36x11-32 creates some very loose small-ring combinations and will result in chainstay slap over bumpy terrain. Not recommended unless you’re planning on squeezing an 11-34t or 11-36t in back.
The chain slaps on the chainstay normally from the top down. But the tension of the chain in the area over the chainstay is fix due to the front and rear crank and the chain below the chainstay is tensioned by the RD.
My experience is the smaller the front and rear combination the more you get chain slaps due to the distance between chain and chainstay. My last bike had 50/34 and many chain slaps on small cogs even the RD was very tight. Or am I wrong?




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Calnago
Posts: 6616
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

You are right, chain slaps from the top down. Small front ring and small cog combos will make the slap easier due to the smaller distance as you say. No one ever puts a chainstay protector on to cover the bottom half of their chainstays, at least on a road bike.
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springs
Posts: 39
Joined: Tue Sep 25, 2012 6:07 pm

by springs

It isn't clear whether you checked the alignment with an aligment tool or if you assumed alignment is good because it's new. New bikes can come with misaligned hangers. I would check it with a Park alignment tool. I had a new bike with a misaligned hanger which caused noise on certain cogs.

Det55
Posts: 9
Joined: Mon Apr 09, 2018 7:28 am

by Det55

I have let the bike checked in a Colnago pro shop today. They checked the hanger alignment etc. The small chainwheel is smooth on all cogs now, and the big one from the smallest to the 5th biggest cog (as before)It starts to get noisy from the 4th biggest cog. Thats what wifli is able to deliver. The noise comes from the crossed chain, chainwheel an pulleys. Nothing is scrapping on the FD.


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by Weenie


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