SRAM Red eTap FD chain drop

Discuss light weight issues concerning road bikes & parts.
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wheelsONfire
Posts: 2949
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

The shim seems to be exaxtly same as the smallest shim, in the Rotor shim kit.
It could be ordered separare or is standard with QXL chainrings.
I have this shim, i also tried it for fun, but for me it doesn't serve well.
I wonder how it can be the FD makes up for such an issue for some, some not at all.
I noted Sram manual was frankly extreme when it came to correct lenghts and angles.
I guess Srams FD is the most picky at the market.
I could even make my FD shift without drops with a change of BB spacers.
That is, changing NDS and DS spacers.
It still worked without chaindrops.
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

by Weenie


coneill0422
Posts: 96
Joined: Wed Dec 10, 2014 7:16 pm

by coneill0422

I will say that you should probably check to make sure that your crankset shims have the proper width from the middle of your bottom bracket. I was having a ton of issues with FD shifting (it hitting the cranks when it was over shifting and dropping chains). Finally called up sram and they told me the proper width from center of BB to outside chainring teeth, re-did the shims and no more issues.


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stevec1975
Posts: 301
Joined: Tue Nov 24, 2009 12:37 pm
Location: London

by stevec1975

Is your crank arm spider running straight? A change by one Mm here will throw the shifting off. I have etap on fibre lyte rings with no wedge and the shifting is perfect every time

JeanMarc
Posts: 16
Joined: Sat Jul 28, 2018 12:34 pm
Location: Montbrison, France

by JeanMarc

Guys, since the latest fine tuning I did on Sep 3, no more chain drop over more than 1000 miles (1600kms). :shock:
To be honest, I am not sure why the chain drop issue is gone :noidea: :
First I dismantled the BB90 crankset and checked that the wave washer was in place on the drive side and used a torque wrench for the re-assembly.
Second, as far as the FD I started with a quite high positionning vs. the big chain ring: highest teeth are barely reaching the cage mark lower limit and the resulting distance between teeth and FD cage is somehow 3-4mm: Note that here I am no more following the SRAM recommendation to the letter.
Thanks to this high starting point, it was possible to set the FD cage "more inside" without having the cage upper internal profil "machined" by the chain when using biggest cogs (also this gives room between FD cage tail and drive pedal crank).
I think this "more inside" tuning helped with preventing the chain drop...

sungod
Posts: 1701
Joined: Fri Dec 24, 2010 9:37 pm

by sungod

with non-yaw rings i used a higher position, otherwise there is a 'lump' inside the cage that was causing noise as the chain touched it, with yaw rings i could move it lower buti think there is still some contact, thinking of moving it higher again

good that you have a solution!

JeanMarc
Posts: 16
Joined: Sat Jul 28, 2018 12:34 pm
Location: Montbrison, France

by JeanMarc

Thank you sungod, I think the lump you are talking about is what I described as the "cage upper internal profil" in my previous email.

TobinHatesYou
Posts: 4173
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

It's a guide that keeps the chain from lifting too much when you shift off the big ring.

JeanMarc
Posts: 16
Joined: Sat Jul 28, 2018 12:34 pm
Location: Montbrison, France

by JeanMarc

Hi TobinHatesYou, thank you for your clarification.

gloscherrybomb
Posts: 2
Joined: Mon Jan 21, 2019 5:55 pm

by gloscherrybomb

Hi all,

Sorry to drag this thread back up. I am having umpteen issues with my SRAM Red eTap FD and my 105 crankset. Mainly that I can set it up to change nicely on a stand, but as soon as any pressure is applied to the pedals when you change, it either wont go on to the big ring at all or throws it over. I want to give the wedge a go - but I have no idea how you install it and cannot seem to find any guide online, only numerous references.

How do you install the wedge?

Thanks

Jugi
Posts: 539
Joined: Sun Jun 24, 2018 8:10 am

by Jugi

Wedge installation depends on your frame's seat tube shape, as in how much space there is behind the FD to adjust the wedge's position. In most cases you'll need to install the wedge before fine tuning the FD's position.

There is a small attachment screw in the back side (opposite to seat tube) of the FD. Just screw it on, test & adjust.

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wheelsONfire
Posts: 2949
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

There are 3 of them (wedges), you find the one holding the FD in right position against seat mast tube (1 of these 3, should fit well).
Wedge is just on the rear of the FD, held in place with a small head screw.
I find wedge best mounted after tuning (or when checking when you finally got it right)
But i guess what is working for you is the way to go)
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

TobinHatesYou
Posts: 4173
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Basically installing the wedge will only improve your chances of making the shift during the overshift. If for some reason big ring fails to pick up the chain during the overshift, the chain will never make it onto the big ring even with the cage in the outer position. The problem is the geometry of the Yaw FD cage combined with that eTap overshift. The cage is very wide, so in order for the inner plate to push the chain onto the big ring's ramps/pins, it needs to move a greater lateral distance. At least with mechanical Yaw derailleurs, you can "feather" your front upshift with your hand. Unfortunately electronic shifting is less subtle than your hand...it overshifts, and during that split second, the outer plate is far enough away for the chain to throw itself over the big ring.

Wear on the drivetrain components seems to be the best long-term fix for the thrown chain issue. I get it more often with brand new chains, and perhaps with certain very light dry lubes.

gloscherrybomb
Posts: 2
Joined: Mon Jan 21, 2019 5:55 pm

by gloscherrybomb

Thanks all, with give it a go tonight. I've got a new 105 9700 crankset which hopefully will help matters too.

DaMaDo
Posts: 14
Joined: Thu Jan 31, 2019 1:42 am

by DaMaDo

I'm having the same issue of jumping onto the crank arm under load.

On the stand it works great, but not in actual use.

I set up everything as per the videos and the pdf instructions.

Either it won't shift into the large ring, or it shifts and jumps over onto the crank arm. There's no middle ground.

This is on a Focus Paralane Factory that I'm upgrading.

I'm using the middle size wedge.

Sigh.

by Weenie


NickJHP
Posts: 268
Joined: Wed Feb 14, 2018 2:22 am
Location: Canberra, Australia

by NickJHP

My eTap FD throws the chain off every so often - I think twice in the last week, which is about par for the course. I 've actually set the clearance between outer cage and chain in top gear to be slightly less than SRAM's minimum recommendation, as when initially setup to their instructions it was throwing off more frequently, but it still barfs occasionally. I suspect it's the deliberate overshift built into the mechanism, as none of the dozen or so bikes that I have with mechanical shifting have this problem, and none of them have deliberate overshift built into them in this manner.

With the reduced clearance, it sometimes hesitates before the chain catches on the big ring and shifts, but I find that preferable to having the chain regularly come off when shifting.

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