Question eTap Front Derailleur Setup - Guidance Requested

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fherman
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by fherman

Quick eTap question for anyone out there in the know.

Just setup eTap last night and have everything dialed in perfectly except the FD.

I followed the instructions and have the lines aligned to the chainring, the height appropriately set, the limit screws dialed in. Shifting to the small chainring is butter smooth. However, regardless of position on the cassette, I can't seem to get enough throw to get the chain to catch and fully engage with the large chainring. It tries but can't seem to make it to the top of the rotation (12 o'clock) and this remains caught between the two until I shift back down on the FD.

Normally, I'd recheck the limit screws (done), and then add a little tension to the cable.

However, with no cable, what should I do with FD to tune in the shifting to the big ring? I started over with installation of the FD and ran into the same issue again. I could continue to dial in on the alignment marks and height, but I think I'm pretty well within the error.

Thanks in advance for the assist!

by Weenie


sungod
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by sungod

sounds like you need to undo the upper limit screw a bit

the way the fd works is to initially 'overshift' to force the chain up onto the big ring, then after a few hundred milliseconds it shifts back to normal position

if you listen you'll hear the motor runs for the first part, stops, then another short burst as it moves the cage back in a little

nohands
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by nohands

so these are withing spec?
Image
Image

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sugarkane
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by sugarkane

The hight needs to be tallest tooth at the bottom of the line..
And you need to dial out the top limit until she wants to throw the chain over the top and come back 1/2 a turn. It's a fine line between throwing the chain over and the perfect set up. 0.5mm of clearance isn't enough

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Dan Gerous
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by Dan Gerous

I also found the best height is having the tip of the tallest tooth lower, I'd say in the bottom half of the height guide line, and forget the 1-2mm between tooth and outer cage plate when on the big ring position as SRAM says later in their instruction, that's waaaay too low, it would mean the tooth would be way above the height mark on my bike.

In my case, it upshifted fine if the tip of the tooth was higher as long as it was within the guide line (so, derailleur lower) but if the tip was closer to the top of the line, it resulted in the chain rubbing against the outer cage plate's front 'bent' section (you can see that area from the front in the picture above) when on the big ring and in the three biggest cogs in the back (52/36 and 11-28). I wonder how precisely is that height guide line made during the manufacturing process...

The high limit on mine is set pretty much with the 0.5mm gap, maybe a tad more but under 1mm and it shifts to the big ring very well, crisp and fast, from in any cog in the back even from the biggest cog (not that I will ever need to do that in real life)...

Krackor
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by Krackor

sugarkane wrote:And you need to dial out the top limit until she wants to throw the chain over the top and come back 1/2 a turn.


Note that the upper limit screw on the eTap derailleur does not work in the intuitive way that a mechanical limit screw works! To fix underthrow on a mechanical limit screw, you would turn the screw anti-clockwise which backs the screw out of the derailleur body, allowing the derailleur to swing farther outboard.

The eTap derailleur upper limit screw is reverse threaded, so turning anti-clockwise will push the screw farther inside the derailleur body. Also! Pushing the screw farther into the derailleur body actually makes the derailleur swing farther outboard, the opposite of how it works on a mechanical derailleur! The end result is that to fix underthrow on eTap, you turn the upper limit screw anti-clockwise (same direction you would turn the mechanical limit screw).

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sugarkane
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by sugarkane

Note I've build a lot of it and ride it :thumbup:

JackRussellRacing
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by JackRussellRacing

sugarkane wrote:The hight needs to be tallest tooth at the bottom of the line..
And you need to dial out the top limit until she wants to throw the chain over the top and come back 1/2 a turn. It's a fine line between throwing the chain over and the perfect set up. 0.5mm of clearance isn't enough


+1 I built up two of these systems in the past 30 days, and agree 100%. It seems hard to believe some of the tolerances here, but I too found the SRAM videos didn't really account for the thickness of their drawn lines. On my second eTap build, I used a digital caliper to set up both derailleurs. (then I promptly f*ked two perfectly good rolls of bar tape in my rush to finish the job.... :oops:

wingguy
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by wingguy

Krackor wrote:The end result is that to fix underthrow on eTap, you turn the upper limit screw anti-clockwise (same direction you would turn the mechanical limit screw).

Did you really need to write all that just to note that you turn the etap limit screw the same as any other limit screw? :lol:

fherman
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by fherman

All,

Thanks so much! Spent last night training in ERG so I didn't get a chance to try these adjustments, but I will tonight and report back.

I truly appreciate all of the guidance!

fherman
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by fherman

sugarkane wrote:The hight needs to be tallest tooth at the bottom of the line..
And you need to dial out the top limit until she wants to throw the chain over the top and come back 1/2 a turn. It's a fine line between throwing the chain over and the perfect set up. 0.5mm of clearance isn't enough


Thanks all, especially @sugarkane !

This advice was the key. I took it a lot further out, until it threw, then backed it in 1/4 to 1/2 turn until it didn't seem to throw any longer. I'm still dialing it in as I was a bit paranoid about throwing it over. But I'm at least right in that sweet spot zone now and know what I need to do for micro-adjustments.

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sugarkane
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by sugarkane

fherman wrote:
sugarkane wrote:The hight needs to be tallest tooth at the bottom of the line..
And you need to dial out the top limit until she wants to throw the chain over the top and come back 1/2 a turn. It's a fine line between throwing the chain over and the perfect set up. 0.5mm of clearance isn't enough


Thanks all, especially @sugarkane !

This advice was the key. I took it a lot further out, until it threw, then backed it in 1/4 to 1/2 turn until it didn't seem to throw any longer. I'm still dialing it in as I was a bit paranoid about throwing it over. But I'm at least right in that sweet spot zone now and know what I need to do for micro-adjustments.



I'm not just a pretty face :wink:

fherman
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by fherman

So I checked tailing the rear out a bit. This made me realize that one issue was that the front of the derailleur as a bit high - the marking for chain ring height clearance had about a mm gap between the bottom of the mark and the top of the tallest tooth. If I set this back down, it was impossible to tighten and keep the rear high enough to not hit the rear facing teeth when shifting down into the little ring. So I'm wondering if my braze-on mount needs a slight bend (bottom back a bit) to allow for a more level placement when tightened down. I have it now in a position of best compromise and about a hair width between cage and teeth when shifted into little ring.

I have the chain off soaking to apply some Squirt, so I'll try some shifting and see if this has helped.

fherman
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by fherman

UPDATE:

I continued to dial in. I also decided to try swapping out the Extralite chainrings for something more 'robust' and went with the heavy Red 22 rings. The combo of continued trial and error along with the chainring swap seems to have me hitting the small to big shift just fine.

However, everything seemed dialed perfect for a shift, but I'm not rubbing the inside of the cage when in the big ring and the largest two (maybe three) cogs on the cassette. This is 52 front going to 11-28 cassette. It's the front-most portion of the cage that's just barely rubbing. Granted, this is a cross chain situation, but I'm just curious if this signifies something is still a bit off.

by Weenie


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sugarkane
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by sugarkane

Ohhh I can't imagine Extralite rings been much good with any electric groupset.. They all use brute force do get the job done..

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