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PostPosted: Wed May 01, 2013 9:43 pm 
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Joined: Tue Feb 05, 2013 8:29 pm
Posts: 236
Stamping can be something that simple, but if you take a look at Sram's rings you'll see that they are actually shaped where the ramps are. Usually what happens is there is a series of progressively more refined dies that slowly stamp/forge the metal into a secific shape, cutting out the excess metal in the process.

But I think we're getting a bit off topic here!

OP: Let us know about the chain orientation and whether that changes anything. If that doesn't do it, the chain length/B-knuck are the next things to look at.


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Posted: Wed May 01, 2013 9:43 pm 


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PostPosted: Wed May 01, 2013 9:43 pm 
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Joined: Fri Sep 30, 2011 4:48 pm
Posts: 48
goodboyr wrote:
I know that you've used the big/big plus 2 method, but that basically creates a length that's the absolute minimum you can have. In other words, big/big without the "plus 2" will usually be too short. Depending on the bike and the chainstay length, that still could be too much tension. I've had this happen to me on another bike, and adding 1 pair of links did the trick. Longer is ok as long as you don't get any chain sag. If its possible, try to add a pair of links. Or, as an alternative, try winding in the B screw on the rear derailleur to marginally reduce chain tension.


Gotcha - thanks. When I test the KMC chain, I'll test with extra pair of links.


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PostPosted: Wed May 01, 2013 9:48 pm 
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Joined: Fri Sep 30, 2011 4:48 pm
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sigismond0 wrote:
OP: Let us know about the chain orientation and whether that changes anything. If that doesn't do it, the chain length/B-knuck are the next things to look at.


Yep, will do. Here's my draft order of operations (edits welcomed):

1. Check 7901 chain orientation
2. With 7901, adjust b-screw for more slack
3. Try KMC chain (with extra links)
4. Try KMC chain with same links (if slack in #3)
5. Try SRAM red chainrings (last resort)


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PostPosted: Wed May 01, 2013 9:51 pm 
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Joined: Wed Mar 06, 2013 4:23 pm
Posts: 284
Location: Austin, TX
sigismond0 wrote:
But I think we're getting a bit off topic here!


Good call! my bad. No further interruptions from me unless I can substantively add something. :wink:

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PostPosted: Wed May 01, 2013 10:06 pm 
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Joined: Wed Oct 03, 2012 11:47 pm
Posts: 68
Location: UK/Industry
@op I posted a topic on a similar subject before seeing yours, it seems you have the issue as one of my builds(abeit mechanical 6700 with praxis), was solved by going back to the shimano rings. I'd suggest trying that first, also, from that first pic your chain is installed correctly.


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PostPosted: Wed May 01, 2013 11:56 pm 
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bmxbandit wrote:
@op I posted a topic on a similar subject before seeing yours, it seems you have the issue as one of my builds(abeit mechanical 6700 with praxis), was solved by going back to the shimano rings. I'd suggest trying that first, also, from that first pic your chain is installed correctly.


Thanks for the additional feedback. I just read your thread (http://goo.gl/N18aC) and agree it may be related. I have access to a compact Ultegra crankset. Aesthetics aside, seems like I could try FC-6750 chainrings on my compact Quarq Elsa if all else fails. Similar to this FC-7900 + Quarq Cinco setup:

Image


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PostPosted: Thu May 02, 2013 6:41 am 
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415brian wrote:
Yep, will do. Here's my draft order of operations (edits welcomed):

1. Check 7901 chain orientation
2. With 7901, adjust b-screw for more slack
3. Try KMC chain (with extra links)
4. Try KMC chain with same links (if slack in #3)
5. Try SRAM red chainrings (last resort)


Update:
1. 7901 orientation was correct: no change
2. Add slack to 7901: no impact (slack was pretty good to start)
3. KMC chain with extra links: too much slack, so proceeded to #4
4. KMC chain with same links: seems better, was not able to reproduce the chain jump in a short test. I need to confirm with a longer test tomorrow morning (my girlfriend and neighbors can only tolerate so many zipp freehub clicks).

Thanks all. Goodnight.


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PostPosted: Thu May 02, 2013 6:01 pm 
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415brian wrote:
4. KMC chain with same links: seems better, was not able to reproduce the chain jump in a short test. I need to confirm with a longer test tomorrow morning.

Just did a slightly longer test outdoors: no chain jump. Hallelujah! I'd like to test some more, but I'd probably recommend anyone running Praxis rings to run a KMC X10SL chain.

Thanks all for your help. Super valuable!


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PostPosted: Thu May 02, 2013 8:42 pm 
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Posts: 303
my RD hanger was slightly bent awhile ago. shifting on the rear also affected the front because of alignment.

took it into my LBS, and sure enough, the RD hanger was out of alignment. straightened it out and no more issues. just a suggestion to check that as well. the KCNC chain may be more forgiving at the moment.

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PostPosted: Mon May 13, 2013 8:10 pm 
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Joined: Fri Sep 30, 2011 4:48 pm
Posts: 48
415brian wrote:
I have access to a compact Ultegra crankset. Aesthetics aside, seems like I could try FC-6750 chainrings on my compact Quarq Elsa if all else fail

I wanted to compare the performance of my Praxis rings with Ultegra FC-6750 (compact) rings. It turns out, the FC-6750s will not fit on Sram/Qaurq crank arms, at least not the compact version (110BCD). The 3D profile of the Shimano rings conflicts with the wide Sram crank arm (see red circles below). Modification might be possible, but I didn't try:

Image


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PostPosted: Fri May 17, 2013 3:29 am 
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Joined: Mon Apr 04, 2011 9:59 pm
Posts: 65
Location: Santa Cruz, CA
Hi 415Brian,
Just saw your thread and wanted to chime in. Give us a call tomorrow at our Santa Cruz office. Would be glad to chat and see if we can help or if you figured it out. We love our rings with Di2...so just curious about your set up. It sounds like just a tweak is needed but would like to help if we can.

NOTES for those inquiring on the thread :
- We do highly suggest using a Shimano/KMC/Campy chains...you choose for your pref. All work/test very good on our profiles.
- We make our own rings : Exclusively at our own factory with our in-house Cold Forging process. This is how we create the complex tooth profiles and the great benefit of the process is the AL grain alignment for hardness & durability. You can see more about our forging process on our site. http://praxiscycles.com/pages/forging

Hope this helps!
Adam@Praxis

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PostPosted: Fri May 17, 2013 3:48 pm 
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Posts: 48
AptosBigRing wrote:
Hi 415Brian,
Just saw your thread and wanted to chime in. Give us a call tomorrow at our Santa Cruz office. Would be glad to chat and see if we can help or if you figured it out. We love our rings with Di2...so just curious about your set up.

Thanks Adam for reaching out! After switching to the KMC chain, my shifting has been flawless with Praxis rings + Di2. So, no help needed at the moment. In hindsight, my original problem could have been an edge case: TT bike (short chainstay) + compact rings + maybe a flawed Dura-Ace chain.

I've been very happy with my Praxis rings. I just ordered another pair for my road bike. Thanks for the continued, excellent customer service.


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