Problems with praxis rings, help please?

Discuss light weight issues concerning road bikes & parts.
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bmxbandit
Posts: 69
Joined: Wed Oct 03, 2012 11:47 pm
Location: UK/Industry

by bmxbandit

Have recently installed the following combos;

695sr, zed crank, 52/36, 6700 chain
Bianchi Oltre xr, DA 7900 crank, 52/36, praxis bb, 6700 chain
Neil Pryde Alize, Ultegra 6700 crank, 52/36, praxis bb, 6700 chain

On all of these I've had issues with the chain dropping either off the inside or outside, or the chain riding up onto the tops of the teeth. On both the Oltre and 695, when in small/small, it also tries to upshift without any shifter input. I'm inclined to think it relates to chainline but I can't see how that could be resolved easily and when I put the shimano rings back on (albeit in 50/34) there are no issues whatsoever. I am certain the installation is spot on in all cases. Has anyone else encountered these issues with praxis and if so what solution was offered? My local praxis agent (I'm outside the US) isn't all that clued up on the product.

sigismond0
Posts: 236
Joined: Tue Feb 05, 2013 8:29 pm

by sigismond0

The solution is simply to not cross chain. Once you get to the 7th sprocket, upshift the front ring and downhift the back three times. That's usually equivalent to one upshift, and keeps your chainline where it should be. There's really no reason to be in small/small or large/large unless you're doing some insane climbing and can't afford trying to change rings.

IIRC, Praxis rings tend to have pretty aggressive pins/ramps, so it makes sense that it's trying to cross-chain-shift when your Shimano rings don't.

by Weenie


bmxbandit
Posts: 69
Joined: Wed Oct 03, 2012 11:47 pm
Location: UK/Industry

by bmxbandit

That was just one small issue(that I'd expect on bikes with short chainstays). Not cross chaining will not solve the other issues as they happen in various circumstances, for example the top gear(52/12) on the Alize was the worst culprit for the chain riding onto the tops of the teeth(and trying to jump off the outside).

sigismond0
Posts: 236
Joined: Tue Feb 05, 2013 8:29 pm

by sigismond0

Gotcha. If it's falling inside of the small ring or outside of the large ring, are you sure the FD is set up properly? Make sure there's about 1mm between the teeth of the big ring and the bottom of the cage, then set your limit screws so that you're a half turn-ish away from little-big and big-little chain rub. There shouldn't be enough physical space to let the chain drop without significant load. I know that you said you're sure the installation is spot-on, but it's worth giving it a double check especially if you're switching rings like you mention.

bmxbandit
Posts: 69
Joined: Wed Oct 03, 2012 11:47 pm
Location: UK/Industry

by bmxbandit

I'm sure everything is set up correctly, I'm a full time wrench ;) I've checked and double checked that everything is installed and set up spot on. Besides the problems with the chain riding up on the teeth in certain combinations happens without any fd rub.

sigismond0
Posts: 236
Joined: Tue Feb 05, 2013 8:29 pm

by sigismond0

Very good, just gotta cover all the bases you know? There's another thread going on about a guy with Ui2 and Praxis rings having trouble, so it might be worthwhile reading through it.

viewtopic.php?f=3&t=115434&start=15

bmxbandit
Posts: 69
Joined: Wed Oct 03, 2012 11:47 pm
Location: UK/Industry

by bmxbandit

I appreciate the suggestions, I saw that thread right after I posted this one, seems he's having the same problem I had on the Oltre. I'm really stumped as to the cause, it's all brand new kit with no apparent flaws in the praxis rings, yet they work fine with shimano rings or the look zed rings on the 695.

upside
Posts: 601
Joined: Fri Mar 09, 2007 1:26 am
Location: USA

by upside

I recently installed a set of Praxis rings (52X36) on a 9070 group and the shifting is flawless here.

thisisatest
Shop Owner
Posts: 1980
Joined: Sat Jun 13, 2009 4:02 am
Location: NoVA/DC

by thisisatest

If you email Praxis, they may say it's a flawed ring set and send you another one. They have very good customer service, and it's the only true solution to your problem.
Inner ring is facing the correct direction, right? just checking...

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rmerka
Posts: 618
Joined: Wed Mar 06, 2013 4:23 pm
Location: Austin, TX

by rmerka

On that note your rings are lined up properly, with the little tab and all?

by Weenie


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