7900 chainring on normal crank: Improvement? I think so.

Discuss light weight issues concerning road bikes & parts.
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endershan
Posts: 83
Joined: Thu Jul 14, 2016 3:56 am

by endershan

As my Praxxis Works chainring became untrue (which is disturbingly common, 2 other riders reported the same problem, causing chain drops on big ring), I recently tried this unusual combination of chainring and crank: Dura-Ace 7900 rings on S-works Quarq powermeter.

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I actually saved 15g by replacing this chainring:
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This new rings are noticeably stiffer. In fact, they are so stiff that the crank creaks under load. I switched to the old rings, no creaks. In the end I had to tighten the spider lock ring to eliminate the creaks, which means that the Praxxis rings are not stiff enough to make the spider deform and creak.

The shifting is also very good. Improved lateral stiffness makes shifting quicker. Not that Praxxis rings shift poorly, I do think 7900 rings are better.

by Weenie


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toiyuet
Posts: 173
Joined: Wed Dec 14, 2011 2:47 pm
Location: Hong Kong

by toiyuet

7900 chainring is for the first Di2 system, I have one SRM 7950 and two SRM 9000, I feel it's much stiffer than 9000 chainring, IMO the 4 arm design just a gimmick.

endershan
Posts: 83
Joined: Thu Jul 14, 2016 3:56 am

by endershan

toiyuet wrote:
Mon May 07, 2018 10:29 am
7900 chainring is for the first Di2 system, I have one SRM 7950 and two SRM 9000, I feel it's much stiffer than 9000 chainring, IMO the 4 arm design just a gimmick.
I agree, I would love to see FWB to test 7900’s drive side stiffness against 9000 and 9100.

RussellS
Posts: 783
Joined: Wed Feb 03, 2010 1:31 am

by RussellS

7900 rings? My G-d!!! That means you are using 10 speed! Do you have to wear a bag over your head and hide in shame when riding with all the new cool riders with their 11 speed bikes? I also use several 9 speed bikes so I am retro cool. My 7950 crank shifts perfectly all the time.

SilentDrone
Posts: 126
Joined: Fri Sep 22, 2017 5:55 pm

by SilentDrone

RussellS wrote:
Tue May 08, 2018 4:02 am
7900 rings? My G-d!!! That means you are using 10 speed! Do you have to wear a bag over your head and hide in shame when riding with all the new cool riders with their 11 speed bikes? I also use several 9 speed bikes so I am retro cool. My 7950 crank shifts perfectly all the time.
lol.

by Weenie


endershan
Posts: 83
Joined: Thu Jul 14, 2016 3:56 am

by endershan

RussellS wrote:
Tue May 08, 2018 4:02 am
7900 rings? My G-d!!! That means you are using 10 speed! Do you have to wear a bag over your head and hide in shame when riding with all the new cool riders with their 11 speed bikes? I also use several 9 speed bikes so I am retro cool. My 7950 crank shifts perfectly all the time.
Hhhhha, I think the rings don't matter much as it comes to speed numbers. I actually use 11 speed Dura-Ace 9170 components and they shift very well.

I think I read somewhere that the ring distance is slightly different from 7900 to 9000 to 9100, but couldn't feel the difference.

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