7900 vs. 9000 chain set + advice req.

Discuss light weight issues concerning road bikes & parts.
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diegogarcia
Posts: 470
Joined: Sat Apr 24, 2010 7:31 pm

by diegogarcia

Hi,

Building a di2 set up and looking at chain sets. Common sense says 9000 with the 52/36 option. However, here in the UK I can get a 7900 compact or double chain set £110.00 cheaper which is a big saving. The questions I ask are is the 9000 chain set a marked improvement and how...? Also, will it accommodate the 11 speed chain..? My search says yes, but worth asking the experts here. I do prefer the looks of the 7900 chainset over the 9000 but that's another story. Thanks in advance.

D.

maico
Posts: 8
Joined: Wed Oct 09, 2013 5:17 pm

by maico

The 9000 is a fraction lighter according to my scales. I took some photos and it's clear nothing is the same. Teeth profile, alloy colour, paint type, distance between rings and BB bearings are all different.
The crank arms are huge but weigh less therefore the 9000 alloy must be thinner. You can also see the joint on the back of the arm which is a bit ugly !

I can't talk about function, but the 7900 feels a bit better quality in the hand and the 9000 a bit more bling. The gloss black paint finish of the 9000 probably does match more frame colours than the satin grey.

Merlin recently had the 9000 compact up at £300 GBP and currently the 7900 at £259.

Six photos :

Image

7900 teeth alloy is more tungsten in colour.
Image

9000 teeth
Image

Outer teeth more pointed profile on 7900 and inner ring teeth flatter
Image

Image

Image
Last edited by maico on Thu Oct 10, 2013 3:45 pm, edited 1 time in total.

by Weenie


headwind816
Posts: 335
Joined: Mon Mar 12, 2012 4:43 pm

by headwind816

What did the two cranks weigh in at please?

maico
Posts: 8
Joined: Wed Oct 09, 2013 5:17 pm

by maico

9000 compact 180 452g, arm 179g

7950 compact 172.5 477g, arm 183g, BB 89g

Ultegra 6800 compact 172.5 489g, arm 197g

The 9000 BB was a fraction lighter too. Requires a special size plastic ring to tighten which is included in it's box.
Last edited by maico on Thu Oct 10, 2013 4:44 pm, edited 1 time in total.

Briscoelab
Posts: 1728
Joined: Thu Jan 26, 2006 6:01 pm

by Briscoelab

I think the real good news there is the outstanding weight on the Ultegra chainset. With the new style BB, it essentially weighs the same as a 7900 crank.

maico
Posts: 8
Joined: Wed Oct 09, 2013 5:17 pm

by maico

Briscoelab wrote:I think the real good news there is the outstanding weight on the Ultegra chainset. With the new style BB, it essentially weighs the same as a 7900 crank.


I've got some detailed photos of that too. It's not all good news though, there are 3 messy bonded joints which I'll post about in due course.
No such thing of course on Dura Ace which is constructed in a different way.

6800 compact 172.5 totals 686g and 6750 712g

maico
Posts: 8
Joined: Wed Oct 09, 2013 5:17 pm

by maico

On the 9000 arm you can see a seam running around the edge where the two parts have been joined together.

Image

Image

headwind816
Posts: 335
Joined: Mon Mar 12, 2012 4:43 pm

by headwind816

@maico - thank you for the detailed pictures and information. I am anxious to see the pictures of the 6800. I am currently trying to figure out which of these cranks to purchase.

Do you think the "messy bonded joints" found on the 6800 is an issue beyond cosmetics?

maico
Posts: 8
Joined: Wed Oct 09, 2013 5:17 pm

by maico

headwind816 wrote:@maico - thank you for the detailed pictures and information. I am anxious to see the pictures of the 6800. I am currently trying to figure out which of these cranks to purchase.

Do you think the "messy bonded joints" found on the 6800 is an issue beyond cosmetics?


I'm sure it works great. Like on the 6700 the hollow chainring is two parts bonded together

Image

Shimano appear to have taken the process further as the spider is also bonded.

Image

Maybe a materials expert will chime in and say it's just edge sealing mastic..............

You can see a 6700 crankset here, supersize the frame and watch in 1080p

http://www.youtube.com/watch?v=JBx-ifA1awg#t=80

by Weenie


diegogarcia
Posts: 470
Joined: Sat Apr 24, 2010 7:31 pm

by diegogarcia

Thanks for the exhaustive post.

I am no closer to a decision, as what I like about one, I loathe about the other. 7900 just looks so much better to my eyes.

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