7900 shimano crank

Just wondering if anybody tried the new 7900 shimano crank with the 7800
coponents, and would it work?

It would work fine as long as you use the matching 7900 BB. No real difference in chainring spacing, etc, both are '10s'.

what is different with the 7900 BB?

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Precision Sports

6mm width bearing ala Campagnolo rather than the previous 7mm one on all the other external bearing shimano BBs.

About 2004 shimano swapped the 7800 BB to 6mm as well, but didn't change the model numbering. Assuming the spacing of all the BBs are the same (hence no model numbering change) then you can use a 7800 BB with 7900 cranks. Infact I'd say yu can use 6600 and 5600 with 7mm bearings if you don't want to spend as much (thats an assumption!!)

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Precision Sports

Don't think so. We just swapped the bearings in a 7800 cupset and the new, Phil BBs are indeed 7mm. In addition, just checked QBP online and they list replacement hollowtech bearings as 7mm as well. 7900 are 6mm for sure but 7800/6600/105 are all 7mm, pretty sure. Called shimano but they didn't know(DOH!).

BTW-7800 came out in 2004.

http://www.superflycycles.com/servle...Bearing/Detail

7mm width.

Hmm I'm going off the boca bearings website. They list DA from 2004 onwards as 6805 6mm. 2003 is 7mm.

Shimano wouldn't tell you even if they knew, they want people to buy new units from them, not use after market bearings.

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Precision Sports

So what about those with an SRM Dura-Ace 10speed (7800 series). If you want to mate it to the rest of a system that is 7900, what BB do you use?

Mark Cavendish's Scott Addict is this setup, but they use the pressfit BB arrangement and not External BB's.

Use the standard 7800 bearings. Scott's have a propriatary BB shell methinks tho.

6805 bearing, according to bearing makers, is 7mm. I'm not surprised you could get a 6mm ceramic bearing into the shimano cups with some sort of wavy washer or something. Ala Trek BBs

From Sheldon Brown-
"For the 2004 Model year, Dura-Ace had major revisions, designated by the new 7800 series. In addition to moving to 10 speeds in back, the rear Freehub was totally redesigned, and so was the crank and bottom bracket.
The new crankset uses the "Hollowtech II" design pioneered with last year's XTR group (also shared with 2004 XT and Saint)."

No Hollowtech II crank in 2003. It was still Octalink.

What DA BB would take a 6805 7mm bearing in 2003 then? Boca must have it all stuffed up.


I'll have to go change all my adverts from saying 7800 are 6mm, to saying 7900 is 6mm and all other shimano are 7mm. I already have an ad for shimano being the 7mm size.
Luckily haven't sold any 6mm size to shimano customers! However as you siad easy enough to fit a 6mm bearing each side with an extra washer.

So Peter - has the external spacing of the 7900 BB/crank actually changed, or have the outer faces stayed the same and the bearings got narrower? I'm guessing they have done this for weight, and to try and stop people replacing the bearings as they are harder to come by. However if you go to a bike specific bearing supplier they should have the 6mm size as a lot of people replace the standard campy bearings.

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Precision Sports

I was trying to remember when Shimano first reached perfection and it was of course, Peter, 2004. Amazing how that 7800 chainset is still exactly the same as the 2008 edition- unchanged and perfect....well perfect, if only they had made a 50-36 or 50-34 in the 7800 and an 11-25 cassette. I run a 52-38 DA crankset. Wonderful!!

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Scott Addict 2008 R4
HED JET 50mm 2007
Record/Chorus/Centaur/Ultegra mix
50/34 12-25
7,54kg

Cannondale Six13 Pro
Mavic Cosmic SL 2009
Dura Ace 7900/7800
12-25 52/39
7.70kgs

Don't know what changed, I've only seen one 7900 bike and I didn't have a chance to take it apart. I'm thinking the crank spindle/bearing combination changed, with the chainrings and stance staying the same. Not surprised shimano changed the bearings when they changed the crank. They want you to buy the whole magilla.

'A lot of people change the Campagnolo bearings', why? I would think they would change the sram/shimano bearings since they are so sluggish. Campag, by comparison, seem very smooth.

I just heard that many people seized the campy bearings, the ones that came out with seals on one side only.
Plus they are made to be replaced, so when they do wear out people are more inclined to replace just the bearings, not the entire unit.
Now you've got a bit more marketing behind campy changing to ceramic as well. I haven't sold that many hybrids for BBs yet (although sales have picked up a lot in the last week!) Most of the sets I've sold so far have been for ultra torque, but it is still a small sample set. Only sold 1 set of 7mm bearings (for raceface).

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Precision Sports