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PostPosted: Tue Apr 20, 2010 8:40 am 
Retro Guru
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Joined: Wed Dec 19, 2007 10:05 am
Posts: 961
Location: Brussels
I have a compact 50/34 crankset to go onto my roadie to replace a 53/39 that's currently on there. I was just wondering if I can still use the Dura Ace 7700 front mech that I have on, or do I need to buy one of these new 'compact compatible' front mechs? I know that Shimano claim that the 7700 one is for 15T ring difference or less and that the new 7900 and Ultegra 6800 ones are the ones to use with a 16T difference compact setup - but how much of that is marketing vs engineering??

I've not had two examples together to compare them closely, but how much do the cages differ in terms of length and curvature? My mech is a braze-on type so could be lowered sufficiently, I would expect. On top of that, I could shim the top of the clamping section a bit to rotate the cage anti-clockwise and match the smaller rings a bit.

Has anyone tried this, with any success? Apologies if it's been covered before, I tried a quick search but didn't see the answer.

Cheers, Gareth.


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PostPosted: Tue Apr 20, 2010 2:00 pm 
Dirt Disciple
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Joined: Wed Oct 21, 2009 1:51 pm
Posts: 96
Location: Kingston
Should work fine. I had a 5600 mech with a 50/34. Didn't like the 50/34 but it shifted ok.


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PostPosted: Thu Apr 22, 2010 2:51 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8202
Location: New Forest, UK
A lot of this is marketing. I ran a Campag Record road mech with a Middleburn Duo 42/29 setup - and it was absolutely fine.


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PostPosted: Thu Apr 22, 2010 6:14 pm 
Retro Guru
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Location: Norfolk
Should be fine. I used an Ultegra 6500 double front mech on a Tiagra 4550 compact without problem.


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PostPosted: Thu Apr 22, 2010 11:11 pm 
Old School Hero
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Joined: Tue Oct 06, 2009 11:23 pm
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Location: South Oxon and North Pennines
Should be fine. I'm currently using a normal Shimano 600 double chainset front mech on a 30-42-52 triple and it works fine.

That's what everyone did back in the day. There was no alternative so you had no choice.


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PostPosted: Thu Apr 22, 2010 11:12 pm 
Old School Hero
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Joined: Tue Oct 06, 2009 11:23 pm
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Location: South Oxon and North Pennines
Should be fine. I'm currently using a normal Shimano 600 double chainset front mech on a 30-42-52 triple and it works fine.

That's what everyone did back in the day. There was no alternative so you had no choice.


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PostPosted: Wed Apr 28, 2010 12:53 pm 
Old School Grand Master
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Joined: Wed Jul 25, 2007 2:04 pm
Posts: 3363
Location: Completely in the dark, thanks to me good mate Terry....
hamster wrote:
A lot of this is marketing. I ran a Campag Record road mech with a Middleburn Duo 42/29 setup - and it was absolutely fine.


+1 - I use a Mavic 862 double mech to run a modified Middleburn RS7 (46/36 with the granny ring taken off) and it's fine.

David


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