What derailleur to use?
 

I am putting some different components on my bike and I have a ultegra 6700 derailleur plus a 7800 dura ace. I am not really sure what one is better since the ultegra is a newer version. Neither one some signs of alot of wear or anything and I am using a dura ace 7800 crankset.

Go for the panache. I'd use the DuraAce. If you can't get that one to work to your satisfaction you can always try the Ultegra.

Of the two, the DuraAce is "better". Ultegra is way more than perfectly adequate at a much lower cost.

front or rear?

Rear derailleur. Sorry.

The Dura Ace is much better looking, but you may need the 6700 if you want to use a 30t cassette. It depends on the bike.

Thanks for the help guys. I am running a 53/39. I will go with the dura ace.

If you already have DA, go with DA 10 times out of 10! All of my bikes have some sort of Dura Ace on them whether it is the brakes on my fixed gear (which I got used real cheap) or the shifters (9 speed bar ends don't come in anything but DA) and triple front derailleur (used real cheap) on my touring bike or the full 7400 gruppo on my Cilo. Dura-Ace is simply the best and there is a reason for that.

Though if you didn't have the Dura-Ace already go for Ultegra it is plenty fine quality for the average person and still looks quite nice, it might just be a wee touch heavier and maybe not quite as smooth in the shifting but not by a whole whole lot.

I have a question.

It's common to hear that Shimano lets the technology trickle down as new technology comes into production. With that shouldn't the 6700 Ultegra of 2009 be the same as the 7800 Dura Ace of 2003? I'm not looking for an argument, I'm not saying they are the same I'm asking what's the difference?

You hear a lot about the trickle down but it's not correct to say "this generation Ultegra is the same as last generation Dura Ace." The functionality may trickle down but the aesthetics will always favor Dura Ace, often the weight as well. Compare 7700 Dura Ace to 6700 Ultegra for example. Two generations difference but almost anyone would choose the DA if the gearing worked for them.

How thinly can you slice the baloney?

When I built up my recumbent I found some XTR derailleurs from about 2 decades ago in my parts box. Within my tuning ability I can't imagine anything working any more crisply. If new ones really are better I'm thinking it would take laboratory grade instrumentation to document the difference.

A couple of years ago on a training ride with a group of friends one of the guys had a problem when his lightweight vest fell out of his jersey pocket and was sucked into his cassette, destroying his Dura Ace rear derailleur. We were on vacation away from home so he took his bike to the closest local bike shop. The shop didn't have a Dura Ace derailleur in stock so they had to substitute a 105 derailleur as a temporary measure so he could finish the rest of our week of training. A year later, I noticed that he still had the 105 derailleur on his bike, so I asked him why he hadn't replaced it. He told me that as far as he could tell the 105 derailleur worked every bit as well as the Dura Ace so he couldn't justify replacing it for no functional gain. Shifters make a bigger difference in performance than derailleurs

Trickle down doesn't mean they are the same, it just means 'some' of the features or tech used does migrate down. Much like when fuel injection replaced carburetors in automobiles... at first it was the higher end models then within a few years even the low end economy models had it. That doesn't mean a Ford Escort was the same as a Cadillac just because some of the new technology trickled down to it.

For one if you look at them they are quite different...

http://ecx.images-amazon.com/images/...RL._SY300_.jpg http://thumbnail.image.rakuten.co.jp...6700g-gs-1.jpg

One is elegant and polished and more classy looking. I'm using that for a buildup of my vintage bikes. The Ultegra is more modernish styled and darker color and not polished.

Many times just looks alone decide things. But there is still many mechanical differences as well. I don't know myself but I've heard the metallurgy is different in Dura-Ace, and that it has never 'trickeld down' fully, its always had the best alloys for the best strength to weight ratio.

There are also differences in all the specs... I mean every single one, total capacity, largest sprocket, weight etc... (edited to add that many of the specs are actually better on the Ultegra, not trying to say DA is better except in the weight spec here, just that they are indeed not the same).

Perhaps a simple google search will show the differences...

All that being said as long as they fit your needs and looks aren't a big factor I doubt you could tell much of a difference.

[MENTION=307184]T Stew[/MENTION]
Good answer, that all makes a lot of sense and put things in perspective.....................You might get the nuts and bolts function of the Dura Ace of yesterday in the 105 of today but the elegance of Dura Ace only comes at the price of Dura Ace.

Art's Cyclery - Shimano Groupsets: Where to spend your money.

If you want the best value for your money, this is a pretty good article.

GH

Yes, and it confirms the thing I was talking about in my previous post. The rear derailleur is one of the least important components for shifting performance, yet it is one of the first components that manufacturers will "upgrade", mostly because it is very noticeable. An upgrade from 105 to Ultegra costs a bike manufacturer very little money, yet yields hundreds of dollars in market appeal

Damn good, actually. And mirrors my admittedly limited experience.