# Foolish to stockpile 7800 rear derailleurs?



## Clevor (Sep 8, 2005)

To those who are enslaved to life to DA 7800, I presume there is no need to bid foolish prices on Ebay for rear derailleurs, because the DA 7900 rear is absolutely, positively, compatible with 7800/7801/7803 shifters, correct???

Has there been any improvements of the 7900 rear over the 7800?


----------



## zac (Aug 5, 2005)

Clevor said:


> To those who are enslaved to life to DA 7800, I presume there is no need to bid foolish prices on Ebay for rear derailleurs, because the DA 7900 rear is absolutely, positively, compatible with 7800/7801/7803 shifters, correct???
> 
> Has there been any improvements of the 7900 rear over the 7800?


Not understanding your first part.

But as to the second, the 7900 is a bit lighter, has garish graphics, and to many, myself included, does not work as well as the 7800 mech. 

Took me about a week to determine I liked the 7800 rear better, and took me about a month to put it back on. So I ride all 7900 except for the disposables (crankset, cassettes and chains) and the rear mech. 

zac


----------



## fast ferd (Jan 30, 2009)

Well, the eBay price for a 7800 rear seems to come in at about half the price of a 7900.

As Zac said, the two work interchangably. I find both units perform well. One bike with 7800 and the other with 7900 - complete gruppos. For the price, I'd go 7800.


----------



## Clevor (Sep 8, 2005)

zac said:


> Not understanding your first part.
> 
> But as to the second, the 7900 is a bit lighter, has garish graphics, and to many, myself included, does not work as well as the 7800 mech.
> 
> ...


What I mean't by the first part of my OP is it's well known that with 7900 shifters, you have to use 7900 front derailleurs and brake calipers. But pretty much everything else is interchangeable with 7800, such as rear derailleur, cassettes, crank, chain. So if I am running all DA 7800 but need a new rear derailleur in three years, no need to get a spare 7800 rear now and I can just use a 7900 rear.


----------



## Clevor (Sep 8, 2005)

fast ferd said:


> Well, the eBay price for a 7800 rear seems to come in at about half the price of a 7900.
> 
> As Zac said, the two work interchangably. I find both units perform well. One bike with 7800 and the other with 7900 - complete gruppos. For the price, I'd go 7800.


That's true now, but say I need a new rear derailleur in three years, by then maybe DA 8000 will be out and the 7900 prices may come down to what the 7800 is right now. So I really don't need to stockpile spare 7800 parts except maybe front derailleurs (which I have done).

I know that officially, Shimano now says the 7900 rear will work with up to a 28 tooth rear cog, but everybody knows the 7800 did that too.


----------



## zac (Aug 5, 2005)

Clevor said:


> What I mean't by the first part of my OP is it's well known that with 7900 shifters, you have to use 7900 front derailleurs and brake calipers. But pretty much everything else is interchangeable with 7800, such as rear derailleur, cassettes, crank, chain. So if I am running all DA 7800 but need a new rear derailleur in three years, no need to get a spare 7800 rear now and I can just use a 7900 rear.


Ah ok, thanks. Absolutely the 7900 rear will work just fine.

As to the need for the brake calipers too: Search under my name and 7800/7900 interchangeability. I have some extensive posts about what works with what. In a nutshell, just the STI and FD are all that is needed to stay homogenous and running well, the rest can be mixed and matched at your leisure. You can keep the 7800 calipers with 7900 levers, and you can run 7900 calipers with 7800 STI. I have done both, and they work just fine...BUT, either is a step down from the superior braking that 7800STI/7800BR or 7900STI/7900BR offers.

All in all I think the one biggest noticeable difference between the two groups, other than feel of the hoods, and the different shifting capabilities...which are either pros or cons, depending on your individual tastes...are the brakes. The 7900 brakes are absolutely impressive in power and modulation even under the worst of conditions...wet on carbon.

Right now, and for the foreseeable future, the 7900 consumables are just too expensive. I run too many cassettes and chains to justify their cost. Plus at $400 a wack for the big ring on the 7900 chainset...that is not worth it either...I go through one or two 53 rings a year...just not worth it.

zac


----------



## rock mafia (Aug 1, 2009)

I see 7400 DA rears on ebay alot, so I think there will be 7800 stuff around for years to come.


----------

