# 7800 - 7900 Mix



## Roadplay (Jan 2, 2007)

I have a Tarmac frame module with the integrated 30BB crank, all DA 7800. I am thinking about converting over to 7900 with minimal components. Looking at the compatibility chart, I’m thinking about changing out both shifters, FD and RD only. There is a comment in the compatibility chart about possibility of slow shifting if not changing to a 7900 crank.

Has anyone done this minimal change over? If so, have you experienced any problems with performance?


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## bdaghisallo1 (Sep 25, 2007)

The minimum you absolutely need to change, assuming it's the 7900 shifters you really want, is the the FD. 7800 RD will work fine. It is also advisable to get the 7900 brake calipers if you want good braking. The different cable pull ratio of the 7900 levers will make braking with the 7800 calipers a little sub-par.

You don't need the 7900 crank nor even 7900 rings. The spacing between rings and cogs and also chain dimensions have not changed from 7800 to 7900.


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## Roadplay (Jan 2, 2007)

So, I was checking the availability of a FD on Competitive Cyclist and the last sentence of the product review states, "According to Shimano it (the 7900 FD) is not compatible with the DA 7800 series crankset and chain". 

Is this a fact?


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## Argentius (Aug 26, 2004)

Roadplay said:


> So, I was checking the availability of a FD on Competitive Cyclist and the last sentence of the product review states, "According to Shimano it (the 7900 FD) is not compatible with the DA 7800 series crankset and chain".
> 
> Is this a fact?


I haven't ridden the bike yet, but my coworker has an FSA crankset of some kind and just put on 7900 shifters and FD. All works fine.


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