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Shimano 7800 Shifters With 7900 Rear Der.

Mar 19, 2009
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Hi,
Along the lines of the previous thread......I would like to know if the 7800 shifters are compatible with the 7900 rear der. I understand that the front der. works on a different pull ratio and is not 7800 compatible but what about the rear?
I am not happy with the shape of the 7900 shifters (especially for big hands) and they have not received very good reviews.
I would like to put a group together with 7800 shifters and frt. der. and all remaining components to be 7900. Will that work?
Thanks for your help
 
Mar 18, 2009
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luv2bike said:
Hi,
Along the lines of the previous thread......I would like to know if the 7800 shifters are compatible with the 7900 rear der. I understand that the front der. works on a different pull ratio and is not 7800 compatible but what about the rear?
I am not happy with the shape of the 7900 shifters (especially for big hands) and they have not received very good reviews.
I would like to put a group together with 7800 shifters and frt. der. and all remaining components to be 7900. Will that work?
Thanks for your help

7900 brakes with 7800 brake levers/shifters are also not fully compatible. Cycling news recently reported:

'Mixing brake components yields either a too-firm lever with reduced power (7900 levers with 7800 calipers) or a somewhat spongy lever with grabby response. In either case, the distinction is decidedly subtle but still noticeable nonetheless and definitely doesn’t come close to matching the performance of a properly matched 7900 set.'

I personally just got a 7800 groupset at an excellent price - the A$1500 premium for 7900 wasn't worth the extra for my meager talents.
 
Mar 11, 2009
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luv2bike said:
Hi,
Along the lines of the previous thread......I would like to know if the 7800 shifters are compatible with the 7900 rear der. I understand that the front der. works on a different pull ratio and is not 7800 compatible but what about the rear?
I am not happy with the shape of the 7900 shifters (especially for big hands) and they have not received very good reviews.
I would like to put a group together with 7800 shifters and frt. der. and all remaining components to be 7900. Will that work?
Thanks for your help

7800 STI are compatible with a 7900 rear derailleur but not the front derailleur, brakes. They say not the crank since the rings are closer together than 7800 but like a 9s FD/STI on a 7800 crank, probably be made to work. What you cannot do, I understand, is use a 7900 LH STI/FD with a 7800 crank since the rings are farther apart and you'll get rubbing.
 
Apr 12, 2009
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I am using 7900 levers with a 7900 FD and 7800 cranks and rings and have no issues with front shifting. If the dimensions of the chain haven't changed, and they haven't, why would 7900 rings be made to be closer together than the 7800 rings?
 
Mar 11, 2009
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bdaghisallo said:
I am using 7900 levers with a 7900 FD and 7800 cranks and rings and have no issues with front shifting. If the dimensions of the chain haven't changed, and they haven't, why would 7900 rings be made to be closer together than the 7800 rings?

For Di2 is what I have heard but if the 7900, trimless FD/STI works on a 7800(and 6500 and 5600) that is good.
 

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