FC-7800 with 9-Speed, compatible?

tomUK said:

I have just brought a FC-7800 and installed it on my bike which has the Dura Ace 7700 group set on; however, in the lowest 3 gears there is a noise - i've looked and it appears that the chain doesn't quiet line up straight when in these 3 gears.

Has anyone done this successfully? I've been told that I might need to change the chain. Any ideas?

7800 is 10s, 7700 cogset is 9s. Shifters are not compatible with 9s. They shift 10s spacing, which has the cogs closer together. Get a 10s cogset and chain, adjust rear derailleur-go ride.

Peter@vecchios said:

7800 is 10s, 7700 cogset is 9s. Shifters are not compatible with 9s. They shift 10s spacing, which has the cogs closer together. Get a 10s cogset and chain, adjust rear derailleur-go ride.

Don't think you got the question; I want to change the FRONT crank only. Not back cassette nor shifters, not derailleurs.

It should work fine. A friend did the same thing. The front mech should be a double, not a triple, if that is applicable to your situation.

tomUK said:

I have just brought a FC-7800 and installed it on my bike which has the Dura Ace 7700 group set on; however, in the lowest 3 gears there is a noise - i've looked and it appears that the chain doesn't quiet line up straight when in these 3 gears.

Has anyone done this successfully? I've been told that I might need to change the chain. Any ideas?

I'm running the exact setup you are inquiring about on one of my bikes, full Dura Ace 7700 9sp with the 7800 10sp crankset, it works fine. Not a problem at all.

Tech72 said:

I'm running the exact setup you are inquiring about on one of my bikes, full Dura Ace 7700 9sp with the 7800 10sp crankset, it works fine. Not a problem at all.

That's interesting. What chain do you have CN-7701? And rear cogs? CS-7700?

tomUK said:

That's interesting. What chain do you have CN-7701? And rear cogs? CS-7700?

Yes, Shimano CN-7701 chain, CS-7700 cassette, FD-7700 front derailleur, RD-7700 rear derailleur and ST-7701 brifters. The bike that I have this set-up on also used to have the FC-7701 9sp crankset but I upgraded to the FC-7800 10sp crankset (the only "10sp" part in the mix). All components are working happily together.

Tech72 said:

Yes, Shimano CN-7701 chain, CS-7700 cassette, FD-7700 front derailleur, RD-7700 rear derailleur and ST-7701 brifters. The bike that I have this set-up on also used to have the FC-7701 9sp crankset but I upgraded to the FC-7800 10sp crankset (the only "10sp" part in the mix). All components are working happily together.

Yep, that's exactly what I have. Do you have to re-adjust the derailleurs when you removed the FC-7700 and put on the FC-7800?

All the other gears on mine work fine 3-9 and 10-18 seem great but 1 & 2 just make excessive noise -- I can see what is happening; the chain is hitting the lowest cog on the crank slightly off-centre (to the right) and making the noise as it re-aligns itself.

Seems so odd as I just can't figure it out.

Tech72 said:

Yes, Shimano CN-7701 chain, CS-7700 cassette, FD-7700 front derailleur, RD-7700 rear derailleur and ST-7701 brifters. The bike that I have this set-up on also used to have the FC-7701 9sp crankset but I upgraded to the FC-7800 10sp crankset (the only "10sp" part in the mix). All components are working happily together.

Yep, that's exactly what I have. Do you have to re-adjust the derailleurs when you removed the FC-7700 and put on the FC-7800?

All the other gears on mine work fine 3-9 and 10-18 seem great but 1 & 2 just make excessive noise -- I can see what is happening; the chain is hitting the lowest cog on the crank slightly off-centre (to the right) and making the noise as it re-aligns itself.

Seems so odd as I just can't figure it out.
p.s. what frame do you have?

tomUK said:

Don't think you got the question; I want to change the FRONT crank only. Not back cassette nor shifters, not derailleurs.

ahhh 'FC-7800'. Should work fine, done that many times, put a new 2 piece, 10s crank onto an other wise 9s system.

Peter@vecchios said:

ahhh 'FC-7800'. Should work fine, done that many times, put a new 2 piece, 10s crank onto an other wise 9s system.

Chain tickling the big ring when in smallest few cogs is unavoidable. Small ring is closer to big ring and 9s chain is fatter than a 10s. DON'T use a 10s chain just shift to the big ring and p the cogset to a lower gear for the same ratio.

Peter@vecchios said:

Chain tickling the big ring when in smallest few cogs is unavoidable. Small ring is closer to big ring and 9s chain is fatter than a 10s. DON'T use a 10s chain just shift to the big ring and p the cogset to a lower gear for the same ratio.

Nope - that is not the problem; When the chain is on the smallest cog on the crank and the three LARGEST cogs on the cassette there is a noise coming from the front crankset. its almost like the chain doesn't layoff onto the small cog (front crankset) correctly.

i'm not sure why I would be getting this. possible my Carbon Fiber frame is bent? or the new crankset? The old crank set works just fine.

Fix to this - changed chain to SRAM - seems to make less noise. Also added a shimano spacer on the rear cassette. This did the trick 🙂