Any help you can give would be greatly appreciated. My local bike shop is having one heck of a time with getting my new 7800 durace rear derailleur to shift correctly. It has never shifted correctly since it was new 2200 miles ago and we can not keep it from lurching/delaying while shifting on the last two small gears in back when in the small front chain ring. This is what we have done so far…New cable three different times, Shimano sent a new 7800 derailleur (still did not work), new chain and even tried a different cassette. The only way it works is if you put a 600 ultegra 10 speed derailleur on it. I am as loyal as it comes with my local bike shop, but I would like to have it work in my lifetime. Again, any suggestions would be helpful at this point!
I am not a mechanic, not at all, but when it comes to shifting, small differences make big changes and the 600 might just “work” with the a bent hanger. Someone else should chime in on this that knows more and can shed more light on it, but if you look at the knowns, unknowns, the constants, and the variables it might just be the hanger. Hell, they might be able to bend it back. Anyone else???
Ya know, when you get down to the last 2 cogs and you’re in the little ring, the problem with slow shifting is often one link too many in the chain and/or too much friction somewhere in the shift cable/housing.
Would there be a reason the 600 would work and the Dura-Ace does not with the chain length where it is? Or is that simply because the 600 design may make up the difference. Thanks!
Here’s your trouble shooting checklist: Is the rear wheel in the dropouts straight? Is the rear axle intact? Are the cogs properly torques onto the casette body? Are the cogsets/cogs correctly assembled and oriented? Is the rear derailleur correctly threaded into the mount on the frame? Is the rear derailleur hanger bent or twisted? If it is a removable derailleur hanger, are the bolts holding it on the frame tight? Are the guide pulleys correctly installed with the Centeron guide pully on top? Is the chain correctly installed in the “pulling” orientation per Shimano installation instructions? Is the chain the appropriate length for the gearing? Are there any stiff links? Is the rear derailleur inner cable clean, un-kinked, and running freely through the housing? Is the housing the correct length, with ends ground flat and 90 degrees on a grinder, Shimano logos oriented upright and toward the front per Shimano installation instructions and installed with the correct ferrules in the appropriate locations? Are the ends of the housings “throated” so the inner cable enters and exits the housings without excess friction?
These are the primary sources of poor shifting performance from the shift back. At the shifter, it is important to be sure it is installed in compliance with Shimano instructions and is not damaged.
Off hand, I would be very careful about checking the frame and the derailleur hanger.
You guys are lucky enough to have some excellent retailers down there in Ohio such as Tri-Tech Multisport and A1 Cyclery- both the very finest of shops.
Are you using a 10-speed cassette? Presuming that you are, and that you’re using it on a wheel that was originally built for a 9-speed cassette, there’s a very small spacer that needs to go on the freehub body first, before you put the 10-speed cassette on. Without it, everything at the back of the drivetrain is a disaster.
Thanks for the suggestion. The wheels are Brand new Bontrager Race X-Lites and I stress again with the 600 Ultegra rear Derailluer it works fine. We just can’t get the Dura-Ace rear Derailluer to shift on the two smaller cogs without pausing…FRUSTRATING!!!
Crap…I forgot to mention that it works fine on the workstand but as soon as you test ride it and put it under load the problem rear its ugly head. Thanks again!
The bike is possessed by an evil spirit. Look in the Yellow Pages for an Exorcist in your area. Check references before hiring him and make sure he has experience with derailleur demons.
