tprevost

We pulled the DA7800 off of my bike and put it on VMC's bike... everything is exactly the same with the exception of the chain; we bought a new 7900 chain...

The cassette is a 12-27 and it won't shift onto the 12 gear. He's a pretty good bike mechanic so its something out of the ordinary I'm guessing... we took it to the shop today; they couldn't figure it out but did get it to shift onto the 12... but now that the bike is home, it won't go onto that gear again...

any ideas for where to look next for the issue?

jonathanb715

Maybe too obvious, but is the derailleur hanger straight? Hopefully the shop checked that one!

JB

JoelS

Only time I had that problem was when the rear wheel wasn't centered.

tprevost

yeah, they checked that... we are really perplexed...

bam

cassette spacer (too big) or derailleur limit (too high)

tprevost

okay, nevermind... he got it to work by using a different cassette... still not obvious though. We put an old 12-27 on and it works okay... the newer one doesn't... who knew...

thanks for the ideas!

UmneyDurak

Is the spacer the same?

JourneyLightly

+2 on guessing it's the spacer. For example, if you pulled the cassette off a Ksyrium along with the spacer and put them on a non-Ksyrium wheel, you'd have the problem you described. My bike came with Ksyriums, which I promptly sold. I mistakenly removed the Ksyrium's spacer along with the cassette, which I found out after the buyer called me from his LBS wondering why his cassette didn't fit his new wheels. Oops! Luckily the LBS gave him what he needed. I didn't need a spacer at all for my new wheel.

tprevost

might have been it.... its really wierd... I'll have him double check it (since I'm sure he'd rather use the bright shiny new cassette) ... This cassette was out of the package and put onto a Ksyrium wheel... the old one (that worked) came off of an American Classic wheel....