DA Teeth Worn?

[Rpoole8537]

I purchased this used Dura Ace crank, but the rings, especially the 39 and the 30, look a bit worn out to me. I don't wish to ruin my chain and cassette by installing this crank. Plus, these rings are a bit tough to find. So what are thoughts on the wear pattern? What choices do I have on rings. DA rings only ones that fit?

[oldpotatoe]

I purchased this used Dura Ace crank, but the rings, especially the 39 and the 30, look a bit worn out to me. I don't wish to ruin my chain and cassette by installing this crank. Plus, these rings are a bit tough to find. So what are thoughts on the wear pattern? What choices do I have on rings. DA rings only ones that fit?

Those look pretty normal and in good shape to me. Even new rings have a lot of 'treatment' for ease to get the chain onto and off the CR with ease while there is pedal pressure of riding.

30t..so triple and DA and yes, the middle and small rings are proprietary..The big ring is a standard 130mm BCD but the middle and small..gotta be DA, 7703..

BUT a new chain will be noisy is the CR is worn out..you won't really 'hurt' the chain if the rings are worn.

[denvervig]

I've got a 7700 double on my Merlin and the original big ring was bent/warped and replaced it with one from an Ultegra 6500 double so I'd expect that the Ultegra triples would work and they're much easier to find

[Rafa]

I stumbled on this page a few nights ago. About 2/3 of the way down the page, there’s an explanation about DA triples and why they’re odd:

https://www.sheldonbrown.com/dura-ace.html

I've got a 7700 double on my Merlin and the original big ring was bent/warped and replaced it with one from an Ultegra 6500 double so I'd expect that the Ultegra triples would work and they're much easier to find

[Look585]

As OldPotatoe (and Sheldon) mentioned, the 7703 crank has some unique characteristics. It is a 130bcd with no inner chainring mounting provision.

The inner ring bolts directly to the middle ring. The actual 7703 chainrings are very hard to find. Your best bet will be to find a NOS crank and harvest the rings. You may be able to sell off the resulting naked arms as single speed riders with a DA fetish really like the DA7703 arms as they make great single speed cranks due to the lack of an "inner chainring shelf" at the bolt circle. (They look like a 130bcd track crank with a wider chainline)

As for substitute rings, you can use the following:

Outer 5703 or 4603 50t "D"
Middle 6703 or 4603 39t "D"
Inner 6703 or 4603 30t "D"

These Ultegra/105/Tiagra rings are not a fancy as DA, but they are available and inexpensive.

[denvervig]

Interesting - so did you interpret that as a problem only for the 2002 models years forward (until they came out w/7800)?

"For the 2002 model year, Shimano introduced a triple chainring crank set in the Dura-Ace line, with corresponding STI shifters, front and rear derailers. While other Shimano "road" triples come with 52-42-30 chainrings, the Dura-Ace version comes with 52-39-30 rings. At first this seemed like a welcome upgrade, offering greater versatility to the road/touring cyclist..."


Never mind - just re-read that excerpt relative to the OP's photo...

[ultraman6970]

Thats the old shimano stuff... it last forever I would not worry about it.

THe teeth are cut like that aswell, just like potato says.

[slambers3]

thats how those look iirc, not particularly worn. Kinda tough to see from the picture, but If that ring was toast, you’d likely see a lot of other signs of wear on the crank. Wrap a new chain around it and see how it meshes