leaping_gnome

Sorry if this is slightly OT but you are the guys I can best relate to. I recently bought this bike, a 95 Specialized M2, with a full Dura Ace 7402 group. That in itself was unusual and I can only assume that the original owner (not the seller) equipped the bike that way, but the gear ratios and rear derailleur really caught my eye. This appears to be a wide-ratio RD-7402 derailleur and Deore XT-M7XX 8-speed cassette. The cage on the derailleur looks like it also came from the Deore line! Was this configuration of Dura-Ace 7400 and Deore ever sold?
I am definitely pleased with the combo because the gear ratios will allow some pretty unlimited climbing potential. The rivets on the 1st gear (Ti?) to aluminum four finger spider are loose, so I will eventually have to repair or replace it. So if anyone wants to chime in with Dura Ace 7402/Deore knowledge I would love to know more. Is it possible to graft a Deore cage onto a 7402 derailleur?

I included a photo of the Deore RD-M730 derailleur cage for reference from Velobase

Tia - Jim BTW - there's more photos of the whole bike on my Flickr album
IMG_5905 by Jim Harris, on Flickr
IMG_5896 by Jim Harris, on Flickr

RD-M730 derailleur cage Photo Credit: VeloBase User tommy

Lazyass

leaping_gnome

Oooookay, care to elaborate? I'm glad to see other types, what model designation were they? What application?

QuangVuong

RD cages are interchangeable. Someone's gone and swapped the short DA one out for a different cage, probably off that Deore RD.

Ive done it myself before on other RDs. The cage length really only allows for a longer chain, which is useful for a triple, but due to the RD body length, you're still stuck at about a max 28t on the 7400 RD. Unless the top jockey wheel of the Deore cage is lower than where the DA jockey wheel was.

T-Mar

I've never seen a catalogued RD-74xx rear derailleur with a long cage. They are easy enough to cobble together with cages from other Shimano models of the same era. However, this is generally done to facilitate running a triple crankset with a granny gear. The substitution of a Shimano ATB cage should not allow you run a larger cog, as the dimension between the pivot to jockey pulley axes are common. You can usually cheat a couple of teeth's worth by moving the wheel back in the dropout but this isn't possible with a vertical dropout. The only way to increase the large cog capacity would be to install a longer dropout hanger or grind the tops of the dropout slot. Beyond that, you'd have to carefully manage the chain length to run the shortest possible chain or get really creative and use new upper and lower pivot castings with a longer drop and/or steeper cog tracking angles.

leaping_gnome

Thanks QV and T-Mar
You've confirmed what I suspected, that this RD may be assembled using a Deore cage. Yup, the cage clears the 28t second cog just fine but rides on the 32t first cog. I guess that's why it's loose. The long cage may be overkill, for sure, but a mid cage may have an advantage for a bike with vertical dropouts.

Thanks

Jim