jamesdak 

Ok, second guessing myself on this and failing with my googling. Plain and simple with the Dura Ace 8 speed STI shifter work with the Shimano 600 Tricolor parts. Main concern is the RD. Can't find if the different cable pull ratio is applicable to the STI shifters or not. Have the new to me Miele now outfitted with a full 600 setup minus the shifting and trying to figure out if I can use the Dura Ace STI ST-7400/7403 (shifter not marked) on it. I'm easily confused anymore and just can't seem to find the answer with my searching . Thanks!

jdawginsc 

Nothing I can speak with any certainty about, but wasn’t the Dura Ace 8 speed the funky one that didn’t play nice with anything else, or was that the 9 speed 7700 series? Or both?

Dave Mayer

Dura-Ace 7400, including the later 8-speed STI shifters have a cable pull of about 10% less than Shimano 600 (per gear). And the 740X rear derailleurs have an actuation ratio of about 10% higher than Shimano 600.

So no, they are not compatible. This difference is well outside the tolerances for acceptable indexed shifting. Before we get any response here that includes any of the following:

• Alternative cable routing
• Shiftmate
• Just try it

Please, no. Just stop.

rccardr 

I’m with Dave. For once.
Others have claimed acceptable shifting with the alternative cable routing method, but you’re too picky about shift quality to accept that.
Buy some nice 6403 STI’s and make it right.

KCT1986

The ST-7400 is not 'natively' compatible with any RD other than the 740? series.

Another concern is the FD. The 6400 series had 2 versions of FD, the later 6401 is designed to work brifters, the earlier 6400 was for downtube shifters and needed more cable pull.

The 6400 pivot design was similar to the FD-A550, that used what Shimano called forward push, which moved the cage forward as well as laterally. This meant that more cable pull was needed to index properly.



And even with the FD-6401, the cable attachment arm was designed to handle both downtube shifter and brifters. It had 2 position on the arm where the cable could be attached, one on the shorter side, closer to the pivot for brifters.use if needed.

Kontact 

Alternate cable routing was a Shimano invention specifically to ensure backwards compatibility. It isn't just a funky hack.

But how hard is it to find a 7400 derailleur? Any of them will work, 6-8 speed.

KCT1986

There was no ST-7403 nor 6403, these early brifters were 2x only. Of these early brifters, you has to go 105 or lower to get triple front.

Kontact 

Brifters are more expensive than derailleurs. I'd buy a 7400 derailleur before I bought a 6400 brifter set.

70sSanO

All Shimano cassettes have the same cog-to-cog spacing. The difference between the Dura Ace 74XX and every other Shimano SIS from the 80’s and 90’s is the actuation ratio of the RD.

Dura Ace RD is 1.9 and the others are 1.7. It ends up being a simple math exercise. If 8 speed cog-to-cog spacing is 4.80mm, just divide that by 1.9 to get the cable pull that your DA shifters have; which is 2.53mm. Standard 8 speed cable pull is 2.82mm.

I ran alternate cable routing with DA 7 speed shifter and an XTR M910 RD. Probably my favorite combination. But I have moved to 8 speed with 6401 shifters.

A DA RD-74XX has a max cog of 26t, but I ran 28t for years.

Supposedly, you can run a cassette spaced for 9 speed, or 8 of 9 cogs, with a non DA SIS RD. The math isn’t perfect, but it is close.

John

jamesdak 

Hmmm, guess I didn't hit enter on my reply post last night.

Thanks Dave, I was thinking I had done it but realized the bike I was thinking about was my old Bob Jackson. Looked back at the pics for that bike and it was all 600.

The Miele is a "project" bike I'm trying not to spend too much on. So I may just settle for finding a 600 series front DT shifter to match the other one and call it good. That will have it setup with all 600 series parts. I was just thinking if this one winds up getting passed on it would be easier to find a new owner if it had STI shifting. I've got a 7400 series RD but I'm thinking there was something wrong with it. That's always an option but then I might as well go full Dura Ace since I do have the brakes, crankset and one final set of SL-7400 shifters. Somehow I always wind up going down a deep rabbit hole on all these cheap "give me something to do" project bikes.

rccardr 

Although it was not my intention to infer that the OP should buy a triple shifter, I stand corrected. 600 Tricolor series STI's are listed to as ST-6400, while DA 740X series STI's are listed as ST-7400.

While there are plenty of 6403 and 7403 parts (brake calipers, brake levers, hubs, etc.) none of them are specifically for triples.

icemilkcoffee 

Everyone else is correct. The ST7400 will only work with the Dura Ace RD74** shifting an 8 speed cassette.

BUT, Shimano, in its infinite wisdom, gave you another way. out. A Dura Ace 8 speed shifter, will shift a 9 speed (well, 8 of the 9 speeds anyways) cassette using the usual 7-10 speed Shimano road RD. That's why you see on the BS77 barcons this label:

Retoocs

The alternate cable routing is in the manual.

jamesdak 

I'm not spending any more money on this one. I'm going to use a nice set of ST-6510 shifters out of my stash with the 6400 parts. I've already got those modern Velomax wheels for it and they will take a 9 speed cassette with no problem. The 6400 RD should cover a 9 speed with no problem.