Senior Ryder 00 

Hi,
I have a Dura-Ace 7401 RD that the cage is labeled “SIS 6-7 speed”. Has anyone tried this RD with 8 speed SIS shifters? I both DT & brifters in 8 speed, but no 7 speed shifters. Thought I’d ask before setting it up.
Thanks & regards,
Van

rccardr 

Works fine, fully compatible.
Or, I’ll swap a set of 7 speed DT shifters for a pair of 8’s.

Gonzo Bob

Dura-Ace 6/7/8 speed rear derailers are compatible with Dura-Ace (but not non Dura-Ace) 6/7/8 speed shifters. Shimano made the Dura-Ace rear derailer cable pull compatible with all other Shimano road shifters starting with Dura-Ace 9-speed. I probably didn't explain it well. So see this page...

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

dddd

Don't be too surprised if the indexing is off when using the largest cog, which would require a possibly-annoying compromise on the cable adjustment.

Not a matter of the derailer reaching it's travel limits, but of the actuation ratio falling off when shifting to the largest cog.

Won't hurt to try it out, since finding the proper "Integrated-8 SIS" rear derailer should not be too hard if you end up needing it.

Follow up with whatever outcome results.

canklecat

Interesting question. I think I have those bits and pieces in a box. I'm about to rebuild my '93 Trek 5900 with Dura Ace 8-speed stuff I've accumulated over the past year (finally got the front derailleur recently, the last bit I needed). But if I think of it I'll try the 7-speed shifters with the DA 7402 RD and see what happens. I'm not sure whether I also have the DA 7401 RD, but if I do I'll give it a try with DA 7402 STI shifters, just out of curiosity.

I do know some Shimano 7-speed rear derailleurs will handle 8-speed cassettes in friction mode, no problem, but won't gracefully handle 8-speed cassettes in index mode. The Exage 500 CX and Deore LX 7-speed rear derailleurs are nearly identical (minor cosmetic differences, reflected in the model numbers: RD M500 vs RD M550), but both have a nubbin molded inside the bodies that hinder swinging/pivoting the derailleur enough to easily clear the largest cog on an 8-speed cassette. In friction mode, the friction will hold it against that stop; but in index mode it'll pop out down to the 7th cog under pressure -- standing to pedal, climbing or sprinting. I've considered taking a moto tool or file to the nubbin stop on one of those RDs to see if it's a feasible modification to make those RDs work with 8-speed indexed shifting. For a couple of years I've used Ultegra 8-speed bar-end shifters in friction mode on my old Univega with 8-speed cassette and the original Exage CX500 7-speed RD. It will work in index mode until I reach a hill, then it'll pop out of the largest cog down to the 7th cog. But it stays put in friction mode.

So if you don't mind using your Dura Ace 8-speed downtube shifters in friction mode, it might cover an 8-speed cassette with your DA 7401 RD.

I tried the DA 7401 7-speed downtube shifters in friction mode for a day or so back in 2019. I guess it was okay but nothing special. I don't remember being dissatisfied, but the feel wasn't as nice as the Shimano L-422 Light Action friction shifters, which are a variation of the retrofriction design with a very nice feel. And once I got accustomed to index downtube shifters it was hard to go back to friction. I still use the Suntour GPX Accushift downtube shifters on my '89 Ironman, although I might switch that bike to MicroShift R7 brifters and Shimano 600 Tricolor derailleurs soon. I sometimes ride that bike on gravel and prefer to keep both hands on the bar at all times on sketchy terrain. With downtube shifters that means either lugging along in a too-big gear, or spinning and flailing away until we reach smooth enough gravel to feel confident enough to reach down to shift.

canklecat

Yeah, those DA 7402 downtube shifters ain't easy to find in working condition. Surprised me. I figured there wouldn't be much demand for those and they'd be easy to find cheap. Nope. Those were original equipment on the 1993 Trek 5900 OCLV, but my 5900 had been modified into a time trial/tri-bike by the time I got it from a friend, who did refit it with the DA 7401 downtube shifters. Back in '93 the 5900 was Trek's flagship bike, apparently set up for minimum weight for mountain stages, so they fit it with downtube shifters while the 5200 and 5500 had the heavier brifters.

I did ride that bike for a few months in 2019 with the 7401 downtube shifters which worked very nicely. But we don't have any mountains here, just lots of short, steep rollers where brifters are much handier and quicker for the rapid shifting needed to keep up with faster roadie club rides. First time I rode with brifters I realized I could shift while standing to pedal, making it easier to hold wheels and close gaps. Couldn't do that with downtube shifters, and taking a moment to sit, shift, then stand again would leave me gapped and eventually dropped by younger, stronger riders on faster club rides.

I checked around for a reasonably priced functioning set of DA 7402 8-speed downtube shifters for about a year but finally gave up the hunt and bought some 7402 STI shifters instead. Gotta admit, after using brifters on a couple other bikes, the wider and longer hoods are more comfy than the old school narrow hooked aero brake hoods.

But I'm still kinda partial to downtube shifters and have kept my Ironman with the original Suntour GPX DT shifters, mostly for casual solo and group rides.

thinktubes 

Works fine for me with recent manufacture SL-R400 8-speed shifters and a 28T.

JohnDThompson 

I remember asking the Shimano tech people about the friction mode on the original SIS shifters back in 1985 when they first came out. Their explanation was that friction mode was a fall-back, not intended for continuous use. E.g. a racer might not want to telegraph a shift change with the distinctive "clunk" of an indexed shift and could make a "stealth" shift by going into friction mode temporarily (that's also why the change from SIS to friction mode is not binary, but gradual). The other reason was to allow racers to use neutral-support wheels that may not have SIS-compatible clusters.

canklecat

Makes sense.

repechage

I can accept the neutral support angle.
in general, the view of the shop workers was that the friction mode provided some security of being able to continue if the index went wonky.

bike racers are a suspicious bunch.

3speedslow

I’ve noticed he does that a lot...