mountaindave 

According to the Gospel of St Sheldon, the 7400 series DA RDs didn't play well with other shift levers. One needed specific 7400 series DA shifters. But then bar ends started coming out labeled as either "regular" 9 speed OR 7400 8 speed. Then 10 speed bar ends come out but could be used for 9 speed with a 7400 RD.

Taking the next logical step, has anyone tried using 11s bar ends to make a 7400 RD work with a 10 speed cassette? That would just be the bomb.

Just Curious,
MD

CO_Hoya 

It is my understanding that all 9sp STI shifters mate perfectly with 7400 RDs, but I don't know if you can do more than 8 speeds with that derailleur (link)

Upon re-reading your message, I realize you know that already. Never mind, I have nothing to add to your query.

mountaindave 

Doh, I just figured it out. Shifter cable pull X derailleur shift ratio = sprocket pitch (distance between sprockets center-to-center). Shimano 11s RDs have different shift ratios allowing more shift cable pull (for more accurate shifting).

Shimano Road shifter cable pull for 10s is 2.3mm. 11s shifter cable pull is actually 2.7mm - almost as much as the old 8s cable pull! Using the old standard Shimano RD shift ratio of 1.7 with an 11s shifter gives us a sprocket pitch of (1.7x2.7mm) = 4.59mm which is good for absolutely nothing.

So much for that. I'd need a cable pull of 2.08mm to get the proper sprocket pitch of 3.95 to work with the 7400 RD shift ratio of 1.9 ... or a new Jtek shift mate to make 10s bar ends work with 7400 RDs.

Who needs ten speeds anyway?

dddd

I knew I would see the day that some of the online compatibility charts contributed to intelligent discussions!

There are now so many possible combinations to chose from, but of course with narrower cog spacings, any error will be more likely to cause problems.

I'm even considering using a SRAM "Exact Actuation" 10s/11s derailer with a pair of Ergolevers now, which might be an economical way to use larger Wi-Fli or Shimano cassettes with Ergolevers.

RobbieTunes

see, I'm already out of this one.....

The combinations already out there boggle my limited mind. I aren't an enginner.

RobbieTunes

I think Zinn already has an article somewhere on that.

CO_Hoya 

It's worth noting that the chart to which I linked assumes uniform cable pull across the gear range, which I'm pretty sure is not true for Campy. Dunno about other systems.

dddd

You know, I remember reading that somewhere, but I don't think that it is true to the extent that it is significant.

I've done several Shimergo systems that indicated to me there was no significant difference in the linearity of the cable pull vs. the derailer.

I also tried to get an Allvit rear derailer to index with an Ergolever, but the Allvit's actuation ratio was wildly non-linear (regressed) as I approached the largest cog.
That was my very first attempt to install Ergolevers on a Varsity. I re-connected the headset "stem" shifters and called it a day.
Perhaps limited to a four-speed freewheel this would not have appeared as a problem(?).

mountaindave 

Shimano 11s sprocket pitch is 3.69mm, pretty small. To keep the shifting smooth, they decreased the RD shift ratio so the linear pull could be increased. (And I thought a simplex shift lever had a large throw!)

Anyway, it appears that the smallest amount of cable pull any manufacturer has gone to was 10s at 2.3mm. Everybody else has more, some much more pull in their shifters. They compensate with smaller shift ratios in their derailleurs. (Perhaps we can all start using friction shifters with these new fangled derailleurs?) Consequently, 11s has ended the backward compatibility of Shimano's STI system.

Art's Cyclery Blog has a lot of good info on this topic. Check it out.

dddd

All that raw data is perfect for choosing an experiment that has a decent chance of working well. I guess it would be too much to ask for them to measure the travel of a bunch of old Suntour and Campy mechs, not that they would index all that well. We already know that Suntour Accushift, pre-SIS Shimano and Campagnolo are about the same as pre-1997 74XX Dura-Ace, but I wouldn't mind trying one of my Ofmega Premier (made by Simplex, seems about like early Shimano) rear derailers with indexing one of these days.

I did notice one typo on their chart for cable pull of the shifters. It shows both the 10s and 11s SRAM road shifters pulling the same amount of cable per click, which is contradicted by the fact that both their 10s and 11s ROAD gruppo's rear derailer is of the "Exact Actuation" type, essentially identical in other words.

You're right about Shimano 10s road shifters having the all-time smallest cable movement, which did not work well for very long with such long cables as STI requires.
It was so sensitive to cable/housing cleanliness and lube that bike shops had to compensate for this by recommending shorter chain-replacement intervals to liven up the shifting that extra little bit. My own fix (particularly when an 11-28t cassette resulted in larger chain gap towards the lower concave portion of the cassette's profile) was to use a lower pully in the top position, such that "zero float" took "slack" out of the entire chain-control apparatus, increasing the service interval by a good bit.
One customer had installed an IRD 11-28t cassette on her 10s bike that literally could not be made to work, so sensitive was the tolerance for insufficient cable throw out back. I threw a used SRAM cassette on in it's place and was immediately able to arrive at an acceptable adjustment compromise. That change, along with reversing the positions of her derailer's top and bottom pullies kept her on the road for the rest of the season, without having to service the cabling or replace the chain.

OrangeBike

So, having recently been through all of this for my Dura Ace setup, let me share what I can...

The only shifters that are compatible with 7400 RD are the 7400s. 7400 = 6 speed, 7401 = 7 speed, 7402 = 8 speed. Except any Shimano 9 speed shifter will work as an 8 speed with an extra click.

The RDs are pretty much all the same within the group even though they have different numbering.

You can use 7400 series shifters with other Shimano derailleurs with the alternative cabling.

Hope this helps.

icepick_trotsky 

Here's a good blog post on a "Srampagnolo" setup as you describe. Looks like she used a Shiftmate, though.

Lovely Bicycle!: Go-Anywhere Gearing: SRampagnolo Drivetrain with 'Frying Pan' Cassette