Quoted post said:Originally Posted by mcginniwa [IMG]/img/forum/go_quote.gif[/IMG]
Hi,
I'm in the finishing stages of putting together my first bike from used parts that I have picked up here and there. The idea behind it was to learn more about bikes via assembling my own "around town/commuter cheapo" road bike. So far there has been a lot of trial and error with parts and such, but that is par for the course for a beginner like me.
Now, to the actual question. I picked up a Dura Ace rear derailleur awhile back. Its part number is RD7402. I have a wheel set with DA hubs and a 8 speed cassette. I've read (cyclingforums.comshowthr...1&page=1&pp=15Open ↗) that DA RD7400 is compatible with the SL-BS77 bar end shifters. Will my DA RD7402 work with the SL-BS77 shifters?
Thanks in advance,
Walter McGinnis
How did that work out for you? :-)
I suspect you ran into the same problem i did,....the shorter cable pull requirement of the Dura Ace RD-7402 was most definately NOT compatible with the (after 1997) modern longer cable pull "standard" in shifters. (Dura Ace and others)
In the interest of helping others to use this early derailleur with commonly available modern shifters, i wanted to clear this up.
Basically, modern shifters (including the Dura Ace SL-BS77) pull too much cable per shift to index properly. This incompatibility cannot be "adjusted" out no matter how much you fiddle with the cable tension.
HOWEVER, the "incompatibility" issue is NOT an "impossibility", and there is a way to overcome the matchup! I recently completed the task, and it works as smooth as glass.
Basically, you will have to use a 9 speed chain. and REDUCE the standard cassette spacing thickness to about .113" to .115" on each of the 6 spacers between cogs 3-8.
On my setup i found i didn't need to reduce the Sram built in spacer thickness on my conversion, as it's the 1st jump after getting the lowest gear centered over the derailleur jockey wheel and therefore not enough difference to impede that 1st shift.
However, my jockey wheels were replaced before i bought the derailleur with higher end jockey wheels, and there is virtually NO play side to side with the ball bearings precision. Using the original DA jockey wheels you may find the need to trim this built in low gear spacer if you don't shift smoothly to 2nd or if it seems to interfere with either side gear once engaged. I suspect it will be fine, however.
Here's the post i made at another site that covers a bit more detail:
[quote]The 8 speed Dura Ace rear derailleur RD-7402 is pre-1997, and has a .SHORTER movement of the cage than the standard of today!
Shimano's Index Shifting (SIS) will NOT index properly with the modern standardized cable pull, in use since 1997 foreward, without the period correct dedicated shifters listed directly below.
Bar End Shifter needed: Dura Ace SL-BS50-8
Downtube Shifter: Dura Ace SL-7402
[B] TIP: You CAN get the Dura Ace RD-7402 rear derailleur to work with later shifters using modern bar end shifter if you're handy and have some patience,.....
......i just did one! :-) [/B]
I just posted how i went about it on VeloBase, and will include it here also: VeloBase.com - Component: Shimano RD-7402, Dura-Ace (8sp)
joejeweler;4132949 said:Getting the Dura Ace RD-7402 8-speed Derailleur to work with modern standard cable pull shifting levers:
As most who have this derailleur know, the cable pull design was shorter on these, and modern shifters will not work. You generally need the mated shifters from that time period and group. I've been looking awile for the bar end shifter version, but no luck up to now.
However, i just completed an "exception", and found it is indeed possible to get these working with modern shifters! :-) I'm using a modern Dura Ace 8-9 speed shifter, with the rear derailluer locking out the unused 9th gear with the low end stop screw. I had TWO of these wonderfully machined derailleurs sitting around, and wanted to put one on my late 1980's Serotta steel frame and run it as a 1X8 speed commuter. (had it set up fixed gear! :-)
It was not an easy conversion, as i was working with several slightly used cassettes from Shimano and Sram. Some of the larger cogs i wanted to use were on a spider, and could not be used alone if separated. By mixing and matching cogs from differing cassettes, i was able to come up with usuable cogs of 12/13/14/15/17/20/23/26 , which is representitive of the outside extreme cog sizes for this derailleur. (12-26T)
I figured "if" i could arrive at a proper spacer thickness, then i could get this deraillure to work with my later Dura Ace bar end shifter. (now mounted to a Paul "Thumbie"😉 Because the deraillure is a bit short on it's movement with a modern shifter's cable pull, a smaller spacer than the 8 speed norm is called for.
The workable spacer thickness for this derailleur proved to be a bit more than the average thickness of a nine speed (2.56mm or 0.100787 inch), and 8 speed spacer (3.0mm or 0.11811 inch). A quality dial caliper is needed, and i made my spacers to .113 inch to .115 inch. That's close enough to the 0.1094485" average, and the extra thickness gives you some "adjusting" room if needed. (i needed it!) '
It's best to work only one side when flat sanding, as it's easier to keep the sides parallel when one side is known flat. My setup was complicated more i believe because i used cogs from 2 different manufactures, and a little fine tuning on a few spaces was needed later. Some of that could be avoided using just one maker's cogsets. Check often when sanding, (i used 220 grit on the hard plactic/nylon? spacers), and be prepared for sore fingers. I used several band-aids on my fingertips to help cushion the sharp edges, but i'm still sore.
If one part of the sanded spacer is measuring more than a few thousands thicker than the rest of that spacer, you can true it up by only sanding that part and keep the thinner part OFF the sandpaper for a few strokes.
Note: You will need to use a NINE SPEED chain, as your 8 speed spacers will be made thinner, making an 8 speed chain unuseable in the more restricted space between cogs. The actual cogs can be either 9 speed or 8 speed, as they are generally within .02mm difference as listed on Sheldon Brown's site.
I used what i had on hand,...9 speed cassettes and some old 6 speed spacers. Save yourself some grief and a lot less sanding and sore fingers,....and use an 8 speed cassette(s). The 8 speed spacers are much thinner than the 6 speed ones i had on hand. Best to find one with individual cogs and no spiders, or you'll have to break apart cogs from different sets to get the range you want. (as long as it's 12-26T inclusive).
Anyway, after several hours of work (i ended up making TWO sets of spacers, as the 1st ones were a bit too thin :-( One other thing, i was using a new derailluer cable, and the initial stretching was creating it's own problems at times. After a day it's much better now, and holds the settings. Best to get set up using a well used but solid cable!
Oh, ....the 1st cog with the built in spacer (if using an 8 speed cassette to start) will probably need a bit of sanding on the spacer side to thin it. Funny, the steel is MUCH easier and quicker to sand down than those fiberous/nylon ones! :thumbsup:
I am thrilled to finally be able to use this great looking (and now functioning) derailluer! I went on a 9-10 mile ride today to a LBS, and bought a few more slightly used cassettes...... ......after all, i still have another Dura Ace RD-7402 collecting dust! :-)
BTW,....the Dura Ace spec sheet called for a 12-26T cassette on these, but i found a 11T high gear worked fine on mine. Haven't tried a 27T on the low end, but may try it as i've found Shimano conservative in their ratings.
Also, i did have to add a thin spacer behind the largest cog in order to get it tightened up. I used one in aluminum less than 2mm thick,
but will eventually make a steel one as its a lot of pressure on such a thin piece of aluminum. The spacer makes up for the thinner individual cog spacers you made :-)[/quote]
[b]A few pics set up as 1X8:[/b]
[b]I like all the wheelbase i can get! :-)[/b]
[b]Here's the shifter i'm using (Dura Ace SL-BS77), mounted on a "Paul Thumbie". Without the custom fit cog spacers this would NOT be compatable.[/b]
