Classic & Vintage - Enlighten me on 6-sp DA UG freehub/cassettes
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11-16-11, 07:32 AM
I redid a Cilo for a relative/friend. All I did to the rear was clean it up and re-lube.
I always take these projects to a bike shop, and as this one was making some noise, I took it in. They swapped out the chain and it quieted down, but skipped on the 15t cog.
The owner called, so I pulled a 6-sp freewheel off one of my wheels, and sent it in, only to learn that it was a freehub/cassette (which I never thought about, actually).
Of course, that wasn't correct, so the shop got a regular 15t HG cog and filed the notches, etc so it would work, and it does. I set about finding another 6-sp cassette for him.
I see by several ads that the UG cassette for DA is different than the UG cassette for non-DA? This, of course, complicates the search, and drives the price up. I'm starting to think we should just be replacing the worn cogs one at a time, filing if necessary, rather than pay $100 for some 13-18 near-corncob that he can't ride, anyway.
I'm not up on this older stuff. Can somebody clue me in?
11-16-11, 08:03 AM
I believe that the only difference with a Dura Ace UG is the top (threaded) cog. All the other cogs are the same, whether DA or 600. You can file HG cogs to fit UG, as you've found. 26t is the largest cog that is usable with a 7400 RD.
Loose screws has some cogs in stock.
11-16-11, 10:47 AM
The Pachuco suggestion is good, buy a 7spd 26-13 or a 28-14 HG cassette. File off the large notch to match the freehub and use the 5 larger cogs and the original threaded 13. If you have a longer hanger or long drop out the 7400 RD can take a 28, if not it's hard to find a 27.
11-16-11, 11:22 AM
If you use a HG cassette keep all the sprockets in their original orientation since the ramps are aligned and are meant to line up in a certain way. And don't forget you can flip UG sprockets around so they can be worn down on both sides.
+1 on the only different for a DA UG cassette is the locking cog. It's noticeably smaller than the others and won't interchange with a non-DA hub.
11-16-11, 11:43 AM
On the other hand, Shimano 600 from that era fits right on a 7400 body. I've got a 13-26 7-speed that I need to replace the 17 and 19 cogs on, come to think of it.
Cyclone shifting over UG is the smooovest thing I've found yet. Love it.
11-16-11, 12:28 PM
26t is the largest cog that is usable with a 7400 RD
I've run my 7400 RD on a 30t cog with no problems.
UG splines are symmetrical as are the UG teeth so you could also try flipping the 15t UG cog as a temporary solution.
11-16-11, 12:36 PM
A HG cog to replace the UG one? So they make 6s HG cogs?
I've seen 6sp HG cassettes before. They're not very common though. But the main difference between 6sp & 7sp cassettes is the spacer width. The cogs are usually the same width or very close to it. So you could use 7sp HG cogs and the old 6sp UG spacers on a 6sp UG freehub.
Another possible solution is to find a old 8-speed Dura-Ace HG freehub (I think it is model 8403) and transplant as described here http://sheldonbrown.com/dura-ace.html#transplants The problem is that the 8sp Dura-Ace HG freehub is very difficult to find these days.
11-16-11, 07:55 PM
Thanks for the responses. I think he'll be fine for quite a while. I'm going to pick up a spare cassette, and when he wears out that 15t cog again, I'll have him swap in the new one, along with a chain. It's a 2x6 indexed 7400 group, and he wants to keep it that way.
11-17-11, 05:09 AM
My heads spinnig from all the mis-information in the thread.
Very simply put, if the splines are full length a complete HG cassette will work. If the splines are full length with threading a NON-DA UG cassette will work or a HG cassette will work. If the splines are NOT full length all but the 2 high gear (small diamter) threads are smaller hybrid style cassette is needed, in this instance you need to use 2 high gear Dura Ace specific UG cogs due to their smaller diamter than non-DA cogs.
Splines w/ small diamter thread: First 2 cogs must be DA UG, remaining cogs can be whatever
FULL length splines w/ threading: Check for internal threading. IF internal threading exisits you can use either a HG or UG cassette that uses large diamter threaded cogs. Sometimes internal threading isnt apparent, remove the DS dustcap, if you see threads its HG compatible, a HG comaptible dsut cap may be required.
Full length splines with no threading: HG only
11-18-11, 06:03 AM
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