copperfind

Okay so I know the conversion question has been asked over and over and Sheldon has a great article on it... But everything I have read doesn't answer all my questions.

So I have a nice set of Dura Ace 7400 hubs I am wanting to put on an old Centurion with 126mm rear spacing. Can not find UG sprockets and if you do on ebay they are crazy money because from what I understand 7400 will accept only Dura Ace UG.

So I was thinking of converting to a HG 7sp freehub body but I think the older Dura Ace freehub requires another out dated tool to remove.

So my question if I was able to get it off would the newer shimano7sp freehub body fit following the conversion process.

ThermionicScott 

I believe Dura Ace freehub bodies attached differently from the rest during this period. User @stronglight has a scan of the FH-7400 datasheet here: https://www.flickr.com/photos/strong...7621660773432/

Sir_Name 

So just to be clear, have you tried the method Sheldon mentions of filing the wide HG spline to get a HG cassette to fit on the UG body? This still requires the small UG sprocket to hold things together. I've had good luck finding 13 or 14 tooth UG sprockets on eBay for a fair price considering the problem they solve - haven't checked prices in a few months though.

rccardr 

Forget trying to upgrade a DA UG freehub to HG. The parts and tools required are so rare and expensive that it's just not practical. Instead, as SirName suggests, modify HG cogs to fit the UG freehub (each cog takes about 20 seconds with a Dremel and a cutting wheel) and use a UG small cog to lock it down.

plonz 

I'd also suggest you confirm which 7400 hubs you have. Forgive me if you're already familiar with this but 7403 will accept both UG and HG.

Here is a great post from @miamijim that demystifies 7400/7402/7403 hubs. Helped me a bunch. Unfortunately the images were lost in the recent photobucket scandal. Maybe Jim would be gracious enough to reload them.

https://www.bikeforums.net/classic-vi...403-101-a.html

frantik

the only freehub body that will take hyperglide came on the 7403 hub..the hub is the most rare of the 7400 series and the tool even more rare than that.

i see two UG cassettes on ebay right now for under $50.. not terrible. the main thing you need is the lockring, the rest of the UG cogs can come from any UG cassette. or you can dremel down a HG cassette

Sir_Name 

Oh, an additional note on modified HG cassette + small UG sprocket - 6 and 7 speed UG small sprockets are different thicknesses to account for the difference in spacing. Make sure you get the correct one for your application (maybe get two to future-proof as small sprockets wear quickest). DA UG small sprockets also have a different inner/thread diameter from non-DA (going from memory here pre-coffee, so worth a double-check).

LeicaLad 

Okay. You've opened up an entire can of worms here.

The 7400 hubs are fabulous, and they look great, too. HOWEVER, they have major limitations.

First, if you are talking 7 speeds, you need not one, but TWO special cogs. The first position is threaded, but the second position has a spacer built in. This is required to assure it doesn't spin between the threads and the splines.

Finding the first position cog is tough, but finding the second position cog is ultra-tough. I've spent some years hunting for them.

I "might" have a 14t second position cog I'd be willing to trade, especially for a 15t second position cog!

I'd post a photo, but I'm also a photobucket user seeing all my photos disappear. sigh.

copperfind

Ugg thanks for the responses all

nashvillebill

I see talk of opening up the slots on the cogs themselves to fit the hub, but wouldn't it make more sense to merely grind back the offending spline on the hub instead? This one-time grinding keeps the HG cogs indexed properly and allows cogs to be substituted easily later on.

The grinding of the spline doesn't need to be high-precision, the other splines will transmit the torque load nicely.

ThermionicScott 

I'm sure it could be done, and newer hubs (I'm thinking Campy in particular) use fewer splines to transmit the torque. Just be careful not to get metal particles into the wheel bearing or freehub mechanism.

miamijim

In theory yes yes but I think it's more practical to quickly buzz down 1 wide spine on the cog. Freehub bodies are exceptionally hard and you also run the risk of an uneven grind and also possibly cracking the freehub.

It's easy to properly align HG cogs without the the wide spline... just align the grind marks and most hg cogs have alignment marks.

Sir_Name 

Filed down wide HG spline:



UG small sprocket:



All together now:

copperfind

Nice thanks for the pics... So you ground it with it together I am guessing... Dremel and finish with file or just a file?

copperfind

is it correct they will only fit Dura Ace HG sprockets.

16Victor

I will check my box o' crap when I get home - may have what you need.

Sir_Name 

Pictured is a spent 7sp HG50 from my MTB I used as a test, you can find a new HG50 for around $20. I used an aggressive file to knock back the width of the wide spline, it took a bit of time though wasn't too bad. Dremel would be faster, though no experience or advice there for you. On the HG50 the 6 largest sprockets are a single unit with a separate small sprocket plus spacer and lockring. I kept the 6 largest sprockets together while filing and did not use the spacer, small sprocket or lockring. Once the large spline is filed back to match the freehub body splines, that unit slides onto the freehub and the UG small sprocket is used to tighten things down (two chainwhips will help with removal once needed, though you could find a workaround).

Unfortunately, this project is stalled while I order spokes, so I don't have experience shifting across the HG/UG cassette first-hand yet, but measuring the spacing between the smallest and second smallest sprockets it should work w/o other modification. Others have made this work. If shifting into/out of the smallest sprocket is rough (assuming indexed shifters) the spacing between those two sprockets can be altered as necessary.

Maybe I'll get this hub+cassette into the bike and onto the work stand tonight so I can see how the shifting works out. It won't be under load of course, but should tell me if I'm at least close on the spacing at the small sprocket.

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Or if 16Victor has what you need, then there you go!

miamijim

Grind off the rivets. Buzzing down one cog at a time is probably much easier....

copperfind

Thanks

16Victor

Alas, only a few stray UG cogs, a few HG sets, and a D/A AX rear hub needing a new home

frantik

The older UNIGLIDE freehub body requires a special lock ring but that is the only thing that is specific to Dura Ace. I you get the HYPERGLIDE body version then nothing DA specific is required

Sir_Name 

Very true. The ends of the rivets protrude past the #2 sprocket, so may have to grind those down anyways to get the spacing between the #1 - #2 positions correct for indexed shifting.

Sir_Name 

Okay, I spent far too much time trying to figure out how to upload video here...what you see below is the best I can do for tonight. This HG+UG nonsense does work, confident it will on the road. HG should provide better shifting than UG anyways. Below would be better with sound and higher resolution, but this is it for now...

Didn't we have an "upload video" utility?


Shift levers are (indexed 7sp) SL-7401.
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As an alternative, you could always go to 8sp and just spread the rear triangle. Then you've got HG w/o hassle. But if you already have the wheels/hubs/levers...

Speaking of which, plonz's q in post #5 is important, whatcha got in terms of hub?

...and what's the Centurion BTW? I absolutely loved mine.

trainman999

Copperfind
A HG shell will fit on the guts of a DA 7400 UG freehub. I have assembled one and test fit it to the hub shell at this point I don’t see any reason why this will not work, but I haven’t assembled it all and tested it on a bike yet hopefully some time this week.
You can make the 3 tools to dissemble it for about $6 each and 15 min of your time each
Watch this Things you are going to need
1 a doner HG freehub body
2 a dremmel and cut off discs to make #3
3 a13/16 and a 7/8 socket to make the 4 and 2 prong tools to remove the races. ( I used Sears other brands you better measure.)
4 7/16 square key stock from the hardware store ( file sharp edges slightly to fit in 8 sided removal bolt. A ½ in one could be filed for a more exact fit in a little more time.)
5 a 14 and an 18 gauge machine bushing 5/8 id to space the freehub body from the hub shell (the Ug body has a lip on it where it fits into the hub) you will need to grind the id slightly to fit

miamijim

Nothing in that video covers a Dura Ace UG to HG conversion.... I'm not saying it cant be done as I've never tried.

Besides, why go through all the conversion fuss when you just buy a 126mm 7s HG hub and swap the freehub bodies straight up? (non-DA).