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PostPosted: Sat Jun 02, 2012 12:18 am 
Dirt Disciple

Joined: Thu May 31, 2012 2:13 pm
Posts: 36
Location: Romford
I have a road bike with Dura Ace 7400 (20 years old) and I want to swap the small cassette with something bigger (my older legs cant cope with the high gear ratio!)

I've been looking on ebay, but the sizes dont seem to come up - I want something like 25 (or bigger). Does anyone know if "any" 8 speed block will work just as well if I cant find Dura Ace?

I also want to reduce the whole gear ratio so ideally want to ditch the 53 ring and get a 50 instead. Anyone out there with one they want to sell? (or exchange)

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PostPosted: Sat Jun 02, 2012 12:20 am 
Retro Guru
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Joined: Sat Dec 16, 2006 7:51 am
Posts: 1281
Location: Norfolk
Any 8 speed shimano-compatible cassette will work. I think the maximum cog size for a 7400 rear mech is 26t.

sram one on ebay: http://www.ebay.co.uk/itm/SRAM-PG-850-P ... 231cdd227b


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PostPosted: Sat Jun 02, 2012 12:37 am 
Dirt Disciple

Joined: Thu May 31, 2012 2:13 pm
Posts: 36
Location: Romford
Wow! Thats brilliant! Thanks for that


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PostPosted: Sat Jun 02, 2012 3:15 am 
Old School Grand Master
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Joined: Wed Feb 20, 2008 12:21 pm
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Location: Lost in Translation
otherself wrote:
Any 8 speed shimano-compatible cassette will work.

Not so fast!

There were two different 8-speed Dura-Ace cassette hubs, Uniglide (FH-7402) and Hyperglide (FH-7403). The Uniglide model will only accept a Dura-Ace Uniglide cassette. The Hyperglide model will take any 12-up (or 13-up) Hyperglide-compatible 8-speed (or 9-speed) cassette.

If you have the Uniglide model, and have trouble finding a suitable cassette, you can replace sprockets individually.


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PostPosted: Sat Jun 02, 2012 12:43 pm 
Dirt Disciple

Joined: Thu May 31, 2012 2:13 pm
Posts: 36
Location: Romford
Well, now I think i may have made some assumptions here - it doesnt even look like a shimano block (I dont know if its a cassette type or the old "block" unit) So heres a photo. The only markings I can see are "7-8s MG" and its a 13-21.

I dont have a bike shop local...my local halfords didnt have a clue!

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PostPosted: Sat Jun 02, 2012 1:30 pm 
Gold Trader
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that's definitely not an HG cassette, and I think UG was only available up to 7s (but I might be wrong). are you sure it's not an 8s screw on freewheel?


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PostPosted: Sat Jun 02, 2012 2:42 pm 
Dirt Disciple

Joined: Thu May 31, 2012 2:13 pm
Posts: 36
Location: Romford
No, not sure at all! :? :?

I referred to a "block", meaning a freewheel (sorry, couldn't remember what it was called). But yes, it certainly doesn't look like a cassette.


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PostPosted: Sat Jun 02, 2012 2:46 pm 
Retro Guru

Joined: Wed Nov 02, 2011 11:29 pm
Posts: 554
Location: Sheffield
It looks like the old Shimano system to me: all sprockets splined apart from the smallest which screws on. If so, remove the smallest sprocket with two chain wrenches and the rest will slide off.
I might still have some larger sprockets that were for a 7 speed freewheel. My hunch is that they're the same width as for 8 speed, but I don't know for sure (haven't used a Shimano cassette for a very long time).
Nick


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PostPosted: Sat Jun 02, 2012 3:19 pm 
Retro Guru

Joined: Wed Nov 02, 2011 11:29 pm
Posts: 554
Location: Sheffield
Here you go:
http://velobase.blogspot.co.uk/2010/02/ ... -7400.html

http://velobase.com/ViewComponent.aspx? ... &AbsPos=12

I'm pretty sure that what you have is 7400-8 Uniglide (corrected).

I've got a Dura Ace 7400-7, but i've just checked and it is only 13-23 (I used to think that was big...). The lockring has 7S MA on it. I believe the MA is the date code: Jan 1988. Your MG is July 1988. I still have the box it came in, and it says on the side "Max 24T", so you will probably struggle to find Dura Ace at 25 teeth or above. Note that at this stage, the cassettes were all individual sprockets (not riveted together), so you can indeed change individual sprockets if you can find anything.

I might have some larger 105 level UG sprockets somewhere, but I couldn't see them just now. Let me know if you want me to look.

Note that the SRAM one on ebay has the more modern style small sprocket fixing, which is not the same as on your hub.

Nick


Last edited by nammonk on Sat Jun 02, 2012 11:40 pm, edited 1 time in total.

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PostPosted: Sat Jun 02, 2012 3:31 pm 
Gold Trader
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You learn something everyday on RB! I thought uniglide was only used up to 7s, and all 8s and above was hyperglide. I think I have some 7s UG sprockets that are larger than 23t, but I'll need to check. If I'm not mistaken (again!) then you can also use HG sprockets on a UG-only body, all except the last (smallest) one that must be UG. The difference in thickness between 7 and 8 speed sprockets is minimal, you shold have no trouble at all mixing them up a bit. I'll try and find the sprockets I have later on this afternoon


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