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 Post subject: 7 speed to 8
PostPosted: Mon May 16, 2011 11:12 pm 
Dirt Disciple

Joined: Thu Apr 28, 2011 10:59 pm
Posts: 32
Hi lads
Have a dynatech 755ti with 7 speed block. Is it possible to change this to an 8 or 9 speed easily enough? Has anybody done this?


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 Post subject:
PostPosted: Tue May 17, 2011 10:20 am 
Old School Hero

Joined: Mon Apr 12, 2010 3:05 pm
Posts: 162
If you have a rear wheel with a shimano cassette freehub then that freehub can be removed and changed for a 8 speed freehub. The wheel will likely require a slight re-dish afterwards. Obviously unless you are running it in friction mode you will need 8 sp shifters too

As you are currently 7sp its likely your frame is spaced to 126mm. 8 speed requires 130mm. Most steel frames can be either permanently respaced or you can just squeeze the wheel in there. Not sure about dynatech ti frames, i seem to remember they had steel stays. Worth checking.


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 Post subject:
PostPosted: Tue May 17, 2011 10:29 am 
Retro Guru
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Joined: Fri Sep 04, 2009 9:37 am
Posts: 936
Location: Bristolcestershire
Or, if it's a 7 speed cassette, you can make it ghetto 8 speed by using 8 cogs (with associated spacers) from a 9 speed cassette. AASHTA, see here:

http://www.sheldonbrown.com/k7.html#897


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 Post subject:
PostPosted: Tue May 17, 2011 11:12 am 
Old School Hero

Joined: Mon Apr 12, 2010 3:05 pm
Posts: 162
djoptix wrote:
Or, if it's a 7 speed cassette, you can make it ghetto 8 speed by using 8 cogs (with associated spacers) from a 9 speed cassette. AASHTA, see here:

http://www.sheldonbrown.com/k7.html#897


Yeh, i didnt mention that as a possibly slightly harder option (or one a LBS is not likely to undertake for you). You'd also need 9 speed levers for indexing and probably a 9 speed narrow chain. But would be cool to do :D


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 Post subject:
PostPosted: Tue May 17, 2011 11:43 am 
Retro Guru
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Joined: Fri Sep 04, 2009 9:37 am
Posts: 936
Location: Bristolcestershire
Yes, you would need a narrow chain, if you're willing to forego indexing then there are more lever options.


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 Post subject:
PostPosted: Tue May 17, 2011 11:44 am 
Dirt Disciple

Joined: Thu Apr 28, 2011 10:59 pm
Posts: 32
Thanks for the great advice..perhaps I'll leave it at 7 and replace the block chain shifters and rear derallier.. Is it easy enough to pick up the 7speed stuff or hassle..? Frame and wheels are great. Bars stem saddle and post fine... Still never cheap to go retro is it??!!


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 Post subject:
PostPosted: Tue May 17, 2011 4:38 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8209
Location: New Forest, UK
Personally I'd stick with 7 speed. I still run it on my tourer. All the parts are available if you look around, and bar-end levers / indexed downtube levers are simple and mine are still going strong after 50,000 miles. STi-type clicky stuff simply isn't that robust.


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 Post subject:
PostPosted: Wed May 18, 2011 9:23 am 
Retro Guru
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Joined: Fri Sep 04, 2009 9:37 am
Posts: 936
Location: Bristolcestershire
Depends if you think you need more speeds - ie you need a bigger or a smaller cog, or there are jumps in ratios that you'd like to eliminate. I still have 12 speeds on my road bike with 42/52 Biopace at the front! But on a tourer, I would definitely need more choice. So it depends if your current setup is giving you what you need, really.


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