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Buying a new rear derailleur
#1
Hi,
I have a vintage touring bike made by Olmo, Italy, in 1987. It has a triple by gipiemme in the front (32-42-52) and a six cog cassette behind (34-14). I guess the capacity should be 40. But any advice about what would be a good one to buy? And a middling one too (I am not sure I'll have the money for a really good one) if you know of one.
Thanks!!
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#2
You need what is now call a mountain bike or MTB rear derailleur - back in the day, it was called a touring derailleur.

[broken_link]

What is your budget? "middling" is not specific enough to make a recommendation. Any of the current Shimano derailleurs, even the cheapest ones work well. Escalating price brings mass reduction, and greater fragility, with minimal improvement in shifting smoothness and speed - many will argue this point, but they are ones who spent the money......
Nigel
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#3
Actually there is quite some improvement from the very low level stuff to the mid range (on road bikes: 105) when looking at the group as a whole. However, once you are past the mid range you might be able to measure stuff in the lab, on the bike you cannot tell. There was a blind test in the German cycling magazine "Tour Magazin" a while ago. They put the bikes on trainers in dark rooms and had the testers describe the performance. While they could tell apart the brands (different levers) they could not really make out much difference between highest and and mid range stuff. I think they tested the 105, Ultegra, DuraAce and equivalents from SRAM and Campagnolo.
My personal experience is that (at least the shifters) that are lower than Tiagra are... not good. And that is putting it in a nice way: they feel wobbly and unsafe.
Also the low end stuff is not durable. At least five years ago (when I last looked in the tech docs of ... dunno... Alivio?) Shimano warned against off road use, clearly stating that the stuff was not designed for this.

My general way of choosing stuff: Getting last years mid-to-high-range stuff for half the price.
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#4
What is your budget? "middling" is not specific enough to make a recommendation.
===
Thank you guys! My middling is 50 dollars I can double it, if need be. I am wondering -- and sorry for the naïvité --, my bike has the old fashioned kind of down-tube friction shifters, attached to the oblique tube of the frame. Will I have no problem with the kind of rear derailleur you suggest?

After reading yours, I was thinking of a shimano deore LX RD T660. Or Deore M591 SGS Long Cage RD. Do you think they would work? They seem to be for a 9 speed cassette but mine is only six. Would there be problems there?
Thank you for your help
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#5
Check out this info .

http://sheldonbrown.com/speeds.html

http://www.amazon.com/Shimano-6-Speed-RD-TY18-Derailleur-Attachment/dp/B003EQ71R2
Never Give Up!!!
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#6
The problem with a 9 speed derailleur is that it will require a 9 speed chain, which may not be happy with the cog spacing of your six speed.

The other question you need to answer is how is your current derailleur attached to the bike; does it have a open clip like this one:
http://www.amazon.com/Shimano-Tourney-TX35-Derailleur-Speed/dp/B003ZMH69S/

or does the rear drop out have a mount, like this frame:
http://www.amazon.com/gp/product/images/B004S0M858/
for mounting a derailleur like this one:
http://www.amazon.com/Shimano-Tourney-TX75-Speed-Derailleur/dp/B003ZM9REA/

Unless you are willing to spend $$$$ to change your ride to 8 or 9 speed; stick with the Tourney derailleurs - they are reliable and smooth shifting. I have over 5K miles on one on my World Tourist.
Nigel
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#7
Hm. I know that 7 speed chains work in 9 speed dérailleurs. How much wider is a 6 speed chain? Surely not too much (I guess...).
Yeah, +1 on the mounting of the RD problem. Do keep this in mind when deciding for a RD.

And upgrading to 8 or 9 speed is expensive, even when getting last year's stuff. Shifters + crank set (though my old one did work with 9 speeds) + cassette + chain + FD and RD. In fact this is almost the full group and will set you back a couple of hundred bucks.
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#8
THANK YOU all for your help. The frame has a dedicated mount for the RD so I went for a Shimano Tourney TX75 6/7 speed. The cage seems really short. But it is pretty cheap. I shall let you know how it goes and how long it lasts. I guess the six speed chain and the friction down tube shifters should work with that. That should avoid replacing all the components -- at least for the moment. I mounted RD's before but never this brand and model. Tthe original one on the bike, back in the day when I was in Italy, was a campagnolo Mod. 980 but the bike was pretty much abandoned in a basement for close to 20 years.
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#9
(04-12-2012, 07:33 AM)Joe_W Wrote:  Hm. I know that 7 speed chains work in 9 speed dérailleurs. ........

Not ALWAYS !!! I had a KMC 7 speed chain (new) that made awful noise going thru a Shimano RD2200 8 speed derailleur; the heads of the pins were rubbing on the inside of the derailleur's frame. Switched to a SRAM 8 speed PC 830 - no noise.
Nigel
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#10
Thanks, so I was lucky (this time). It is (I believe) a mid-range Shimano one for 6-8 speeds, so this probably explains why it works.

(There'll be upgrade time soon, though. The chain rings (riveted to the crank set, this is a Frankenbike) are pretty worn, so I might as well get new shifters (on top of the consumables chain and cassette and the crank set). The shifters are from the time when Deore was a high-ish end group, so probably 20+ years old and springs / ratchet parts are starting to fail...)
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