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Bruce27 03-08-14 03:35 PM

Shimano Deore M591 SGS Rear Derailleur Long 9 SPD Help
Looking for some help from the knowledgeable members on this forum regarding this rear derailleur. This is advertized as 9 speed cog compatible but does anyone know if I can use a basic chain with this? I'm referring to the chains used on 1980's 10-12-18 speed bikes with a 6 speed freewheel, or does it require a more narrow chain?
Thank you

cny-bikeman 03-08-14 03:52 PM

I'm not familiar with the width of the pulley section on that derailleur but why use a 9 speed derailleur at all if you're on a 6 block in the rear? Even if the chain will pass through the pulley assembly the narrower width would make shifting very twitchy, would tend to overshift.

Bruce27 03-08-14 03:58 PM

I'm open for suggestions and options. I have friction shifters with a triple crank in the front, 6 speed in the back, with a chain wrap total of 37.
Prefer not to go the used route. Thanks

cny-bikeman 03-08-14 04:14 PM Shimano 105 long cage also works 39t wrap. RD-5701-GS

Friction can use any derailleur, but as I noted probably best to get one designed for fewer cogs. I'll admit I'm out of the loop a bit on recent equipment but I believe derailleurs designed for 8 speed and below would work

Al1943 03-08-14 04:24 PM

Here are some possibilities:

Retro Grouch 03-08-14 04:24 PM

If it was my bike I'd try it. Rear derailleurs guide the chain from the center so I doubt chain width matters much if any.

cny-bikeman 03-08-14 04:27 PM

That is true - unless the pulley cage is too close to the chain pins, and there might be less play in the pulleys as well. Again, I don't have first hand experience, but I certainly would not buy the 9 speed without assurance it will work. Perhaps ask the merchant you intend to use. If you get assurance and it does not work you can return it. But better to get something more certain to work.

cny-bikeman 03-08-14 04:31 PM


Originally Posted by Al1943 (Post 16560713)

Yep - that looks better than what I suggested - reasonable prices.

peterw_diy 03-08-14 04:49 PM

My medium cage 9s Tiagra had chain rub on its cage in some gears whose chain line isn't bad when I used a 7/8s chain. Works fine with a 9s chain. Some say the rule of thumb is to use a chain designed for the narrowest of your RD, FD, and crankset.

Bill Kapaun 03-08-14 04:55 PM

If you have friction shifters, you have the ability to trim the RDER to keep it centered regarding the chain.
I think you'll be OK, but it'll be just a little "fussier" to prevent chain rub.
You can use 9 speed chain though.

Bruce27 03-08-14 05:03 PM

Thanks all. I called the merchant. According to the fella I spoke with, it would work. So I'm still checking and looking at different RD's but it's good that this is another viable option. Appreciate all the responses. Thanks again.

Bruce27 03-08-14 05:07 PM I see the responses about chain rub. Maybe I should have specifically asked that question.

Bruce27 03-08-14 06:20 PM

I did come across this statement about this RD - 9 speed bicycle derailleur will work on 8 and 7 speed systems. This does imply it should work fine.

lopek77 03-08-14 06:34 PM

I would just try to find older Shimano RD for your setup. I know for sure that 9 speed RD will work just fine with 9, 8, and 7 speeds. I think 6 speeds older chains may be little different and you may or may not have some issues with it. Check . You may find some good info in their documents.
I woould just use older Shimano Tourney for your application. Its around $12-$14 at your LBS...

edwardlui531 03-08-14 06:52 PM

Dont use 7s chain or 9s cassette

Al1943 03-08-14 07:01 PM

I think that a 7-speed RD would stand a better chance of functioning well than a 9-speed. And based on the OP's wrap capacity needs, and possibly big cog size needs, a mountain type RD may be the best choice.

Bruce27 03-08-14 07:19 PM

I'm intent on picking out an RD this weekend. It's interesting... I found the chain width spec's.
My chain varies between 7.3-7.5mm at the post. A 9 speed derailleur may be asking too much. Although, looking at a 0.040"/1.2mm, the span doesn't look like too much.

  • 6 speed - 7.8mm (all brands)
  • 7 speed - 7.3mm (all brands)
  • 8 speed - 7.1mm (all brands)
  • 9 speed - 6.6 to 6.8mm (all brands)

icon_cycles 03-11-14 03:42 PM

You would need a 9 speed chain as they are different from 6/7/8 speed chains.

Gonzo Bob 03-11-14 03:56 PM

It will work. I have a Deore MD510 SGS 9-speed rear derailer and I run 7-speed with a 6/7/8-speed chain. The current 6/7/8-speed chains are narrower than the "old" 6-speed chains. When I first got my 6-speed roadie in 1986, it came with Uniglide chain that was kinda noisy and didn't shift that well so when it wore out, I switched to the narrower Sedisport. The width of that Sedisport is what most 6/7/8-speed chains are these days.

dedhed 03-11-14 05:01 PM

I run a 9 spd 105 rear on my daughter's old Schwinn with 6/7/8 speed chain on six indexed cogs without issue.

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