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7 speed to 9 speed questions.

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7 speed to 9 speed questions.

Old 01-12-21, 08:49 PM
  #1  
Lbxpdx
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7 speed to 9 speed questions.

My 1991 Trek 990 project has been on the back burner, but I was wondering about going to a 9 speed cassette. The only reason why I知 considering it is I知 going with mustache bars with bar end shifters, micro shift BS-T09 which are both index and friction. I dig index and I found an SRAM cassette and new chain for $35. The bike currently has the stock Deore XT drivetrain.
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Old 01-12-21, 09:36 PM
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Your Free Hub body is too short for more than 7 unless you do this-
https://www.sheldonbrown.com/k7.html#897
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Old 01-12-21, 09:42 PM
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You will need a new rear wheel or, at a minimum, a new 8/9/10-speed freehub body as a 9-speed cassette won't fit on a 7-speed body. Also, measure your rear dropout spacing. It may be 126 mm (7-speed spacing) or 130 mm or 135 mm which is fine. It may also be 128 mm which will take either a 7-speed or 8/9/10-speed hub. Get a suitable rear wheel.

There is a work around: "8 of 9 on a 7", i.e. remove one cog, usually the largest, from a 9-speed cassette and the remaining 8 will fit on a 7-speed freehub body. You will still need the 9-speed shifter and it will have an extra unneeded click.

Edit: Ahhh, Bill typed faster than I did but we both gave the same advice.
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Old 01-12-21, 09:46 PM
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Will you use the 9 gears? Some people get more and more because they are available. Those riding a lot of hills might actually use them. For others, some gears will never get used.

I have just gone from 9 to 7 gears. I did it primarily because I would have travelled to the city to get 9, and paid more. I think the sprockets on the 7 speed are a little thicker, and should last a little longer. I don't even need all the gears on the 7 speed.
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Old 01-13-21, 07:50 AM
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Here's another plug for 8-of-9-on-7 approach. I recently upgraded my Trek 750 from an 11-28 7-speed to a 12-32 8-speed by dropping the 36t sprocket of a 12-36 9-speed cassette. I like the wheels and the freehub cannot be exchanged because it's on a Shimano silent clutch roller hub (which uses a completely different freewheel attachment style, and they don't make 8/9/10 freehubs for this hub type). I have a Microshift 9-speed thumb shifter on it (indexed) and it shifts through the 8 speeds beautifully. You'll need a 9-speed chain of course.
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Old 01-13-21, 04:13 PM
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The drop outs on a 1991 Trek 990 will be 135mm.

I've done the freehub swap on a Deore DX wheel and it worked fine, but I had a spare wheel with a similar freehubs to do it. It is easier to just find a slightly newer wheelset, or do the 8-of-9-on-7 approach.
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Old 01-13-21, 06:23 PM
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Don't listen to the haters (well listen to some of what they are saying it is good advice) but 9 speed is great. Love all my 9s which is 3 of my bikes. Especially on the 1x side the 1x7 didn't do it for me but 1x9 works like a charm.
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Old 01-13-21, 08:54 PM
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Originally Posted by hokiefyd View Post
Here's another plug for 8-of-9-on-7 approach. I recently upgraded my Trek 750 from an 11-28 7-speed to a 12-32 8-speed by dropping the 36t sprocket of a 12-36 9-speed cassette. I like the wheels and the freehub cannot be exchanged because it's on a Shimano silent clutch roller hub (which uses a completely different freewheel attachment style, and they don't make 8/9/10 freehubs for this hub type). I have a Microshift 9-speed thumb shifter on it (indexed) and it shifts through the 8 speeds beautifully. You'll need a 9-speed chain of course.
I like the idea of not dealing with a useless for many of us, 11T cog.
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Old 01-14-21, 05:06 AM
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Originally Posted by alo View Post
Will you use the 9 gears? Some people get more and more because they are available. Those riding a lot of hills might actually use them. For others, some gears will never get used.

I have just gone from 9 to 7 gears. I did it primarily because I would have travelled to the city to get 9, and paid more. I think the sprockets on the 7 speed are a little thicker, and should last a little longer. I don't even need all the gears on the 7 speed.
I've you don't use all gears the problem may not be "too many gears" but "incorrect gear range" instead.

You can have an 11-32 9sp casette, and 11-32 11sp cassette. Both of them have the same range, but the 11sp has less gaps between gears which lets you pedal at a better cadence in most situations.
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Old 01-14-21, 08:56 AM
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I致e read about someone who removed the innermost spacer of a 9-spd cassette, dished the biggest sprocket and got it all to fit on a 7-spd f/h body.
I壇 be concerned about the derailer snagging a spoke, but it sounds mechanically doable.
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Old 01-14-21, 11:37 AM
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Originally Posted by Bill Kapaun View Post
I like the idea of not dealing with a useless for many of us, 11T cog.
+1. Unfortunately finding 10 or 11-speed cassettes even starting with a 12T cog is difficult these days. My former favorites were Campy's 13x29 10-speed and Shimano's 12x27 10-speed. Both had the extremely useful 16T cog
which is the first to disappear when an 11T cog is added. I can still find a Shimano 12x30 10-speed cassette but they are getting rare too.
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Old 01-14-21, 12:19 PM
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Here is my take...

What is the condition of your current wheelset?

If your wheelset has 30 years of use and worn out so that you will have to replace it soon anyway, get a new wheelset with an 8-10 speed freehub body and keep the project moving. If you have an excellent wheelset with little use, you might want to consider swapping out the freehub body for one that will accept 8-10 speed cassettes.

I have found that it is becoming increasingly tougher to get a "good" rim brake 26" wheelset. I'm not talking some generic co-op set, or maybe a get lucky with a higher end one sitting around, but an older XT/Mavic, or equivalent, that has little to no use. I'm not saying you can't find them, but they are getting pretty pricey. I'm thinking around $200 for something decent. I'm sure there will be stories of paying $50 for some XTR set, but unless you have connections or get lucky, new 26" rim brake wheels are not very high on most mfg's list of things to do. Buying used may be just getting someone else's problem. I bought a new Rhyno LIte (which isn't really light) and T610 hub wheelset just to have around in case I am pressed to need something. It cost a little less than $200 shipped.

If you swap out the freehub body there are a couple of basics that have to do with a shallow flange or a deep flange. I swapped out my 7 speed on my DX hub with an NOS Ultegra 6402 8 speed freehub body (will accept 9 speed) and an NOS axle for DS cone for around $60. Here is a pic of the different flanges.



John

Last edited by 70sSanO; 01-14-21 at 12:27 PM.
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