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Two questions regarding Shimano 8/9 speeds compatibility

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Two questions regarding Shimano 8/9 speeds compatibility

Old 11-17-19, 12:59 PM
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Benbenishti81
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Two questions regarding Shimano 8/9 speeds compatibility

Hi all,

I read Sheldon Brown's article about speed compatibility but I'm confused about mixing 8 and 9 speeds. I would really appreciate if you can help me here. Thanks!

So actually I have two questions:

1- Right 9 speed shifter to an 8 speed cassette.

According to Sheldonbrown.com: "a shifter with an extra click also can work, as long as the spacing is OK"

How can I know, for example if I can use a contemporary Sora right 9 speeds shifter with an 8 speed cassette?

What does Sheldon Brown mean by "as long as the spacing is ok"? is it the sprocket spacing or the amount of cable pulled by the shifter itself?

As I understand, it is only the rear durailleur that matters. An 8/9 speed rear durailleur will pull the correct amount of spacing: 4.8 mm for 8 speed and 4.34 mm for 9 speed. Am I right about that?

What would happen if I try to lift the durailleur beyond my largest sprocket? would it be possible or do I risk my chain falling off somehow (I'm not even sure that in my case it has a space to fall between the cassette and the wheel spokes)?

2- my second question deals specifically with an oddity, or so it seems, about Microshift's specific product.

So Microshift offers a rear durailleur, RD-M46L, which is advertised to be compatible with both Shimano's 8 and 9 speeds.

According to Mr Brown, there is a special "trick" with cable rerouting that may work when converting between 8 and 9 speed rear durailleurs. A second option is to add an additional conversion wheel that helps to modify the pulling ratio.

I opened the instruction manual of that product and it doesn't mention anything about spacing modification. Do you know how does this product can be matched with two different spacings?


Thank you
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Old 11-17-19, 01:11 PM
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3alarmer
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...the quantity that you're concerned with in this instance of the word "spacing" refers both to the distance between the rear sprockets and the distance the rear derailleur moves with each click. It cn vary with both the number of speeds, the make of the products (Shimano is different from Campagnolo, for example), and even within the same makers products over the years. For example, Dura Ace shifters and rear derailleurs from Shimano were different from your Sora example for many years early on. But the combination of the DA shifters and derailleur pulled the same distance, so it uses a standard Shimano spaced cluster.

If your using Shimano, 8 and 9 speed clusters are pretty cheap to buy (maybe you might have to shop for the Sunrace versions). They fit on the same freehub, so you're usually better off just going with a cluster that matches the number of speeds for your shifters. Anyway, that's what I do. I can make different stuff work together, but it never seems to work quite as well as just using 8 with 8 and 9 with 9.
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Old 11-17-19, 01:15 PM
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Bill Kapaun
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An 8 speed shifter pulls a bit more cable than the 9 speed.
RDER will work for either SHIFTER. (except some obscure Dura Ace 8 speed?)

IF you have a 9 speed shifter, just get a 9 speed cassette & chain and utilize the extra cog.
9 Speed has a much better variety of cog combinations.

I think you're reading enough various bits of info from Sheldon to confuse yourself.
The extra click is probably with 8 of 9 on 7?
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Old 11-17-19, 06:45 PM
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Even if you could get a 9-speed shifter to shift an 8-speed cassette, you would still have to choose between the extra click sending your derailleur off of the inside (likely destructive) or outside (still annoying) of your cassette. You could block it with the limit screws but still not ideal.
The same Shimano-compatible derailleur can work on an 8- or 9-speed (or 6- or 7-speed for that matter) cassette because the shifter cable pull is speed-specific, not the derailleur ratio. This is not just a property of Microshift.
https://bike.bikegremlin.com/1278/bi...compatibility/
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Old 11-17-19, 07:33 PM
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Those cable pull adapter wheels cost much more than a brand new shifter. A new Shimano shifter is $12, or with dual way release for $25. I think the adapter wheel costs more than $35.

A new Shimano cassette is $16-20. A new kmc chain is $14-18.

So just get a matching 9 speed shifter for 9 speed cassette and 9 speed chain, or an 8 speed shifter for 8 speed cassette and 8 speed chain. The modern Shimano RD for both 8 and 9 speed could be interchangable, but I wonder if the pulley jockey wheels are different thicknesses. 8 and 9 speed chainrings maybe slightly different thicknesses too.
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Old 11-17-19, 10:07 PM
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Originally Posted by tomtomtom123 View Post
Those cable pull adapter wheels cost much more than a brand new shifter. A new Shimano shifter is $12, or with dual way release for $25. I think the adapter wheel costs more than $35.

A new Shimano cassette is $16-20. A new kmc chain is $14-18.

So just get a matching 9 speed shifter for 9 speed cassette and 9 speed chain, or an 8 speed shifter for 8 speed cassette and 8 speed chain. The modern Shimano RD for both 8 and 9 speed could be interchangable, but I wonder if the pulley jockey wheels are different thicknesses. 8 and 9 speed chainrings maybe slightly different thicknesses too.
OP HAS the 9 speed shifter.
It's a no brainer to upgrade to 9 speed at this time. They already have the "expensive" part.
IF it came factory, the bike may also have a 9 speed chain? If that's the case, a 9 speed cassette is less $ than an 8 speed shifter unless going to bottom feeder level.
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Old 11-18-19, 06:08 AM
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To answer your questions, as you posed them.

1 - You can not use an 8 speed cassette with a 9 speed shifter. The amount that the 9 speed shifter will move the rear derailleur and the cassette spacing do not match. You need a 9 speed cassette to go with the shifter that you have. NOTE: You seem to misunderstand the cable pull issue. The shifter is the thing that determines the amount of cable pulled per shift. As you noted, the amounts are different between 8 and 9 speed. The smaller amount of cable pulled by the 9 speed shifter, causes the derailleur to move a smaller amount to match the 9 speed cassette spacing.

2 - There is no trick to making that Microshift(or any Shimano compatible) 8/9 speed rear derailleur work with either 8 or 9 speed shifters. Just hook up the cable in the normal fashion and the shifter will determine the number of cogs it will shift, by the amount of cable pulled.
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Old 11-18-19, 08:22 AM
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OP - Sheldon Brown was talking about putting 8 or 9 cogs with 9 or 10 speed spacing, respectively, on a 7 speed freehub. In that case you would use a 9 or 10 speed shifter for the appropriate spacing. There would be an extra "click" that would be effectively locked out by the high or low limit on the derailleur. So one can fit 8 of the 9 cogs and spacers from a standard nine speed cassette on a 7 speed freehub body. You then have 8 "speeds" with 9 speed spacing. To make shifting work you need to use a 9 speed shifter. If you are using a standard 8 speed cassette with the standard 8 speed spacing of the cogs, a 9 speed shifter will not work. The shimano 7, 8, 9 speed derailleurs are less fussy and will usually work within this spectrum of speeds (like an 8 speed derailleur with 9 speed cassette) as long as the cassette and shifter match.
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Old 11-19-19, 04:06 PM
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Thank you all for the answer. I really appreciate it.
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Old 11-19-19, 04:37 PM
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Look at it this way:

A Shimano 9-speed cassette puts 9 cogs into essentially the same amount of space that an 8-speed cassette puts only 8. Obviously the 9-speed cogs have to be crowded more closely together.
This requires: 1. A shifter with 9 detents that pulls a little less cable pull for each shift. 2. A narrower chain to fit between the more closely spaced cogs.

What that means is your 9-speed shifter doesn't pull enough cable with each shift to match your 8-speed cassette. One way to make your derailleur think your shifter is pulling more cable than it really is would be to attach the cable to the "wrong" side of the attachment screw. That little bit closer to the fulcrum, if you are either lucky or not too particular, may just work. A "Travel Agent" device properly sized for that purpose can also increase the amount of cable pull at the derailleur with each shift but they are kind of an expensive add on for a pieced together bike and are frankly a pain to set up the first time that you do one.

I've monkeyed a lot with mis matched bicycle parts but I've never tried either kluge because, as another poster already mentioned, you already own the expensive part. If it was my bike I'd install a 9-speed cassette and be done with it forever.
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