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8 of 9 ... on 8/9? Help in doing 8 out of 9 speeds on "regular" hub

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8 of 9 ... on 8/9? Help in doing 8 out of 9 speeds on "regular" hub

Old 12-18-18, 06:03 PM
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8 of 9 ... on 8/9? Help in doing 8 out of 9 speeds on "regular" hub

Hello, all.

I am asking for help on something that may be easy, but I have truly searched and I haven't found the answer.

I have a bike that is 130 mm and I want to go from the 1x8 I put together to... 1x8.

A few years ago, while living in Korea, I rode a 1x7 in a 126 mm frame with the chainline fairly centered..I think it was 43.5 mm. That was fine. Now I am on a plain 1x8 and the range of gears is just too much. I can never get the chainline to be tolerable. I can use 7 gears max. If I move my crank to the inside of the double, then the outer cog is unusable (scrapes with second most outer). I move my crank to the outside, then the innermost is nigh unusable (high friction and noisy). Any fiddling in between with spacing doesn't help much or makes both ends miserable.

I think a good idea for my use case is to buy a 9 speed 11-34 and drop the 11t cog and tighten the lockring on the 13t and put a spacer behind the final sprocket (13-15-17-20-23-26-30-34). It would reduce the total spread of my cassette from 35.4 mm (8 speed) to 36.5 mm (9 speed) less 4.34 mm, which is 32.16 mm. This avoids dropping the biggest sprocket (often on spider arms) and also favors bigger crank and bigger gears (better lifespan).

But wait, how do 8 and 9 speed cassettes fit on the same hub? According to <www dot sheldon brown dot com slash cribsheet-spacing dot html>, 8 speed cassettes measure 35.4 mm and 9 speed cassettes measure 36.5 mm. What is up? Do lockrings on 9 speed cassettes not screw down all the way, with every sprocket more outboard by 1.1 mm and cutting into the chain clearance from the last cog and the frame dropouts???? Does the biggest sprocket of the 9 speed (on an arm) extend below the position of the biggest sprocket of the 8 speed cassette (by 1.1 mm)?

What kind of spacer should I use? Do I need 4.34 mm of spacing or 3.34 mm of spacing? (Obviously I may have to round off or file a spacer and use a 1.5 mm spacer with a 2 mm or a 3 mm spacer)

Thank you!


PS: For anyone about to preach the wonders of 11-40, etc....


My height is 6'2" and my legs are disproportionately long -- I am not sure why but I am baffled as to some of the ratios that people run, especially on smaller wheels (e.g., 34/40 or 24/38). I got by most places in (mountainous) Korea on a 46 up front and 14-28 in the back, 46/28 on 700C 19 mm rims with 32 mm tires. Not always fun and I sometimes had to zig-zag up 45-degree inclines, but I could always do it.

Nowadays I ride a loaded heavy bike over some small but steep hills and 44/28 has been plenty for everything. I've tried 44/34 (35 mm tires) and I spin as fast as I can, but I go so slowly that I tip over. I may replace my chainring, perhaps 46t or 48t Wolf Tooth narrow-wide, eventually. Maybe someday the 34t will come in handy...

For now, I think 46 or 48 over 13-34 is plenty for speed in the city and light touring, even steep climbs.
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Old 12-19-18, 09:45 AM
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You climb a 45* incline? In any gear? No wonder you have no problem with "normal" steep hills. That 45* is what we would call a 100% incline. For every 10m of horizontal travel you also go up 10m of elevation. I suspect you have your inclinometer is way off. A typical REALLY steep hill is in the teens of % of grade. The steepest I know of that's also paved approaches 30%. A 100% climb will have cyclists from all over the world checking it out so please share it's location (and make yourself famous).

The cog to cog spacing (often called the center to center) for an 8 speed (Shimano spec) is 4.8mm. For a 9 speed it's 4.34mm. So as the less c-c cogs add up with a 9 speed they total about as wide as an 8 speed is (34.72 VS 33.6mm, so the 9speed is only about 1.1 wider, well within the ability to use the same freehub body and axle length). But if your shifter control is indexed it will want to move the rear der the wrong amount per shift if you mix 8 and 9 speed parts.

You say you have a 1x8 already. Why not just get another 8 cog cassette? Or is there an error in your post, besides the likely one of miss judging how steep hills are? Perhaps one reason no one else has replied is that your post makes no sense as written. Andy
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Old 12-19-18, 10:04 AM
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I re-read OP several times and it still makes about as much sense as this:

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Old 12-19-18, 10:13 AM
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Originally Posted by JaJonKo View Post
I am asking for help
I too find your post kind of hard to follow. Do you want to ride an 8 or 9 gear cassette? If you want to stay with the 8, but change the ratio by using the gears from a 9 that you have to purchase...why not just purchase a new 8 gear cassette instead of trying to manipulate a 9 gear cassette?

And yeah...more info about the steeply graded hills you ride.


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Old 12-19-18, 10:27 AM
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Sheldon is talking about using 8 cogs of a 9 speed cassette on a 7 speed freehub body. 7 speed freehub bodies are narrower than 8 speed freehub bodies. Shimano just made 9 and 10 speed cogs and spacers incrementally thinner (than the receding design) such that the 9 and 10 speed cassettes use the same freehub body as 8 speeds. So yes, you could use 8 cogs from a 9 speed cassette on you current freehub (which I assume is the 8,9, 10 speed spaced freehub), but would need to use an appropriate thickness spacer so the lockring tightens up and the cogs aren't loose. If you take off the 11T small cog, then you need to change both the 13T cog to one designed for the 1st position (outside position) and also a larger lockring. Maybe you could put the spacer between the smallest cog and lockring but I don't know if this will work. My parting warning is if you are not understanding Sheldon's article and the concept of slope (discussed well by Andy above), then this project is just a crap shoot.
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Old 12-19-18, 01:13 PM
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Make sure you are using friction shifters if you are swapping between 8-speed and 9-speed (or 10-speed).

If you go with more speeds, you may need to use a narrower chain, but the narrower chains may also be more flexible, and better able to handle the whole range of gears.

I've found that in some cases shifted from large front ring (outer) to large rear ring (inner), I can torque shift my bike, so some kind of drop-stop ring may be helpful. Make sure the ring is designed for 3/32 chain, rather than 1/8 chain.

You may be able to do some chainline adjustment by getting a longer or shorter bottom bracket spindle.

Rather than leaving off specific cassette cogs, I'd simply adjust your limit screws to block the derailleur from going into the undesired rings.
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Old 12-19-18, 02:32 PM
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Let me preface this with the admission that I have never had a 1x set up. If I understand the OP correctly he is using a double crankset with one chainring removed. So if the remaining chainring is installed at the inner position he is cross chaining in the smallest (outer) cassette cog. If he installs the single chainring at the outer position he is cross chaining in the largest (inner) cassette cog. Isn't the answer to purchase a true single crankset and get the single chainring in the correct position? Or perhaps a BB with a spindle length that puts the outer (or inner) chainring position in the correct chain line?
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Old 12-19-18, 11:06 PM
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I have a longer comment awaiting moderator approval, but for now I will say that you will see stretches in the backcountry and in cities that are like Baldwin Street or Canton Avenue (and similarly undrive-able if covered in snow or ice), but these would be unsurveyed roads or technically alleys. Up until the 2010s most roads and streets in South Korea were unnamed. Addresses would be based on neighborhood, block number and building number. An equivalent would be "USA, New York, New York City, Manhattan, the Upper West Side, 102-49, Daewoo Apartments Building No. 5, Room No. 1312." These are the stretches I would avoid or zig-zag up or walk up. No matter what the gearing is, going up that straight would just end in me tipping over because of the angle and because going at an appreciable speed is impossible. Yes, 45-degree angle was an unwarranted exaggeration. This forum is full of seasoned bicyclists who know and care. There are stretches of 35-degrees for sure and long stretches averaging out 25 degrees.
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