Dropout question:

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spakbros
Participant
#

How horizontal does a dropout need to be to be to convert to singlespeed without installing a chain tensioner? My trusty old Rockhopper looks to be around 45 deg. Can I make this work?

Thanks, Ryan


rachel_ding
Participant
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Sheldon Brown goes over this:

http://www.sheldonbrown.com/singlespeed.html

Also, I’ve never tried it, so I don’t know if any of the methods he described, such as filing the drops to make them longer, work well.


spakbros
Participant
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thanx Rachel, should have just automatically gone there


spakbros
Participant
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Read what Sheldon has to say. Looked at the diagram. Still don’t really understand at what point the angle of a horizontal drop becomes a vertical. AARGH


alankhg
Participant
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The issue isn’t whether the dropout is horizontal or vertical, it’s whether the distance from the center of the BB axle to the center of the hub axle changes sufficiently to allow you to tension a chain. Tie a piece of string around the BB axle and see if you need different lengths of string to reach different parts of the middle of the dropout. Or something like that.


brian j
Participant
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“Horizontal” dropouts are never exactly horizontal, primarily because the angle allows you to actually remove the wheel from the frame. If the dropout was completely horizontal, the chainstays would need to be really, really long to give you the space you need. The angle also allows you to adjust the chain tension without having to futz with brake pad position.

Fork ends, since they face backwards, can be truly horizontal because you can just drop the chain off the front ring and pull the wheel out. Note, however, that some folks, most notably Rivendell, have produced frames with angled fork ends to allow brake pad position to remain static over chain length changes.


eMcK
Participant
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I read the same thing about Rivendels. I was riding a Quickbeam around last year for a bit, ended up wanting to flip the rear wheel to the larger cog on the other side.

Brake pads didn’t line up. Bummer. False advertising? User error? Wishful thinking? Whatever, had my tools out anyway, another 2 minutes with a 5mm allen got me rolling again.

Good luck with the conversion. I have an old KHS road frame with similar dropouts. I managed to set it up fixed with a bit of filing and a half link. Unfortunately once the chain stretched a bit it was too slack to ride. If you are not going to set it u fixed, just use a tensioner or old derailleur to take up the slack in the chain.


dmg
Participant
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The most foolproof way is to use a White Industries ENO hub, which is designed to rotate on the axle and provide sufficient adjustment thataway. They are a bit expensive though (although probably less than getting new dropouts put on by a shop), but will last forever and can be moved to a new bike.

Chain tensioners aren’t a bad way to go, though. Definitely the cheapest option if the bike is just going to be a single speed and you can’t get decent tension with the dropouts.


pratt
Participant
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I have a used White Industries ENO hub laced up and available for purchase. I’ll check it out and let you know what cog is installed and what rim it’s on.

My guess is it’s on a 18 tooth white industries cog and some sort of mavic cross country disc rim like a 317 or something.

It is in good shape.

If you are interested.


mark
Participant
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once upon a time i found a website that you would put in the chainstay lenth and gear ratio you want and it would tell you what gears to put on your single speed to get that precise chain length… it would sometimes get goofy but i assume it always worked


TheLivingTed
Participant
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i’m a dropout.


erok
Keymaster
#

turn on, tune in…


varun5
Participant
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mark – this is the site you are talking about:

http://eehouse.org/fixin/fixmeup.php

also, forward components makes this for use with a new style shimano hollowtech II/sram gxp crankset/fsa mega-exo:

http://forwardcomponents.blogspot.com/

I’ve been thinking about getting one of these. Its not as tested and proven as the White Industries ENO hub, but is about the same price new and might be worth it if you already have that type crankset sitting around or can get one for cheap (you can for sure) as opposed to building up a wheel. As for durability – I don’t know. just thought i’d bring this into our collective consciousness.

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