"Manual shifting" single speed w/ freewheel

[cribbit]

My commute is slightly downhill to work, slightly uphill back which is great but has made settling on a gear ratio tricky. Flip flop hubs are nice but the amount of work to switch gears is too high.

I see dual speed freewheels from White Industries and others, and some 3-5 speed from for similar uses or vintage stuff. Clearly I'm not the first person with this issue.

I have three questions that have been proving annoying to research.

1. What's the largest tooth jump I can do without needing to re-pull my wheel for chain tension? I see things like 16 & 20t freewheels but that seems like I'd definitely need to adjust my chain tension if I switched gears. A corollary, what's the largest tooth gap that can use the same chain length, only adjusting chain tension when changing cog?

2. Single speed chains are thick. Multi speed gears are close together. Should I consider going for an 8 or 9 speed chain? White Industries' page about their freewheels seem to indicate this is going to be case by case.

3. Ignoring vintage/oddball stuff the threading on a ss and freewheel should be the same. I'm struggling to find good examples of thread length for ss vs freewheel rear wheels. Am I likely to run into issues trying to put a 5 speed freewheel onto a single speed wheel? I'm guessing the distance from base of freewheel to dropout is a little different.

[HTupolev]

Originally Posted by cribbit

1. What's the largest tooth jump I can do without needing to re-pull my wheel for chain tension?

Zero. If you're able to derail the chain between cogs while riding single-speed, then it's not adequately tensioned.

A corollary, what's the largest tooth gap that can use the same chain length, only adjusting chain tension when changing cog?

Depends on how long the track ends or horizontal dropouts on the bike are.

The amount of fore-aft wheel motion provided by a dropout generally doesn't give you very much wrap, though. Moving the wheel backwards by an inch only takes up four teeth of chain!

People who build single-speeds with a "wide" gearing range sometimes facilitate it by using multiple chainrings. For instance, a 46-17 and a 42-21 use about the same amount of chain.

2. Single speed chains are thick. Multi speed gears are close together. Should I consider going for an 8 or 9 speed chain?

Yes. If you're going to use a multi-speed cluster, you'll need to use a 3/32" road chain, not a wider 1/8" chain.

Although single-speed drivetrains usually use 1/8" chains, there's nothing wrong with 3/32" chains in single-speed or similar applications.

Am I likely to run into issues trying to put a 5 speed freewheel onto a single speed wheel? I'm guessing the distance from base of freewheel to dropout is a little different.

Yes. Sometime fixed/SS wheels can be re-dished and re-spaced so that a 5-speed freewheel can fit on one side, sometimes they can't. Vintage 5-speed hubs were 120mm wide, the same as modern fixed/SS hubs...

Really though, if you want to be able to shift the chain across a 5-speed freewheel without dismounting the bike, what you're looking for is a derailleur.

[jtbadge]

I used to have an SSCX bike that I set up multiple ratios on. It had 130mm spaced track ends, so I used a standard 10 speed road wheel, a spacer kit, and two single speed cogs, sized a couple of teeth apart, immediately next to each other, and ran a 9 speed chain. There was enough room in the track end to account for the difference in chain length in a 2-3 tooth gap, so it was pretty easy to regear for racing or riding around, depending on terrain, but as the previous poster said, you'll definitely need to re-tension the chain.

Alternatively, if you had a geared bike with a derailleur hanger, you could use a tensioner and then you'd just have to manually move the chain between the cogs.

[cribbit]

Originally Posted by HTupolev

Really though, if you want to be able to shift the chain across a 5-speed freewheel without dismounting the bike, what you're looking for is a derailleur.

Not without dismounting, just doing it before a ride.

Thanks for the help though!

[Davist]

Originally Posted by HTupolev

Yes. If you're going to use a multi-speed cluster, you'll need to use a 3/32" road chain, not a wider 1/8" chain.

Although single-speed drivetrains usually use 1/8" chains, there's nothing wrong with 3/32" chains in single-speed or similar applications.

Be careful, you may need to replace one/both the chainwheel and the freewheel, this happened to me in BMX (didn't learn) and later on a track bike.. Both chainwheels and freewheels come in 1/8" and 3/32" pitch

[cribbit]

Originally Posted by Davist

Be careful, you may need to replace one/both the chainwheel and the freewheel, this happened to me in BMX (didn't learn) and later on a track bike.. Both chainwheels and freewheels come in 1/8" and 3/32" pitch

Well aware of that one actually! I once tried to convert a Peugeot to 1x and the crank I selected had teeth that were too wide to fit into the narrow chain. Took me embarrassingly long (and multiple bottom bracket rebuilds) to figure it out.

[cribbit]

Originally Posted by jtbadge

Alternatively, if you had a geared bike with a derailleur hanger, you could use a tensioner and then you'd just have to manually move the chain between the cogs.

Derailleurs hurt my A E S T H E T I C

[donevwil]

Sturmey S3X ?

[monkeybanana86]

Yes, Sturmey Archer and it will be nice and clean.

[AngryScientist]

as mentioned, to change ear ratios manually, you will need to reset chain tension, which is no big deal if you are within the adjustment range of the dropouts. the alternative is the SA option mentioned above. surly makes the "dingle cog" just for this application by the way.

i dont know how much downhill and uphill you're talking about, but part of the fun and challenge of riding SS/FG is the selection of the single gear ratio that takes you wherever you need to go.

[Look585]

http://www.whiteind.com/double-double/

Get a two speed freewheel and run a double crank with the same tooth difference.

16/18t freewheel with a 42/40t chainring setup would result in the same chain length.

The "outer" 42/16 would generate ~71" gear, while the "inner" 40/18 would generate ~60" gear.

With any length of horizontal dropouts/trackends, you may be able to push this a couple teeth either way.

[sg8357]

Look for Vernon Blake, he invented the "floating chain system"
2 or 3 rings in front, shifted without the use of a tensioner
or derailer. He used a pulley near the drop out to keep the chain
on the rear cog, the rest of lower run was slack.