amedias

I love my Monocogs !
I went through a phase for about 5-6 years where I didn't own a bike with gears, just several with one (MTB and Road and commuter) and did ride them anywhere and everywhere.

These days I ride about 50/50 geared to single.

Yes, very much so, it's one of the best things about them :-)

Tooth counts and ratio is totally dependant on personal fitness, wheel size, intended use and terrain, what works for me won't necessarily work for you so I tend to steer clear of such discussions other than to say 'experiment and work out what you like'

What I will say is odd toothed chainrings and sprockets (and non-divisible combos) are better for longevity, as are bigger rings/sprockets (at the same ratio), and bigger is also better for fine-tuning on short dropouts, so I always try to go for the biggest appropriate tooth count that gets the ratio I want, and odd counts if possible (not always possible!)

rustystrings61 

I'll add to what Gresp15c said - first question, what sort of riding do you envision doing, exactly? Hinted at by Gresp15c, but I will bluntly go there, is - do NOT feel compelled to set your fixed-gear conversion up in the currently fashionable style. I have three fixed-gear bikes, and all of them have dropped bars and full brake sets, because I regard them as road bikes with a fixed-gear drivetrain. I like having two brake lever hoods to hang onto while climbing, I like having frame geometry that balances comfort with performance, and I like being able to use all the classical "body English" of using different positions on the bike that dropped bars encourage.

The quick answer for conversion would be a vintage road frame with long "horizontal" dropouts. I put that in quotes because you want the classical forward opening road dropouts that came into use in the 30s or so for lightweights, because the slots for the rear axle run perpendicular to the chainstay and therefore the brake bridge, giving you the most options for different cog sizes working with the same brake pad settings with the same length chain. The marginal difference in bottom bracket height caused by running the rear wheel at the back of the dropout slot is minimal for road use, and the greater flexibility of cog choices could be helpful, depending on what sort of ride experience you want. My lone purpose-built fixed-gear has true rear-opening track ends, and I deeply regret not specifying that what I really wanted was long forward opening ends. The track ends are a nuisance when it is time to remove the wheel, and they greatly limit the difference in cog sizes I can use. I think I can safely run about a 3-tooth difference, i.e., a 16T fixed cog and a 17/19T Dos Eno freewheel, but no more than that.

If you like narrow section zippy-feeling tires, tire clearances aren't as big a deal. If you're going the total minimalist route, some sort of old crit bike might be fun, or something with really upright angles and close clearances.

I'm heading towards geezerhood, though, and for conversions, I like French and English bikes built with nice light butted alloy steel like Reynolds 531, though I wouldn't turn my nose up at Vitus or Durifort or even the nice Italian steel stuff. Ideally I like frames with a rear triangle spacing of 120 mm simply because that's the current de facto standard for fixed-gear hubs, though I am currently running a bike widened to 126 with a couple of spacers added to widen the over lock nut distance to match. I like clearance for at least 28 mm tires with fenders, but 32 is better, and one of my bikes currently has 35s and could take fenders as well.

My oldest current conversion is a 1971 Gitane Tour de France; before the Francophobes get rolling, it came with a good Stronglight headset (which is kinda redundant), Nitto stems play nicely with French 22.0 mm steerers, and I fitted Phil Wood French thread mounting rings and a used Phil BB, and that settles the French dimensions/thread issues. It's nice and nimble and zippy, the long Simplex rear dropouts give me options for cog sizes, and for many years it has been by beater/vacation/pre-work Dawn Patrol riding bike. If it could take something bigger than a 28 mm tire with more clearance for fenders it would be an awesome fixed-gear brevet bike. Contra to Gresp15c's note, I am running long obsolete Stronglight cranks with their proprietary 122 mm bcd chainrings, but between the 45T currently on the bike and 46T I have squirreled away and my age, I think I can make it - and if not, there's always French eBay!

My most recently built fixed-gear conversion is a '73 Raleigh Competition Mk. II. which has outrageous gobs of tire clearance. It's currently running 35 mm Continental Cyclocross Speed tires and there's plenty of room for mudguards. The Raleigh Comps built c.1971-76 with the rapid taper chainstays are very flexible bikes to build up in all sorts of formats. This one currently has a 17/19T Surly Dingle cog on the back and 42/44T chainrings up front, which lets me run a 70-in fixed-gear on pavement and a 60-in gear on gravel roads. Someday I'll spend the money for a 20/22T White Industries Dos Eno freewheel for a near 60-in freewheel gear and a 52 or so for gentle singletrack. The long Huret "horizontal" dropouts running perpendicular to the brake bridge's line, generous clearances and long wheelbase allow that.

The conversion I am pondering is a '73 Raleigh Gran Sport, which has identical frame geometry but slightly less clearance in the back. I think I'm limited to 32 mm tires with fenders, which is fine. Both of the Raleighs have front end geometry that would lend itself to front mini racks and handlebar bags.

The purpose-built Mercian fixed-gear reflects my thinking in 2002 when I ordered it. So long as I stick with 28 mm tires and mudguards and am content to limit my baggage to a (capacious!) Carradice saddlebag, it's lovely. But there are days I wish it had forward opening dropouts, more tire clearance and low-trail front geometry.

Moisture

How do You find tire sizes tend to affect gearing?

We all know that 26" rim will help with acceleration a little bit, maybe at the expense of top speed. But I find that top speed seems to be held more effectively with the 26er if anything unless we're talking about an absurdly high top speed.

As for 700c, i was never a fan until trying them on my big norco frame which seemed to be particularly well suited in dimensions to the characteristics of a bigger wheel. You can easily compensate for any drawbacks in acceleration with gearing while having a nice top speed and that smoother ride quality. Plus, the bike seems to be well balanced between steering precision and fluidity/stability.

Good question. My idea is to have it set up as a secondary bike for when I dont plan for any serious hill climbing. Lol. Just a speedy, time trial type road or gravel bike for maximizing efficiency and going even faster.

rustystrings61 

Perhaps something like this?



Running 700 x 35 tires on Sun CR-18s with 2 chainrings and a Surly Dingle for 70-in pavement, 60-in gravel - something like this?

mack_turtle

1. that's what I do. I own two bikes and zero shifting bits.
2. it's not about efficiency but more a matter of just choosing a simpler bike. it's not the best tool for the job most of the time, but it gets the job done in a different way.

Gresp15C

Here's my vanity picture.

It's not a fixie, but you get the idea. One of the family bikes has a flip flop wheel, and we've committed to taking turns with it this summer, to see what it's like, but for now I'm not even convinced that I can ride fixed safely. Meanwhile, this bike sports a rear coaster brake and front hand brake. The frame was 15 bucks, and the rest is from my parts bin. It's 28-630 smooth tires, gearing is 65 GI.

It's my favorite bike, and I ride it everywhere: Commuting, shopping, going to the opera, weekend leisure rides on pavement and rail-trails, etc. Realistically I'm not a particularly athletic rider (65 GI should be a clue), and things get pretty hilly to the west of here (so called "driftless region"), so I prefer a geared bike for more than maybe 30 miles. But sometimes I get out of town and just keep riding.

I prefer to have gears if I'm riding with other people. I've described single speed as "always being in the wrong gear." That's OK if you can set your own pace, but matching speed with other cyclists gets old without gears.

More efficient? Probably not. First of all, a lot of my power is sacrificed by riding with an upright posture. Second, I have no way of measuring it. Third, whatever I gain from a simple drivetrain, I give up by always being in the wrong gear.

I work with a lot of engineers, and they tend to be an analytical and skeptical bunch. They've asked me why I ride such a primitive bike. I don't have a good answer. At the end of the day you might find that it doesn't make sense in terms of things like efficiency, but that you ride it anyway. Then you will be enlightened.

rustystrings61 

That's actually THE gear the old British guys writing c.1930-1960 recommended for a gentleman's bike with one freewheeling gear, and it works out pretty well with the old theory that your crank length should be approximately 10 percent of your gear, i.e., a 6.75-in crank for use with a 67-in gear, a 6.5-in crank for a 65-in gear, etc. H.H. England, editor of Cycling was very direct about it, and I think Reginald Shaw of the old CTC also recommended it. F.J. Camm in his 1936 book indirectly pointed to that gear as well.

Gresp15C

Well there you have it. Of course I should be riding a genteman's bike.

Moisture

Oh absolutely. That is a beautiful bike. As long as it's around 64cm, I would gladly.

I'm fine with drop bars, but never with that sort of stem, irrespective of whether flat or drop bars are attached to it.



If there wasn't a steady stream of wind slowing me down 96% of the time I am riding, a properly geared fixie would work out fantastic for me needs.

As long as you are in sufficient physical shape and use the correct ratio according to the amount of hills you will encounter, it's basically "always in the right gear."

That bike is not exactly what I would call overly upright in terms of fit.. your seat is higher than your bars and the bars are not exactly ergonomic. There's nothing wrong with being a bit more upright on a properly set up bike. (seat level or slightly lower than the bars)

Moisture

I'm currently on the fence with converting to singlespeed. Can't decide if I want to give up my gears or not..

PIFFLE

Go for it, brother, you have nothing to lose but your chains derailleurs

mack_turtle

if the bike has a derailer hanger and you have shifters and parts to make the bike geared, go for it. play around with some cog/ chainring combinations. if you give it an honest try ad you hate it, put your shifters and stuff back on. it's not like converting a geared bike to SS means you're committed to that forever. you can buy a different bike or keep changing the parts around. bikes are amazingly modular (most are, at least). aside from the money, which is probably not a whole lot, what have you got to loose?

Speedway2

Everyone should have at least one SS in their stable......go for it!

ofajen

If you have the self-discipline, you can ride a geared bike in a single speed and see how you like it. First go around a few years ago, I just tried that for one ride and decided it would be ok. I rode only SS for the better part of a year. I’m not really sure why I put the rear clusters back on.

This year I spent all spring riding the MTB with a 1x7 but pretty much only using 42/21 on hills and 42/16 otherwise. I rode the road bike switching the FD from 48/19 to 39/19. In the summer I started riding just 42/16 and 48/19 respectively and by August when I actually made the change to remove the gearing, I was already used to riding that way. The main change was not having a derailleur clog up with trail dust and grit.

Otto

Dylansbob 

Different tire/wheel sizes makes a gear combination add up to different numbers on different bikes. Before it got stolen, I had a 48/15 on a 20" wheeled bike that's about the same as 700c with a 36/15. It works out to be about ~63 gear inches. I've been mostly running that on fixed gears for the last 15yrs. It's not the fastest, but it's always been a good spot for me to quickly get up to speed and navigate tight turns whether on- or off-road. My old commute was 15m each way with ~900ft of climbing. I could spin out ~200rpm going downhill, but still get to the top of those hills without having to *strain* to get the cranks around.

Moisture

It would probably make more sense to have a spread of ratios to choose from in that case.

Foxonabike

I have 4 bikes, 3 are single speed.

bykemike 

I just picked up my first fixie, but I am going to add a freewheel before I take it out at all. For the month before I did this I did what Ofajen said a few posts back, I rode my Scott hardtail w/Sram 1 x11 in one gear on a 9 mile dirt trail everytime I was on it.

It gave me an idea of what I would be seeing with a single speed. No issues at all, a lot more standing than I usually do.

BTW I picked up an almost new Wabi Lightning SE for a good price and am doing the modes I want in my shop this week. I'll post a picture sometime today

veganbikes

Don't worry about the freewheel. Keep it fixed and enjoy it. I swapped my Langster to fixed as soon as I got it and didn't go freewheel till much much later because I had another fixed bike and wanted to try a freewheel after many years.

If you need to fixie your bike you might bring it to a shop so they can get it repaired so you don't get a brokie.

pbass

Have not read through this whole thread but...I have for the last 10 years always had a ss of some variety (ss 29'r MTB, ss Cross Bike, etc) along with my "serious" geared bikes. I would never have it any other way, and if I didn't live in such a mountainous region, I'd be stoked to be all-in on ss. I have the most fun, get a great whole-body workout, and come back with a smile on my face every time I take the ss out (even if some walking was involved). I also would grab my ss when the next Zombie Apocalypse hits, over my geared ride, FWIW

pbass

Proper bike, this one.

ZIPP2001

Originally Posted by Moisture View Post
Good question. My idea is to have it set up as a secondary bike for when I dont plan for any serious hill climbing. Lol. Just a speedy, time trial type road or gravel bike for maximizing efficiency and going even faster.

If your looking for time trial single speed here's what I ride 52/15.

I guess you can call this my beach cruiser (lol).

acideraser

Nice, pretty much same as the one I built for my wife (different bars same frame)

acideraser

With the fixed you benefit from momentum which help to push the other crank.
I recently had an accident 20km from home when my crank arm snapped and had to ride back using only left crank. Had to walk up couple of hills but rest pedalling. around 20kph on average.
Thanks to momentum as I doubt I would have been able to ride back on a single speed.

Mikefule

Ask the engineers to define "efficiency" then turn it back on them.

There are two ways of defining efficiency: (a) achieving the desired outcome with the minimum use of resources, or (b) achieving the best possible outcome from the resources available.

Clearly a single speed or fixed bike uses considerably fewer resources (money, materials, energy to manufacture, maintenance time) compared to a geared bike.

A little bit of analysis then shows that the definition of "outcome" is crucial. It is not necessarily "top speed" or "average speed" or even anything to do with speed or anything to do with distance covered per unit of energy expended.

If the desired outcome is "enjoyment" then a single speed or fixed can be considerably more efficient than a geared bike: it indisputably needs fewer resources to produce the same amount (or more) of the desired outcome.