Single Speed For Dummies
 

I am looking through this forum with interest and think I may want to try single speed but I confess I do not understand a good deal of the discussion regarding gears. I have a hardtail 29r with slicks on it that I like to ride on the extensive network of MUPs that are a short drive away from me. There are no long steep hills on these paths. I do have to stop frequently for crosswalks/lights. I am thinking about the possibility of converting it to single speed but have not been able on my own to figure out what gears I might want.

It looks like 48X16 is some kind of standard on factory bikes. My bike has 40-30-22 3X chainrings, with a 9 speed 11-34 cassette. I am old and slow and tend to stay pretty much on 40 X 16 most of the time, but at times that is a bit too low. I have some questions if someone would be kind enough to help.

Would a new gear train of 48X16 be fairly close to the 40X16 I like, or might I find it too high?
Would the conversion be expensive?
Is there anything about a mtb, other than the drive train, that would make it a bad choice for a single speed?

Do you mean a fixed gear (can't coast) or a single speed with a freewheel and the ability to coast?

Assuming you mean single speed and not fixed gear, there are gear charts where you can convert a 48x16 to some gear you currently have on your MTB, so you can try the gear combo out and see how you like it.

https://www.bikecalc.com/gear_inches


https://cimg7.ibsrv.net/gimg/bikefor...e65a92db69.png

Thanks, I need the ability to coast but a quick look at that chart makes me think I may lack the strength for a single speed. I will take a closer look at it.

Start by picking a gear on your current set-up and just not shifting out of it. If you find a gear that works, configure your single-speed to use that same gear ratio.

... or just stay in that gear ratio all the time, and pretend you have a single speed. :)

Because you tend to stay on 40x16, that gear selection is probably real close, if not exactly what you should go with for a single speed. "At times that is a bit too low" is better than the opposite, IMO. You can always just pedal faster when the gear feels too easy, which is a lot better than mashing with old knees. (I'm a middle aged guy with troubled knees, by the way.)

I think my Ramp Rat was set at 36x16, which is a bit low for getting anywhere fast, but worked great for getting around the airport ramp. Still much faster than the tug or fuel truck, which were both a pain to use if all I needed was to get my happy butt to a particular hangar... and didn't need to tow or fuel an airplane. Kept a tool bag handy that I could carry on the bike, so I could take care of a good bit of minor maintenance on the planes.

By tradition, gears are measured in "inches". For example, a "60 inch gear" is equivalent to a 60 inch diameter wheel being driven directly through the hub with no chain or gear mechanism — like an old penny farthing.

To calculate "gear inches" there are 3 things you need to include. The formula is
Number of teeth on the chain ring divided by number of teeth on the rear sprocket multiplied by the diameter of the wheel in inches.

As most people ride 700c (roughy 28 inch diameter) it has become common shorthand to refer only to:
Number of teeth on the chain ring X number of teeth on the sprocket.

If you understand this formula, you will see that if (for simplicity) you double the size of the chain ring, you will double the gear.

Same principle, if you change from a 40t chain ring to 48t, the new gear will be 48/40 of the original. That's an increase of 20%.

A 20% increase is easily enough to make a serious difference.

If you wish to ride single speed, then choose the ratio that will get you up your steepest local hill. You can coast back down.

If you live in a very hilly area, this principle can result in a low ratio that is uncomfortably twiddly to ride on the flat.

This is why gears were invented. Riding single speed is a choice. It gives you savings in terms of weight, complexity and maintenance, but there is a penalty in terms of reduced versatility.

Another option that is simple ad low maintenance is a 3 speed hub gear. Various companies make hub gears. In the UK, the standard for many years was Sturmey Archer.

Set up a bike with a Sturmey Archer 3 speed so that the middle gear is good for general riding. Something like 60 —65 inches.

The higher gear will be 33% higher, and good for down hill, or when the wind is at your back.

The lower gear will be 25% lower, and good for up hill or when the wind is in your face.

Ride a 3 speed like a "selectable single speed".

Alternatively, there is nothing wrong with a derailleur set up. Back in the day, we used to ride simple 5 speed (1 x 5) derailleurs huge distances.

Modern gears are well made and easy to operate. Just because you have gears, doesn't mean you have to keep changing gear every 30 seconds. On my geared bike, I will often complete a 5 or 10 mile ride without changing gear.

There are no prizes for what you choose, except the enjoyment of the ride.

I am “old and slow” myself. l am 68, a bit overweight, with bad knees. I don’t try to mash big gears or maintain 20 mph like in my youth (10-12 mph is more like it).

Anyway, my Shinola single speed came with a 38T chainring and an 18T rear cog. Short hills were easy, but I was spinning out on level ground. I went down to a 16T cog, and now I can cruise at my usual speed and climb some short hills. My area is pretty flat.

You may have to experiment and you may not nail it the first time.

38/16 is what I have on my single speed. With the 700x42 tires on that bike, that works out to approximately 66 gear inches. I only have to contend with wind, since we don't have any natural hills around here. :)

You've been given a ton of good information and a lot to think about, but why should I let that stop me from giving yet more advice? :lol:

Leave your current bike alone. I'm sure it is a fine bike and can be used for all of the varying terrain you might need it for. Is your goal to reduce the weight of the bike by removing the extra chain rings, derailers, etc.? If so, I urge you to reconsider. Unless you have no room for another bike or your finances are strictly limited.

If I were you I'd look for a bike you can make your dedicated single speed and/or fixed-gear bike. That might end up being something you find locally on Craigslist or it might be something you purchase online, perhaps from Bikes Direct. There are a ton of threads here dealing with the Kilo TT and the Kilo WT. Personally, from what little I know about your needs, I'd opt for the Kilo WT as it can run much wider tires and will ultimately be more comfortable for you.

If you choose to peruse Craigslist or another local source, then see if you can find a suitable bike to convert. It should have a frame that fits you to begin with. Don't choose a bike that requires a bunch of changes in order to fit. Then, if you find a good candidate, check out Sheldon Brown's website where you can find an article on converting the bike to single speed and/or fixed-gear.

That's what I would do. I'm just afraid that after removing a bunch of stuff from your current bike, you might regret it.

Good point, TugaDude. Having a geared bike is a good thing to have just in case the weather or ride scenario makes riding a single speed more difficult. Not to mention having an easy to pedal bike if the knees need a break from a one gear bike.

Funny thing about Craigslist is there always seems to be single speed bikes for sale that were formerly geared bikes.

I have just converted an mtb to single speed and it is an easy and cheap process nowadays by these cog conversion sets sold online. But there are some things to consider:
1. Conversion sets on themarket are only for cassette cogs. If you have a threaded cog it may become quite complicated (you may have to re-dish the wheel for single speed). If you are not familiar with bike mechanics, I think it is safer to buy a single speed bike second hand for your first time.
2. For the crank set i recommend using a new chainring specific for single speed. And dont forget the chainline.it is important for single speed. Even if you use your original 40 ring, you may have to remount it to the crankset to align the chainline. Sheldon Brown has a good article about chainline,
3. I strongly recommend choosing the gear you are comfortable with. High cadence is good for the knees. 48-16 may be too high for that. 40-16 is good. But if you go to gravel or hilly roads often you can try even lower.

Thanks for all the great advice. Much there I had not considered. I am going to sleep on it for now, though I have been riding my mtb on pretty much two gears for the last several days.

I just built a 700c wheelset bike with 42T/17T and it seems to ride pretty good in the city.