Digital Gee

Okay, I have to confess I simply and completely don't understand bicycle gears. I know only enough to shift up or down when the going gets harder or easier. That's it. I also now realize that I rarely shift the left shifter. It's always on the so-called toughest ring. As I write this from my hotel I can't even remember if that's the big ring or the small ring! See? I am clueless!

Can someone explain the numbers to me in such a way that a 12 year old could understand -- or give me a link where there is such an explanation? And -- is there a difference between my basic MTB gearing and a road bike (or hybrid, for that matter) gearing? Of course there must be, but howso?

Now you can see why I didn't go into any profession that involves numbers. My eyes just glaze over.

So -- bicycle gearing for dummies -- anyone care to help me out here?

GrannyGear

If it weren't so late Gary we could have a nice confusing crash course, but I'll let one of the East Coast early risers do it. In the meantime, at least let me correct your "My eyes glaze over" to the more correct "My EYE glazes over". GoodNight all!!.

** First you wanted to be a "Fred", now you want to go and be a "Gearhead". Jeez Gary, and I'm just getting used to you being a Pirate. Go to bed so you can be fresh for all the numbers on this thread tomorrow.

Digital Gee

pinerider

No numbers, Gary, just some principles. These have come from years of friction shifting with downtube shifters. Indexed shifters make things a little easier (most of the time!)
The front gears (chainwheel or crank) are sort of opposite to the back gears (freewheel), depending on how you look at them. The easier gears to push are the smaller rings on the front (inner ones), bigger ones on the back(inner ones too!).
You want to avoid combinations that make the chain go (looking from a vertical perspective) from inside to outside or visa versa, it puts a lot of side tension on the chain and derailleurs. For example, avoid having the chain on the big ring on the front and the biggest ring on the back. You can usually get the same gearing and be a lot more efficient by using the middle or smaller ring on the front and and intermediate ring on the back.
Shifting the front derailleur is usually more difficult than shifting the back so people tend to use the rear derailleurs more. I tend to stay in the biggest front ring on my road bike unless I'm getting into a lot of uphills, and on my mountain bike I usually keep it in the middle ring when I'm on the trails.
Another principle is down shift before you absolutely have to - It keeps you spinning better and puts a lot less strain on the shifting system

Hope this helps!!

Greg

MichaelW

The best advice or gearo-phobes is to leave the chain in the middle ring up front. That will give you adaquate range usng the rear cogs and avoid the issue of cross chaining.

When you feel ready to advance (or your hills get too steel), flip to the small chainring (uphill) or big ring (downhill).
You will find a lot of overlap between the 3 gear ranges. In practice, the 2 outer rings are only used with a few of the rear cogs. You generally get a better chainline using the duplicate gear on the middle ring.

Lots more info here

berts

Gary - knock yourself out..
https://www.panix.com/~jbarrm/cycal/cycal.30f.html

HiYoSilver

I was going to pose this question but since DG asked. I'll try it here, I just don't know if we'll get good answers in this subforum.

I understand Gear Inches. Gary just think of them as a way of measuring both how far you will travel each revolution of your cranks and what speed you'll be traveling. Lower numbers mean you are going slower but it takes less effort to keep going. Higher numbers mean you are going faster and it takes more power. So if you're finding your cadence/revolution speed is dropping and you have to push too hard, then it's time to switch to a lower numbered GI gear. When you're helicoptering and legs are going too fast with little resistance, it's time to switch to a higher numbered gear.

The other variable is the % change when you switch gears. The panic site is super for showing the % changes between gears. Changes under 4% are usually not a big enough change. Changes over 13% are usually too big [ unless at the very bottom of the scale. ]. Gear inches of 20 or 22 are considered ideal by loaded touring riders. Lower than that is not useful. Gear inches higher than 110 are of limited value as usely only need them on downhills.

Ok, all that is preliminary. I really don't understand torque. I've noticed that 2 similar GI results will feel much different. I can take a middle front chainring and and a the lowest rear cog and go up hills at about 10 mph. But when that gets too hard and I switch to the lower front chain ring to get up a steeper section, or just give out, then my speed will drop to 8 or 9, if that, mph. When the hill's slope eases up, I expected to find I could stay in the low front gear ring and shift up the rear cassette to higher gears so I could go faster. But for some reason it doesn't work. The gear inches of low chainring and middle chainring will be similiar, but I can't go as fast up hills with the low chainring. It is only after I switch back to the middle ring, that I recover my speeds.

Long post, but there is more to understanding gears than gear inches. I don't know what else there is. I suspect it's a physics torque issue, but this is just a guess.

BlazingPedals

Consider the imaginary plane down the center of the bike. No matter which you're talking about - chainring or cassette gear, further away from the plane equals a higher gear.

If you want to know the math, it's (C*W)/F, where C is Chainring Teeth, W is the actual wheel diameter, and F is the freehub cassette teeth. From the formula, you can see that a bigger wheel or a bigger chainring will give you a bigger number result, which equals a higher gear. So if you want to go fast down a big hill, simply use a bigger wheel! As a learning aid, you can make a chart showing the gear-inches for each gear combination you have, and tape it to your top tube.

DnvrFox

Small ring up front, big cassette in back = go up hills easily

Big ring up front, small cassette in back = go fast on level ground!

Mtn bikes have gears arranged for steep, slow hills, road bikes for faster riding. They are different.

marmotte

with a 28'' wheel racing bike and a frequence 60:

If you have 42 / 26 , it means 12.8 km/h
If you have 45 / 15 , it means 24.1 km/h
If you have 52 / 14 , it means 29.9 km/h



with a 26'' wheel Mountainbike and a frequence 60:

If you have 42 / 26 , it means 11.9 km/h
If you have 45 / 15 , it means 22.0 km/h
If you have 52 / 14 , it means 27.8 km/h


1 km/h = 0.55 mph


(I think I calculated right, but excuse any faults )
marmotte

Old Hammer Boy

Wow! You sure got a lot of meat to chew on there, Gary. Excellent answers from our little community. Now my .02. One thing I've noticed, and learned the hard way when it comes to shifiting; It's best to shift the chain ring before you run out of rear cog. In other words, if you are climbing and you need to downshift numerous times, when you are 2 or 3 gears out from your largest cog and you know you'll need to continue to downshift, now shift to a smaller chain ring, don't wait until you've arrived at the largest cog. As you guys probably know, my stoker/wife and I ride a tandem a lot. It can be easier to throw a chain on a tandem because the frame can flex more. I've found that if I shift my chain ring one or two cogs "early," I never have a problem throwing my chain. Doing this also puts less cross pressure on the chain which is a good thing. I hope I've made myself clear on this... OHB

MichaelW

It may be a bit misleading to quote a speed for a certain gear. Note that in the above example pedalling cadence is constant .
In real world cycling, the constant is your power output. You may be able to sprint a little but basically, your sustainable power output is fixed.
For cruising, your cadence should be fairly rapid (>80rpm) and your pedalling force quite low. Sprints and climbs require higher force.
Gearing matches your power, your desired pedalling cadence and the various drag forces on the bike. Any speed is a resultant outcome. If you are riding into a headwind you dont go as fast.

cyclintom

More than you EVER wanted to know about gears, gearing and why.

Ken Kifer's Bicycle Pages.

The late Ken Kifer was run over by a car. These pages were written by him before the fatal accident and are retained in his memory. Ken was a good friend to all cyclists and he is now going over the top of the worst climbs in the big ring.


https://www.kenkifer.com/bikepages/touring/gears.htm

GrannyGear

Gary, now I'm all rested and the others have done the details. So much for the cognitive.....now go for the tactile sense of what gears mean and do. Do some shifting on your rides-- change chain rings, go up and down the cogs, drop it into a small cog and come off your saddle for a few yards. Your legs will teach you about gears. Hills would be good to demonstrate their usefulness, but short little sprints in higher (smaller cog & bigger chainring) gears will help. So will hummingbird spinning in low gears. (Strange how those silly, easy, go-nowhere gears become serious, even not-so-easy on climbs. Try a "harder" gear with the wind behind you. Before your memorized gear chart really seems understandable, your legs will tell you which cogs mean what level of effort. Most riders have a "home cog" on the flats with no wind, then one with wind, and so on. My flat, not much wind cruiser is in the low/mid 70's. My first few miles "warm up/cool down" gear in the upper 50's, and so on.

Maybe a tactile, personal knowledge of gears should precede just the sterile numbers...later they'll really mean something.

LOL, then you can start fooling with gear charts, pondering compact vs. triple, which cassette, which chainrings should you upgrade to, learn to resent redundancy, etc.

madli

GrannyGear, Awesome post! Experiential learning! Let your body (legs mostly I guess) tell you what gears to be in. That can change as well as some days the legs are jelly-like, some few days like steel, and most days somewhere in between.

madli (hopefully not grinding the gears mentally and otherwise!)

oldguy52

Gary,

Here's a real nice gear calculator program that you can download for free.

https://www.kinetics-online.co.uk/K_Gear.exe

Once you know the gear inches for a particular gear on your bike, just take that times 3.141 (pi) and you will then know how far your bike will travel for one revolution of your pedals.

Less distance per turn of the pedals is easier and slower.

More distance per turn of the pedals is harder and faster.

Rik

Al1943

If you're serious about learning gears get a bike computer with a cadence meter (like a Cateye Astrale). Ride in gears that allow you to maintain a cadence of 80 to 100 rpm, and don't cross-chain. Good advice above about riding on the middle chainring until you have a better idea what you are doing.

Gearing on a bicycle is like gearing in your car, whether manual or automatic. A car's engine has an rpm range where it runs smoother and developes more power. Your body is the engine for your bike.

Al

stapfam

You scare me. According to your calculations I have just worn out my knee joints on a 26" wheel, 48/11 gearing and 44mph. No wonder it hurt.

Never bothered about the technicalities of gearing- but only one gear to be in- the one you are comfortable with and DON'T CROSSCHAIN.

NOS88

Agree with madli, great post GrannyGear. Keeping in mind that when I first started riding you could only get a five cog cluster in the rear. Then it was 6, then 7...8...9, and now (big drum roll)...10. I gave up trying to keep gear numbers in my head and just let my legs (and lungs) tell me when to shift. Before I'd get involved in endless discussion about duplicate gears and how to avoid them, if half-step plus granny was the way to go on a fully loaded tour, what my high gear in inches was and how fast I'd be going when I reached the spin limit with it. Not any more. I let my legs tell me what I need to know. If you get all of your gear numbers down for your current rig, you'll just have to do it again with the next one. Having said all of that, I know some folks have a greater ability to jump into and enjoy the details of this kind of thing. I say knock yourself out!

HiYoSilver

Sorry to hear that, he was a good positive force for promoting cycling.

jppe

Being an engineer I just can't help but salivate with this kind of topic. It's some of the "technical" aspects of cycling that I've come to enjoy. I just love those formulas and numbers and equations.....

Here's the cliffs notes version that might be of help. The "numbers" on the gears or cogs are the number of teeth that a gear has on it. A typical set-up on a triple road bike these days is 3 chain rings on the front with the gears being a 52-42-30. The 52 being the largest chain ring. A typical set-up on a double road bike is a 53-39. A more recent addition to these two set-ups that is increasing in favor is a 50-34 double.

When the chain is in the largest gear in the front chain rings, it is hardest to pedal.

The rear gears are assembled together and called a cassette. Older bikes might only have 3-5 gears in the rear cassette. The newest arrangement is 10 speeds or gears in the rear cassette. Probably the most common rear gearing on road bikes today is either 8 or 9 speeds because 10 speeds have only been around 1-2 two years.


I know this is going to blow your mind but converse to the front chain ring, when the chain is in the largest gear in the rear cassette next to the spokes, that is the easiest gear to pedal. As you change gears from there, the chain will move outward and those gears get harder to pedal.

Thus if you have a double front chain ring and a 10 speed rear cassette-you have a total of 20 different gears.

I'm playing with my gears (both my front chainring and rear cassette) to try and optimize my gears. The advantage of a triple is that it provides a wide range of gears. The disadvantage is that there is some "duplication" (or at least close to it) where you don't really need or probably use all 30 gears. If you calculate the "gear inches" you can see where the crossover is between the chain rings.


With the terrain I ride I need both the high end gears (combinations hardest to pedal) and the very lowest gears (easiest to pedal), if that makes sense. Where I'm probably headed is towards a compact crank on the front chain ring and will probably go with a 50-34. I'll probably put a mountain bike rear derailleur and rear cassette gearing on it so I'll have some even easier gears for the mountain climbs. By doing that I'll lose a little on the high end but gain a little easier gear on the lower end and optimize the number of overall gears I have. That's not a combination that works for everyone but I think it will best suit my needs.

I hope this has not been too tough a subject for you especially since you're saddled with mono vision......I do hope you're feeling better.

bkaapcke

To really 'get' bike gearing, you have to come to a Zen awareness of the various ratios that are on YOUR bike. After many hours of deep meditation you will come to; Shift up when the pedaling gets too hard and shift down when it gets too easy. Then you will have it. Intellectual, engineering or mathematical understanding is an illusion born of overeducation and ego worship. Once you have the zen aspect down, all you have to do is ask your legs. They will 'know'. bk

DnvrFox

I find the different approaches to "understanding gears" to be fascinating.

It reflects the varied personalities (somatypes?) of the folks here who ride bicycles, from the highly technical, engineering-type explanations of gear inches to the "If you want to pedal easier, shift small front and big back" to "listen to your legs" and the "Meditate yourself into gear shifting nirvana" to "All I care about is keeping a constant cadence!"

I'm not sure what DG is/was looking for, but he sure got a variety of answers!

ken cummings

I am an engineer too Gary but I take an entirely different approach. There are automatic shifts for bicycles out there. Get one and stop worrying.

Digital Gee

Well, I just had the chance to read most of the responses to my initial question. I'm not sure I put it right, although all of these responses are appreciated. Some of them kind of got to what I was looking for, while others are just darn good advice.

I know to shift up or down when it's getting harder or easier. What I didn't understand was what the numbers mean, and how a mountain bike is configured differently from a road bike, for example. Does the MTB have lower gears overall, and the road bike have higher gears (for more speed)? I'm still not sure I understand that.

Secondly, I'm wondering if someone will comment on this: I hardly ever ever shift my front gears. I'm always on the fastest one, not the granny gear except in very rare instances on hills. On the back, I tend to ride on 6, 7, or 8 almost all the time, occasionally shifting down to 2-3 on hills. What does this mean, in terms of my fitness? Am I sort of outgrowing this bike's gearing? Should I switch to the middle gear up front for most of my rides? That's how I started nine months ago,but then I discovered I could go faster with the higher gear, and it quickly became the only one (in front) that I use.

What difference would I detect (if any) when i switch to a road bike? Even higher gears? Perhaps higher AND lower gears (and the MTB is somewhere in themiddle?)

Anyway, that's what I'm wondering and I'll also check out all those links. I want to get my brain around this one of these days!~

PS: My eye is healing pretty well. Still a bit sensitive to light, but not red anymore. I should be putting the contacts back in by Saturday. Thanks for the concern!