Gears (in idiot language)

[pepecat]

Question cos I'm stupid.....
So gears..... the numbers that are bandied about on here (11-25-34 etc) - that refers to the number of teeth on the cog?
Here's the stupid question.....why do these matter?? I've seen comments on here saying things like 'I wouldn't run on a 25/36/47 (or whatever)...... but don't understand what all that's about?

 

[Rando]

Question cos I'm stupid.....
So gears..... the numbers that are bandied about on here (11-25-34 etc) - that refers to the number of teeth on the cog?
Here's the stupid question.....why do these matter?? I've seen comments on here saying things like 'I wouldn't run on a 25/36/47 (or whatever)...... but don't understand what all that's about?

Oh good someone else who doesn't understand all these numbers !! thought it was just me. Makes it all very confusing when trying to pick a new bike.

 

[Cheule]

For some it's mostly personal preference. I like a larger chainring (48T) at the front, with 13T at the back for fast commuting. My next cassette will be an 11T to squeeze that bit extra

You are correct, the numbers do indeed mean the number of teeth on the cog. I suppose the next question is, what do you have on yours?

 

[monnet]

Right I'll start off and then I'm sure others will chip in to fill in any gaps. I will caveat that my examples stand for road bikes but the principles hold true for all types of bikes.

The numbers relate to the number of teeth on the cogs at the back or the chainwheels at the front.

So, people may talk of running a 12-25 cassette. That means the smallest cog will have 12 teeth and the biggest 25. Depending on the number of cogs, your preferences and the manufacturer will vary the number of teeth in between but on a Shimano 10 speed it would typically be 12, 13, 14, 15, 16, 17, 19, 21, 23, 25.

The chainwheels obviously have more teeth. So people may talk of a 53-39 (53 being the bigger ring, obviously). This is a 'standard double'. Or there is the compact, often 50-34, or triples 50-39-30. These are standard sizes off the shelf sizes - it is possible to spec your own.

The gear you ride is often quoted front teeth first, rear teeth second eg: 53x12

Why does this matter? Well, the gearing you use depends on the kind of rider you are and what sort of riding you do. As well as your fitness level.

Lower gears - so more teeth at the back, fewer at the front - are good for climbing. In the above examples, a 30x25 would be the lowest gear on the triple, ideal for cycling the north face of the eiger.

Higher gears (eg: 53x12, which is very high) is probably only truly useful for long downhills and racing.

The important thing is that you can turn the gear comfortably without straining but not so easily you go nowhere fro lots of effort, it's about finding the optimum - which varies according to the person. The other point is some people prefer/need the skips in the gears to be minimal (big jumps in racing are bad for maintaining a rhythm) but for hilly sportives you need a mix of very low gears to get up the hills but also big gears fro the flat sections and the downhill.

So, when people say 'I wouldn't ride 53x12' They are (probably) saying that is too high a gear for them. If they say 'Iwouldn't ride a 12-25' they are saying that size cassette is not suitable for what they do. They might want an 11-21 for pure racing with very small gaps between the cogs, or they may want a 14-27 because they need the lower gears fro touring or getting up big mountains.

In summary big at the front small at the back means big gear ideal for racing. Small at front big at back, good for pedalling up hills. Alot of the 'I'd rather ride...' is about personal preference. One person may say '53-39 with an 11-21 is ridiculous, get a compact and a 12-27' but someone who races would need an 11-21 to survive in a race.

Hope that helps.

 

[alecstilleyedye]

pepecat, once you start thinking about gears it's a bit of a slippery slope. you can ride perfectly happily in blissful ignorance of gear ratios and how they're calculated. however, once you start considering your gearing and how a different setup might suit, you're on your way to being a more complete cyclist, imho of course.

i was once of the opinion that none of that stuff mattered, not any more…

 

[pepecat]

Thanks monnet - that does make more sense. Especially the stuff about gearing depending on the type of riding you're doing. My bike has a triple at the front and nine speed at the back, though as to numbers, I haven't a clue - I haven't counted! I think that's a pretty good range at the moment; I tend only to use the middle chainring but pretty much all of the cogs at the back; but I've not encountered any 'real' hills yet, so have not made use of the bigger chainring.
I understand that a good range it probably what you need for 'general' cycling, which is what I do - it was just the numbers bandied about here that confused me slightly!!

*ok - just looked at my bike specs - chainrings are 50/39/30, cassette - Sram 11-26, 9 speed* That sounds kinda 'middle ish' for general road riding...
So I generally run 39, not 11 or 26, but the ones in between at the back.

Ooo - I'm a cycle geek....kind of......

 

[jimboalee]

Gearing is a bit complicated for beginners, newbies and novices.

I was lucky enough to have a good LBS.

I bought a race bike when I was a junior. It had 42/52 and 14 - 24 five speed. Being a junior, there was a gearing limit, so the 52 ring came off and the front mech locked up.

As soon as, the 52 was replaced and a 38 went on with it instead of the 42 which was worn. The rear end changed to a 13 - 23 six speed.

Gearing was explained in depth by the LBS man's Mrs, plus some 'folklore' and 'witchcraft' concerning gear choice for terrain.

With modern bike having so many gears, changing rings and sprockets before a ride is no longer necessary. In other words, today's 'off the peg' bike will have a sufficient number of gears to get the rider by without going to the bother of studying the route and making gear choices. Therefore, gearing knowledge is becoming a dying art amongst the amatuer ranks.

 

[byegad]

pepecat; You seem to have the 'right' gearing for the moment. As you gain experience, and climb some big hills you'll learn whether you need more lower gears, or higher ones.

OR; If you find you are never in the highest gear, (biggest front ring, smallest rear,) or the lowest gear, (smallest front, biggest rear,) you'll decide to go for a smaller range at the rear.

monnet's examples are for road bikes. Tourers will typically use a wider spread, usually with fewer teeth, front and just a wider range at the back, so a typical tourer might be 48 36 24 front and 11, 13, 15, 17, 20, 23, 26, 30, 34 rear. So you get a lower top gear, although 48/11 on a full size wheel is pretty high! and a much lower bottom gear.

Another way to use numbers is to work out the equivalent Penny Farthing front wheel size each gear gives you. This is old fashioned and came into use when the first safety bicycles (What we mostly ride today.) came on the market as the old 'Wheelmen' looked at the smaller driven wheel and thought they'd be much slower than their high wheelers. Of course it wasn't as the difference in front and rear cogs gave the same distance travelled as a directly pedalled front wheel.

No need to work it out yourself, use this link; http://www.kinetics.org.uk/html/k_gear.shtml to load a free program from Kinetics in Glasgow, you fill in the relevant numbers and out comes the gear inches. The bigger the number the further the bike travels for one turn of the pedals, the smaller the number the easier it is to turn the pedals. The program will also calculate 'development' which is the continental way of working out exactly, in metres, how far you travel for one pedal turn, something 'gear inches' doesn't do.

<br>Hope this helps. The numbers are there to help after all.

 

[guitarpete247]

As you will see from any gear calculator (and here's another for you) there is going to be some repetition, or very close, gears. So you can change up on your chainring (front) and down on the back and have a smaller change in gearing.

Don't just stick it in smallest front, biggest back and go through gears on the back only then move to middle front, biggest back and go up again and so on. Remember to try to keep your chainline fairly straight.

Smallest at the front use on the biggest to the middle at the back.

Middle at the front use the middle section of the rear cogs.

And biggest front use the middle to the smallest at the back.

If you are going big to big or small to small you will be putting a lot of strain on your chain and if you are grinding uphill you will also be putting a lot of twist into the teeth on the chainrings.

 

[MacB]

I would add that some, myself included, make the mistake of assuming they have X amount of gears, so a triple chainring and 9 speed cassette gives 27 gears....well, not really. Once you've removed the duplicates, and gears too close to notice, that reduces the 27. Then you need to take away the gears you shouldn't use, these are the ones that make the chain run at the most severe diagonal. How many you avoid depends on who you listen to, not uncommon is to avoid 2 gears from the inner and outer ring each and sometimes one gear at each end of the middle ring. All this reduces your alleged 27 gears down to 13 if you avoid via the middle ring and 15 if you don't...roughly.

After that it only matters if you want to change gearing, replace parts or are getting another bike. Then it pays to understand the sort of size of gear you do most of your riding in and how you like to ride. If you try to keep a consistant tempo, and constantly flick through gears to do so, then more gears and closer ratios would suit. If you tend to vary tempo and avoid gear changes then fewer gears or wider spreads suit. Some people also try to select gearing to minimize the amount of front ring changes.

Then you need to consider where you ride, how much you carry, how fit you are and how fit you intend to get. You see comments from people saying things like 'you could climb the Eiger in that gear'. Well, maybe if you're a racing whippet on a stripped down bike. But if you're not in shape, are hauling panniers etc, doing a long ride, in a very hilly area, this may not be the case.

It's all relative and can change as your fitness changes etc, but understanding gear inches will help you select what works for you. Listening to what works for others only helps if you also know things about how/where they ride, how fit they are, what their bikes weigh and what kit they haul. The more you ride and understand the less it will matter what others do as you'll have your own frame of reference.

 

[rodgy-dodge]

Another newbie who found the gearing language all a bit techy...
reading the reply's written in laymans terms makes good sence for the last three months I've been riding using instinct and what gears I may have been using then for steady inclines or hills are not what I'm using now as my fitness and stamina have much improved.

I this site for good sound knowledge and advise from those more experienced than me

 

[HLaB]

Question cos I'm stupid.....
So gears..... the numbers that are bandied about on here (11-25-34 etc) - that refers to the number of teeth on the cog?
Here's the stupid question.....why do these matter?? I've seen comments on here saying things like 'I wouldn't run on a 25/36/47 (or whatever)...... but don't understand what all that's about?

Its probably been explained above but the larger (more teeth) on the rear cogs the easier it is to spin/ cycle up hill but visa versa if its too large its too easy to spin and you spin out when you need to go faster. For example this is the number 11-23 or 12-25. The number you see qouted that take the form of 25/36/47 or 38/52 refers to the chainrings at the front of your bike (the former having 3 chainrings, the latter having 2). This is the exact opposite of the rear cogss, the smaller the chain ring (the less teeth) the easier it is too spin/ go up hill. If it too small it too can be too easy to spin making it hard to go fast this is why some folk will say 'I wouldn't run on a 25/36/47' they feel that it is too small and they would spin out making it nigh impossible (unless you're Lance) to go fast; this can be a problem downhill but if you're cycle up hill it isn't, so depending on your fitness/ terrain/ cycling style, you need to get the gear ratios that suit you best.

 

[Lien Sdrawde]

Thanks for asking this question. I may have to read it through again but its here for reference.

Is this why some of the more expensive bikes i've seen only have 2 front cogs... cos there's little point having 27 or so gears?

 

[Cheule]

Weight is one reason.

 

[HLaB]

Thanks for asking this question. I may have to read it through again but its here for reference.

Is this why some of the more expensive bikes i've seen only have 2 front cogs... cos there's little point having 27 or so gears?

The main reason I think a compact double on a road bike (34/50 or 36/50) will only have two chain rings is fashion. There's a miniscule weight saving too and there's less to go wrong. Whilst they will give almost the same range as a tripple, a tripple still has one or two more gears at the upper or lower range or both.