Gear ratios

FSR_XC

I know this has probably been explained on here a number of times but . . . . .

I need gear ratio's explaining.

How do you work out the difference between a 50/12 and a 53/13 for example?

What is the lowest gear an average rider goes down to?

Will 39/25 get me up any hill?

Shadowduck

I have a standard double so my lowest gear is 39/25 and that gets me up most (but not all!) hills. Many people prefer a compact double which will give you a slightly lower bottom gear (34/25 for example) at the expense of a slightly lower top speed. Of course, there's always the option of a triple to get the best of both worlds.

I chose standard gearing because my strength, fitnesss and technique are still improving quite quickly - there are plenty of hills I can get up easily now on 39/25 that I used to struggle on with my previous bike, which had a compact. The idea is to adapt myself to the standard gearing to become a stronger rider, I can always swap to a compact or triple in the future if I decide to start doing double-centuries around Cumbria!

redddraggon

Shadowduck wrote:

I have a standard double so my lowest gear is 39/25 and that gets me up most (but not all!) hills. Many people prefer a compact double which will give you a slightly lower bottom gear (34/25 for example) at the expense of a slightly lower top speed. Of course, there's always the option of a triple to get the best of both worlds.

I chose standard gearing because my strength, fitnesss and technique are still improving quite quickly - there are plenty of hills I can get up easily now on 39/25 that I used to struggle on with my previous bike, which had a compact. The idea is to adapt myself to the standard gearing to become a stronger rider, I can always swap to a compact or triple in the future if I decide to start doing double-centuries around Cumbria!

A 50/11 is a bigger gear than 53/12, so with a 50/34 and 11-25 I've got a wider range of gearing than most people have with a double eg 53/39 and 12-25. Although to be honest I'm rarely out of the 50 ring and only use the 34 ring on long hills. Next time I'll probably go with a standard double and a 11-25

Shadowduck

Okay, okay... I should have said "at the expense of a slightly lower top speed all else being equal." :P

Should I have specifically said I was assuming you kept the same size wheels, too?

robbie the roadie

Ah good this is putting some of my sportive fears to rest. I've entered the white rose classic, Richmond 4 dale and a few others. I currently ride 53/39 with 11-25 cassette and can get up all the hills where I live. (In fact I ride single speed all winter and can do most of them on that even on a 65 mile ride) A lot of my club mates have suggested
I get a compact for the sportives. However from what i've seen they very rarely use the inner ring so I would say it's maybe a bit undergeared.

Bearing in mind I'm only doing the middle distance in the two mentioned sportives will I be ok on a standard chainset as I don't want to buy a new chainset especially for the events. I know I could put a bigger cassette but it's still an expense I could do without.

graham_g

Given that you are used to riding SS and evidently have the strength, I wouldn't worry too much about it!

Time for the obligatory gear calculator link:

http://www.sheldonbrown.com/gears/

I'm finding a 34/50 compact (with 12-25 cassette) really difficult to get used to - whilst I definitely need the 34 for hills, I struggle finding 'cruising' gears around the 60-70" mark with a decent chainline. Perhaps I'll go for the standard double next time but with a 13-29 cassette, otherwise it'll have to be a triple (a pain if I want to go with Campag).

dennisn

Here's a quick example. Let's assume, for the sake of arguement, that your tire has
an 85 inch circumference. First we divide 50 by 12, this gives us 4.16667, we then
multipy 4.16667 by 85 inches, this gives us 354.1667". This number is how far you and
your rear wheel will travel in one revolution of the crank. If we do the same math with
a 53-13 we find that we travel 346.53 inches, or slightly less distance than the 50- 12.
This shows that the 50-12 is a slightly bigger(taller) gear than the 53-13. One of the selling points of a compact(50-34) crankset is that a 50-11 gear is bigger than a so
called regular cranksets 53-12 gear. Either one of which is tough to spin.

Dennis Noward

dennisn

Graham G wrote:

Given that you are used to riding SS and evidently have the strength, I wouldn't worry too much about it!

Time for the obligatory gear calculator link:

http://www.sheldonbrown.com/gears/

I'm finding a 34/50 compact (with 12-25 cassette) really difficult to get used to - whilst I definitely need the 34 for hills, I struggle finding 'cruising' gears around the 60-70" mark with a decent chainline. Perhaps I'll go for the standard double next time but with a 13-29 cassette, otherwise it'll have to be a triple (a pain if I want to go with Campag).

You could try a 50-35 or a 50-36 to help out and just use the 34 tooth ring for when
you are in the mountains. I live in a really flat part of the US and I run a 50-34 with a
11-21 on the rear. If I head for the mountains(rarely) I'll switch out to a 50-33 with a
12-27 on the back. Works for me.

Dennis Noward

peanut

this has got to be a windup hasn't it ?!

I see the OP has made over 300 posts so one assumes that they have been been on the forums for a year or more and they have'nt read any of the previous prodigious threads on gearing, gear ratios, climbing and gear equipment nor can they apparently use the search facility. Nothing makes me more cross than someone who cannot be bothered to put one foot in front of the other and expects others to do all the legwork for them. Grrrrrrrr

ok ok thats a bit harsh I suppose but I do wish people would use the search facility occasionally. Some of us spend hours every night typing out advice and links etc and seem to have keep repeating it.

Take a look at Sheldon Brown's site it has everything you need to know about gears ratios cassettes chainrings everything. You can do an online gear calculation to see the difference between various sproket and chain ring combos
sheldon brown

redddraggon

Graham G wrote:

it'll have to be a triple (a pain if I want to go with Campag).

Why? Campag is easier than Shimano to setup a triple - for a start the shifters are the same for triple or double.

dennisn

peanut wrote:

this has got to be a windup hasn't it ?!

I see the OP has made over 300 posts so one assumes that they have been been on the forums for a year or more and they have'nt read any of the previous prodigious threads on gearing, gear ratios, climbing and gear equipment nor can they apparently use the search facility. Nothing makes me more cross than someone who cannot be bothered to put one foot in front of the other and expects others to do all the legwork for them. Grrrrrrrr

Really good point, as this subject has been run into the ground, dug up, and run into the
ground many times over.

Dennis Noward

Shadowduck

peanut wrote:

this has got to be a windup hasn't it ?!

I see the OP has made over 300 posts so one assumes that they have been been on the forums for a year or more and they have'nt read any of the previous prodigious threads on gearing, gear ratios, climbing and gear equipment nor can they apparently use the search facility. Nothing makes me more cross than someone who cannot be bothered to put one foot in front of the other and expects others to do all the legwork for them. Grrrrrrrr

He's been on the forum six months, according to his join date.

Since the question was asked in a polite and reasonable way, I didn't have any problem trying to help him out. Sometimes, if you're having trouble getting your head round something, a dialogue can make the difference where reading an old thread won't.

If we all refused to respond to any question whose answer could be found in the archives this would be a very quiet forum! How many "which bike" threads are going right now? I have problems when someone expects me to research every bike on their shortlist of fifteen and give my opinion (which is usually then ignored anyway) but a straightforward answer to a technical question isn't that big a deal.

robbie the roadie

Normally i would agree. but in the picutre it's a mountain bike so maybe they are not new to the forum but new to road riding?

Cajun

FWIW:
http://www.panix.com/~jbarrm/cycal/cycal.30f.html
http://www.analyticcycling.com/

peanut

well ok maybe thats a tad harsh I suppose but I do wish people would use the search facility occasionally. Some of us spend hours every night typing out advice and links etc and seem to have keep repeating it.

Take a look at Sheldon Brown's site it has everything you need to know about gears ratios cassettes chainrings everything. You can do an online gear calculation to see the difference between various sproket and chain ring combos
sheldon brown

I would recommend anyone prints out a gear chart to refer to . I have a niffty one as a laminated postcard calendar
gear chart
heres the recommendations of veloroute which is sure to create some discussion lol
low-gear ranges based on strength
From "Complete Guide to Bicycle Maintenance and Repair" By Jim Langley:

Type of riding Terrain Gear Inches
Loaded Touring Steep hills 20-27
Medium hills 32-42
Sport Touring Steep hills 27-37
Medium hills 32-42
Flat 37-47
Road Racing Steep hills 47-60
Flat to rolling 57-66
Mtn bike Steep hills 17-20
Technical trails 17-20
Dirt roads 20-27
Fixed Gear* Track 80-90
Road 60-70

* fixed-gear data thrown in by veloroutes.org

oldwelshman

robbie the roadie wrote:

Ah good this is putting some of my sportive fears to rest. I've entered the white rose classic, Richmond 4 dale and a few others. I currently ride 53/39 with 11-25 cassette and can get up all the hills where I live. (In fact I ride single speed all winter and can do most of them on that even on a 65 mile ride) A lot of my club mates have suggested
I get a compact for the sportives. However from what i've seen they very rarely use the inner ring so I would say it's maybe a bit undergeared.

Bearing in mind I'm only doing the middle distance in the two mentioned sportives will I be ok on a standard chainset as I don't want to buy a new chainset especially for the events. I know I could put a bigger cassette but it's still an expense I could do without.

ou may be in for a shock
It will be totally dependent on the conditions and how hard you ride.
In races I use a 12/23 rear but for sportives I use a 12/27 and my new bike is having a compact.
The reason is, that races are normally less distance and shorter climbs which can be handled on a 23.
Actually I have never fialled to get up any climb on a 23 yet and have ridden some really long and steep hills in Wales. But there is a difference riding them for leisure, training and club runs compared to doing them at a good pace in a sportive over longer distances.
I often end up using a 25 or 27 where I would normally use a 19/21 or 23
Just beware your club mates may have given you good advice
On the other hand you could be a budding pro and can mash up these hills easily

hodsgod

As an engineer first, I will try to explain the gears in a simple way, and without cycling jargon. Any purer cyclists than me, please tell me if I get it wrong

First of all, to know which is a higher or lower gear, you can forget your wheel diameters, as they are constant.

You sinply need to work out your gear ratios at a common denominator, then you can compare easily.

For examples sake lets use easy numbers. 50 front and 50 rear, is a ratio of 1:1

A 50 front and 25 back will give you a mechanical disavantage, every one revolution of the front will make two revolutions at the back, 1:2 this would be good for cruising at high speeds, but tough to start off with.

25 front and 50 back gives you the opposite, two revolutions at the front and one at the back, this is easy to pull away with, but high speed is impossible, ratio is 2:1.

To find out the difference between 50/12 (1:4.16) and 53/13(1:4.07) just divide 50/12 this gives the actual ratio in an easy to compare format.

Many people talk about gear ratios in inches, this refers back to the days of Penny farthings, It is a complicated system, if you mention gear of 100inches outside cycling, people will say you are mad! I am not trying to change the world, just to make it easier for one person to understand.

FSR_XC

peanut wrote:

this has got to be a windup hasn't it ?!

I see the OP has made over 300 posts so one assumes that they have been been on the forums for a year or more and they have'nt read any of the previous prodigious threads on gearing, gear ratios, climbing and gear equipment nor can they apparently use the search facility. Nothing makes me more cross than someone who cannot be bothered to put one foot in front of the other and expects others to do all the legwork for them. Grrrrrrrr

ok ok thats a bit harsh I suppose but I do wish people would use the search facility occasionally. Some of us spend hours every night typing out advice and links etc and seem to have keep repeating it.

Take a look at Sheldon Brown's site it has everything you need to know about gears ratios cassettes chainrings everything. You can do an online gear calculation to see the difference between various sproket and chain ring combos
sheldon brown

Peanut

Sorry I got your back up.

As it has been spotted, I normally ride an MTB. My only experience of a road bike is one I borrowed last year.

When riding an MTB I rarely use the 'granny' ring as I rely on leg power instead of cadence.

My concern at the moment is that as I am looking to buy a road bike, I don't want to get one with too high a gearing & find I need to get off on hills. On the other hand I want it high enough geared to get a good speed down hills.

My first impressions of Compact 'v' standard chainsets was that real bikers use standard. Yet by the sounds of the posts on here, I would need a 53-11 (not 53-12) gear to get any higher than a 50-11 from a compact set. I wonder how often it would make any difference at all?

A slightly different way of looking at this.
If my cadence is (eg) 80rpm what speeds could I expect from the following?
53-11
53-12
50-11
39-25
34-25

Not meaning to be thick, but gearing on an MTB is basically standard. I just get on & pedal!

FSR_XC

dennisn wrote:

Here's a quick example. Let's assume, for the sake of arguement, that your tire has
an 85 inch circumference. First we divide 50 by 12, this gives us 4.16667, we then
multipy 4.16667 by 85 inches, this gives us 354.1667". This number is how far you and
your rear wheel will travel in one revolution of the crank. If we do the same math with
a 53-13 we find that we travel 346.53 inches, or slightly less distance than the 50- 12.
This shows that the 50-12 is a slightly bigger(taller) gear than the 53-13. One of the selling points of a compact(50-34) crankset is that a 50-11 gear is bigger than a so
called regular cranksets 53-12 gear. Either one of which is tough to spin.

Dennis Noward

Is 85" about a standard circumference?

Any idea what an average MTB wheel circumference would be?
This way I could at least compare road gears to what I have.
I know there is more resistance etc from an MTB, so speed & effort won't be exactly the same.

dennisn

FSR_XC wrote:

dennisn wrote:

Here's a quick example. Let's assume, for the sake of arguement, that your tire has
an 85 inch circumference. First we divide 50 by 12, this gives us 4.16667, we then
multipy 4.16667 by 85 inches, this gives us 354.1667". This number is how far you and
your rear wheel will travel in one revolution of the crank. If we do the same math with
a 53-13 we find that we travel 346.53 inches, or slightly less distance than the 50- 12.
This shows that the 50-12 is a slightly bigger(taller) gear than the 53-13. One of the selling points of a compact(50-34) crankset is that a 50-11 gear is bigger than a so
called regular cranksets 53-12 gear. Either one of which is tough to spin.

Dennis Noward

Is 85" about a standard circumference?

Any idea what an average MTB wheel circumference would be?
This way I could at least compare road gears to what I have.
I know there is more resistance etc from an MTB, so speed & effort won't be exactly the same.

It's your bike. Get the ruler out and measure it.

Dennis Noward

Shadowduck

FSR_XC wrote:

Is 85" about a standard circumference?

Any idea what an average MTB wheel circumference would be?
This way I could at least compare road gears to what I have.
I know there is more resistance etc from an MTB, so speed & effort won't be exactly the same.

Position your wheel with the valve at the bottom. Make a mark next to it. Push your bike forward one complete revolution of the wheel, so the valve comes back to the bottom. Make another mark.

The distance between the marks is your wheel (well, tyre) circumference.

milese

I've got a compact 34/50 and changed the cassette to a 12/27 from a 12/25 shortly after getting it.

Basically I'm training for sportives and dont want to burn out on big long hills so that I can't get the distance in. In reality I didn't notice much difference between the 25/27, and on some hills, when I'm tired I go down to about 4mph! Max speed is generally around 40mph.

I find it difficult to push myself hard on my own, so do end up in the saddle in easy gears. When i go out with my (fit) Dad I find it much easier to go faster and work harder. My HRM see's numbers that I never see on my own, whilst my percieved effort is the same, but thats a different story about me being competitive I suppose.

Cornwall is a hilly place, I would get another compact or a triple if I bought again, but it depends on what type of riding you want to do and how fit you are.

graham_g

redddraggon wrote:

Graham G wrote:

it'll have to be a triple (a pain if I want to go with Campag).

Why? Campag is easier than Shimano to setup a triple - for a start the shifters are the same for triple or double.

I was just thinking in terms of availability of the groupsets as a triple - not many places seem to stock them. The idea of a non-indexed front shifter is fantastic though.

FSR_XC

dennisn wrote:

It's your bike. Get the ruler out and measure it.

Dennis Noward

I'm at work, but thank you anyway.

It is around 81"

John.T

FSR_XC. I think you are making too much out of gearing. You can relate most of them from your MTB. A 53*11 will be 'about' 25% faster than the 44*11 you probably have on the MTB for the same cadence. Due to the extra drag of an MTB you would probably achieve about the same cadence on both bikes using the highest gear. You probably have a 32 middle ring on the MTB so this will give very similar gear ratios to a 34 on a road bike for the same cogs. If you can ride a hill on the MTB (on road) using say 32*32 you should get up it about as easily on 34*19 or 21 on a road bike. These are aprox only but are somewhere near. I use a compact with 12/27 for most riding and a 12/23 for racing. I have not found the need for an 11 yet but if I did it would only be for racing. You do not need big gears to go fast down hill, only big hills (and some would say small brains). My best speeds are 66mph on road and 55mph MTB (also on road). I was not pedalling either time.

dennisn

I officially give up on this post. It's beat me down. I'm not even sure what the original
question was, let alone where it's all going(downhill to say the least). Out of curiosity
I probably will check in with it once a week or so just to see where it has gone.
Good luck guys.

Dennis Noward

Shadowduck

dennisn wrote:

I officially give up on this post.

...officially... :shock:

Now that's serious. Thanks for keeping us in the loop. Who knows what might have happened if you hadn't kept us informed?

dennisn

Shadowduck wrote:

dennisn wrote:

I officially give up on this post.

...officially... :shock:

Now that's serious. Thanks for keeping us in the loop. Who knows what might have happened if you hadn't kept us informed?

I know, I didn't want to leave you guys all alone on this one but that's how it goes
sometimes. Wait a minute didn't I just get back IN on this?????

Dennis Noward

geoff_ss

There are only two things you really need to know about gearing -

1 Are you comfortable in the one you're pedalling?

2 If you're not racing, the low ones are more important than the high ones. Particularly if you're doing a long ride and/or you live in a hilly area.

1 depends on how fit/strong you are and the gradient. If the gradient is up then change down if you're uncomfortable. If there are no more gears and you can't cope engage the 24" gear (ie 2 feet). If the gradient is down change up. If there are no more gears stop pedalling and freewheel.

Geoff

John Stevenson

hodsgod wrote:

To find out the difference between 50/12 (1:4.16) and 53/13(1:4.07) just divide 50/12 this gives the actual ratio in an easy to compare format.

Many people talk about gear ratios in inches, this refers back to the days of Penny farthings, It is a complicated system.

The nice thing about gear inches is that they produce numbers in a range that people can easily understand and compare. I can't see there's anything easy about comparing a pair of ratios that contain decimal fractions.

On a bike with 700C wheels (tread diameter 26.5inches) 50/12 is 110 inches and 53x13 is 108 inches, which I think shows pretty clearly that they're almost the same - far more so that trying to compare 1:4.16 and 1:4.07.

The original poster is, I think, a mountain biker, so probably wants to be able to compare gears between different wheel sizes. You can't do that with bare ratios.

Mountain bikes typically have 44/34/22 chainrings and 11-34 cassettes. On a 26in wheel that gives a top gear of 104 inches, so you can see that the common 53x11 (128 inches) top gear of road bikes is a lot higher.

It has to be said that mountain bike and road bike wheel sizes are so close to identical that this isn't a big issue. A fat mountain bike tyre (say a 2.3) and a skinny road tyre (the very common 23mm) are within a fifth of an inch.

As hodsgod says, gear inches date back to penny-farthings ('Ordinaries', as bike history purists call them; the term differentiates them from 'safety' bikes which is what we all ride now).

A penny-farthing's gear was just the size of the wheel. The bigger it was, the further you went for a pedal stroke and therefore the faster you could go. The limit was your leg length as you had to straddle the wheel.

Gear inches, calculated as wheel diameter in inches times chainring teeth divided by sprocket teeth, gives you the size of penny-farthing wheel you'd need to get the same gear.

Sure, it's a bit mad and archaic, but it's also wonderfully English, in a chewy beer, beans-on-toast, pubs that let your dog in sort of way. I rather like that.

Shadowduck

John Stevenson wrote:

Sure, it's a bit mad and archaic, but it's also wonderfully English, in a chewy beer, beans-on-toast, pubs that let your dog in sort of way. I rather like that.

That's the most persuasive argument for the use of gear inches I've ever heard.