Gear ratios

FSR_XC

Thanks for the answers.

I am glad some were more patient than others (this is 'Road Beginners' after all).

Particular thanks to John.T, Geoff_SS and John Stevenson for the informative answers. & thanks to Graham G & Peanut for the link.

As I said earlier, on an MTB you basically get what you are given when it comes to gearing. Road bikes have a lot of choice & I had hardly any idea of what would be most suitable for me.

oldwelshman

As one of the other posters previously mentioned, forget wheel diameters, sizes etc, it is too confusing, just divide the fron teeth by the back for a ratio.
Don't worry about gearing anyway, just go for a compact 50/34 with 12/27 and thatshould be ok for most routes for a fittish cyclist unless you are unfit and plan to go up hills over 400m with 30% grade.
Forget worrying about 53/11 gear for top end speed, you will be going fast enough on a 50/12 and to be honest if someone is flat out with a 53/11 you could just freewheel behind them easily and at that speed would probably have to use your brakes
On steep decents you would actually spin out even with a 53/11 and I have not seen many riders who use a 53 x 11 on the flat, not even for sprinting. Now I expect loads to come back and say thats what they use for sprinting
If they do, look at track sprinters and see what they use !! They go fast enough!!

peanut

this is all so much bull really. :roll:

the op just needs to get on a road bike and cycle it for a few weeks locally. He'll soon work out if any of the rear sprockets are redundant or more sprockets are needed to get up hills.
It all depends on your cardio-vascular fitness, strength, stamina,will power, weight , and local geography and bike
Whats good for one of us will be totally wrong for another. There is no answer to this question as there are too many variables. Sorry but it is a dumb question imho
just get on a bike and try it and you will soon know what you need for certain

COVEC

+1 for the Sheldon Calculator,

If you select the output to the ratios it gives you a very easy reference guide. Just been going through the thread and followed the link provided, it helped me understand the principal quite readily

COVEC

johnbirkby46213

just to add my bit to this. I thought this was an excellent page and download:
http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3521

JB

richardjallen

When I started thinking about this I decided to just divide the number of teeth on the chainring in question by the teeth on the sprocket in question. This gives a ratio that describes the number of turns of the rear sprocket and therefore rear wheel will turn for every complete turn of the pedals. The higher the number the harder to push but the further you will travel for one turn of the pedals. I know that it works because really it is dividing the cirmference of one wheel by the other - the teeth are the same size on both the chainring and the sprocket so the number of teeth is a quick way of measuring the circumference. Not only that but I tested it by watching the number of times the valve spins round for one revolution of the pedals - it works.

So:
53/12 = 4.416
52/12 = 4.333
50/11 = 4.545 - highest ratio

39/25 = 1.56
34/25 = 1.36 - lowest ratio

A 50 34 double with 11 - 25 cassette gives both high and lower gears than a 53 39 with 12 - 25 cassette. I even ploted and excel spreadsheet to see the curves and compare them.

Then I thought I would not need the lower gears of a 50 34 and instead got a 52 39. Now I wish I had got the compact. Doh.

Ken Night

richardjallen wrote:

to just divide the number of teeth on the chainring in question by the teeth on the sprocket in question. This gives a ratio
.

Whether you compare these ratios or gear inches, it's the comparision that counts

richardjallen wrote:

A 50 34 double with 11 - 25 cassette gives both high and lower gears than a 53 39 with 12 - 25 cassette. I Now I wish I had got the compact. Doh.

But do you need a higher gear? To get a lower gear you could get away with an Alpine cassette (Campag's 13-29, or if you're a Shimano user, you could fit an MtB cassette)


A compact gives you a lower gear with the same cassette (small gaps), which is the point-I believe compacts came about on the continent by old racers wanting a lower gear, than available on a "standard double"-applies to most of us, as the SD was developed for racers and professionals.

The other thing to take into account is the useability of a compact-the original double came equipped with 42/52, which was a nice step between chainrings

50/34 is too great a step, often meaning a triple change at the rear when changing down into the 34

So 48/34 with 12-27, would appear to cover most bases

I like 50/36, with 13-26, which gives me a run of 7 sprockets with 1T gaps, and the ability to use an Alpine cassette if I want-I've done very fast French sportives, and not found I wanted a higher gear, if anything a lower one was required-put on the Alpine cassette and the problem is sorted

48/12 of course is a higher gear than 50/13, so maybe 48/34 is the way to go

I hope that helps

Foz72

I'm sorry but I think this is the sort of subject that brings out the worst in roadies. At least on this thread we haven't really had the usual lurkers to casually drop in the days they used to ride reps on Winnats Pass on a fixed gear ('never bothered me, you'll be fine'). But there's still a lot of status-anxiety bubbling under whenever this subject comes up.

My advice, from a cr*p-but-keen perspective.. If you're starting out, unless you're interested in racing in the near future, just get as many and as low gears as you can lay your greasy little hands on. You might never (or almost never) use the last one but one day you'll be tired, or not feeling too great. Maybe riding into a desperate headwind through a high pass, soaked to the skin. Maybe with a knee injury that makes it hard to ride out of the saddle.

Then you'll be glad

redddraggon

Foz72 wrote:

I'm sorry but I think this is the sort of subject that brings out the worst in roadies. At least on this thread we haven't really had the usual lurkers to casually drop in the days they used to ride reps on Winnats Pass on a fixed gear ('never bothered me, you'll be fine'). But there's still a lot of status-anxiety bubbling under whenever this subject comes up.

My advice, from a cr*p-but-keen perspective.. If you're starting out, unless you're interested in racing in the near future, just get as many and as low gears as you can lay your greasy little hands on. You might never (or almost never) use the last one but one day you'll be tired, or not feeling too great. Maybe riding into a desperate headwind through a high pass, soaked to the skin. Maybe with a knee injury that makes it hard to ride out of the saddle.

Then you'll be glad

My next bike is going to have a 54/42 and 11-21

richardjallen

Ken Night wrote:

Whether you compare these ratios or gear inches, it's the comparision that counts

It is, except I don't know what gear inches are and did not know of them at all when I first looked into this. It seemed obvious to me to divide the chainring teeth by the sprocket teeth. If gear inches are any more involved than that then is there an added benefit?

Ken Night wrote:

richardjallen wrote:

A 50 34 double with 11 - 25 cassette gives both high and lower gears than a 53 39 with 12 - 25 cassette. I Now I wish I had got the compact. Doh.

But do you need a higher gear? To get a lower gear you could get away with an Alpine cassette (Campag's 13-29, or if you're a Shimano user, you could fit an MtB cassette)

I rarely need the highest gear that I already have. I only come close to using it on decents and going fast enough to need it scares the life out of me. I need lower gears far more often. But I was pointing it out because covers greater range than even the standard (except when using a 11 tooth sprocket on a standard). What I mean is you do not lose the high end but gain at the low end.

I know you can fit a MTB cassette. For shimano I think it requires a long cage derailleur. On my get-to-work bike I am thinking of doing this and perhaps having just a single chainring with no front derailleur.

Ken Night wrote:

50/34 is too great a step, often meaning a triple change at the rear when changing down into the 34

I like 50/36, with 13-26, which gives me a run of 7 sprockets with 1T gaps, and the ability to use an Alpine cassette if I want-I've done very fast French sportives, and not found I wanted a higher gear, if anything a lower one was required-put on the Alpine cassette and the problem is sorted

I've read alot of people say 34 is too low and I have considered 36. They seem to be harder to find on off-the-self chainsets. Currently I have a 12-27 cassette which I put on if I think I will need it. It does not really give much lower gears though and I have thought of a MTB cassette but that means a new derallieur. So its either a chainset or cassette and derallieur for me I think. Another thing to consider with swapping cassettes is chain wear. I do not use the 12-27 much so it will not be worn to the chain. I would not get this problem by using a compact chainset and the same cassette all the time.

richardjallen

Foz72 wrote:

I'm sorry but I think this is the sort of subject that brings out the worst in roadies. At least on this thread we haven't really had the usual lurkers to casually drop in the days they used to ride reps on Winnats Pass on a fixed gear ('never bothered me, you'll be fine'). But there's still a lot of status-anxiety bubbling under whenever this subject comes up.

I think thats partly why I got a standard. I had one on another get-to-work bike and it was fine. I rationalised that where I live is flat and would not need one. For the most part this is true but there was also the worry of having wussy gearing. Other people said not to worry but I mistook the advice as being the devil on my shoulder when really it was the angel.

But as everything I suppose it depends on the individual. Reddragon there is going to have the highest gearing known to humankind. I bet he has legs like tree trunks.

dennisn

redddraggon wrote:

My next bike is going to have a 54/42 and 11-21[/quote]

I like your optimism Red. I think my next bike is going to have a motor. And it won't be me.

dennis noward

redddraggon

dennisn wrote:

redddraggon wrote:

My next bike is going to have a 54/42 and 11-21

I like your optimism Red. I think my next bike is going to have a motor. And it won't be me.

dennis noward

I want a TT bike, so it's probably not that optimistic.

dennisn

redddraggon wrote:

dennisn wrote:

redddraggon wrote:

My next bike is going to have a 54/42 and 11-21

I like your optimism Red. I think my next bike is going to have a motor. And it won't be me.

dennis noward

I want a TT bike, so it's probably not that optimistic.

650 wheels??? If not, a 54-11 is a monster. Although I have noticed a lot of triathelets
are real low RPM pounders. When I ask them about it their usual reply is something like
"well, if you push bigger gears you go faster". Obviouslly spinning is not in their
vocabulary. Then again some of them are really successful with this approach.
Whatever it takes I guess.

Dennis Noward

heavymental

redddraggon wrote:

My next bike is going to have a 54/42 and 11-21

Fck that! Both my bikes have a 34/50 and a 12-28. Suits me at home and twiddling in the mountains. I had a 12-25 before but swapped that for a 12-28 on a trip to the mountains and now I just leave it on all year. Each to their own of course, it depends what your local terrain is like and wether you like to grind or spin. I like to spin up the hills so it suits me to have plenty of low gears. I don't have an issue with my sxy bike having a 'dinnerplate' on the back. I never get off to walk and I'm as fast/faster as anyone I ever ride with.

redddraggon

Heavymental wrote:

redddraggon wrote:

My next bike is going to have a 54/42 and 11-21

Fck that! Both my bikes have a 34/50 and a 12-28. Suits me at home and twiddling in the mountains. I had a 12-25 before but swapped that for a 12-28 on a trip to the mountains and now I just leave it on all year. Each to their own of course, it depends what your local terrain is like and wether you like to grind or spin. I like to spin up the hills so it suits me to have plenty of low gears. I don't have an issue with my sxy bike having a 'dinnerplate' on the back. I never get off to walk and I'm as fast/faster as anyone I ever ride with.

Well the TT bike is off as my next bike. It's now a winter bike, which I've started to order bits for.

53/39 with 12-25 is my answer this time.

FSR_XC

Well I tested 3 bikes on Saturday and have ordered one.

As recently mentioned the gearing seemed to make bu66er all difference.

The bike I'm getting has standard chainset (53-39) with a 12-27 cassette.

heavymental

Nice one. You might find it makes a difference as you notch up the miles though. You'll soon know if thats good for you or not. 12-27 is a decent enough range so I don't see why not although you might struggle on tougher climbs.

oldwelshman

FSR_XC wrote:

Well I tested 3 bikes on Saturday and have ordered one.

As recently mentioned the gearing seemed to make bu66er all difference.

The bike I'm getting has standard chainset (53-39) with a 12-27 cassette.

Well I suppose it depends how fit you are and where and how far you intend to ride and what hills
Testing a bike on a short ride is not much use for testing gears, I doubt there is a hill in the uk I could not get up on a 39 x 21 when starting straight off, but it is a different story after 100 gruelling miles
However I cramped up on a couple of sportives last year on steep hills using 39 x 27 thats why I have gone for compact on my new bike, just in case I cannot get over the cramp
The standard set you have chosen will be ok for general riding and most hills.

redddraggon

oldwelshman wrote:

[I doubt there is a hill in the uk I could not get up on a 39 x 21 when starting straight off

Even Hardknott and Wrynose?