Double or Triple chain rings ?

[MacB]

I live near the Peak District and have just bought a second hand Cannondale with double ring. Previously i was riding a Hybrid with a triple and i found the hills a lot easier.

I have an Ultegra groupset, would it be expensive to switch to a triple?

I would imagine it would be cheaper, and easier to change sizes of rings or the cassette

 

[jimboalee]

OK people, here it is.

It does involve weight, as everything in cycling does.

Weigh everything. Yeh, put everything on the bike that is going to be on the bike. Bottles, computer, saddlepack, etc.

For simplicity of calculation I will load two bottles on my Pug 531 and the entire weight of the bike will be 25lb.

Reciprocate 25. 1 divided by 25 = 0.04.

Multiply 0.04 by 1000 = 40.

That is the gear length that should be on the bike to get me up a 10% all afternoon. 40"

The Pug has a 52/38 chainset and if I'm going climbing, I fit a 13 to 25 six block.

38 and 25 = 40"


Those of you who have a triple with 30 and a 25 sprocket on a 23lb bike can carry another 8 lb of goodies to make 31lb total for that gear.


Choosing the longest gear involves a lot of honest self appraisal.

 

[Fab Foodie]

OK people, here it is.

It does involve weight, as everything in cycling does.

Weigh everything. Yeh, put everything on the bike that is going to be on the bike. Bottles, computer, saddlepack, etc.

For simplicity of calculation I will load two bottles on my Pug 531 and the entire weight of the bike will be 25lb.

Reciprocate 25. 1 divided by 25 = 0.04.

Multiply 0.04 by 1000 = 40.

That is the gear length that should be on the bike to get me up a 10% all afternoon. 40"

The Pug has a 52/38 chainset and if I'm going climbing, I fit a 13 to 25 six block.

38 and 25 = 40"


Those of you who have a triple with 30 and a 25 sprocket on a 23lb bike can carry another 8 lb of goodies to make 31lb total for that gear.


Choosing the longest gear involves a lot of honest self appraisal.

Nuuurse!
Jimbo's forgotten his medicine again...

 

[jimboalee]

Nuuurse!
Jimbo's forgotten his medicine again...

The Earth is ROUND.

 

[Fab Foodie]

The Earth is ROUND.

I'll eat my Brooks with a whole bottle of Peri-Peri if you can make your last post understandable and then true.

 

[jimboalee]

Sorry FF, the Earth is spherical. Not exactly due to rotational forces about the equator.

Anyway,

Let us consider JonhyC's bike from another thread on the same subject.

JohnyC has a 30 ring and a 32 sprocket on what he calls his road bike, but I would call a 'light tourer'.
According to my rule, JohnyC could comfortably climb a 10% with the bike loaded up with camping kit to a total combined weight of 40lb.

I mentioned this on that thread, but no-one took any notice. It is the reason why I said 'hat's off' to JohnyC's knowledge.

Now let's consider Merckx's 'flat-stage' bike from the early seventies. 20lb all up. What gears had Merckx packed? 43 ring and 23 sprocket. That's 50". Why, that's just about on my theory. Fancy that.
BTW, a 'flat-stage' would have a couple of Cat 3 hills thrown in, which could be 10%.


I tell a lie. It's not MY theory. It was a bike builder in Brum who explained this to me.

 

[MacB]

Sorry Jim, but to calculate in that manner is that not assuming that available power input is a constant, or at least will not fall below a certain mark? This site gives a gear inches recommended range for a given type of riding:-

http://www.hubgear.net/selection.html

This would indicate that a solo road rider shouldn't need less than 30 inches or more than 110. As it's about selecting hub gears I'd guess that he hasn't included recommendations for serious racing as I'm sure that's a whole different ball game.

On a personal level I still like the idea of a 8/9 speed bike with about 6 gears in fairly even steps from 40 inches to 90 inches. The other 2/3 gears can be a sort of over/underdrive. This can be done with one chainring if the extremes don't need to be too severe or a second ring(like JohnyC) if you want some really low bail out options.

 

[rich p]

There is surely a difference in strength and fitness of riders, the temporary weight (Food, wine etc) carried and the state of my joints. I have 2 dodgy hips and one dodgy knee so I like to be able to relieve the effort on them with a lower gear than some people.

 

[jimboalee]

Something else you won't believe.

My Mom owned a Hurcules ladies Mixte 531 with a Sturmey 3 speed hub. It weighed 25lb with a saddlebag containing her PRK. I weighed it when I was thirteen after learning about the formula.

The good bike builder changed the gearing on that bike to 42 ring and 22 sprocket. That gave 52" ( J.K.Starley ) in middle gear and 39" in first. Low and behold, it was damned close to what the good bike builder professed.

Third gear would have been just over 68", an 'easy' cruising gear for my Mom.

 

[MacB]

now Jim that makes sense, I can see a lot of rides being comfortably achieved with those 3 gears. But I'm still not sure about a formula to arrive at them. If starting out you may want them all 10 inches lower and then gradually increase as you get fitter.

I suppose that once a certain level of fitness is achieved then a natural cadence should become apparent. Surely this would also have an impact on appropriate gearing?

 

[Chris James]

So Jimboallee's pet theory has it that his mum and Eddy Merckx would need the same bottom gear if riding the same bike?

Hmmm.........

 

[Crackle]

If you ride in one area, your views on gears are going to be limited to that experience. You need to experience lots of different terrain to make your final selection, either that or be prepared to change your gearing set-up when you do something different.

Must admit to being intrigued by hub gears but the premium is way too high,

 

[jimboalee]

Sorry Jim, but to calculate in that manner is that not assuming that available power input is a constant, or at least will not fall below a certain mark? This site gives a gear inches recommended range for a given type of riding:-

http://www.hubgear.net/selection.html

This would indicate that a solo road rider shouldn't need less than 30 inches or more than 110. As it's about selecting hub gears I'd guess that he hasn't included recommendations for serious racing as I'm sure that's a whole different ball game.

On a personal level I still like the idea of a 8/9 speed bike with about 6 gears in fairly even steps from 40 inches to 90 inches. The other 2/3 gears can be a sort of over/underdrive. This can be done with one chainring if the extremes don't need to be too severe or a second ring(like JohnyC) if you want some really low bail out options.

What that website fails to take into consideration is the bike's weight.
The figures quoted would be true for a bike of certain weight, not ALL bikes.

Road, leisurelyHilly40

Yes, this is true for my Mom's 25lb Hercules. Strange

 

[Over The Hill]

riding at 40mph would add the need for another five or six gears stright away, I doubt too many on here need gearing for that

it's not just about 'needing' an extra ring, it's about considering the gearings between front and rear surely?, if te small chaing ring is small enough for hills and he big big enough for anything usual then where's the problem? I haven't used the smaller ring of my double yet, granted I don't do hills but that includes dun and a Southend via Greenwich

I notice that on a double I can use the whole cassette, I couldn't do that on a triple, different bike granted

As a triple fan I can see that there is more overlap with a triple and (in theory) you can have the same range of gears with two cogs if you space them out.

But if you look at that in reality all you are doing is taking away the middle ring: the one you use the most. I quite accept that I could do without the middle ring and still have the range of gears but if you start from say the big ring running to the small on the back and you start to meet a hill, you change to bigger rings on the back and at some point will need to jump down to the small ring on the front, at that point you may then aloso need to change the back rings to smaller as the jump is huge from big to small on a two ring. That is a lot of messing about.
Also the fiddly area from big to small and back in the mid range is the range you use the most.

By contrast on a triple I can sit in the middle ring and cope with most conditions simply by changing the back. Only on sprints changing to big and with steep hills to small.

The overlap is not surplus but is essential to stop you needing to keep changing up and down to maintain a steady flow of gears.
Put it another way I can simply use the front change as an equivelant change to a rear change to hop across to a more suitable range for the road ahead.

 

[MacB]

As a triple fan I can see that there is more overlap with a triple and (in theory) you can have the same range of gears with two cogs if you space them out.

But if you look at that in reality all you are doing is taking away the middle ring: the one you use the most. I quite accept that I could do without the middle ring and still have the range of gears but if you start from say the big ring running to the small on the back and you start to meet a hill, you change to bigger rings on the back and at some point will need to jump down to the small ring on the front, at that point you may then aloso need to change the back rings to smaller as the jump is huge from big to small on a two ring. That is a lot of messing about.
Also the fiddly area from big to small and back in the mid range is the range you use the most.

By contrast on a triple I can sit in the middle ring and cope with most conditions simply by changing the back. Only on sprints changing to big and with steep hills to small.

The overlap is not surplus but is essential to stop you needing to keep changing up and down to maintain a steady flow of gears.
Put it another way I can simply use the front change as an equivelant change to a rear change to hop across to a more suitable range for the road ahead.

OTH, it seems to be the norm that the double drops the 'middle' ring, and useage involves a lot more front ring changes. Whereas a double based around a middle ring set up, with a granny ring for tough bits makes more sense. As long as you accept/setup for all of the cassette accessible from the main ring.