2 chainring versus 3 chainring crank

General cycling advice ( NOT technical ! )
reohn2
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Re: 2 chainring versus 3 chainring crank

Postby reohn2 » 26 Aug 2019, 9:48am

To the OP.
I'll try not to get too technical.
You first need to ask yourself how fast you're likely to want to go on a flat road and down hill
You then need to ask yourself how slow you're prepared to climb hills

These two speeds are dictated by a combination of leg power and cadence rate.
Leg power is obvious to the individual and needs the person to be honest with themselves about their strength and overall fittness.

Cadence(pedalling rate or speed the legs turn)is determined by what feels right and comfortable to the individual,but remembering a slow cadence say <65rpm needs more outright power for any given speed,whereas a really fast cadence say 110>rpm needs a specifically learned technique to be efficient.

Most people's optimum cadence rate(OCR) is somewhere in the range of 75 to 95 rpm.
The purpose of gearing is to keep the rider in OCR for any given terrain whether that be climbing or descending.
The wider the gear range the more the opportunity to have the right gear for OCR.

But there's another consideration,gaps between individual gears,which also play a very important part in keeping OCR.
If the gaps are to wide changing from one gear to another can leave the rider struggling to maintain OCR and therefore in the case of changing up to a higher gear loosing power immediately,unless they have the leg power to overcome the loss of OCR.
Or OTOH if they have the technique to spin up a lower gear out of OCR when changing to a lower gear.

It's fair to say that overall many bikes on sale are over geared ie; their range of gearing is set too high for most people's needs,as a result the forum gets asked many times by riders how to lower their overall gearing.

So,with the above understanding you need ask yourself what set of gears will suit you best,bearing in mind the terrain you intend to cycle in and at what speeds you intend to cycle at.
When that's determined a better answer and recommendation of what gearing's needed can be given.
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Audax67
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Re: 2 chainring versus 3 chainring crank

Postby Audax67 » 26 Aug 2019, 10:24am

@byrononabike: you know, you're wanting to cover longer distances & longer hills than on your current MTB. I think that simply changing to a road bike, "hybrid" or not, will already make a huge difference. And if you want the hybrid so that you can also do the odd toddle to the shops then stick a rack on your MTB and get a pure road bike: it'll feel like growing wings.

As to double vs triple, I rode almost every serious ride I did on a variety of triple set-ups, then switched to a double in 2015. I love the newer bike for really long, solo rides and climbing, but on the triple I find it's easier to match speed with others if I'm riding in a pack. The triple will also provide you with a deeper introduction to the pestilential quirks of drive-trains, the double in my experience being easier to adjust by a couple of Irish miles. Components do wear out faster on a double, but that's a very marginal consideration.

Honestly, though, I'd say to just get a dedicated road bike, of whatever gearing, and fly.
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NetworkMan
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Re: 2 chainring versus 3 chainring crank

Postby NetworkMan » 26 Aug 2019, 8:43pm

Please, please don't just buy any old road bike without being sure the gears will go low enough. As Reohn2 rightly points out many, many write in to this forum asking how they can get lower gears on a road bike with a compact double chainset. We virtually never get anyone complaining that their gears don't go high enough!

reohn2
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Re: 2 chainring versus 3 chainring crank

Postby reohn2 » 26 Aug 2019, 9:31pm

NetworkMan wrote:Please, please don't just buy any old road bike without being sure the gears will go low enough. As Reohn2 rightly points out many, many write in to this forum asking how they can get lower gears on a road bike with a compact double chainset. We virtually never get anyone complaining that their gears don't go high enough!

And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.
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Paulatic
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Re: 2 chainring versus 3 chainring crank

Postby Paulatic » 27 Aug 2019, 7:15am

reohn2 wrote:
NetworkMan wrote:Please, please don't just buy any old road bike without being sure the gears will go low enough. As Reohn2 rightly points out many, many write in to this forum asking how they can get lower gears on a road bike with a compact double chainset. We virtually never get anyone complaining that their gears don't go high enough!

And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.

I reserve those three for downhill only :) and it’s fairly steep before the very smallest is employed.
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thelawnet
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Re: 2 chainring versus 3 chainring crank

Postby thelawnet » 27 Aug 2019, 8:04am

reohn2 wrote:
NetworkMan wrote:Please, please don't just buy any old road bike without being sure the gears will go low enough. As Reohn2 rightly points out many, many write in to this forum asking how they can get lower gears on a road bike with a compact double chainset. We virtually never get anyone complaining that their gears don't go high enough!

And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.


That depends on what the top three gears are, surely. There are plenty of MTB hybrids with relatively low top gears.

Also I see a lot of people grinding big gears without really thinking about it - they are being used even if not optimal.

reohn2
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Re: 2 chainring versus 3 chainring crank

Postby reohn2 » 27 Aug 2019, 8:19am

thelawnet wrote:
reohn2 wrote:
NetworkMan wrote:Please, please don't just buy any old road bike without being sure the gears will go low enough. As Reohn2 rightly points out many, many write in to this forum asking how they can get lower gears on a road bike with a compact double chainset. We virtually never get anyone complaining that their gears don't go high enough!

And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.


That depends on what the top three gears are, surely. There are plenty of MTB hybrids with relatively low top gears.

I beg to differ,my 29er MTB's top is 40x11 = 106inch,just about useable off a cliff!


Also I see a lot of people grinding big gears without really thinking about it - they are being used even if not optimal.

But that's what we're discussing,effecient useable gears.Grinding away at a biggger gear than necessary isn't the best use of energy.
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reohn2
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Re: 2 chainring versus 3 chainring crank

Postby reohn2 » 27 Aug 2019, 8:22am

Paulatic wrote:
reohn2 wrote:
NetworkMan wrote:Please, please don't just buy any old road bike without being sure the gears will go low enough. As Reohn2 rightly points out many, many write in to this forum asking how they can get lower gears on a road bike with a compact double chainset. We virtually never get anyone complaining that their gears don't go high enough!

And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.

I reserve those three for downhill only :) and it’s fairly steep before the very smallest is employed.

That's your prerogative but personally at 25mph I usually let gravity do it's thing these days
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Cugel
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Re: 2 chainring versus 3 chainring crank

Postby Cugel » 27 Aug 2019, 8:54am

reohn2 wrote:
Paulatic wrote:
reohn2 wrote:And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.

I reserve those three for downhill only :) and it’s fairly steep before the very smallest is employed.

That's your prerogative but personally at 25mph I usually let gravity do it's thing these days


I've passed many a heaver going down hill whilst not pedalling myself. Many don't have much understanding of the huge difference it makes to get aerodynamically crouched upon the bicycle. In fact, their flapping knees and sticky out elbows, as they heave down hill in 53X11, is making them rather unslippery to all that air rushing over them!

But they never learn. "You must have better wheel bearings", declared one. "What tyres are those", asked another.

Cugel, highest gear 52X14, used for sprinting for the village sign and little else.

wearwell
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Re: 2 chainring versus 3 chainring crank

Postby wearwell » 27 Aug 2019, 9:01am

There has been a recent burst of fashion for the double chainring, basically for people who fancy themselves as racing cyclists. :lol:
Bt there's a distinct disadvantage - having the narrow range of gears which a racing cyclist would be happy with is a big disadvantage to the general user especially if in hilly terrain and carrying loads. Having the wider range offered by modern doubles and rear blocks is part solution but leaves you without the range of closer ratios which you really need when the going gets tough (or the hills get steep or you get tired, wind against etc etc).
I've had both and was very glad to swap back to a triple.
PS AVOID! I had the SRAM Apex "compact" set up which was utterly cr@p. Never worked well and eventually failed altogether with broken lever gear change mech. Luckily it's quite easy to remove the mechs so I still have the brakes, but bar end shifters instead. Much better!

thelawnet
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Re: 2 chainring versus 3 chainring crank

Postby thelawnet » 27 Aug 2019, 9:17am

reohn2 wrote:
thelawnet wrote:
reohn2 wrote:And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.


That depends on what the top three gears are, surely. There are plenty of MTB hybrids with relatively low top gears.

I beg to differ,my 29er MTB's top is 40x11 = 106inch,just about useable off a cliff!


Really?
This is about an average -0.7% gradient, I was in 40/11 for most of it (the first part is poorly surfaced, the rest is tarmac, and there's a hill at the end).

orly.png
orly.png (9.39 KiB) Viewed 255 times


MTB on road because not all the roads are surfaced here, so a MTB seems to be the most useful thing.

The more-or-less continuous downhill isn't steep enough to be visible to the naked eye, so it's not steep enough to coast, but it's enough of an aid to want a big gear.

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Tigerbiten
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Re: 2 chainring versus 3 chainring crank

Postby Tigerbiten » 27 Aug 2019, 11:15am

Paulatic wrote:
reohn2 wrote:And I'll guess a vast majority of riders very,very rarely ever use the top three gears,particularly on road geared bikes.

I reserve those three for downhill only :) and it’s fairly steep before the very smallest is employed.

Same here.

There are very few hills around Northampton at are both steep/long enough to warrant shifting up into my top range and that I think are safe to go down at +35 mph.
The converse is also true, there aren't many hills that are steep/long enough to warrant me using using my bottom three gears around here.
I freely admit that only having spare/unused low gears is better than only having spare/unused top gears.
But you cannot beat having both as the ultra wide range on my recumbent trike (1800% :shock: ) matches my riding style.

YMMV ......... :D

james01
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Re: 2 chainring versus 3 chainring crank

Postby james01 » 27 Aug 2019, 1:46pm

+1 for triple. I've spoken to so many newbies who get persuaded to buy high-geared doubles ("...nobody uses triples any more, sir"), then get thoroughly demoralised when they do the walk of shame up a not-very-steep hill. And the simple answer to the difficulty in fine-tuning a triple to avoid front-mech rubbing is to revert to friction shifters - do we really need indexing at the front?

NetworkMan
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Re: 2 chainring versus 3 chainring crank

Postby NetworkMan » 27 Aug 2019, 2:10pm

thelawnet wrote:
reohn2 wrote:
thelawnet wrote:
That depends on what the top three gears are, surely. There are plenty of MTB hybrids with relatively low top gears.

I beg to differ,my 29er MTB's top is 40x11 = 106inch,just about useable off a cliff!


Really?
This is about an average -0.7% gradient, I was in 40/11 for most of it (the first part is poorly surfaced, the rest is tarmac, and there's a hill at the end).

orly.png

MTB on road because not all the roads are surfaced here, so a MTB seems to be the most useful thing.

The more-or-less continuous downhill isn't steep enough to be visible to the naked eye, so it's not steep enough to coast, but it's enough of an aid to want a big gear.

If I read it right an average of 30 kph with a 106 inch gear is a cadence of only 59. I'd call that pretty low which may explain the difference of opinion.

thelawnet
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Re: 2 chainring versus 3 chainring crank

Postby thelawnet » 27 Aug 2019, 3:53pm

NetworkMan wrote:
thelawnet wrote:
reohn2 wrote:I beg to differ,my 29er MTB's top is 40x11 = 106inch,just about useable off a cliff!


Really?
This is about an average -0.7% gradient, I was in 40/11 for most of it (the first part is poorly surfaced, the rest is tarmac, and there's a hill at the end).

orly.png

MTB on road because not all the roads are surfaced here, so a MTB seems to be the most useful thing.

The more-or-less continuous downhill isn't steep enough to be visible to the naked eye, so it's not steep enough to coast, but it's enough of an aid to want a big gear.

If I read it right an average of 30 kph with a 106 inch gear is a cadence of only 59. I'd call that pretty low which may explain the difference of opinion.


30 mean, mode is more like 32.5 and a 27.5 wheel, so it works out around 69 rpm. 40/13 would be well undergeared