70sSanO

Years ago it had to do with the stiffness of the frame. If the bottom bracket shell is flexing some of the power is being lost. At least that is what was hyped.

That may not apply to modern carbon frames. All things being equal of a rider’s ability to climb, a lighter shorter wheelbase bike would probably outperform a heavier bike with the same rider.

John

rbrides

Hey, John, you are the first to mention wheelbase as a factor. Could you elaborate on the effect wheelbase has on climbing?

70sSanO

This is really my personal preference, and I imagine a lot of tourers will disagree, but I like having a nimble compact bike especially out of the saddle.

Admittedly I'm biased having ridden an '88 Cannondale Criterium for years that is super stiff and I can't fit my index finger between the tire and the downtube.

John

Leinster

A short wheelbase might also be easier to whip around high-speed tight corners on steep winding descents, much like riding a Crit. I love climbing on my Criterium, and on my CAAD10, with their aggressive geometry. Descending on them is a blast.

When people talk about a "climbing bike," they're usually talking about a bike that is designed to get rider and machine uphill quickly, with no other ballast. Tourers may well prefer long wheelbases to keep their ride steady under load up and over long passes, but their primary concern is to get over the mountain in comfort, and speed is a secondary consideration.

Drew Eckhardt 

I like 50-39-30 x 13-14-15-16-17-18-19-21-23-26 which is 1.15 for the Santa Cruz and Diablo mountains, but in peak form am the same size as Alberto Contador - 5'9.5", 135-137 pounds.

Twenty years ago I liked 50-40-30.x 13-14-15-16-17-18-19-21 which is 1.4 for the Rocky Mountains. Same low as 42x28 for the mountains west of Boulder, CO plus a 13-19 straight block for plains east.

It's about grade, length, power to weight ratio for the resulting duration plus how many hours you want to be fresh afterwards.

That varies enormously. Most people just use whatever the bike company will sell them.

ofajen

Good point! The wind resistance force will be approximately kAsv**2, where k is the coefficient of air resistance, A is the combined frontal surface area, s is the speed on the road and v is the speed in the air (road speed plus headwind).

So absolutely, a headwind can suddenly put the wind resistance term into a high speed value (without the reward of actually moving at high speed). Climbing uphill into a headwind will be made significantly harder by both the work against gravity and the work against wind. For any given hill and rate of climb, there will be a wind speed at which the air drag exceeds the gravitational term. Additionally, as head wind increases, the importance of aerodynamic efficiency of rider and bike (or purposeful inefficiency in your case) will increase and at an increasing rate.

Otto

ofajen

Foliage will have an effect on the wind. A lot of my riding is in hilly neighborhoods or roads lined with trees or on various trails that are also mostly tree-lined and many of my climbs are either coming out of sheltered valleys or up tree-lined hill sides. At this time of year, the foliage often knocks down the wind. In the winter... not so much! Of course, with the leaves down, the headwinds always seem strong on the flats all winter long.

Otto

ZHVelo

In no realistic world is this a climbing bike for the average person. 36-30 is a joke on long, steep climbs. The amount of watts you would have to churn out just to do say 60 RPM.

Toespeas

id say a climbing bike is a bike that focuses on hills , its built to be in a climbing position , its less aero focused and more focuses on light weight stiffness , and an 11/30 is great climbing gear set , like you said the double rings allow you to take on all terrain , but its mostly for hills and not for flats

rbrides

ZHVelo, Thanks for being focused on the correct context of my question. Is the bike aero enough and light weight enough for the 1.2 final gear to effective on long stead climbs? I don't know. As I mentioned in my OP, that does not seem to be a particularly low gear by today's standards.

rbrides

For what its worth. An article from bike radar on "best" climbing bikes.

https://www.bikeradar.com/advice/buy...limbing-bikes/

Leinster

Most of them with an 11-30 as stock, some even with 11-28.

Thing is, with most of these bikes, they're trying to build something that will sell in multiple regions. Yes, if you're biking in the Swiss Alps, you will more than likely need a lower gear than 1.2. But you're unlikely to need anything that low on the roads of northern Europe, large swaths of the US, anywhere in Australia, etc. And if you're buying a System 6 with Di2 Dura Ace, you should be able to climb the Matterhorn in 36-30 (and if you aren't strong enough to do that, then at $9,000 for a bike, you're rich enough to swap your cassette, derailleur, chainrings out). If I still lived in Ireland, a 34-34 gear would go unused on anything with slick tires.

ZHVelo

I agree, but if you call it a 'climbing' bike you can expect that it should be for climbs. Be that longer steepish ones that will tire you out and you can't grind on 36-30 forever unless you are very strong, or short but very steep ones where again a 36-30 would be hell (I would not want to do 20% or more on 1.2).

I guess that is why mostly they don't call it climbing bikes, bike brands themselves usually use race, endurance, and aero. Which is why that article on 'climbing' bikes is silly imo.

bikejrff

I had to laugh when I realized as I was reading your post I was eating an ice cream sandwich.

Dave Mayer

Climbing gear ratios? Marco Pantani used 54/44 rings together with a 11-23 cassette - on the tough climbs. Like Ventoux, where he would ascend long 8 percent grades at 20 mph. LMMV.

Climbing bike: as light as possible (<15 pounds), particularly minimizing wheel rotating mass. So carbon frame and low-profile carbon tubular wheels - obviously. 300 gram rims with 200 gram tires. No discs or other useless ballast - obviously.

I've seen the studies that imply that a couple of pounds on the bike will make little difference. These miss the fact that every pedal stroke incurs an acceleration, and the power for these thousands of accelerations per climb come from you.

HTupolev

Inertia works in both directions. A higher-inertia object resists acceleration, but also resists deceleration.

Increasing mass does increase gravitational drag, but there's no micro-acceleration secret sauce.

ofajen

Wow. That’s about 700 watts! He weighed about 55 kg, so rough estimate of 8 kg bike (total 63 kg) means about 440 watts for the climbing term, about 240 watts for the aero term at 20 mph (8.9 m/sec) and another 10 watts per tire plus 10 watts for drivetrain.

Otto

ZHVelo

Yes, the average Joe is definitely as strong as Pantani and able to put out the watts he did.

rbrides

heck yeah!