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Designing a bike for hill climb

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Old 02-09-23, 11:52 AM
  #26  
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Ultra-climber vs Fargo Street:

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Old 02-09-23, 11:56 AM
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As others have said, it makes a difference whether you're talking about a bike that's better at climbing hills as part of your ride or you're making a bike that's specifically for a hill climb race like the Mount Washington Auto Road Hill Climb (or your area's equivalent).
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Old 02-09-23, 11:58 AM
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Originally Posted by mschwett
if all you cared about was getting to the top of a hill as fast as possible, it might look something like this? a (sorta) fully functional 10lb bike.




https://www.bikeradar.com/features/p...alized-aethos/
Notice the brake levers. Big, set way below the seat and very far forward. The levers are close to horizontal. She can ride so stretched out she has full use of her diaphragm for breathing and no compressed anything in her torso, Great oxygen utilization. Like I said in my first post - it's all about fit! Being able to do all that with her wrists rotated thumbs forward. pinkies back means she should be able to "honk" on those levers forever without chronic wrist/hand issues.

This bike looks like a super comfortable all day climber. Mt Washington (with slightly bigger tires unless it is now paved all the way up). Repeats on Dead Indian Memorial Highway. (See my last post.)
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Old 02-09-23, 12:27 PM
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A 4.7kg bike isn't much an advantage when you're 83kg with 3.0 w/kg ftp

There is a lot to the 'ride more,' but it's all about power/weight. Gearing that maximizes cadence@ftp and comfort for an hour is what I try to achieve.
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Old 02-09-23, 12:56 PM
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Originally Posted by 79pmooney
Notice the brake levers. Big, set way below the seat and very far forward. The levers are close to horizontal. She can ride so stretched out she has full use of her diaphragm for breathing and no compressed anything in her torso, Great oxygen utilization. Like I said in my first post - it's all about fit! Being able to do all that with her wrists rotated thumbs forward. pinkies back means she should be able to "honk" on those levers forever without chronic wrist/hand issues.
Brake levers look like they are in a pretty standard position to me. Bar drop doesn’t look very unusual either.
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Old 02-09-23, 01:57 PM
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Originally Posted by PeteHski
Brake levers look like they are in a pretty standard position to me. Bar drop doesn’t look very unusual either.
I came here to write the same thing.

Looks like a fairly common race bike fit to me. If I were to set up a hill climb-specific bike, I would want it to have the same fit as the bike I ride all the time.

Changing your "event bike" fit to something other than what you've spend a bazillion hours training on does't seem like a good strategy.
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Old 02-09-23, 02:06 PM
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Originally Posted by PeteHski
Brake levers look like they are in a pretty standard position to me. Bar drop doesn’t look very unusual either.
Originally Posted by terrymorse
I came here to write the same thing.

Looks like a fairly common race bike fit to me. If I were to set up a hill climb-specific bike, I would want it to have the same fit as the bike I ride all the time.

Changing your "event bike" fit to something other than what you've spend a bazillion hours training on does't seem like a good strategy.
yeah, except for the lack of bar tape it looks like my setup.
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Old 02-09-23, 02:18 PM
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I was really hoping this thread would be more about pushing the limits of what is actually climbable, not "hill climbing racing". I would love to see some custom bikes with ultra low gears, stretched chainstays so the bike doesn't flip over backwards, and unusually forward canted riding positions.
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Old 02-09-23, 02:21 PM
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Originally Posted by freetors
I was really hoping this thread would be more about pushing the limits of what is actually climbable, not "hill climbing racing". I would love to see some custom bikes with ultra low gears, stretched chainstays so the bike doesn't flip over backwards, and unusually forward canted riding positions.
See that ultra-climber bike video, above.
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Old 02-09-23, 02:27 PM
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Originally Posted by PeteHski
Brake levers look like they are in a pretty standard position to me. Bar drop doesn’t look very unusual either.
I'm trying to get over the size of the chain wheel! How steep is that hill?
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Old 02-09-23, 02:31 PM
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Originally Posted by freetors
I was really hoping this thread would be more about pushing the limits of what is actually climbable, not "hill climbing racing". I would love to see some custom bikes with ultra low gears, stretched chainstays so the bike doesn't flip over backwards, and unusually forward canted riding positions.
Usually racing is what pushes the limits. I certainly couldn't climb some of the steeper sections they climb in many grand tours and especially in races that are all about climbing.

I'm still not understanding what you are wanting. We have bikes with what to me are ultra low gear ratios. How steep a hill and for what distance are you wanting to climb would probably answer the questions most of us want to know.
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Old 02-09-23, 04:52 PM
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Originally Posted by rsbob
Adlai apparently is MIA. Lots of good questions posed as to intention but just….crickets. Bueller? Bueller? Anyone? Anyone?
it’s his m.o.
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Old 02-09-23, 06:05 PM
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Originally Posted by Iride01
I'm trying to get over the size of the chain wheel! How steep is that hill?
The hill was around 12% average with 17% max. Steep, but not ultra-steep. It’s a 32T chainring, so not unusually small. Only 2 teeth less than a standard 34T on a compact double. It just looks small because there is no 50T outer ring.
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Old 02-09-23, 06:22 PM
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Originally Posted by terrymorse
To minimize drive train friction, bigger is better. The reason: big cogs and chainrings require the chain to bend less.

Let's say you want a 1:1 gear ratio. A 50 chainring with a 50 cog will be more efficient than a 34 chainring with a 34 cog.
An advantage of bigger gears of the same ratio as that of smaller ones is less chain tension for an equal power output. Total chain "angular displacement" (sum of the angles of the individual links) will be the same.
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Old 02-09-23, 06:27 PM
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Originally Posted by superdex
A 4.7kg bike isn't much an advantage when you're 83kg with 3.0 w/kg ftp

There is a lot to the 'ride more,' but it's all about power/weight. Gearing that maximizes cadence@ftp and comfort for an hour is what I try to achieve.
I'm about 92kg, was 100kg when I joined the road club 33 years ago. I always thought that being heavier put me at such a disadvantage and I was already working hard to stay near lighter climbers so any additional weight on the bike just made things worse. Of course, I can't use super light parts because they break. That little climbing bike pictured wouldn't last very long for me.

I did a 5 day tour with a bunch of climbing and a friend who was much faster than I actually added weight to his bike so that we were close in total weight. I liked that and I try to pitch it to the small climbers on club rides but they won't bite.
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Old 02-09-23, 07:23 PM
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Originally Posted by rsbob
Adlai apparently is MIA. Lots of good questions posed as to intention but just….crickets. Bueller? Bueller? Anyone? Anyone?
So one of my current bikes is kind of a frankenbike. From what I've read here it doesn't look like I can improve much more of it.

it is an advent rear derailleur that goes I think 11-42 or 46 9 speed.

I actually have a double on the front. 50/36. Advent supposedly doesn't support it but it works fine.

The 50 is too tall and I end up spending most of my time on the 36. But it can go below a 1:1 ratio. All the climbers have around a 36 front and a 36 back.
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Old 02-09-23, 07:30 PM
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Trek calls its Emonda a climbing bike, and puts rather high gearing on it.

I climb with a 30T in the front and a 36 or 34 T in the back.
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Old 02-09-23, 07:50 PM
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Originally Posted by Polaris OBark
Trek calls its Emonda a climbing bike, and puts rather high gearing on it.

I climb with a 30T in the front and a 36 or 34 T in the back.
A 48/35 + 10-33 on the Emonda AXS doesn't seem like very high gearing.
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Old 02-09-23, 09:05 PM
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Originally Posted by adlai
So one of my current bikes is kind of a frankenbike. From what I've read here it doesn't look like I can improve much more of it.

it is an advent rear derailleur that goes I think 11-42 or 46 9 speed.

I actually have a double on the front. 50/36. Advent supposedly doesn't support it but it works fine.

The 50 is too tall and I end up spending most of my time on the 36. But it can go below a 1:1 ratio. All the climbers have around a 36 front and a 36 back.
The questions asked were:

1. Are you in a hill climb competition?
2. Are you a recreational cyclist that just wants to climb more easily?
3. How steep is the hill in percent grade?
4. How long is the climb?
Scroll up to see how people are trying to help you by trying to understand the challenge and your goal.
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Old 02-09-23, 09:13 PM
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Originally Posted by tomato coupe
A 48/35 + 10-33 on the Emonda AXS doesn't seem like very high gearing.
I did see that one. Oddly, it seems to have a bit of a weight problem...

It is still > 1:1 gear ratio. (48/35 seems kind of odd. The big sprocket is low and the small sprocket is high.)
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Old 02-09-23, 09:56 PM
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Originally Posted by rsbob
The questions asked were:

1. Are you in a hill climb competition?
2. Are you a recreational cyclist that just wants to climb more easily?
3. How steep is the hill in percent grade?
4. How long is the climb?
Scroll up to see how people are trying to help you by trying to understand the challenge and your goal.
Right ... a re you designing a climbing bike or a bike for a hill-climb? Lots of climbing or one climb? Climbing competitions or rides with a lot of climbing? Seems all those have been covered anyway.
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Old 02-09-23, 11:53 PM
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Originally Posted by son_of_clyde
An advantage of bigger gears of the same ratio as that of smaller ones is less chain tension for an equal power output. Total chain "angular displacement" (sum of the angles of the individual links) will be the same.
I think that explanation is backwards:
  1. A larger cog/chainwheel pair has a smaller chain link angular displacement.
  2. As long as gear ratios are the same, chain tension is the same for all cog/chainwheel pairs.
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Old 02-10-23, 12:44 AM
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Originally Posted by Polaris OBark
I did see that one. Oddly, it seems to have a bit of a weight problem...

It is still > 1:1 gear ratio. (48/35 seems kind of odd. The big sprocket is low and the small sprocket is high.)
It's still considered a road racing bike, so I doubt 1:1 gearing is a high priority.
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Old 02-10-23, 03:11 AM
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Originally Posted by terrymorse
I think that explanation is backwards:
  1. A larger cog/chainwheel pair has a smaller chain link angular displacement.
  2. As long as gear ratios are the same, chain tension is the same for all cog/chainwheel pairs.
Chain tension actually does decrease with larger cogs with the same ratio. But the chain also moves faster and power is a function of chain tension x chain speed.
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Old 02-10-23, 07:07 AM
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Originally Posted by PeteHski
Chain tension actually does decrease with larger cogs with the same ratio. But the chain also moves faster and power is a function of chain tension x chain speed.
Right. For the same speed (and thus, the same power), and same gear ratio (and thus, same cadence), a small-small ring-cog has lower chain speed -- so chain tension must be higher. That is, a 52/26 and 36/18 are the same gear ratios. At a constant 80 rpm (so the bike's rear wheel would be moving at the same speed, so the power must be the same), the chain in the 52 ring would be moving 80*52 = 4160 links per minute, while in the 36 ring the chain would be moving 2880 links per minute. Power is same, chain speed is 1.44x faster in the 52 ring, so chain tension must be 1.44x lower.

As an historical aside this is how the old Polar power meter worked: it had a chain speed sensor and a chain tension sensor. The proof-of-concept for the tension sensor was a guitar pickup.
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