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Originally Posted by RonH
(Post 19129441)
I see this is your first post. Tell us about yourself, your bike(s), where you live/ride, etc.
I'm 71. I'd recommend any decent brand of padded cycling shorts or bibs (nashbar.com, performancebike.com, etc), minus any underwear. I've been riding on saddles with a center cutout since about 2003. Both of my bikes have a Selle Anatomica X series. Love them. :thumb: https://cdn.shopify.com/s/files/1/01...g?v=1472675578 |
I submitted a reply,but it didn't post
Originally Posted by RonH
(Post 19129441)
I see this is your first post. Tell us about yourself, your bike(s), where you live/ride, etc.
I'm 71. I'd recommend any decent brand of padded cycling shorts or bibs (nashbar.com, performancebike.com, etc), minus any underwear. I've been riding on saddles with a center cutout since about 2003. Both of my bikes have a Selle Anatomica X series. Love them. :thumb: https://cdn.shopify.com/s/files/1/01...g?v=1472675578 |
You guys are great!
|
Originally Posted by rawly old
(Post 19080207)
Look, suit yourself, But I know for a fact & utterly without a doubt that it iis easier
to pedal a 24/11 that it is to pedal 39/18... . |
Originally Posted by McBTC
(Post 19158569)
Put these two gear ratios into BikeCalc.com and both are 2.2 gear inches. Facts are facts.
being more distant from the fulcrum. Archimedes once said," Give me a place to stand, and I shall move the world," He was referring to leverage. Think of your 170mm crank as the lever & the chainring as the fulcrum. Your pedal will be closer to a 39T ring than a 24t ring. the further from that ring, (fulcrum), the more leverage you can exert. Basic physics. |
Originally Posted by rawly old
(Post 19158582)
Correct, absolutely correct. However one offers considerably more leverage against the pedal
being more distant from the fulcrum. Archimedes once said," Give me a place to stand, and I shall move the world," He was referring to leverage. Think of your 170mm crank as the lever & the chainring as the fulcrum... I'm no expert but I don't believe you have a proper handle on the physics. The crank arm is the lever; and, the bottom bracket is the fulcrum (axis or pivot). Your leg of course provides the turning force. Gearing does not change the length the lever arm, nor the amount of force (or power) that a cyclist is capable of generating. Depending on the gear ratio of the bicycle, a (torque, rpm) input pair is converted to a (torque, rpm) output pair. By using a larger rear gear, or by switching to a lower gear in multi-speed bicycles, angular speed of the road wheels is decreased while the torque is increased, product of which (i.e. power) does not change. ~wiki |
[QUOTE=McBTC;19158682]I'm no expert but I don't believe you have a proper handle on the physics. The crank arm is the lever; and, the bottom bracket is the fulcrum
The 'Fulcrum' changes every time you move from one chain ring to the next. That's what gears do. I'm sorry you don't grasp the concept. Probably diminished blood flow to the brain. you should ride more & post less. It will improve function. |
The force applied by the tire to the tarmac is determined by the ratio of the crank arm length to the radius of the rear tire, multiplied by the gear ratio. Period. All of this analysis of intermediate forces and torques gets canceled out. Yes, it is true that you are applying more torque to a smaller chainring than to a larger one, but this is exactly canceled out at the rear wheel as the smaller cassette cog applies less torque to the wheel than does the larger one!
One can try this out on a typical road bike by comparing the effort of pedaling a 50/25 gear combo to 34/17 (or something similar depending on your gearing). |
[QUOTE=rawly old;19158851]
Originally Posted by McBTC
(Post 19158682)
...
I'm sorry you don't grasp the concept.... . |
Originally Posted by DougG
(Post 19159281)
...
One can try this out on a typical road bike by comparing the effort of pedaling a 50/25 gear combo to 34/17 (or something similar depending on your gearing). All fine up to here-- in this instance a call out to subjective reasoning can only perpetuate scientific ignorance. Old Rawly already informed us about what he knows, "for a fact & utterly without a doubt that it is easier to pedal a 24/11 that it is to pedal 39/18. I have bikes on which I can use both arrangements, and I have tried both! there is significantly less resistance with the 24/11. I am not imagining it." |
[QUOTE=McBTC;19159333]
Originally Posted by rawly old
(Post 19158851)
I doubt it but thanks for making me feel so much smarter than I really am... can assure you it has been tried, tested, & proven. Though the ratio is the same 24/11 is easier to pedal than 39/18. I'm glad you feel so much smarter than you really are. And Doug, No it's not. All either of you need do is try it, but your stubborn mind set & ego will never let that happen. It's really extremely simple, 24/11 has a mechanical advantage due to increased leverage! |
Originally Posted by rawly old
(Post 19159672)
Perhaps you think this is just something I made up of the top of my head, But I can assure you it has been tried, tested, & proven... . |
If the ratios are the same then the resistance should be the same. If it's not, then there is a problem in your drive-train.
If anything, because the chain has to wrap around a smaller radius with the 24/11 the drag might be higher. |
Originally Posted by Speedskater
(Post 19159740)
If the ratios are the same then the resistance should be the same. If it's not, then there is a problem in your drive-train.
If anything, because the chain has to wrap around a smaller radius with the 24/11 the drag might be higher. |
Small chain-rings have more friction than large ones. But it would take some good equipment to measure the difference.
|
First, the arithmetic in Spoke Calc is rounded off. Let's get it right.
The 24:11 ratio = 2.181818.... The 38:18 Ratio = 2.11111..... So, the 24:11 is about 3% lower than the 38:18, and therefore is in fact easier. Now with that said, if the real ratios were identical, there would be no difference in pedal force. The longer chainring lever length on the 24:11 is offset by the shorter lever length on the 11 tooth cassette gear. The analysis that the true measure is the wheel inchs per pedal revolution is the correct analysis. In the real world, there is a tint difference in the force required caused by friction differences between the two different combinations. There, now go ride your bike and pedal however feels best to you. |
And, a 39:18 ratio is...?
|
Is this STILL raging? I`m surprised that somebody`s mother hasn`t yet been brought into the fray . . . .Curmudgeons Rule!
Don`t ask . . . For the record, when I (rarely) use the small chainwheel in anticipation, I invariable change up on the gears so the ole legs rotate at the same liesurely pace . . . never noticed any change in effort needed. So there you are! End of. |
come on admit it, you can't agree to disagree********************?? so what, move on
|
Repeat an inaccurate statement often enough and someone besides yourself will likely believe it.
|
During the mindless seemingly unending miles of distance riding (long,long ago) I used to amuse my mind wondering this very conundrum.
It had been precipitated by reading that at Indy in 1967, the Granatelly #40 Turbine car, which was 4 wheel drive, somehow divided the applied power 60% to the rear wheels and 40% to the front (or, something along those lines.) The only way I could figure that was by differing gear combinations arriving at the same ratio, assuming front and rear tires were the same size (also unknown.) I had posed this question some time ago on the Bike Mechanics thread, and as I recall, the determination was that the large/large combination was potentially easier due to the larger diameters resulting in more chain wrap at reduced deflection angles between links. But, I would have to revisit that thread to be sure. Anyway, I thought I was looking forward to joining this group in 3 months or so, but now I'm not sure. Y'all are far too cerebral for my capabilities......... |
Originally Posted by Ronno6
(Post 19190841)
During the mindless seemingly unending miles
......... |
Originally Posted by McBTC
(Post 19191612)
Each wheel travels a different distance when cornering so a fixed split between front and rear is no long good enough (except on wet and slippery surfaces)-- we also need a differentials between the axles of 4x4s... :)
I'm sure that the STP #40 Turbine Racer had front and rear differentials to handle the distance difference between inside tire and outside tire arcs...........that is not the point of my ponderance... The issue is: how did the designers achieve a power differential between front and rear wheels? For example, say the turbine generated 500HP. (actual HP was 550) How did the Ferguson 4 wheel drive system transmit 40%, or 200HP to the front wheels, and 60%, or 300HP to the rear wheels?? |
Originally Posted by Ronno6
(Post 19191634)
...........that is not the point of my ponderance...
The issue is: how did the designers achieve a power differential between front and rear wheels? Viscous couplers? |
Originally Posted by McBTC
(Post 19191698)
Viscous couplers?
t even have a CV joint in the driveline....if it had, it probably would have won.............. |
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