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Oversized Pulley System Questions

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Oversized Pulley System Questions

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Old 04-17-19, 07:43 AM
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afham07
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Oversized Pulley System Questions

Hi Guys,

I am not quite sure about ospw. As I know, ospw suppose to be helping on the climbing but my question is how it helps? Some saying giving extra gear ratio, some saying pedalling at lower power needed at the same gear ratio comparing to normal pulley.

Am I understand ospw correctly:

Example
1. Normal pulley: gear at 53x11, cadence 90, power is 200, speed will be 30kmp.

2. Ospw pulley: gear 53x11, cadence 90, power is 180, speed will be 30kmph?
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Old 04-17-19, 08:32 AM
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I don't have, nor have I ever used, over-sized pulleys, but I think that even the marketing departments of manufacturers like Ceramicspeed would dismiss your power savings numbers as being 2-4x too optimistic.

I think, and it's very possible that I'm wrong, that the claimed benefit has to do with the frictional losses as chains wrap around a smaller radius - the more the chain has to bend, the more friction it'll see (much like track cyclists avoid really small cogs on the rear and would rather achieve their desired gearing ratio by going with chainrings larger than typically used in road riding scenarios). Going to over-sized pulleys helps to flatten out the (relatively) tight S-turn that the chain has to pass through, so it should help, but I would be shocked by anything on the order of 10% (I think that an ordinary, well-maintained drivetrain transfers well more than 90% of your effort, so 10% should be a non-starter).
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Old 04-17-19, 08:59 AM
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I think the claims are more on the scale of 1-3 watts saved.
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Old 04-17-19, 05:23 PM
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Originally Posted by afham07 View Post
Hi Guys,

I am not quite sure about ospw. As I know, ospw suppose to be helping on the climbing but my question is how it helps? Some saying giving extra gear ratio, some saying pedalling at lower power needed at the same gear ratio comparing to normal pulley.

Am I understand ospw correctly:

Example
1. Normal pulley: gear at 53x11, cadence 90, power is 200, speed will be 30kmp.

2. Ospw pulley: gear 53x11, cadence 90, power is 199, speed will be 30kmph?
fixed it for you. There is no change in gear ratio or help with climbing
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Old 04-17-19, 05:52 PM
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Benefit is so small that I would not bother.
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Old 04-17-19, 05:54 PM
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Originally Posted by datlas View Post
Benefit is so small that I would not bother.
+1
Waste of money.
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Old 04-17-19, 06:14 PM
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Originally Posted by datlas View Post
Benefit is so small that I would not bother.
Well, small efficiency benefit, but what about the swagatron quotient? Very high, my friend.
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Old 04-17-19, 09:41 PM
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Originally Posted by afham07 View Post
Hi Guys,

I am not quite sure about ospw. As I know, ospw suppose to be helping on the climbing but my question is how it helps? Some saying giving extra gear ratio, some saying pedalling at lower power needed at the same gear ratio comparing to normal pulley.

Am I understand ospw correctly:

Example
1. Normal pulley: gear at 53x11, cadence 90, power is 200, speed will be 30kmp.

2. Ospw pulley: gear 53x11, cadence 90, power is 180, speed will be 30kmph?
The size of the pulleys has nothing to do with gear ratios. The ‘gear ratios’ are determined by the size of your chainrings and cassette cogs.
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Old 04-18-19, 02:26 AM
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Thank you all. I will strike ospw off the list. Thanks again. Appreciate it.
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Old 04-18-19, 04:18 AM
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Ceramic Speed claims 2w savings for the pulleys, and more power savings if you use their other ceramic bearings and chain products - up to a total of 16w. You can see their claims here, with time savings claims on flat and hilly (2% anyway) courses.

The time savings come because you would either increase cadence or shift to a higher gear and apply the power that used to go to drive-train friction to moving the bike forward faster. Think of it like a reduced headwind, or a more aero position - albeit, a really expensive one...
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Old 04-18-19, 05:31 AM
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Originally Posted by afham07 View Post
Hi Guys,

I am not quite sure about ospw. As I know, ospw suppose to be helping on the climbing but my question is how it helps? Some saying giving extra gear ratio, some saying pedalling at lower power needed at the same gear ratio comparing to normal pulley.

Am I understand ospw correctly:

Example
1. Normal pulley: gear at 53x11, cadence 90, power is 200, speed will be 30kmp.

2. Ospw pulley: gear 53x11, cadence 90, power is 180, speed will be 30kmph?
Oversized pulleys do not give you a magical 20 watts that propel you down the road.

They may reduce friction in the drivetrain by a watt or so, or fractions of that, but then you're probably losing that back in aerodynamic drag because they're so gigantic.
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