Sram Force 1 problem

Discuss light weight issues concerning road bikes & parts.
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cerro
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by cerro

I got a Specialized Tarmac with S-Works crankset with a 50t Sram Force1 chainring.

Sram 1170 11-28 cassette
Sram RED22 chain
Sram Force1 rear derailleur

ceramic bottom bracket and all parts run smooth. But together I feel a resistance, feel it even in the workstand. Something isn't going all smooth and all I can think of is the pulley wheels. Anyone know a better option to make my bike work properly? Or know why it doesn't go as smooth as my other bike with Shimano Ultegra/Absolute black 2x11 drivetrain?

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/jonas l
http://cerrol.wordpress.com (my cyclingblog)

by Weenie


Marin
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by Marin

Probably the clutch derailleur, it can put a lot of tension on the chain.

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743power
Shop Wrench
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by 743power

Let it break in a bit. The teeth on the pulleys are probably what you're feeling
"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."

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cerro
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by cerro

how long is a bit? Done almost 1000km on it. Did change to a Red derailleur to try and it goes so much smoother.
/jonas l
http://cerrol.wordpress.com (my cyclingblog)

djcharlou
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by djcharlou

The upper pulley need to be closer to the cassette cogs no ? Looks on closer on my setup

jeanjacques
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Location: France

by jeanjacques

Hello,
Did you resolve your problem ?
I have this derailleur, works without problem but it's little bit noisy. Maybe a fine tuning to do.
Like you, I'm looking at pulleys and can't understand the idea behind the narrow wide teeth. I'm thinking to change it for KCNC 12 teeth, maybe somebody already did that ?

Marin
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by Marin

For your setup, you can use a regular short cage mech anyway, and save over 100 grams too.

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DMF
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by DMF

It's not the pulleys, it's the clutch, all SRAM CX-derailleurs have a very strong clutch and it steals a lot of watts putting that extra tension on the chain.

Disclaimer, CeramicSpeed will tell you that the watt savings will differ depending on which spring tension setting you set the OSPW cage system on. This stuff matters and as for clutch derailleurs it's very noticeable compared to a standard non-clutch system.

youngs_modulus
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by youngs_modulus

I'd be careful using phrases like "steals a lot of watts" here...we're hardly talking 50 watts.

The SRAM 1x derailleurs have relatively strong springs, but the clutches don't come into play unless you've got an oval chainring, in which case clutch friction directly dissipates pedaling input. Even in that case, it's a relatively small number of watts.

Drivetrain friction is vexing because it's easy to feel small differences, but they still don't add up to much. Chains' apparent efficiency actually goes up with increasing chain tension. Essentially, the absolute losses are somewhat constant no matter the tension. A rider putting out 100 watts might only see 90% drivetrain efficiency (100 watts output, 10 watts absorbed by the drivetrain), while the same rider on the same drivetrain making 400 watts would get 96.5% efficiency (400 watts output, 14 absorbed by the drivetrain). I'm making these numbers up, but the're a reasonable first approximation.

For the OP: DMF is still probably right that strong springs are the culprit. Other factors may include friction between the chain and your narrow/wide chainring. Doesn't AbsoluteBlack use a different tooth profile than SRAM? In any case, it seems pretty straightforward to swap out parts to find the exact cause.

If you're worried about spring tension, using the longest chain you can get away with will minimize the spring tension. Yes, a few more links would add weight (and maybe preclude you from using a smaller chainring with that chain) but you could get some of that back by trimming your rear derailleur housing. ;)

I've seen a Friction Facts report that suggests the SRAM Red chain has more friction (a little over three watts) than a Dura-Ace chain when both have the stock lube applied. That same report suggests that you can get those three watts back by flushing the Red chain with solvent and re-lubing with something like Rock-N-Roll Gold or Finish Line Wet or FL Dry Teflon.

I understand why this bothers you, but rest assured that (a) you're not losing 50 watts or even 25 watts on your new bike, and (b) by removing the old lube and putting on something less viscous, you'll narrow the drivetrain friction gap.

Marin
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by Marin

youngs_modulus wrote:but the clutches don't come into play unless you've got an oval chainring


On most non-round chainrings, chain uptake doesn't change a lot, but the lower part of the chain does move up and down. You can run a singlespeed with an oval chainring, IIRC Sheldon Brown demonstrated this.

youngs_modulus
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by youngs_modulus

That's a good point, Marin, and I mostly buy it. It should be easy to measure the angular displacement of the derailleur cage with a non-round chainring. Any pedaling-induced angular displacement on a clutched derailleur cage is wasted energy, but I agree that the movement may be small enough that the wasted energy is also very small. Anybody got a video?

Marin
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by Marin

Image

I just switched back to a round ring (the 36 oval is for touring) but I can make a video next week.

by Weenie


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