Author Topic: Pedals turn when pushing bike  (Read 7499 times)

Chris Spray

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Pedals turn when pushing bike
« on: July 02, 2017, 08:56:53 pm »
Quick Q

When I push my bike (at stations etc) the pedals still spin - is this normal or should the Rohloff behave like a free hub.

Bit of a pain as my pedals have half cages that scrape on the ground as I push along.

Chris

geocycle

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Re: Pedals turn when pushing bike
« Reply #1 on: July 02, 2017, 09:27:29 pm »
Welcome to the forum, quite normal for a rohloff. If it's a pain, you could deploy a Velcro strap?
 

Matt2matt2002

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Re: Pedals turn when pushing bike
« Reply #2 on: July 03, 2017, 02:12:49 pm »
Welcome to the forum, quite normal for a rohloff. If it's a pain, you could deploy a Velcro strap?

Velcro?
Have you seen the price of it?
A complete rip-off!
 ;)
Never drink and drive. You may hit a bump  and spill your drink

John Saxby

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Re: Pedals turn when pushing bike
« Reply #3 on: July 03, 2017, 05:28:31 pm »
Oddly (?), my pedals turn only when I roll the bike backwards. They're well-behaved & pretty much immobile whenever I push it forward.

As for Velcro: unlike Matt, I'm loopy about the stuff. ;)

Danneaux

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Re: Pedals turn when pushing bike
« Reply #4 on: July 03, 2017, 06:00:55 pm »
Quote
As for Velcro: unlike Matt, I'm loopy about the stuff.
I'm hooked on it.  ;D
=====
In regard to the OP's question: Yes, it is normal to a degree, given the friction caused by the seals. Mine does it too. Here's Rohloff's take on it:
Quote
Crank rotation whilst pushing
Should the bike be pushed, it is possible that the cranks could also start to rotate.

This occurs due to the hub seal automatically activating the sprocket.

A very light running bottom bracket with poor quality seals will make it much easier for the cranks to rotate.

A drop of Rohloff cleaning oil (Part No. 8402) through the holes in the sprocket onto the hub seal will reduce this acivating effect.
Source: https://www.rohloff.de/en/service/faqs/

This issue is quite apart from a problem with the rear axle's internal spacing being askew, where there is an excess of friction that prevents the wheel from spinning freely. For that, a whack on the axle end with a soft-faced mallet usually clears things up.

Best,

Dan.
« Last Edit: July 03, 2017, 06:06:55 pm by Danneaux »

Chris Spray

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Re: Pedals turn when pushing bike
« Reply #5 on: July 03, 2017, 07:54:25 pm »
Thanks all for comments so far.  Don't think Velcro will be deployed.  Too nervous about forgetting it after a long day in the saddle and pole axing myself.

Will have a go with the cleaning oil and maybe move to clueless pedals to stop the jangling as I push the bike through train stations.

Love the Rohloff and particularly love how beuaiftully it rolls downhill.  Also appreciating how low [it] goes on hills - not fast but always capable on a climb.


[Edit for language. -- Dan.]
« Last Edit: July 03, 2017, 08:13:42 pm by Danneaux »

mickeg

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Re: Pedals turn when pushing bike
« Reply #6 on: July 04, 2017, 01:52:41 am »
I think with time the hub seals loosen up some.  I do not recall my crank turning now when I push the bike where I know that it did four years ago when it was new.  Or maybe it still does but I am now used to it?

JimK

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Re: Pedals turn when pushing bike
« Reply #7 on: July 04, 2017, 04:50:53 am »
my pedals turn when I push the bike along, despite the fact that I am using a chainglider. I take this as good evidence that the friction of the chainglider is quite low!

Matt2matt2002

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Re: Pedals turn when pushing bike
« Reply #8 on: July 04, 2017, 08:12:31 am »
Me to JimK.
I often wonder what goes on inside my ' glider. I run a chain on the slack side and see the straight lines of the ' glider. There must be some drag/friction there.
Anyone else a chain of thought on this?
Never drink and drive. You may hit a bump  and spill your drink

mickeg

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Re: Pedals turn when pushing bike
« Reply #9 on: July 04, 2017, 02:28:01 pm »
Me to JimK.
I often wonder what goes on inside my ' glider. I run a chain on the slack side and see the straight lines of the ' glider. There must be some drag/friction there.
Anyone else a chain of thought on this?

There are tiny little elves that pick up and carry each link from chainring to sprocket.

David Simpson

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Re: Pedals turn when pushing bike
« Reply #10 on: July 04, 2017, 05:11:59 pm »
Me to JimK.
I often wonder what goes on inside my ' glider. I run a chain on the slack side and see the straight lines of the ' glider. There must be some drag/friction there.
Anyone else a chain of thought on this?

There are tiny little elves that pick up and carry each link from chainring to sprocket.

George, don't be silly. Everyone already knows about the elves. Matt is asking how much friction the elves generate.  :)

Seriously, I have also wondered about the friction. I figure that it must be fairly low, but I prefer to not have any unnecessary friction. I have found that when the chain gets slack, it starts to make a bit more noise in the Chainglider. When I hear that extra noise, I figure that it is time to tighten the chain. My reasoning (perhaps faulty) is that the extra noise indicates extra friction.

- DaveS
« Last Edit: July 04, 2017, 05:16:19 pm by David Simpson »

Danneaux

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Re: Pedals turn when pushing bike
« Reply #11 on: July 04, 2017, 05:36:23 pm »
Quote
My reasoning (perhaps faulty) is that the extra noise indicates extra friction.
I think your basic reasoning is good, Dave. If the chain is slack enough to create noise, it means more of the chain is in contact with the 'Glider. No matter how small the coefficient of friction, the greater the contact, the greater the friction; it goes to reason.

However (you knew this was coming), the friction of chains against some kinds of plastic can be amazingly low. I am in the midst of crafting a recumbent from a child's full-sus MTB and am playing with chain routing. My most recent effort involves running the chain partly through a polypropylene tube (the kind commonly used in yard irrigation systems) secured to the frame with nylon P-clips. The tube is slick to the touch and when the chain is lubed, the friction is very low (I belled the ends by heating and expanding so the chain doesn't snag on entry/exit). There is some noise, but it is much less than I anticipated.

I suspect much the same effect is going on inside a Chainglider with a slack chain -- more friction than if the lower run was "gliding" free, but not so much overall.

There's another thing to keep in mind: If the Chainglider does indeed "glide" partially along the upper run of chain, this will still hold true even under drive with a slack chain. The only additional friction would be from the untensioned, lower run of chain making internal contact. I postulate the greater noise from a slack chain comes from the additional lower-run contact area coming into play.

All's well till the elves go on strike and become slackers...and the chain excessively so.  ;)

All the best,

Dan. (...who is still lusting after a 36t chainring x 17t splined-sprocket-on-slim-carrier Chainglider)