Ease of Crank Spin

23scadoo

I've noticed lately that my crank down't spin backwards very easily, especially in comparison to my wife's. Here are our specs

Wife's Bike
Felt AR3
Ultegra 6800 front, rear derailleur and crank
Reynobonds R4 wheels
FSA BB30 bottom bracket

My Bike
Felt AR5
105 front, rear derailleur and Ultegra 6800 crank
Zipp 404 NSW wheels
just changed my bottom bracket from the FSA BB30 to Praxis

If I spin my wife's crank backwards it will spin about 3 times around but if I spin mine then it will maybe go around once. I though that the bottom bracket could be the problem so I put the Praxis in but that hasn't helped. My next thought is that it's the rear derailleur since shes riding an Ultegra and I'm on 105 but a difference to this extent seems a bit much. It's worth mentioning that the crank also doesn't spin well when I have my trainer wheel on which is the stock wheel that came with the AR5.

Could the Ultegra to 105 make this much difference?

Matthewfalle

What if you spin it forwards? Surely that's the one you want to worry about?

23scadoo

My thinking was that if it didn't spin as well backwards that it wasn't spinning as well forward either.

Matthewfalle

Best to check I'd say then back brief.

cooldad

If it's smooth and turns easy, don't worry.

Especially if it's new. Nice thick new grease instead of old nasty watered down stuff. It will be tackier.

23scadoo

I also put my trainer wheel on my wife's bike to see if it would spin easy and it did so the issue isn't with the trainer wheel hub and I put my wife's R4's on my bike and it didn't spin well either so I don't think the issue is with the wheel hubs. It's got to be something else.

Matthewfalle

Can you post a video of both bikes' cranks when you turn them? There has to be an answer to this issue.

23scadoo

cooldad wrote:

If it's smooth and turns easy, don't worry.

Especially if it's new. Nice thick new grease instead of old nasty watered down stuff. It will be tackier.

Both our bikes are less than a year old so I would imagine that they should spin about the same. Granted, having different wheels and rear derailleur would make a small difference but certainly not this much.

cooldad

You are obsessing over nothing.

keef66

Take the chains off and compare how easily the cranks spin? That will tell you if the difference in resistance is down to drag in the BB rather than the rest of the drivetrain.

Ultegra jockey wheels have bearings vs the bushings in 105?

I'd not be worrying about it though. I'd prefer to spend the time riding rather than faffing about spinning things backwards.

Matthewfalle

But if its occurrin' there has to be an issue or a reason d'aitre.

Video?

dannbodge

I'd be more upset that she's running ultegra and you are "only" on 105

23scadoo

cooldad wrote:

You are obsessing over nothing.

You're probably right but i just can't hep but think that I could be riding faster if the crank was spinning more smoothly.

cooldad

Just ask her to slow down a bit. If she loves you she will.

23scadoo

Here are two videos of what I'm talking about. The first one is my bike and the second is my wife's. If it matters, both bikes were in the same gear.

https://youtu.be/SSHZ0_-gXVA
https://youtu.be/WRmUcstsaoY

trailflow

Different rear hubs can have different freehub designs with different pawls shapes,more pawls,more ratchet teeth etc. which will cause the freehub to come to a stop faster.
The bearing used in the freehub (and bottom bracket) can also have different levels of resistance depending how new they are or how were designed and amount of grease that is packed inside. All of these will effect how long it spins. Other things that will effect how long it spins is the chain and cassette weight. And the preload of the crank arms.

a crank that doesnt spin backwards (or forwards) for very long doesn't mean something is wrong. a crank that is harder to spin and requires extra effort to spin forward does mean the resistance is too high and the tolerances are too tight.

Spining your crank backwards (or forwards) to see how many rotations it will get doesn't show you much and it should not be used to gauge how well your cranks perform because 1. you dont ever need to pedal backwards. and 2. When you pedal the crank forwards with your legs, the weight and force of the rider is much greater than the force you can get by doing it by hand and that weight/force will push through that resistance much more easily. So they do not compare in the same way.
a 'spinnier' bb with a light load does'nt mean your cranks spin any better with a heavier load.

Remove the chain from the chainring, sit on the bike and pedal, you will soon know if there is too much resistance or not.

23scadoo

trailflow wrote:

Different rear hubs can have different freehub designs with different pawls shapes,more pawls,more ratchet teeth etc. which will cause the freehub to come to a stop faster.
The bearing used in the freehub (and bottom bracket) can also have different levels of resistance depending how new they are or how were designed and amount of grease that is packed inside. All of these will effect how long it spins. Other things that will effect how long it spins is the chain and cassette weight.

a crank that doesnt spin backwards (or forwards) for very long doesn't mean something is wrong. a crank that is harder to spin and requires extra effort to spin forward does mean the resistance is too high and the tolerances are too tight.

Spining your crank backwards (or forwards) to see how many rotations it will get doesn't show you much and it should not be used to gauge how well your cranks perform because 1. you dont ever need to pedal backwards. and 2. When you pedal the crank forwards with your legs, the weight and force of the rider is much greater than the force you can get by doing it by hand and that weight/force will push through that resistance much more easily. So they do not compare in the same way.
a 'spinnier' bb with a light load does'nt mean your cranks spin any better with a heavier load.

Find a steep hill, put the bike into the easiest gear and ride up it, you will soon know if there is too much resistance or not.

Thanks for the input trailflow.

But what doesn't make sense is that if I put her wheel on my bike then pretty much everything is equal (other than the new BB and Ultegra vs. 105) and should spin close to the same.

Matthewfalle

Chain both lubed the same?

23scadoo

Matthewfalle wrote:

Chain both lubed the same?

My chain is brand new and my wife's chain needs to be replaced and cleaned. Even before my new chain it spun this bad.

pinno

As said before, take the chain off the bike and see if the chainset spins easily. There's no other way to ascertain if the chainset needs bearings/needs re-greasing or is over tightened or that it is simply drag or a problem with drag, freehub, r mech etc.

sungod

^this

how they spin backwards is irrelevant, a rear mech is not designed for a chain going that direction, don't waste time on wondering why two different things being badly misused behave differently

if you're concerned about the bb, remove the chain, see how the cranks spin, if they do about 3 revs before stopping it's fine

Matthewfalle

23scadoo wrote:

Matthewfalle wrote:

Chain both lubed the same?

My chain is brand new and my wife's chain needs to be replaced and cleaned. Even before my new chain it spun this bad.

Hmmm. Jockey wheels all ok?

Matthewfalle

sungod wrote:

^this

how they spin backwards is irrelevant, a rear mech is not designed for a chain going that direction, don't waste time on wondering why two different things being badly misused behave differently

if you're concerned about the bb, remove the chain, see how the cranks spin, if they do about 3 revs before stopping it's fine

This is a good point very well presented, but the OP won't be riding his bike with no chain and therefore wants to find out why his bike is not working as well as his Mrs'. It's an understandable point and I hope we can help him.

23scadoo

Pinno wrote:

As said before, take the chain off the bike and see if the chainset spins easily. There's no other way to ascertain if the chainset needs bearings/needs re-greasing or is over tightened or that it is simply drag or a problem with drag, freehub, r mech etc.

I took the chains off and found that my wife's crank spins much more free than mine does.

23scadoo

Matthewfalle wrote:

23scadoo wrote:

Matthewfalle wrote:

Chain both lubed the same?

My chain is brand new and my wife's chain needs to be replaced and cleaned. Even before my new chain it spun this bad.

Hmmm. Jockey wheels all ok?

I haven't taken the chains completely off but was able to spin the first/highest jockey wheel and mine spin a little better than hers.

pinno

23scadoo wrote:

Pinno wrote:

As said before, take the chain off the bike and see if the chainset spins easily. There's no other way to ascertain if the chainset needs bearings/needs re-greasing or is over tightened or that it is simply drag or a problem with drag, freehub, r mech etc.

I took the chains off and found that my wife's crank spins much more free than mine does.

Then investigate. You say you fitted a Praxxis BB? Is it over loaded? Is any of the BB protruding and interfering with a crank arm? Are the bearings free? Have you dislodged a seal? Is the crank in line and not offset slightly? That's improbable but not impossible.

23scadoo

Pinno wrote:

23scadoo wrote:

Pinno wrote:

As said before, take the chain off the bike and see if the chainset spins easily. There's no other way to ascertain if the chainset needs bearings/needs re-greasing or is over tightened or that it is simply drag or a problem with drag, freehub, r mech etc.

I took the chains off and found that my wife's crank spins much more free than mine does.

Then investigate. You say you fitted a Praxxis BB? Is it over loaded? Is any of the BB protruding and interfering with a crank arm? Are the bearings free? Have you dislodged a seal? Is the crank in line and not offset slightly? That's improbable but not impossible.

Since I don't have the tools to install the Praxis BB it was installed by my LBS. Just looking over it, it appears to be installed well. There's no wobbling or anywhere that the BB looks to be rubbing on the crank arms.

Matthewfalle

Hmmmm. All nice and clean around/behind cassette?

23scadoo

Matthewfalle wrote:

Hmmmm. All nice and clean around/behind cassette?

Yes. although I don't think the cassette is the issue. I thinks it's the crank and or BB based on when I just spun the BB on each bike. My wife's spun easily for twice as long. I might just take it into another LBS (since I think the original one is tired of my questions) and see what they think.

imposter2.0

23scadoo wrote:

cooldad wrote:

You are obsessing over nothing.

You're probably right but i just can't hep but think that I could be riding faster if the crank was spinning more smoothly.

ffs

Matthewfalle

23scadoo wrote:

Matthewfalle wrote:

Hmmmm. All nice and clean around/behind cassette?

Yes. although I don't think the cassette is the issue. I thinks it's the crank and or BB based on when I just spun the BB on each bike. My wife's spun easily for twice as long. I might just take it into another LBS (since I think the original one is tired of my questions) and see what they think.

Seems like a good idea - can you keep this thread updated with your findings as it's a particularly intriguing case.