Hub gears and chain tension

[RobF]

Could someone explain to me why chain tension seems to have an impact on the performance of a hub gear.

Neither Alex or spinalot on here are cycle mugs, but both have found chain tension to be critical to making the hub gear work properly.

But I don't get it.

The single sprocket on the hub is on its own bearing and common sense tells me the tension of the chain - in the range we are talking about here - cannot make any difference to the way the hub internals work.

 

[flecc]

On unpowered bikes and hub motor e-bikes it doesn't have any effect that I've ever seen.

The problems appear to be with the e-bikes that use crank drive units, particularly with the Panasonic unit which uses a separate motor drive sprocket and front chain-wrapping idler system. It may be that the crank drive units create power surges that "snake" the chain, creating uneven snatches of power into the gear hub.
.

 

[RobF]

On unpowered bikes and hub motor e-bikes it doesn't have any effect that I've ever seen.

The problems appear to be with the e-bikes that use crank drive units, particularly with the Panasonic unit which uses a separate motor drive sprocket and front chain-wrapping idler system. It may be that the crank drive units create power surges that "snake" the chain, creating uneven snatches of power into the gear hub.
.

Thanks, I can grasp that although would never have worked it out myself.

 

[rog_london]

On unpowered bikes and hub motor e-bikes it doesn't have any effect that I've ever seen.

The problems appear to be with the e-bikes that use crank drive units, particularly with the Panasonic unit which uses a separate motor drive sprocket and front chain-wrapping idler system. It may be that the crank drive units create power surges that "snake" the chain, creating uneven snatches of power into the gear hub.
.

I suspect this 'problem' has been dealt with on the later models - certainly my Kalkhoff with 8-speed Shimano hub gear has vertical drop outs for the rear wheel and a derailleur-type chain tensioner.

I can see how horizontal drop outs (to allow chain adjustment) could be troublesome, because with so much power passing through the chain there would be a serious chance of slippage, i.e. the wheel pulling forward in the slots and the chain going slack. A derailleur-style tensioner removes the need for adjustment other than checking the alignment.

On the later models there could be the equivalent of three riders' effort being taken up by chain and sprockets. I've always suspected that the fact that all the power - rider and motor - passes through the drive chain would imply that spot-on adjustment and careful, frequent lubrication would be mandatory.

I find that dry lube isn't enough - I use a sparing application of motorcycle chain lube (which is a grease in a solvent - it penetrates well and then the solvent evaporates).

There's also the matter of riding technique - hub gears don't take kindly to gear changes with the power on. Derailleurs are more forgiving in this respect though it's sensible even with those to take the power off momentarily by 'feathering' the pedals to allow a slick change.

I've had no trouble at all.

Rog.

 

[flecc]

I suspect this 'problem' has been dealt with on the later models - certainly my Kalkhoff with 8-speed Shimano hub gear has vertical drop outs for the rear wheel and a derailleur-type chain tensioner.

Unfortunately they've dropped this arrangement Rog, none of the current crank drive models with hub gears have the rear tensioner arm and vertical dropouts.

 

[Spinalot]

With regards to gear changes whilst moving I have taken to actually stopping on steep ascents because changing gear makes a noise whether I stop peddling, change, and then carry on peddling. So I stop, select a higher gear and then carry on, less drama all round. Although frustrating.
Even on the flat there sometimes feels like a long delay and a bit of banging from the hub. I was told to "ease off" change and carry on. But that is not seeming to work 100% of the time. They are taking some getting used to and I am not sure I like it, if I am honest.

This is why I really like the sound of the N360 NuVinci hubs because there is only one "gear" that is variable like a volume control. If I do not get used to the shimano I will save up for a replacment NuVinci.

 

[rog_london]

Unfortunately they've dropped this arrangement Rog, none of the current crank drive models with hub gears have the rear tensioner arm and vertical dropouts.

Thanks for that, Flecc. A step in the wrong direction, in my humble opinion, though I'm sure their design engineers are far better paid than I am, and therefore they must be right!

Rog.

 

[50 Hertz]

My bike, a Kakhoff, is an early model with an 8 speed Shimano hub and doesn't have the rear tensioner found on some of the newer bikes. I find that chain tension is not an issue. What is an issue is lubrication. Because the chain is expected to change direction through large angles, as it passes from the chain wheel onto the motor sprocket and then onto the chain guide, it has to flex very freely and have no stiff links whatsoever. If the chain isn't properly lubricated, it tends to jump when a slightly stiff link passes through this area. Another thing to remember is to torque the rear wheel nuts up properly. Because of the additional chain tension introduced by the motor, it can pull the wheel out of alignment. From memory, the wheel nuts need to be tightened to 45 NM, but check this figure on the Shimano website first. If correctly tightened, you won't have any alignment slipping problems.

Not wishing to lessen Spinalot's experiences in anyway, but I find the hub gear setup very easy work with. The wheel slots in and out very easily and once adjusted properly, the gears never need any further tinkering.

 

[Spinalot]

I have, so far, found the only thing that gets tense is me. But that could be down to me being a really miserable old sod.

 

[flecc]

My bike, a Kakhoff, is an early model with an 8 speed Shimano hub and doesn't have the rear tensioner found on some of the newer bikes.

Yours is the Panasonic unit, but these chain problems are also being experienced on the models with the other crank power units as well. Those others do not have a motor drive sprocket and wrapping idler, they drive the chainwheel direct. As for that additional rear tensioner on a hub gear chain, the 2007 to 2009 models didn't have one, but then some appeared with it, only to disappear again in the 2012 and 2013 ranges.

 

[103Alex1]

With regards to gear changes whilst moving I have taken to actually stopping on steep ascents because changing gear makes a noise whether I stop peddling, change, and then carry on peddling. So I stop, select a higher gear and then carry on, less drama all round. Although frustrating.
Even on the flat there sometimes feels like a long delay and a bit of banging from the hub. I was told to "ease off" change and carry on. But that is not seeming to work 100% of the time. They are taking some getting used to and I am not sure I like it, if I am honest.

This is why I really like the sound of the N360 NuVinci hubs because there is only one "gear" that is variable like a volume control. If I do not get used to the shimano I will save up for a replacment NuVinci.

This is definitely down to your wheel setup and tuning - my gear changing is completely silent and ultra-smooth. You need to stop riding the bike and fix the noise - if you look up Alfine guidance it all warns strongly against riding with slippage or noise from the hub gears. You can do irreparable damage to the gears if you don't sort this. It's not the gears that are the problem it's the bike setup, Spinalot. Honestly. You won't recognize the bike if you set them up right. Just want to come up & sort it for you. No car unfortunately and in Devon this week.

A front derailleur is a noisy gear system that clanks when you change to a smaller chainring. You should get nothing even remotely like this on hub gears. Best to wipe slate clean and judge bike performance based on correctly set up bike not what you've been experiencing.

 

[Geebee]

The other thing to play with is the cable adjuster, mine requires the alignment marks to be a 2~3mm out of line.
I just tweak as I ride until all gears swap correctly (can take a couple of rides), if I alter any part of the cable run ie. move a front bag, I have to adjust to compensate.
If using in human power mode only the alignment is no where near as critical, which to me suggests that the hubs are being pushed to their limit with the crank drive.
Chain tension has no effect on mine that I can determine, this is on a Tonaro Esprit, same hub.