Cycling UK Forum

Could anyone help?

I'm new to cycling so find it difficult to explain, well, i presume this is why the bike shop cant find the problem.
Every pedal revolution it feels like the is a little notch or slip. Its not a huge amount, just a little blip. Its not there all the time, it develops after about 4miles and its usually just when i begin to push down on the left pedal but is sometimes apparent on both pedals.

The bike has alfine 8 internal hub and its only a few months old. Its been a problem since new so i've taken it back to to the shop twice already. They either dont understand what i'm trying to say or just dont listen as they return it saying all is fixed.

Loose bottom bracket?? although I don't know why it would only occur after four miles or why the bike shop wouldn't have discovered it. Try grasping the pedals one in each hand and see if there is any play there.

Loose crank ??
Depends on the type but see if you can tighten them.

Nothing seems loose, although ther does seem to be a little play before the rear cog engages

it could well be a mechanical fault of some kind, (and the bottom bracket would be the first port of call) but if so its a weird one; bikes are not like cars, they don't 'warm up' as you go down the road.... but the rider does....

So this is going to sound like a daft question but how smoothly do you think you are pedalling? Does this perhaps vary?

The reason I ask is that the A8 hub has roller clutches in it; these have the feature that under certain circumstances they don't engage positively after a short period of freewheeling. Is it just possible that if you are not pedalling smoothly and that mid-pedal stroke there is a tiny amount of freewheeling and then the drive is taken up again...?

cheers

Not sure how i would rate my pedalling, but i would presume that its 'variable'. Any tips for overcoming an unsmooth stroke

years of practice makes for a smooth pedal stroke; trying to pedal much faster than normal for a few miles normally makes pedalling smoother and better at a more normal cadence (pedalling speed). Normal cadence for skilled cyclists varies from around 70 to 120/min with the lower values being more commonplace when climbing. People new to cycling often try to pedal slowly i.e. 'mash' a bigger gear; few carry on like this for ever.

If you can try a bike with a (preferably noisy) conventional ratchet freewheel, once you have done a few miles on your normal bike, you might well feel or hear if you are not pedalling smoothly at this time. Or perhaps have someone lese ride with you, they might spot it.

It could still be a mechanical fault of course... but if it is (say) a systematic hub fault I'd expect it to vary with gear ratio...

cheers

Greenmonkey wrote:Not sure how i would rate my pedalling, but i would presume that its 'variable'. Any tips for overcoming an unsmooth stroke

It sounds from your description as though you are failing to maintain tension on the drive train as your left foot comes through top-dead-centre. I would suggest that you try pedaling slowly at first, and try to feel the pressure on the drive train all the way around the stroke. Try to make the pressure as constant as possible, rather than a hard push when each foot moves down, and very little in between.

In order to maintain pressure when the cranks are vertical, you may need to slightly raise the heel of the bottom foot, and/or drop the heel of the top foot, so that you can push the pedal through that part of the stroke.

For the symptom you are describing, you could try focussing on the bottom of the right pedal stroke, and try to simulate the action of scraping chewing gum of the bottom of your shoe. This should help maintain pressure through the bottom of the pedal stroke, which is the time that your left foot (at the top of the stroke) is indicating that your stroke is "off the pace".

Once you are feeling that continual pressure on the chain, you can speed up the pedalling. It's often considered preferable to pedal reasonably quickly (maybe around 90rpm) as you can put more power through the drivechain for a given level of pedal pressure. However, as you pedal faster there is more momentum in the feet and cranks, making it easier to fudge the issue of maintaining pressure through the top of the stroke, which is why I suggest starting slowly and only speeding up once you understand what you are trying to achieve.

Finally, it's easier, though not essential, to practice smooth pedalling with foot retention, such as clipless pedals or toe straps. If you do this, you can also try the exercise of cycling with only one foot clipped in at a time, making it even more obvious when one foot is failing to contribute at some point during the stroke. Be very careful if trying this - you don't want to catch your free leg with the pedal, and don't do it anywhere near traffic. The best place is a turbo-trainer.

Good luck!

Just a thought. How is the tension on the chain controlled? I had a similar experience when I first has a rolhoff hub with an eccentric bottom bracket. I was convinced that the problem was in my right pedal but finally discovered it was the bolts that secured the bottom bracket in its shell were not tight enough and had a minute movement. Oddly, it only became apparent after 10 minutes or so of riding.

Are the pedal bearings set up correctly? I had some new pedals recently which needed re-adjusting out of the box as the were too tight and didn't spin freely.