While pedaling my relatively new mountain bike Hyper Bicycles 26" E-ride Electric Mountain Bike bought from walmart.com), I feel a bit sticky or grinding feeling for a short part on each crank rotation. I noticed when I initially open the box, there were one or two small metal balls (~2mm diameter) fall out, not sure where it is from. Is this sticky or grinding feeling related to loss of the bearing balls? Or the new bike just needs to be lubricated?

right side bracket

photo showing left side of bottom bracket

  • What exact box did you open? The bottom bracket? Modern ones do not use loose balls but if you did loose some you certainly have to replace it. Snd add some grease. Please give us more details, pictures etc. Nov 17, 2020 at 15:07
  • Very likely the bottom bracket bearing is damaged, although a modern BB should not fall apart. If you grab a crank and push it around in all directions is is a little loose? A picture of the area where the crank goes through the frame will help diagnosis, but if this is a new bike you should be able to simply return it. What model bike and where did you buy it? Nov 17, 2020 at 15:51
  • Sorry, I didn't open any parts of the bike, I mean packaging box. It seems there's one or two metal balls in the packaging box. Maybe I will add some grease. Its a Hyper Bicycles 26" E-ride Electric Mountain Bike bought from walmart.com. Let me add some photos.
    – foxinsocks
    Nov 17, 2020 at 16:22
  • BTW, the crank does not feel loose when I pull it.
    – foxinsocks
    Nov 17, 2020 at 16:35
  • 1
    I would advise against buying that brand. Here is what proper welding looks like. With such poor quality control (putting it politely) there's no wonder that there are problems; that's very likely to break. It's not safe for something to be used as a mountain bike.
    – Rob
    Nov 19, 2020 at 5:22

1 Answer 1


More information on the type of bike you have and maybe a video of the grinding would aid in diagnosis.

As Argenti says - the easiest thing to do is to take the bike back to the shop if that's possible.

I'll take a shotgun approach.
I'm going to assume you had a bike delivered to you in a box and did the final assembly.

If you have a front and / or rear derailleur:
Things to check for intermittent grinding while pedaling:

  • front derailleur rubbing on the chain
  • rear derailleur not adjusted correctly

EDIT 1: If you can get the rear wheel of the bicycle off the ground, pedal with your hand and listen for where the sound is coming from. My guess is that it's coming from the rear derailleur.

If you have a bike with a chain guard the chain might be intermittently rubbing on the chain guard. EDIT 1: You have a ring type chain guard that usually does not rub unless it's badly bent.

If you were missing bearings in your bottom bracket you would be getting constant grinding while pedaling and the bearings would be larger than 2mm. That size sounds more like a headset bearing.

The bearings are probably not related to the intermittent grinding/friction issue.

If the bearings do belong somewhere on your bike you need to figure it out before serious damage occurs. I've seen some strange things show up in a box along with a bike and it is possible that the bearings don't belong to your bike.

There are four places bearings should be on a bicycle:

  • Front hub
  • Rear hub
  • Bottom bracket - crank EDIT: looks like a sealed BB so it should be fine
  • Headset - where the handlebars and fork come together
  • Pedals
    See the Terminology index

On a new bike bearings are usually adjusted too tight. It's best to pull the wheels and check hub bearings, they should spin smoothly with no play. Slip the chain off the crank - it should spin smoothly with no play. Pick up the front of the bike and check that the handlebars move smoothly with no play.

That's all I can think of but hopefully this will get you pointed in the right direction.
More information or a more specific question will enable a more specific answer.

EDIT 2: Pedals
On most of the Wal Mart bikes I've worked on some adjustment is possible.

Here is a diagram of a pedal that might resemble what you have.
enter image description here
Sheldon Brown

There is a cap in the middle on the end of the pedal. With a little creativity is it possible to remove the cap (they are usually pressed in, on nicer pedals they are threaded in). With the cap removed there is a:

  • nut,
  • keyed washer
  • bearing cone
  • ball bearings

The nut locks everything in place. Remove the nut, adjust the cone then put the lock nut back on and tighten everything up. It takes me a few tries to get the pedal to spin smoothly with no play.

About 2mm could be the size of a pedal bearing. If the bearings came from the pedal it's easiest to replace the pedals.

When removing pedals the left hand pedal has a left hand thread (turn clockwise to remove) and the right pedal has a right hand thread (turn counter clockwise to remove)

  • I take back what I said about the BB ‘likely’ being damaged. I agree that the grinding more likely to come from drivetrain. The loose ball bearings is definitely worrisome. Nov 17, 2020 at 16:57
  • Added a right side picture and a link to the bike on walmart.com. It does have front derailleur, but no chain guard. I will check the rear derailleur.
    – foxinsocks
    Nov 17, 2020 at 18:04
  • I tried to lift the rear wheel and pedal by hand, it turns out the grinding feeling is from the pedal itself, as I can feel it by just rotating the pedal. Is that normal? Or I need to add some lubrication in there?
    – foxinsocks
    Nov 17, 2020 at 18:13
  • 1
    @foxinsocks my guess is the pedals that came with this bike are disposable, practically speaking.
    – Paul H
    Nov 17, 2020 at 18:39
  • Thanks for your detailed explanation and the picture showing the pedal adjustment. Mine is a pressed in (plastic cap). I tried to pry it open but not very successful. It appears to be very tight, so the 2mm ball seems unlikely from the pedal. If it is unlikely from the pedal. On the other hand, I am afraid that if I pry it open, it might damage the plastic cap that it cannot cap properly afterwards. Would that be worse than if I just leave the pedal as it is now? Would this grinding feeling cause sever damage to the pedal or even the crank if I ignore it?
    – foxinsocks
    Nov 18, 2020 at 1:27

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