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I'm repeating words that the bike shop told me or from a google search. This bike seems to be defective since purchase. It's a Schwinn Men's GTX3 Hybrid with 700c wheels. Within a few weeks the pedals started to degrade and would randomly make little clanking sounds or have a scraping feeling only for a second here and there. The pedals and the gear wheel started to wobble increasingly worse and worse until it seemed like it would fall apart with any pressure.

It looked like the interior part of the frame that the pedals connect to was the problem, as if it degraded or was breaking down. Google said this is called the crankset so I'm going with that term.

This was from a Dick's Sporting Goods, which is the only bike related store and shop anywhere near me sadly. Being a corporate chain it seems low quality, and it's hard to find good bike parts, repair, info. They've repaired this 3 times now (supposedly) in 6 months. The first repair didn't even fully fix the issue, it wobbled but was improved. The last time seemed fully better but it only lasted 3 days before rapidly degrading. They claim the bearings and brackets need to be replaced each time; this last time I told them to look for other problems but they were extremely disorganized. I'll be going longer distance to find a legit local bike shop.

I just want to know what is actually wrong with the bike, the right names of parts and what needs to be replaced/repaired. Is it defective? It has a 1-year manufacturer's warranty and it's the most expensive bike I've ever bought (supply chain failures presumably).

DavidW
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Jack
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    Have you asked to see the broken parts they've replaced? – DavidW Jan 17 '23 at 16:16
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    The pedals and the gear wheel started to wobble... Where were they "wobbling"? At the pedal end, or the end in the middle where the arm attaches to the bike? If in the middle, and they attach to a square spindle, the bearing surface inside the arm has become bent/distorted and the crank arms are ruined, not the bearings. – Andrew Henle Jan 17 '23 at 17:57
  • Agree with @AndrewHenle, it sounds like the bike has what's known as a "square taper" bottom bracket - if the interface becomes loose, the relatively soft aluminium crank arm can soon become damaged – John M Jan 18 '23 at 12:10
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    What I was referring to is covered here; Loose crank arm If the crank arm retaining/fixing bolts were not properly torqued when your bike was first assembled, your crank arms will work loose. And when they do that, they start wobbling - and damaging the inner surface where they're supposed to fit tightly against the bottom bracket's square spindle. Once they no longer fit properly, there's no way to stop them from wobbling no matter how tight the bolts are torqued. – Andrew Henle Jan 18 '23 at 23:35
  • (cont) The more the crank arms wobble on the spindle, the more they get damaged. The more they get damaged, the more they wobble. If this is what's happened, the root cause was the person who initially assembled your bike did not properly torque the crank arm retaining/fixing bolts. – Andrew Henle Jan 18 '23 at 23:36

2 Answers2

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Part of the question is about names.

I just want to know what is actually wrong with the bike, the right names of parts

There are several bottom bracket designs. After looking up your bike my best guess is that you have a tapered spindle crank.

To help with the right names here is a diagram of a crankset that should be similar to yours. It is not the same make but it should have similar parts.
Exploded view of a crankset with call-outs for all the parts and a table of names and part numbers below

In the question it says:

The pedals and the gear wheel started to wobble increasingly worse and worse until it seemed like it would fall apart with any pressure.

Based on this description it sounds like the Left Hand Adjustable Cup - part number 15 in the diagram - came loose.
It is also possible that the adjustable cup was too tight and during riding the ball bearings in the Steel Ball Retainer - item 13 - were broken or crushed resulting in an effect similar to the adjustable cup being loose.

On your bike - assuming appropriate lubrication and the parts are not defective - if the bottom bracket is adjusted correctly under "normal" riding conditions it will work fine for years. Simplified diagram showing the relationship between the bearings and cups

Based on your description this bike had defective parts or was not adjusted correctly at time of purchase. Dicks should fix this problem under warranty.
If this is not the case the mechanic at Dicks should show you the broken parts and explain why it is not covered.

DavidW
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David D
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The pedals and the gear wheel started to wobble increasingly worse and worse until it seemed like it would fall apart with any pressure.

Relevant parts are:

  1. The crankset.

    This is the pair of arms connecting the pedals to the bike.

  2. The pedals.

    You know what these are!

  3. The bottom bracket (BB).

    This is the bearing assembly inside the frame that holds the axle and allows it to rotate.

So, the pedals could wobble:

  • on their axle - which is screwed into the crank - if their internal bearings are shot (worn or damaged)

    • in this case you need to replace those bearings or (if they're not replaceable, if the races are also worn, or if it simply isn't worth the effort) the pedals

  • on the crank if the threaded socket is shot

    • replacement crank time. You can't really fix the threaded socket

  • with the crank against the axle if the interface is shot

    • the connection between the cranks and the BB is either splined, or a square taper. Either way, if one crank wobbles relative to the frame and the other doesn't (or they both wobble independently), it's time for new cranks and possibly a new axle too.

  • with the cranks+axle against the bottom bracket if that is shot

    If the cranks+axle move together as a rigid unit but wobble relative to the frame, the BB is failing.

    If you've replaced the BB already more than once, see if the BB shell (the cylindrical section of frame it fits into) needs attention:

    • screw-fit BBs can have issues if the threads cut into the shell are damaged or misaligned. Check whether both sides are screwed in securely or_they_ are loose relative to the frame. These threads can be fixed, but perhaps not by Dick's.

    • press-fit BBs can have issues if the shell is not correctly faced (they must be clean parallel surfaces so the bearings are aligned and the axle straight). This can also be fixed, but probably also not by Dick's.

It sounds like the BB is the culprit, but you could clarify whether the pedals+cranks are wobbling together as a rigid unit, or the pedals are wobbling relative to the cranks.

Any of the threaded interfaces could have been damaged by cross-threading during assembly, and any of the threaded interfaces or the crank-axle interface could have been damaged by fretting if they weren't correctly tightened before use.

Useless
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