what's wrong with this bicycle?

June 7, 2011 6:04 AM

when my friend tries to pedal his bicycle, there is a total lack of tension in the pedals and they just seem to 'slip' and fail completely. we're at a loss.

he recently purchased the bicycle (a schwinn windwood cruiser) and rode it for a few weeks without issue. a few days ago while pedaling on a downstroke the pedal just sort of failed and stopped offering any real resistance to the pressure from his foot. the chain doesn't seem to have any issues so we took the bottom bracket apart for lack of any better ideas, but nothing seemed amiss with that either so we put it back together again to no effect.

asking here in the hopes that it's something relatively simple so he won't have to drag it to a bike shop. thanks for any insight!

posted by austere to Travel & Transportation (12 answers total)

If the chain still moves when you turn the pedals, it's probably the hub in the rear wheel. The rear cog may have come loose. Less likely, the freewheel is busted.
posted by backseatpilot at 6:17 AM on June 7, 2011 [1 favorite]

Could he bring it back to the shop where he recently purchased it? This sounds like something that would be covered under a warranty. I bought a "new to me" bike in relatively mediocre shape last weekend at a flea market, and I get 60 days on just about every aspect of the bike (including a refund or replacement if something major turns out to be wrong). Most bike shops should be able to do even better than that, especially on a brand new bike.

(Unless of course he bought the bike at Target - I just saw it listed there when I googled - in which case yeah. Sorry.)
posted by Sara C. at 6:24 AM on June 7, 2011

Does the chain feel loose? - the back wheel nuts may have slipped forward - loosen the nuts, pull the wheel back until the chain tightens (but not too taut), and do up the nuts again. May account for the lack of tension.

If you have a spare rear wheel, try mounting that and see if that fixes it. Could be the single speed hub mechanism is broken (you'll need some specialised tools to repair that though).

Take a good look through Sheldon Brown - the answers to almost anything related to bike maintenance can be found there.
posted by KirkpatrickMac at 6:25 AM on June 7, 2011

Response by poster: thanks, backseatpilot. we just had another look at it and it's a bit stranger than i remembered. if you stand next to the bike and turn the cranks with your hand, everything feels/looks fine and both the chain and rear wheel are rotating smoothly. however, once you actually sit on the bike and attempt to pedal, the pedal slips almost immediately. if we're on flat ground and pedal extremely lightly, there seems to be a very slight bit of propulsion to the bike but as soon as you apply any real pressure with your foot, again it will slip. at this point we are very confused as to how everything can be working perfectly when we use our hands to turn hte crank but not when we use our feet.
posted by austere at 6:26 AM on June 7, 2011

Seconding what the pilot said. Just looking at the specs online they seem to have single speed back pedal brake hubs. Something is busted in there, with the result that the cog is no longer fully attached to or driving the wheel.

Do the brakes work?
posted by Ahab at 6:29 AM on June 7, 2011

It sounds like the pawls inside the rear coaster hub are slipping under load. I used to work for Schwinn corporate customer service (albeit on the bike shop end of things, rather than the department store end), and as long as things haven't changed considerably, they'll send you a replacement wheel if you call. 1-800-626-2811 according to the website.
posted by brozek at 6:32 AM on June 7, 2011 [2 favorites]

Take it back to the bike shop.
posted by Slinga at 7:01 AM on June 7, 2011

Response by poster: indeed, the rear brake works just fine.
posted by austere at 7:06 AM on June 7, 2011

Have a look at this from Sheldon Brown and see whether it's a match for what you've got, and useful. Particularly the How a Coaster Brake Works section and the bit about retarder springs.
posted by Ahab at 7:39 AM on June 7, 2011

Coaster brake innards behaving like that would be very unusual, indicating complete failure. Coaster brakes don't usually have pawls, but rather a cone clutch that cinches up against the hub shell by a screw when pedaled forward. The cone clutch itself is lightly tensioned by a spring so that it won't simply spin on the screw when the cranks are turned.

It probably could be fixed if you know what you're doing, but being that the bike is still new, I'd just take the bike back, or give Schwinn a call if that doesn't help.
posted by 2N2222 at 7:58 AM on June 7, 2011

Has the arm that attaches the coaster brake to the frame come loose? There should be a metal band holding it to the frame, held on by a nut & bolt.
posted by zombiedance at 9:52 AM on June 7, 2011

Response by poster: nope, the arm is still there, zombiedance. my understanding of the whole coaster brake mechanism is pretty sketchy but from what i've read on sheldon brown's website, i think 2N2222 might be right. as i said earlier, we are just really puzzled by the fact that everything seems to function perfectly as long as we are suspending the bike and using our hands to turn the cranks; it's only when you actually sit on the bicycle and try to pedal that everything seems to fail.

thanks again for the help everyone.
posted by austere at 10:04 AM on June 7, 2011