My Mountain Bike ,about ten years old,Three (3) sprockets in front. It backpedals (whizzz) But when I go to pedal there is no engagement - Pedals turn but sprockets don't move..But sprockets move when backpedaling.     edit&lt;- I searched Batman's &amp; the other person mentioned for this "Duplicate question" but found none similar.    It's Shimano parts , the pedal arm is white aluminum, the chaingears, is that the word for sprocket ? The Chaingear/sprocket where the chain rides on is Black Aluminum.     When I look behind the assembly,Down at the crank axle,  and while turning crank by using pedal, A round circular part is turning with the pedal , But it is perfectly round and factory made like that ,Looks like a part of chaingear, It's also Black Aluminum, Maybe there's a catch or pin that's broke ?   While I grasp the pedal and crank forward , both pedals turn as supposed to , But the chaingear/Big circular saw piece remains idle, It does not move ,    But it moves when backpedaling, As does the gears on the rear tire..                  edit edit>>          I proceeded to cross a peculiarly arranged intersection, I deemed the coast clear , 5 feet from safety my pedals gave out , I could pedal easily and freely but no movement on my front chaingear and as a result - No torque available to propel my rear gear into saving my life.        A car whizzed around the corner and straight at me at the same time my 21 speed Mountain Bike with GTX tires Shit thine bed
123842
I just pulled my old bicycle out of the garage. It's about 10 years old (a 21-speed mountain bike). It was working when it was put into storage.  When I tried to ride it today, the crank wouldn't engage properly to make the chain rings rotate; or more casually, when I pedaled nothing moved but the pedals themselves.  I flipped the bike over and if the rear wheel was spinning at a fair speed then the chain rings would engage when the crank was turned and the rear wheel had power driven to it as normally expected.  Is there a freewheel or freehub at the crank / chain ring junction that I should examine?  I read through a few dozen questions but I couldn't find any that addressed this specific issue; I hope this is a new question and not just a serious misunderstanding on my part!    I'll post a video shortly, but to give further clarification...   The chain is on the gears; the chain does not slip I can backpedal and the chains and gears spin, as normally expected However, if I pedal forward, the gears which are located at the pedals will not spin; the pedals rotate freely. They rotate as if the thing they are supposed to be affixed to isn't attached.   Also, I'm certainly misusing terms here! By "chain rings" and "crank" I was referring to the areas of the bike as indicated in this diagram:
120866
I have picked up a bike (Specialized Allez) recently that has a very worn cassette from not replacing the chain for an extended period of time. Therefore am looking to change it. I was wondering what other components need to be replaced at the same time due to chain extension causing wear? My current list is:   Cassette Chain Chainring   Do I also need to replace the Rear Derailleur? And is the chainring required to be changed as well?
77496
I've got a road bike with brake lever shifters, and it's developed a small problem with age: sometimes, the shifter doesn't catch the first time or two I push it. It'll move easily, with no resistance, since it's not actually pulling on the cable, then after a few tries, catch and work normally. The colder the temperature, the more often this happens.  I don't know how the mechanism works internally, so I'm curious what would cause this, and also whether it's (as I suspect) gradual wear of some part of the mechanism, and if it's likely to fail catastrophically, or gradually worsen.
89361
I was trying to adjust the position of my handle bar...but might have turned the screw too hard in the wrong direction or perhaps it was like this earlier...not sure....    Thanks  Update 3 - Thank you All for the help !! This is now resolved, I was messing with the wrong screws...there was one underneath and that was the one I had to loosen to change the position of the handlebar -   and thx to the immediate response from Pacific Cycles (Schwinn) letting me know what had to be done !! Update 2 - I removed the other side screw and am attaching some photos, and a video which might give some more ideas.   Update 1 - thanks for all the great suggestions folks ! I will try out the options and report back !!  The Bad screw (you might see that it is almost gone round)   The Good screw on the other side
85714
So I'm taking the time during the holidays to overhaul my commuter bike. The whole drivetrain was full of old oil, road salt and grime so I decided to take the whole thing apart starting with the back wheel. Once I got it off, I ended up with half of the rear axle in my hand and a bunch of ball bearings on the floor (I found them all eventually).   The bike has been in use for about 18 months, and there were no rust and plenty of lube inside the hub so I don't really think it's natural wear.  What could have caused the axle to break? My theory is that they pulled the nuts too tight when they built the bike.  More importantly, is this a "user serviceable part" or do I need to get it repaired/replace the wheel? Seems to me getting the ball bearings to stay in place while I insert the axle would be quite challenging.
61524
I'm an occasional biker. I bought a mountain bike (nothing fancy) with the idea that I might use it off-road or on mountain trails (of which there are many here in Calgary). However, since I've bought it I've done nothing but bike in the city on streets and paved bike trails.  Is there anything worth doing to my bike to convert it to something more suited to urban biking? In particular, the tires have me wondering; they have large rubber off-roading lugs that surely aren't doing me any favors on pavement. I'm not looking to spend a tons of money on a retrofit, but will do so if its worthwhile.
102645
I'm not sure if oscillation is the right way to describe this, but when I'm riding at speed (say around 35-40 km/h) and take one hand off of the bars, the bars shimmy or oscillate – kind of like they are resonating with something. It's not bad, but it's new – I'm pretty sure the bike didn't used to do this…  Does anybody know what would cause this? Or better yet, what can be done to eliminate it?  In case it matters the bike is a Trek 620. The front wheel is a pretty plain vanilla rim with Schwalbe Marathon tire (32-622) and a Sanyo dynamo hub.
45272
I have an older version of this bike:    They have made some changes to the components since I bought my bike but it is more or less the same.  Here are the .    I was hoping to put a solid fork on my bike for the winter.  I want to keep the mountain feel and have lots of clearance for wide tires, etc but I want to get rid of the weight and give my fork a rest.    When choosing a solid fork what do I need to know?     Will any solid fork fit onto my bike?  Do forks come in different sizes?  Different diameters?  Different lengths?  I heard something like you need a special fork if you are going to put it on a bike that was designed to be used with shocks.   I know that I want a fork with disk break mounts so this makes the search slightly more difficult.  Ideally I would also like rack/fender mounts.  (For future touring).   My wheel size is 26 inches, what would happen if I used a 700c fork on my bike?  This seller claims thats what he was using  for.    Edit:  Thanks for the great information.  After reading I have been looking around for a used local fork.  I think that I found one possibility.  But any feed back would be appreciated.     The fork was designed to be used with 700C or 29 inch wheels but it has an axel to crown length of roughly 17 inches (431 mm).  I currently have 100mm Travel in my suspension fork so  that I should get a fork with a length of 455 mm (17.9 inches).  Is this reasonable?  Does it matter if it was designed for a 700C tire if the fork length is correct? As you can see in the picture of the fork the fork has some rake.  Is this a problem?  Will that amount of rake make the bike ride strangely/differently? The steer tube/ headset size is 1 1/8th standard size which is the same as my bike so no concern there.     Here is a picture of the fork:
23993
I've recently started commuting with a bicycle (Giant hybrid bicycle).  I've been trying to learn a little about bicycling to make my commute easier and my time on the bicycle more enjoyable.  Please forgive me for using the wrong terminology.  I've read that I should keep my pedalling speed mostly consistent and use my bicycles gears to adjust my speed.  The problem I'm having is understanding the 'how'.  My bicycle has 3 gears on the front of the chain and 8 gears on the back.    Low gear == easy to pedal High gear == harder to pedal  What I've found is that the gears don't follow a very logical (to me anyway) progression and because of that - I don't know how I should be shifting.  Currently, I've been keeping my front gear in the middle and using the back shifter to change between gears 3-7 or so.  I'm only use about four gears on my '21 speed' bicycle!  I'm also pretty sure the salesman said it was a 21 speed bicycle - but by my count there are 24 combinations.  I know (now) that I'm not supposed to have the front gear in the lowest position and the back gear in the highest (and vice-versa) but that seems to leave 22 gears.  How should I be shifting?  Should I really use all 21 or 22 gears?  I haven't done the math but it really feels like there is a big amount of overlap between the gears.  I hope this ascii art will make sense to someone.  This is just how it 'feels' to me.  ----1----2----3----4----5----6----7----8---- ------------1----2----3----4----5----6----7----8---- --------------------1----2----3----4----5----6----7----8----   Does that make sense?  Is it right?  It feels like there is overlap between the three front gears and that to shift the most 'smoothly' I'd need to constantly change both gears.  But this seems really complicated to me.  I've ridden bicycles with only three gears and I found myself thinking 'More would be nice' - but now I'm overwhelmed.  I'm also questioning if anyone really benefits from so many gears?!
55607
In a closed system, I know the rider wouldn't be able to change the combined center of gravity of the system by moving his weight around. If he pushes the bike to lean to the right, he would go to the left by the amount that would keep the combined cog the same.  But a bike with tires and a road under it is not a closed system, the tires wouldn't let the lower part of the bike left or right when tryingo to initiate lean. Does this mean it is possible to push with your bodies inertia to the bike, and the combined cog will be changed? I thing if you do so above the cog of the bike, you could, but I am not sure.  Edit: My question is not about if you can move the center of gravity of the bike at all. My question is about if can you change the combine cog of the system by moving around on the bike?  English is not my mother tongue, sorry for the confusion
30850
My father, now in his 70's, had a left knee replacement several years ago. He has limited movement in that knee - probably about 85 degrees on a good day. His knee can extend fully, but cannot bend as much as it should. As a result, he cannot pedal a bike he cannot get his left leg over the top of the pedal stroke.   He is desperate to get back onto a bike, he knows he won't be ripping up the road and winning races like the old days, but wants the freedom to go for a slow easy rides.    Does anyone have suggestions as to a solution to the problem. We don't mind spending money if we know the solution will work, but he can't afford to throw big money at wild ideas that may or may not work. If we find a solution, a new bike is likely.   We have access several mountain bikes in a range of sizes to trail ideas, and we have all the tools and skills to build bikes up from parts and rearrange things as needed.    EDIT: Thanks everyone - all great suggestions. What am am going to do is got tto the LBS and get hold of a cheap set of short cranks for around $30- probably from a kids bike, in the 120-150 size range, and see if he can ride that. Depending how he goes, I'll try a standard right crank and a short left crank. If all else fails, we will go for the Power Cranks   UPDATE: In case anyone else has similar problems. Got some 152mm cranks for $30. Set an old  mountain bike up with the seat as far back as possible. The old man is able to ride reasonably comfortably, now has a smile from ear to ear - any suggestions how to remove it - doesn't fit with the grumpy old man image :)   Has got me wondering how many people with minor knee problems would benefit from short(er) cranks.......
69793
I recently bought a bike with different tire sizes (20" rear and 18" front) now I want to replace both with a 16" tire is it possible? Also, the rear suspension mechanism is totally unknown to me even to the fellow whom I bought the bike from. Is it also replaceable because i want to change it Pardon my imbecilic queries guys, this is my very first bike :)
92221
Yesterday, I was having .  Taking the advice, I messed with the barrel adjusters.  Now, every gear is working great except the highest gear and lowest gear.  I put my bike in the highest gear and I can still click the shifter once more, but nothing happens.  When it comes time to shift down gears, I have to click the shifter once before shifting has any effect.  In the lowest gear, the chain jumps.  I have to hold down the shifter to stay in gear there.
90278
I've recently bought myself a new mountain bike (my first since my schooldays...) and it has front suspension with a lock-out function.  Suspension is new to me and I'm not sure how to use the lock-out.  It seems I have to stop and take my weight off the bike to lock-out the suspension - is this correct?  Or should I be able to operate the lock-out whilst sat on the bike and I'm just not turning the lock-out hard enough?  As I'm not really sure, I've avoided turning it too hard in case I do some damage.
90796
I modelled a part of a bicycle chain added an Array and a Curve Modifier   everything worked nicely until I added cogs and translated and scaled the chain parts to fit the cogs.  I tried to apply transformations, re-added the Curve Modifier but had no success, it still deforms the chain that strange:    Before I messed it up it looked like this:    How could it be fixed?
2474
I'm considering buying a mountain bike and have narrowed it down to two models (make and model aren't important for this question).  One model is a full suspension bike (front and back), the other is front suspension only.    What are the advantages/disadvantages to going with a full suspension vs front suspension? (I'd prefer answers from people with experience riding both types of bikes.)  EDIT  To answer some of the questions looking for more detail...  The 2 bikes are roughly in the same price range, around $1000 USD (the full suspension is slightly more money), and my plans are to ride it primarily in some single track trails that are in the area.  There will be a lot of hills and rocks and such.  I doubt there will be any on-road riding involved.
107548
Is there any way to convert a track bike to a geared bike? I have a track bike with only the rails for the wheel but I've moved out of the city and there are more hills where I am now living so would like to convert to gears if possible and rather than buy a new bike, save some cash.