whats wrong with my new (old) road bike? ?

When I am applying a lot of force starting out in a gear the pedals seem to slip and I hear a clunking noise or two. Now I had a guy run it through all the gears on a bike rack and he said they were all fine, I only have this problem when actually riding. Any ideas?

This is my first road bike, and I am trying to learn as I go. Below are some pics of the gear area and all that good stuff.

http://img57.imageshack.us/my.php?image=47574643xw0.jpg

http://img70.imageshack.us/my.php?image=44567577jm8.jpg

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5 Responses to “whats wrong with my new (old) road bike? ?”

JohnJ79 on December 9th, 2009 at 7:30 am

when they put it on the stand and it goes through all the gears fine, that just means that its mostly adjusted correctly, the more minor imperfections in adjustment show themselves when the system is under a load, like going up a hill or starting really fast. if it is adjusted as perfect as you (or the bike shop) can get it, then the problem could be that one of the chainrings or cogs is bent, the chain has an issue, the derailleur is a little bent or the whole system is just cheap. I don’t know much about your bike brand, but on cheap department store bikes you can adjust them all day and they will never work right, and if they do work right they won’t work right for very long (learned this problem on my first 3 bikes) when i finally upgraded to a $800 bike, i only need to adjust it about once every 500 miles of mountain and road riding, and if i only ride on road it can go 1000 miles without needing adjusted.
Lucky Man 2 on December 9th, 2009 at 8:05 am

As above it sounds like one of the cog teeth may be bent.
intrepidfae on December 9th, 2009 at 8:26 am

What is happening to you is called autoshifting. It can be caused by friction in the derailleurs. You might be able to make some adjustments to make that go away. It might also be the frame flexing when you stamp hard on the pedals. Whenever you want to find out how to do something on your bike, always start at the Sheldon Brown web pages (RIP, Sheldon): http://sheldonbrown.com/derailer-adjustment.html

The Park Tools web pages are also good: http://www.parktool.com/repair/byregion.asp?catid=53

HTH
Bob A on December 9th, 2009 at 9:20 am

I have owned some cheap bikes and the chain will jump the smallest sprocket when you apply too much force. There is an adjustment that moves the derailleur closer to the gears that may help if it has one. It’s called a B screw and is found on all good derailleurs. You will see it on this video.
http://bicycletutor.com/adjust-rear-derailleur/
bikeworks on December 9th, 2009 at 10:03 am

Hm. Sounds that you are only having problems when pressure is placed on the pedals. This can’t be duplicated on a stand.

There are a couple of things that you should check (from most common to least common):

1. Check for chain wear or poor drivetrain lubrication. A worn chain could cause slipping. If the chain was rusted or there is a bunch of dirt and grease on any part of the drivetrain, clean and relube;

2. Make sure that, if the chain was replaced, it is the correct size. A chain too wide will not allow enough space between cogs and it will seem to “ride” between cogs rather than go into gear and one that is too narrow won’t grab and as such just roll over the cog without engaging;

3. Schwinn/ Normandy/ Huret/ Sachs (1970s and earlier) stuff was notorious for having poor spacing between freewheel cogs (note- no indexed shifting) and therefore the chain “almost” gets caught between them allowing a slipping feeling not unlike having a chain that is too narrow or too wide;

4. If you have a frewheel it could be that the freewheel body or one of the cogs has worn splines causing the cog to spin on the body. This is not necessarily repeatable on the stand since you normally need quite a bit of tension before they’ll spin.

5. The chain may be too long. This will show up especially if the rear derailleur is worn and not keeping sufficient tension on the chain. To check this shift into the smallest chainring and smallest rear cog. Push the rear derailleur cage to loosen the chain. There should be a very slight amount of extra “spring” in the cage when you let it go. Note that the symptom is the same as a worn chain.

EDIT: Looking at your pictures I can almost certainly state that your chain and/or freewheel is worn. It is a Shimano freewheel and derailleur and cog spacing or spline damage is unlikely. Buy a new 1/2 x 3/32″ chain and have the freewheel replaced and your problems should disappear. If not, you’ll need a new rear derailleur.