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I'm a complete novice with bicycle maintenance and have a slight problem. I just picked up a 2nd hand bike as taking part in a charity event this weekend and an unfortunate accident meant my mine was totalled and I couldn't afford to be picky.

The bike is an 04 Giant OCR Zero with Campagnolo groupset. An okish bike and would've been fine as a temporary machine. I wasn't able to test ride as my knee is still battered and when I got home I flipped the bike and ran through the gears.

we have 3 on front and 9spd at the rear. When using the biggest ring at the back and biggest at the front, the tension on the chain is so great that it cannot move. If the rear is in mid position or lower then it transitions ok but not otherwise.

Any help or advice on how to fix is appreciated. I thought changing the chain might solve but the chain on there is a 9 spd and as far I know, it should be fine. replacing it with the same length would just result in the same problem.

Edited to add pics and info. Apologies for incorrect use of tension. I've taken a few pics(hopefully they've attached ok) showing the different states of the rear mech as I transition through the gears. There is a lot of crud but no slack on the chain at all

enter image description here enter image description here enter image description here enter image description here enter image description here enter image description here

Thanks again!

  • You need cca 2 more links in your chain (longer chain).. – Jerryno May 28 '15 at 11:24
  • @Jerryno, Would you suggest replacing the chain and adding some links to the newer one? It looks like it's sat still for a while. Can you simply buy separate links? is there a threshold on how many to add? Sorry for all the questions. – null May 28 '15 at 11:25
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    Steve. The cheapest solution is a new chain. I guarantee you that if you try to lengthen your chain, it will snap within the week. Plus I would bet you even money that your chain will endeavour to snap as far away as it is possible to taxi home at... – Aron May 28 '15 at 11:48
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    It is just odd that tension on the chain causes it not to move. Pedaling puts tension on the chain. If it goes into the biggest gear then it is long enough for the biggest gear. Lube and look for other problems. – paparazzo May 28 '15 at 12:05
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    Big big is cross chaining and no real purpose. If you want a lower gear then go middle up front. Same with little little. – paparazzo May 28 '15 at 13:22
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The chain is stuck because of its short length and cross-chaining - the chain links are severely bent. Also with the chain not clean it will not turn nicely in such a scenario:

enter image description here

Also your chain is short, making your derailleur stretch forward (marked blue) which makes the cross-chaining even more severe (marked red). On such a stretched derailleur there are bad side forces (maybe the little wheels in the derailleur get stuck while being bent).

For old drive trains cross-chaining was not accounted for as it is bad practice. Such rear derailleurs usually doesn't have a range like new ones. New bikes are designed to handle cross-chaining and such a chain would be definitely too small for them, but for old bikes it's more complicated. Looking at first picture where you have small-ring + small-gear (the shortest chain length) your derailleur could accommodate for a bit longer chain making the setup safer if you accidentally shift into big-ring + big-gear.

You can have the same gear ratio using other gears instead of cross-chaining:

enter image description here

You can see that 48T front 32T back (big-big) gives the same ratio as 36T front 24T back (middle-middle) which makes the chain straight.

The not-cross-chaining rule:

  • for small chain-ring use only the bigger half of your cassette
  • for middle ring you can use all your cassette
  • for big ring use only the smaller half of your cassette

In practice it's even less as this table of gear ratios explains (this is for 44-32-22 crank and 11-32 teeth cassette):

enter image description here

You only need to cover with the big and small ring what cannot be covered with the middle ring. See how this XTR9000 Di2 Syncro-Shift is shifting. When it shifts the front it also shifts the back at the same time, and it prevents cross-chaining. This video also shows gearing efficiency.

  • To clarify the diagram. The angle of the grey lines is the effective gear (gear ratio). This is how hard it feels to pedal. What @Jerryno is showing, is that each gear ratio appears multiple times on each bike. – Aron May 28 '15 at 16:40
  • I'm sorry to say that part of this answer is simply wrong: this is not the correct chain length. The bike has only a medium-throw rear derailleur and a triple chain ring, so getting the chain length right will be tricky. But at present it's so short as to create a danger, as mentioned in @jimirings answer – andy256 May 29 '15 at 2:18
  • @andy256 Its not correct length for a new bike, but this on old drivetrain which this is normal. And jimirings is talking of danger when you put new links into old chain. Crosschaining on an old drivetrain is dangerous yes. Putting bigger chain there migth cause it to be too big.. – Jerryno May 29 '15 at 8:24
  • @Jerryno No, sorry, it's never been normal. Yes, that is one way of reading his post. – andy256 May 29 '15 at 8:50
  • @andy256 changed the answer and thanks for the comment, I think this way it is more general and also more correct. I included the safety reasoning. – Jerryno May 29 '15 at 9:40
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One thing that is for sure, your chain is too short.

My bet is that when you shift to the big-big chainring combination, something in your derailleur is binding because it's being pulled so tight. If you look at the last picture, it looks like there's a severe lateral bend in your chain where it exits the derailleur. My guess is that's the point where it's binding. It also looks in the second-to-last picture like your derailleur might actually be touching the chainstays. I don't think that would cause the chain to bind, but it's definitely not good.

You might be able to scrounge up a few links and lengthen your chain, but it's not recommended for a number of reasons that I won't go into here. Suffice it to say, that if something goes wrong your chain can snap while you're riding. This is dangerous. It can also cause other things to break and be far more expensive in the long run.

Buy the longest chain you can find. They're usually the same price regardless of length, so that shouldn't be an issue. Use the new chain to measure the correct length to use and remove unnecessary links. The venerable Sheldon Brown has a great article on how to measure the proper length for your chain. Basically, you wrap the chain around the two big rings without passing it through the derailleur and make sure that the chain overlaps by one full link. Keep in mind that a full chain link is two half-links, i.e., two pieces of chain.

If you don't have a chain tool, or this seems beyond your mechanical capabilities, take it to a bike shop to have the chain replaced. Replacing a chain is trivial to a bike shop. If you buy the chain at the shop, they're likely to do it while you wait and labor will be very inexpensive or free.

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    I disagree. You should NEVER use the big-big combination. There are plenty of different gear setups with the same mechanical advantage. It is true that modern bikes have a chain/gear/mech combo that ALLOWS for it, specifically for riders which aren't particularly skilled. – Aron May 28 '15 at 13:25
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    @Aron It's bad practice for sure, but it should at least function in that combination. – jimchristie May 28 '15 at 13:49
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    @Arron. Remember "Ghost Busters" - "Don't cross the streams..." (If not, watch the movie or look it up) I have "crossed the chains" many times and like the movie, results were no as dire as predicted. - hell did not freeze over, my wheels still went round in circles and the sun still cam up this morning. Crossing chains is not as bad as you make out. – mattnz May 28 '15 at 23:50
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    @Aron. I ride decades older gear than this modern (built this millennium or there abouts) thing. The synchro example goes back 80 years. Cross chaining gets lots of attention here and elsewhere, but is not the big deal it's cracked up to be. – andy256 May 29 '15 at 2:24
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    Whether or not cross-chaining is a good idea, brief cross-chaining shouldn't jam anything on a well set up bike. On an unfamiliar bike it's not hard to shift the wrong way in error, or to shift more than planned while trimming the front derailleur, and that shouldn't jam the pedals or the back wheel. – Chris H May 29 '15 at 11:05
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I agree with the answer from jimirings and don't want to start a cross chain debate.

Cross chaining is big big or little little. New a bike should do both but it is not ideal. On an older bike like that you lose some spring in the derailleur so it does not do as good a job at taking up slack. Yes that chain is too short for big big but if you give it enough chain for that you may find it does have enough tension in smaller (tooth count) gears. The cheapest solution is maybe to just stay away from big big and little little. Make the middle front your friend.

It is also possible (likely) that is not the original derailleur and does not have the capacity. In the middle small picture the derailleur is close to maxed out the other diction.

  • +1, however leaving as is would not be my choice or recommendation. OP cannot practically use the top chain ring with that chain length. Knowing the fix was cheap and easy it would frustrate me. – mattnz May 28 '15 at 23:56
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    @mattnz But you don't know it is a fix. There may not be spring in the derailleur for a longer chain. It may not even be the correct derailleur for that range. Look at the top pic - middle small is pretty much topped out the other direction. Little little is going to be a problem. If I can get big gears from my big front I do have practical use and OP stated he could. – paparazzo May 29 '15 at 0:10
  • Thinking about it more, the chain length has probably been selected because deraileur does not have the capacity (forget about spring tension for now). I put money on it he needs a new (longer cage/capacity) derailleur to fix it. – mattnz May 29 '15 at 1:47
  • @mattnz Exactly. The GROUPSET was designed from the outset the assumption that the rider should avoid cross-chaining. It is true that you can't buy groupsets built on that assumption anymore, I also agree that on the whole is a good thing. But the bike was designed on old thinking. – Aron May 29 '15 at 2:04
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    @Aron Let it go. You don't know that is a groupset. We don't know that is the original derailleur. It is an 04. You know for a fact that sold new that bike not designed on old thinking? – paparazzo May 29 '15 at 8:41
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This looks like a standard Campy triple front/ long arm rear setup. Definitely too short a chain, as your small-small picture 1 clearly shows the rear derailleur is not fully "wound up" regarding taking the slack of the chain up. New chain is really the only safe way to go; 9sp has more alternatives, like Wipperman etc. with quick links to facilitate removal, cleaning, versus Campy's pricey chains, fixed pins, pricey tools, etc. Go online before you install, to learn how to measure new chain, but should save your system grief down the line; false economy to try splicing with other chains, especially on Campy. Triples usually have near-redundant gearing combos so the cross-chaining is both bad and unnecessary, and traditionally to be avoided. Good news is you will be sitting and spinning past buddies on steep climbs as their knees cry out. You will be spending a lot more when the G-springs fail in the shifter innards, but hey, that's the price for riding with panache. Caio!

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It should be noted that, before long-cage derailers became common (roughly 1985), it was not uncommon for the large/large cog combo to lock up the chain. This was considered "normal", and cyclists simply knew to avoid that combo (as well as small/small in some cases).

The derailer in the photos appears to have a reasonably long cage, but judging from the slack in the chain in the small/small photo, not long enough for that cogset.

Since this appears to be a reasonably new bike, I'm guessing that some component has been changed (either cogs or rear derailer) and that is the cause of the problem. Simply lengthening the chain would appear likely (based on the first photo) to cause problems with the small/small combo.

(If you still want to try to lengthen the chain, don't try to add links to the exiting one -- get a new chain.)

  • Ah, funny you should that...the bike came with the old wheels which were replaced. Wonder is the cassettes are different spds...will check. I'll swap them out if that's the case. – null May 29 '15 at 12:23
  • Just checked, clearly I don't know a great deal. They appear to be the same exc manufacturer. Both 9s 12. Original is campagnooo with replacement being unknown. – null May 29 '15 at 12:29
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    @SteveGreen - My first guess would be that someone replaced the front cogs with larger ones -- I haven't made an attempt to size them, but they look quite large in the picture. If not that, then the bike may have been designed this way -- the shorter cage produces crisper shifting, and an "experienced" cyclist would never attempt the extreme combos. – Daniel R Hicks May 29 '15 at 19:08
  • thanks for replying Daniel, my first port of call is to find out if the chain I had delivered makes a difference, if not I'll leave it the size as the original and maybe look into replacing the front. Thanks for the help/advice. – null May 29 '15 at 19:10
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Don't use big-big or small-small combination. Chain is too short. Drop by bike shop for confirmation.

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    If the chain were too short, small/small would not be a problem. – Daniel R Hicks May 29 '15 at 12:38

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