mb2509

Hi all,

I replaced my chain today on my Giant Contend road bike. All seemed fairly straightforward with the easy link SRAM chain.

I hopped on to my turbo trainer to test it out and gear changing is very smooth in every gear except when I hit the biggest rear cog and I am on the bigger cog of my front two. Everything then jams and the pedals won't turn.

Any ideas on what is causing this? Have I cut the chain too short? Or is this something to do with my gearing?

I am a bit of an amateur when it comes to anything technical, which you can probably guess by my use of terminology above!

Any guidance would be really appreciated.

Cheers, MB2509.

Andrew R Stewart 

Too short a chain is a strong possibility. Tell us how you determined the length of the chain. A common method is to wrap the yet to be connected chain around the largest rear cog and the largest front ring without threading the chain through the der. Pull the chain tight and add one link pair more. This is the absolute minimum chain length, anything less and you risk doing damage to things. I tend to try two more link pairs and if the guide pully clears the largest rear cog in all front rings then it's good and you have a link pair to "spare", should something happen when riding that needs a chain shortening.

Let's see how many here will say "you shouldn't be in that big/big combo to start with". Which is true but you still want to be able to shift "through" that big/big combo in route to a better combo. Cross chaining will cause more wear, friction, noise and have an easier ability to derail the chain if you pedal backwards. Andy

cyccommute 

Sounds like your chain is too short. Did you change the overall gearing of the drivetrain? If so, you need a longer chain. If you didn’t change the gearing, how did you measure the new chain? Generally, if you are just changing chains, use the old chain to get the proper length.

mb2509

Hi both,

Thanks so much for the responses. I think I've done the chain too short, having seen another thread re chain length ('Chain too short?' one - won't let me post the link) My rear derailleur looks exactly like the pictures within that thread when everything jams.

I threaded the chain through on the smallest front and rear cogs when determining chain length and pulled together until there was enough tension (a couple of youtube videos suggested small cogs was the way to go?). I've obviously pulled it too tight when connecting.

Think I'll be ordering a new chain, fishing my old one out of the bin and measuring up a bit more accurately for a second attempt

cyccommute 

If you are going to do the “small/small” method, you don’t want any tension on the chain at all, assuming that you are running it through the derailer. The derailer arm shouldn’t be rubbing the chain but only just.

The best way to get chain length is to use the existing chain, however. Lay it out, match the new chain as close as possible and, “Bob’s yer uncle”, you are done. If you are changing gearing or don’t have the old chain, “big/big and 3 rivets” is the easiest way.

mb2509

New chain arrived today and fitted using the big cog/big cog method. My old chain was festering in bin juice at the bottom and didn’t fancy fishing it out to measure it.

bike running really smooth across all gears.

thanks all for your guidance on Friday :-)