Chain/derailleur stretched to the max

[overmind]

I have a utility bike (road bike) for just pootling around town.

The bike has an old-fashioned 7 speed screw-on freewheel. I think it is designed for a mountain bike because the largest ring on the rear sprocket is quite a bit larger that the second largest ring (see below). The gradient of the hill was such that I really needed a gear between the lowest and the 2nd lowest (I was in 1st gear).

On the front this bike has a dual-chainset, so I thought I would try changing to the big ring on the front and that it might give me a gear slightly in the middle of first and second.

This was a big mistake! Reason 1: cross-chaining but reason 2 was worse. The derailleur got stretched to the maximum extent and locked the chain in position. The chain would not turn without grinding metal noises. It was so tight I found it very difficult to get the chain back to the small ring. I had to turn the bike upside down - I did not have any tools with me - and physically push the chain off the big ring as I turned the cranks (effectively using my hand as a manual front derailleur). I could have sliced my finger open. I certainly got lots of oil all over my hands.

I'll have to remember not to do that again!

 

[fossyant]

Test before riding...

 

[HMS_Dave]

The mega range freewheel really needs the mega range derailleur too. Was it sold new with it on?

 

[Sharky]

That is a big jump. But looks as if it could be useful sometimes.

 

[Cycleops]

Funny how things change. 'Megarange' is now a fairly common lowest ratio on modern cassettes at 34t.
Big to big won't have a great line but shouldn't be tight and grinding. Sure your chain is the correct length?

 

[overmind]

The mega range freewheel really needs the mega range derailleur too. Was it sold new with it on?

No I bought it on Amazon and fitted it myself. The old sprocket had been ridden into the dust and was badly slipping. I replaced the chain and freewheel. The previous freewheel was like the image below.

I knew if was a bit of a risk and it's just a cheap runaround type bike so I am not that bothered.
Since the front has only two rings (and no granny gear) it was kind of compromise to get a really low gear.

I was more interested in the experience of it locking up. Its probably designed for a long-cage derailleur. I was not going very fast or anything and did not get hurt.

Funny how things change. 'Megarange' is now a fairly common lowest ratio on modern cassettes at 34t.
Big to big won't have a great line but shouldn't be tight and grinding. Sure your chain is the correct length?

That's a good suggestion; I'll add a few links to the chain. I'll put the bike in the gear with the most amount of slack on the chain and see how loose it is then add links accordingly. I just will not use that combination in the meantime.

 

[overmind]

This is basically the model of bike. Its just a regular 7-speed shimano derailleur.
(the one in that picture has a 3 ring chainset; but mine a 2 ring taken off an old 70s racer).

 

[Cycleops]

That's a good suggestion; I'll add a few links to the chain. I'll put the bike in the gear with the most amount of slack on the chain and see how loose it is then add links accordingly. I just will not use that combination in the meantime.

Big ring front to big cog rear (NOT through the derailleur) plus two links and the quick link.

 

[raleighnut]

^^^^^^^^^ wot e sed

 

[boydj]

And don't do big-big again, you naughty boy.

 

[fossyant]

And don't do big-big again, you naughty boy.

You can get away with it on 7 speed !

 

[C R]

You can get away with it on 7 speed !

I may have done it by accident on my 9 speed Sora. It worked fine, so good in fact that I only noticed when I dropped to the small ring and there were no more gears to go down at the back . I am more careful now, mind.

 

[fossyant]

I can do big to big on my 2 x 10 MTB, I try not to though ! It's OK on 7 speed TBH, but not ideal.

 

[fossyant]

You still need to make sure it works in that gear, just in case, and some times you might forget.