Odd issue this morning

[Darren Jeffrey]

I was cycling to work this morning and I pulled off at a set of lights, went to drop down to the bottom front cog and my chain kind of seized up. I couldn't pedal forward. I changed back up to the middle front cog and all seemed ok again. Got a bit of a fright as I was in heavy traffic and not able to pedal. Any ideas what might have caused this?

Bike is brand new T3 so will drop it back to Decathlon but would be interested to know before that what might have caused it.

Thanks in advance

DJ

 

[LosingFocus]

"Chain Suck"? http://www.fagan.co.za/Bikes/Csuck/

 

[Zakalwe]

When you say bottom, do you mean the big big ring or the smallest one?

 

[Darren Jeffrey]

Sorry I mean the smallest front ring

 

[Zakalwe]

Which cog were you on at the rear? If you were on the smallest back there you could run into problems with the small/small combination.

 

[Darren Jeffrey]

Not entirely sure to be fair. I'll pay attention to that moving forward and see if it was that

 

[Nigel-YZ1]

I've only had chain suck when my teeth are turning into shark's fins. Or a really grubby chain could do it.

 

[Darren Jeffrey]

Bike is only 2 weeks old and chain was cleaned at the weekend.

 

[Zakalwe]

Brand new bike, wouldn't expect any shark fins. My guess would be down to either the derailleur having to take up too much slack in the chain when looped over the 2 smallest cogs, or the chain catching the front mech somehow as it's been crossed from left to right.

 

[Darren Jeffrey]

Thanks for the advice will keep my eye in it

 

[Scoosh]

Were you actually pedalling, with weight on the pedals, when you tried to change gear ?

LosingFocus's link has a good - if rather engineering-detailed** - explanation and suggested cures.

I experience this on my 20-yr old hybrid 'shopping' bike occasionally and it is sometimes too much weight on the pedals when changing, sometimes a dirty chain, sometimes a mystery ...

** well, they are an engineering company !

 

[Darren Jeffrey]

Yes I was changing gear to go uphill so there was a whole load of pressure on the pedals

 

[Scoosh]

AHA ! I find that I can change down on the (rear) cassette without too much issue but the front can be trickier.

Ease off the pressure on the pedals when you are changing the chain-ring (front) and it should help. Better yet, plan ahead and change down in plenty of time.