Chain Wrapping Up On Itself When Changing To The Smallest Chainring: Any Ideas?

[davidphilips]

There was significant slack in the chain when on small to small which the new mech has taken out and the strength of the spring is very much greater on the new mech.

Could it be that the pivot is sticking on the old derailleur, if so you could free it up and have a spare, heres a video i just seen that shows what i mean?
View: https://www.youtube.com/watch?v=bgiNuJNynMc

 

[normgow]

So I'm hurtling down a big dipper (30% both sides) trying to get as much speed up as possible so that I can have decent momentum going up the hill on the other side of the dip.

Near the bottom, I flip down to the small on the front but stay small on the back so that I can apply some welly at the start of the uphill section.

Being already on the small on the front avoids me having to use the front to shift down when the bike is under load when climbing.

As I climb the uphill section, I progressively shift down on the back.

There is often quite a difference in size between chainrings especially on a triple. I wouldn't have thought that changing from largest to smallest ring at the foot of the hill is the best way to maintain the speed gained on the descent and surely at first you must be pedalling furiously to no effect until the gradient makes itself felt. Why not change the rear gears but not onto the largest sprocket at first and then further up the hill change chainrings? There's going to be load on the drive train no matter what and this way you should be able to get further up the hill before engaging the lowest gear.

 

[Ajax Bay]

The OP has described the particular challenges of the bottom of the final hill back from work, his choice of gear technique and and the slowness of his bike's shifting at the front under load.

 

[Lovacott]

Could it be that the pivot is sticking on the old derailleur, if so you could free it up and have a spare, heres a video i just seen that shows what i mean?

The pivot moved freely but the spring offered up very little resistance. I'll have a look at it tonight and see if a good clean up will help it.

Replacement only cost £17.99 and it works much better. I've got a new front mech on the way as well.

 

[rrarider]

What are other people's experiences with regard to the springs of older rear derailleurs weakening with age?
I must confess I've not come across this in my bikes and all the bikes I've rescued (bought) from the tip (for family, friends or sale, or parts).

I've always been in the habit of leaving any mechanism containing a spring in its relaxed state, if possible. Thus, when I put my old bike with friction shifters for a 2x6 combination away for the day, I've engaged the small-small combination of 13x42 just before I come to a halt. Consequently for the first few yards when I set off the next time, it's in that "don't use" combination. I notice then, that if there's a stiff link in the chain, that is when I might get the top run of the chain go a bit saggy. This is usually because I've just refitted the chain after cleaning, so a quick tweak with the chain tool will sort out any stiff link.

 

[Lovacott]

I've always been in the habit of leaving any mechanism containing a spring in its relaxed state, if possible.

I've started doing that now as well (never really thought about it before). It's easy for me because my first 100 yards is downhill so I just coast it and select the right gear combo for when I need to start on the pedals. Conversely, my last 100 yards home is up hill so I finish up on small front / middle back which leaves the mech relaxed. Where I wasn't doing this was when I arrived a work on big front and changed down at the back to one of the big rings as I rode through the car park (leaving the bike in an easy gear for setting off at the end of the day, but stressing the mech spring in storage).

The previous rear mech came off my sons very little used bike which had been in the shed for quite a few years and it would have been left in a stressed position.

Also, my commute requires a lot of changes up and down due to the undulations in the route and the fact that the bike is heavy.

My conclusion is that the pivot spring is basically knackered.

Lesson learned!!!

 

[Lovacott]

Update.

I've just removed and cleaned the chainring and I've noticed a few things.

A couple of the rivet heads between the small and middle ring are burred and protrude into the line the chain would take on small to small.

Maybe this has been a contributor to my "chainsuck"?

 

[fossyant]

Update.

I've just removed and cleaned the chainring and I've noticed a few things.

A couple of the rivet heads between the small and middle ring are burred and protrude into the line the chain would take on small to small.

Maybe this has been a contributor to my "chainsuck"?

View attachment 570136 View attachment 570137

They are supposed to be there. They are for picking up the chain !

 

[fossyant]

Six pages and no-one has said....






NEW BIKE !

 

[Lovacott]

Time to hit the ignore button.

How did your lot get on last night?

They are supposed to be there. They are for picking up the chain !

I have no idea whether you are right or just simply taking the piss.

 

[Lovacott]

Six pages and no-one has said....
NEW BIKE !

It was a new bike a few years ago.

 

[Lovacott]

They are supposed to be there. They are for picking up the chain !

I reckon you are extracting the fluid.

In all seriousness though, this doesn't look right to me.

 

[fossyant]

I reckon you are extracting the fluid.

In all seriousness though, this doesn't look right to me.

They are called pickup pins. Really. If I cross chain my triple, it trys to pick up the chain.

 

[Randomnerd]

They’re pick up pins, so your chain doesn’t drop between the rings.
Might be worth taking the advice you’ve been given by the CC massive and adjust your technique.

 

[fossyant]

Here is the back on my 2x chain ring. There are 8 "pins" to pick up the chain.