Stupid lug on chainring

[Mile195]

+1 for turning your chainring round, then rotating it to a point so this pin aligns with the crank.

The idea of it is that if the chain hops over the top of the large chainring, it's supposed to stop the chain slipping down between the crank and the chainring and getting wedged in between them. However, from personal experience I can tell you if it hops over the top enough times it'll soon break off... happened on two of my chain rings.

 

[bpsmith]

+1 for turning your chainring round, then rotating it to a point so this pin aligns with the crank.

The idea of it is that if the chain hops over the top of the large chainring, it's supposed to stop the chain slipping down between the crank and the chainring and getting wedged in between them. However, from personal experience I can tell you if it hops over the top enough times it'll soon break off... happened on two of my chain rings.

Surely you need to take note of the fact that it happened the first time and adjust the mech accordingly. There needn't be a second time, let alone multiple times on two chain rings?

 

[Mile195]

Surely you need to take note of the fact that it happened the first time and adjust the mech accordingly. There needn't be a second time, let alone multiple times on two chain rings?

It's not that simple. Many times I've re-adjusted my front mech. Adjust it enough so it never happens, and it then won't always shift up to the large ring fast enough, which causes me problems getting away at junctions in London where you need to match the acceleration of traffic to justify staying mid-lane to prevent dangerous passes.
It's the frequency with which I shift between upper and lower chainrings that is the problem. I find I make a much faster getaway at lights by shifting on to the small ring every time I have to stop, then shifting on to the large one as my cadence gets high once I'm on the move again. This is as opposed to shifting up through the cassette one by one, staying on the same ring. I won't push away hard still on the large chain ring - I've injured my knees that way before.
Unfortunately that's the nature of mechanically simple things like bicycles. Adjust away as much as you like, but there'll still be odd occasions where it didn't work as well as it did last time, and then next time it does. Odd really.

 

[Ajax Bay]

Actually it is that simple. Get a shifter that operates the FD correctly, adjust the FD correctly, and don't try to shift to the large ring when you're accelerating (eg having ridden away from a traffic light stop line in traffic). As you prepare to stop, keep the chain on the large chainring and shift to a much lower (more teeth) sprocket at the rear. Then set off "a fast getaway", clicking down the cassette progressively after the first and every few/2 seconds. For the drivetrain, changing at the rear is more forgiving than changing chainrings. You can get a fairly low gear if you go large to nearly large eg 50/24 is 56 inches: perfectly OK for standing up and pushing away strongly from stationary. Occasional use of a bit of force should not damage your knees again. What may cause such injuries is prolonged use of higher gears at low cadence (some have said). In fact a good spread of force (high to low) at the pedal is probably a good thing, on the premise that the body appreciates a bit of variety, within bounds.

Unfortunately that's the nature of mechanically simple things like bicycles. Adjust away as much as you like, but there'll still be odd occasions where it didn't work as well as it did last time, and then next time it does. Odd really.

Actually I find that once you've got your gears sorted, and you use them appropriately (and imo you are shifting at the front when you'd be much better shifting at the rear), your gears work for thousands of km without any adjustment required (for me eg end-to-end, London-Edinburgh-London; NB not consecutively obv).

 

[raleighnut]

Shifting up to the big ring at the front is always going to be the slowest change though.

 

[Mile195]

Actually it is that simple. Get a shifter that operates the FD correctly, adjust the FD correctly, and don't try to shift to the large ring when you're accelerating (eg having ridden away from a traffic light stop line in traffic). As you prepare to stop, keep the chain on the large chainring and shift to a much lower (more teeth) sprocket at the rear. Then set off "a fast getaway", clicking down the cassette progressively after the first and every few/2 seconds. For the drivetrain, changing at the rear is more forgiving than changing chainrings. You can get a fairly low gear if you go large to nearly large eg 50/24 is 56 inches: perfectly OK for standing up and pushing away strongly from stationary. Occasional use of a bit of force should not damage your knees again. What may cause such injuries is prolonged use of higher gears at low cadence (some have said). In fact a good spread of force (high to low) at the pedal is probably a good thing, on the premise that the body appreciates a bit of variety, within bounds.

Actually I find that once you've got your gears sorted, and you use them appropriately (and imo you are shifting at the front when you'd be much better shifting at the rear), your gears work for thousands of km without any adjustment required (for me eg end-to-end, London-Edinburgh-London; NB not consecutively obv).

There's plenty of truth in much of that. And indeed, I've varied the way I use gears over the years. Years ago I used to push away hard in big gears, until I strained said knee quite badly as a result. then I went to alternating between the large and small rings. Back to staying on the small ring and shifting all the way down the cassette on acceleration for a while, and in more recent times, back to alternating between the two rings. The latter I find overall works best for me. My one way commute to work is 20 miles, and there are 89 sets of traffic lights over that route. All that stopping and starting is bad for the drivetrain no matter how you do it. Like you say, on long rides I have no problems - I've done Paris and back which was 600 miles, and last year I rode down to Cornwall - 300. Not a days trouble, but then far less shifting (despite the terrain in the South West!)
When I talk about the chain jumping over the top, it's not with particularly great regularity if you take into account the number of shifts between the two over which it occurs. However, because for me there are tens of up/down shifts over a 40 mile return commute, it appears to happen more often for me, but in reality it's probably no more than for anyone else.

 

[bpsmith]

It's not that simple. Many times I've re-adjusted my front mech. Adjust it enough so it never happens, and it then won't always shift up to the large ring fast enough, which causes me problems getting away at junctions in London where you need to match the acceleration of traffic to justify staying mid-lane to prevent dangerous passes.
It's the frequency with which I shift between upper and lower chainrings that is the problem. I find I make a much faster getaway at lights by shifting on to the small ring every time I have to stop, then shifting on to the large one as my cadence gets high once I'm on the move again. This is as opposed to shifting up through the cassette one by one, staying on the same ring. I won't push away hard still on the large chain ring - I've injured my knees that way before.
Unfortunately that's the nature of mechanically simple things like bicycles. Adjust away as much as you like, but there'll still be odd occasions where it didn't work as well as it did last time, and then next time it does. Odd really.

As @Ajax Bay gas already suggested, you could be using your gears more efficiently.

In saying that, I regularly drop down gears in the cassette and also on the chainring, when I come to traffic lights. I then proceed to change up st the back, followed by the chainring gear change when suitable.

My derailleur’s are set up correctly and I have never dropped the chain.

 

[Alan O]

Wow, the things you learn... I've just checked my 3 working bikes, and they all have those little lugs on them, positioned correctly - and I'd never noticed them!

 

[raleighnut]

Wow, the things you learn... I've just checked my 3 working bikes, and they all have those little lugs on them, positioned correctly - and I'd never noticed them!

Didn't you notice the pin when you took the old un off.

 

[Alan O]

Didn't you notice the pin when you took the old un off.

Well, the times I've replaced chainrings individually it's been on an old chainset that I took off last year, and that doesn't have a lug - the new chainsets I now have on two bikes were put on complete, and the third one is still as it came with the bike.

 

[bpsmith]

Wow, the things you learn... I've just checked my 3 working bikes, and they all have those little lugs on them, positioned correctly - and I'd never noticed them!

I am sure you’d have noticed had you fitted them in the wrong place though.

 

[ChrisEyles]

I've found those little pins really good (when fitted correctly!) on my MTB - not only do they stop the chain getting jammed between the crank and the chain ring if it unships over bumpy ground, they also seem to aid in the chain getting back on the chain ring when you pedal again. When riding a rigid MTB with little in the way of finnesse, it's quite helpful!

 

[Alan O]

I've found those little pins really good (when fitted correctly!) on my MTB - not only do they stop the chain getting jammed between the crank and the chain ring if it unships over bumpy ground, they also seem to aid in the chain getting back on the chain ring when you pedal again. When riding a rigid MTB with little in the way of finnesse, it's quite helpful!

Ooh, you know what? That happened to me not so long ago, without me even knowing the lug existed - and there I was thinking the quick recovery was solely down to my skill

 

[ChrisEyles]

Ooh, you know what? That happened to me not so long ago, without me even knowing the lug existed - and there I was thinking the quick recovery was solely down to my skill

Haha, yeah, I was really chuffed first few times I managed it, then found out it didn't work on my other MTB without the pin!