When to change onto a different front ring.

[RedFeend]

Please can you help a beginner.
I have 9 rear gear sprockets and 3 on the front chainring. When is the best time to move over to a different front ring? Is it best to avoid using the largest and smallest (1&9) rear sprockets? I am thinking about the stress on the chain when it is at the extremes of it's working angles (out of true, pulling skewed as against in a straight line).

I hope I make sense.

 

[themosquitoking]

Yeah, you've pretty much sussed it out. Try to keep out of extreme angles, use middle ring on flats, big on downhill and small on uphill if you have to.

 

[SWSteve]

Don't go to either extreme, and try to change down earlier rather than later this should make it easier than grinding the way up in a too higher gear

 

[Shut Up Legs]

Generally you can tell if the chain is "cross-chained", i.e. at too much of an angle: it makes more noise. I normally use the left front ring with the 3 left rear rings (let's call them rings 1-3), then the middle front with rear rings 3-6, then the right front ring with rear rings 6-9. You can of course use other combinations, but it will increase the rate of wear on both the chain and the chain rings.

 

[MaxInc]

There will always be some overlap otherwise the gap in gear ratio will be too big when changing the front ring only. On my compact double disc I find that I usually need to change a couple of rear sprokets every time I change the front rings to keep the transition smooth. And as has been said, increased noise is the best indicator that younmay need a different front disc and gear combination.

 

[fossala]

...On my compact double disc I find that I usually need to change a couple of rear sprokets every time I change the front rings to keep the transition smooth...

That is why I don't like compacts. Use triples for anything that is over 9kg, double (really double I mean) for anything under.

 

[MaxInc]

That is why I don't like compacts. Use triples for anything that is over 9kg, double (really double I mean) for anything under.

On the tripple the same applies although to a smaller degree. I still find that I need to change a sproket on the MTB every time I change the front disc but maybe it's just me trying to keep a steady cadence.

 

[Venod]

On a compact chainset the 16t gap between the 2 front chainrings (50/34) means a big change in gear if you leave the chain on the same back sprocket, I treat the compact much like having an high/low ratio box on a Land Rover & select the front ring for the terrain conditions. I have a cyclo cross chainset (46/36) on 1 bike I use the front shifter much more on this.

 

[gavroche]

Yeah, you've pretty much sussed it out. Try to keep out of extreme angles, use middle ring on flats, big on downhill and small on uphill if you have to.

That is good, non technical, simple, straightforward, honest, easy to understand, idiot proof and sensible advice.

 

[RedFeend]

On a compact chainset the 16t gap between the 2 front chainrings (50/34) means a big change in gear if you leave the chain on the same back sprocket, I treat the compact much like having an high/low ratio box on a Land Rover & select the front ring for the terrain conditions. I have a cyclo cross chainset (46/36) on 1 bike I use the front shifter much more on this.

I get this one totally as I'm a Land Rover (the proper kind) owner since 1989.
The low box is so useful. I get irritated when I hear people backing etc in normal ratio while riding the clutch. Nothing to do with bikes, just a pet dislike of mine.

 

[RedFeend]

Thank you all for Taking the time to reply. It does say in the forum intro 'no question too stupoid'. You are nice people here.

 

[Paul99]

That is why I don't like compacts. Use triples for anything that is over 9kg, double (really double I mean) for anything under.

Does this include the riders weight then? Why the chain rings should be chosen according to the bikes weight doesn't make any sense to me. Surely it should be according to the terrain you are most likely to ride?

 

[fossala]

Does this include the riders weight then? Why the chain rings should be chosen according to the bikes weight doesn't make any sense to me. Surely it should be according to the terrain you are most likely to ride?

Sorry, I was going by heavy bikes are touring/audax, non heavy are racing. More mentality of the ride rather than anything else.