Possible simpleton question

gazman1

Guys, I am riding with a compact double, which chain ring should I be on for riding on the flat, small or large. As I said possible simpleton question so feel free to take the p*@s, gaz

JackPozzi

Whatever you feel comfortable on! As long as you avoid the extreme combinations of small chainring/small sprocket and big/big, it doesn't matter. Basically, pick the chainring that allows you to keep the chain as straight as possible.

ForumNewbie

If you are on the flat and providing you are not going into a strong headwind, you will be faster in the big ring at the front, and probably one of the middle cogs at the back. However best just to go out and experiment with what feels right and moves you along fastest.

Snowy 70

I also ride a compact double and find the larger ring preferable on the flat & slight gradients, I tend to use the smaller ring when my legs start burning, usually up steeper & longer gradients, just for a bit of relief, sit and spin I suppose it's down to what you're comfortable with.

chrisaonabike

The point about the two chainrings is that they give you a different range of gears. The ranges overlap - the big chainring gives you a higher top gear; the little one gives you a lower bottom. As in a car, higher gears for higher speeds in the cruise, lower gears for accleration and hills.

Your cadence (pedal rpm) corresponds to engine speed, and it's usually recommended to aim for a cadence of 80-90, since it's easier on the knees and doesn't fatigue the leg muscles as much, as low, so-called 'grinding' cadences down in the 50-70 range.

So, given that, you choose a gear that gives you the speed you want at the cadence you choose. If that gear (or close to it) appears in both chainring ranges, then it pretty much doesn't make any difference which chainring you use - other than to avoid chain wear with large chain angles (so avoid big ring/big cog, or little ring/little cog).

As the speed increases, it becomes more and more difficult to use the small ring, since your cadence increases to the point where you'll be bouncing in the saddle and exerting virtually no force on the pedals. This is equivalent to trying to drive at 50 mph in first gear - almost impossible and very uncomfortable.

So since you ask which chain ring to use on the flat, presumably this is at a speed where it's physically possible to use either? I'd argue that the chainring to use therefore depends on what's coming next.

So if a hill is approaching, and you're expecting to need low gears, the small chainring is better, whereas if you're accelerating and expecting to need the higher gears, the big one is better.

Mikey41

That's a good point about reading the terrain ahead. Changing up the cassette mid-climb is far better than having to change at the front, which will often destroy your rhythm and your speed.