I am new to bikes not ridden one since I was 11 I am now 63! I have a mountain bike and never used gears before they are mind boggling. I went out and rode it no problem but trying gear changes I don't understand at all.
My problem.. chain fell off, I put it back on easily but I dont know if its on the right cog pedal and wheel and if the gear selectors on handle bars are right... Please advise
If the bike is new, it could definitely benefit from a visit to a mechanic.
Bike gears (among other things on a bike) require occasional tuning. Chain dropping frequently, gears not shifting easily, or bike making grinding sounds is a good sign that something needs adjustment. Your local bike shop will help there.
No need for a long answer... Just give the pedals a turn and the chain will find the right "cog" on it's own.
First off: Welcome back the cycling world!
Yup, gears can take some getting used to. This is a common experience for adults getting into cycling after having not ridden since childhood. It will become second nature before you know it.
A quick guide to the confusing world of gears
Your left hand shifter corresponds to the front gears, the ones attached to your pedals. Your right hand shifter corresponds to the rear gears, the ones attached to the rear wheel.
One of the things that can be confusing is that on the left/front gears, a higher number corresponds to a larger chainring. But on the right/rear gears, a higher number corresponds to a smaller chainring (usually called a cog in the rear, don't ask me why the names are different).
It's easier to think of it as lower numbers being closer to the frame and higher numbers being farther away from the frame. That's true on both the front and rear gears.
Now, to answer your question
You don't mention if it fell off of the front or rear gears. Either way, all you need to do is look at the corresponding shifter and see what number it's on. If the number is high, put it back on the outside gears. If it's low, put it on the inside gears.
One thing I find helpful is to pick up the rear wheel and give the pedals a turn or two by hand once you have the chain back on. This will get the chain back in line where it's supposed to be even if you put it on incorrectly.
One last note about why your chain fell off
There are two likely reasons that your chain fell off:
You were shifting under load. Most bikes aren't designed to shift while you're pedaling hard. You'll want to learn to anticipate your need to shift to lower gears and do it a smidge before you actually need it.
Your bike is improperly adjusted. This is incredibly common for bikes purchased from big box stores like WalMart, Target, or even the big all-purpose sporting goods stores. It also wouldn't be surprising to find on a bike that you purchased used.
Unless you got your bike from someone who is a decent bike mechanic themselves and you trust that person to have put the effort in to make sure it's properly adjusted, I'd recommend taking it in to a bike shop to have everything checked and adjusted. This is especially true if you got your bike from a big box store. Those bikes are poorly assembled, sometimes dangerously so.
Have you ever driven a car? If so, they you've used a transmission. Bike transmissions work by the same principles, you have to match the load to the capabilities of the power source, in this case your legs, for the most efficient power transfer.
Most mortal humans can generally produce decent output from about 70 rpm to about 90 rpm on the crank. Below 70 calls for much more muscle strength and above 90 calls for much more speed that most people can manage for long. So the purpose of the gears is to allow you to select the right gear for the conditions. If you are climbing a hill you will want to select the smaller front chainring and the larger rear gear so that you get more cranks per wheel revolution and the pedaling feels easier.
When descending you want to go the other way and choose the larger front chainring and a smaller rear gear. That way you get fewer cranks per wheel revolution.
On the level you want to be somewhere in between and most bikes today have plenty of choices.
The key as a new rider is to develop the skill of shifting smoothly and in anticipation of the conditions so that you don't find yourself in the wrong gear in the wrong time and loose momentum.
In my experience most novice cyclists choose too "tall" a gear for the conditions. By tall I mean you are too large on the front and too small on the rear. This is where a "cadence" sensor can be helpful. Every cyclist is a bit different but I find that a cadence of 80-90 rpm works best for me. I'm now 64 but as a younger rider I used to be comfortable at 70-80 rpm. Experiment and see what works for you but don't be afraid to shift gears and see how different one affect your riding.
