Bicycle Mechanics - restricted speed?

okay, i'm terrible explaining things, especially bikes since i'm not an expert about mechanical shtuff so i'll try my best...please bear with me!

when i'm riding on a flat road or at a moderate speed there's some resistance to the pedals which actually makes me be able to pedal but whenever i'm pedaling fast or going downhill, at some point my pedals just kind of top out / stop :working: (??) and although i may pedal, it feels like i'm just spinning them but i can't go any faster. the feeling is almost similar to being in a low gear on a flat surface. for example, the other day i was going pretty fast downhill and when the road flattened out the speed from going downhill was still with me but my pedalling had no effect, so i basically had to wait till i'd lost speed from the hill to be able to start "really" pedalling again and at this point i felt like i was going really slow :(

is this normal? how can i change this? it's really frustrating!!
thanks!!

...shift to a higher gear.

If you are saying this is happening while you are in your highest gear (big ring in the front, small cog in the back), then the only solution is to get a bigger ring in front or a different cassette in the rear with a smaller cog. Or you can simply just live with it.

yeah, i'm in the highest gear.
thanks for the suggestion!

Is your bike an MTB? Most of these have lower top gears than road bikes and you will "spin out" at fairly low speeds unless you are capable of a very fast cadence.

my money is in a mtb gearing

It sounds like the bike is moving fast enough that you can't spin the pedals fast enough to keep up. A higher top gear would help with that. One thing to keep in mind is that if you almost never go that fast, you might be better off just coasting and then you can keep all of your current gears. One other suggestion is to look at toe clips or clipless pedals, if you don't have them. You can spin a LOT faster if your feet are connected to the pedals.

God bless!
Wayne J.

Just turn the pedals faster or coast and enjoy the ride. Changing the gearing will likely cause problems in other situations. What you have described is known as "spinning out", as Hillrider said.

Al