bruh asked in SportsCycling · 1 year ago

How fast does a 21 speed bike go in mph?

I’ve recently bought a new bike and it’s a 21 speed bike. I used to have an 18 speed bike. So I searched up how fast a 21 speed bike was but nowhere did it say how fast it goes. Does it depend on how fast I pedal or is there a max speed?

13 Answers

  • 1 year ago

    Since most road bikes have a higher gear than the rider is able to power, the top speed is limited to the rider's ability to turn the pedals. Simply put, stronger riders can go faster regardless of how many gears the bike has.

  • 1 year ago

    Its not the amount of gears that are important. However, 21 speed is a 7x3 set up, which is used by cheap mountain bikes. The 7 cog on the back is most likely a freehub, as opposed to a cassette. You may have an aluminium frame, but it will not be the lightest. Also, I would say that you have a 26" wheel. But the real deal breaker is going to be your tyres. Nobbly off road tyres, probably quite heavy, since the lighter race tyres are going to be expensive.

    So, a heavy bike with a lot of rotational weight and rolling resistance. On a flat road, probably about 16 or 17 mph. However, it is not the bike but the rider. You may get more out of it, although that weight will be a bumber on hills. Another consideration is your gear ratio. Many rear cogs will have an 11 on the small gear, but the larger gear, that depends. Maybe 32 or more. However, the ratio on the front, especially on the big cog, are going to be telling. If you look at a track bike, it is a single speed with a massive cog up front. Slow to get rolling, but as long as you can power through it, you could get a lot of speed if you can maintain a decent cadence. Many mtb gears though are going to be smaller up front, as your bike is going to need smaller cogs to give better performance off road.

    So although you may get a quick bike, it is not going to be as fast as something with big skinny wheels with over 100 psi in the tubes.


  • D50
    Lv 6
    1 year ago

    Let's see. 21 is 1/6 more than 18, so it stands to reason that the new bike will have a top speed equal to 116.7% of the old bike's speed. Look at all those numbers. It must be correct.

  • pmt853
    Lv 7
    1 year ago

    It depends on how fast you can pedal, what your maximum cadence is and what the top gear ratio is. You should know this if you've already ridden a bike with gears. There is no realistic maximum speed though perhaps at wholly unrealistically high speeds the tyres might melt! As just about everyone else has said - it's down to the rider.

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  • David
    Lv 6
    1 year ago

    How fast a bicycle goes is determined by the combination of the overall gearing ratio and the ability of the rider.

    For a given gear, a bicycle can only move a certain distance down the road for each turn of the pedals.

    So on any bicycle, the faster you can turn the pedals - in that gear - the faster the bike will go.

    Unless you’ve specially trained for it, you probably can’t pedal efficiently above 100 rpm.

    On a normally configured 26” MTB, this means you’ll ”spin out” - not be able to move your legs any faster at about 25 mph/40 kmh.

    A hybrid or drop bar bicycle/road bike is likely - but not guaranteed - to be faster b/c of a higher gearing ratio. It might spin out at 35 mph or so. Keep in mind that a higher gearing ratio ALSO makes the pedals harder to turn, so it’ll take more strength to spin out.

    More gears generally don’t mean a higher top speed. The rider being the limit, most (comparable) bicycles have had very similar top gears for decades.

  • 1 year ago

    You answered your own question. How fast can you pedal? 21 speed WHAT bike? Road bike, hybrid, mountain bike or something else? Mountain bikes will be geared lower for off road use. Road bikes geared higher for street use. A hybrid will be somewhere in the middle. Plus 21 speed bikes (3 X 7 = 21) are basically OBSOLETE.

    Here's a really wild idea... For $27.49 and FREE SHIPPING, get yourself a bike computer. Programmed with the correct tire size, it will be deadly accurate. Current speed, max speed, average speed, time for that particular ride in hours, minutes & seconds + more.

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  • 1 year ago

    0 mph without the rider. The number of speeds a bike has has nothing to do with how fast it can go. First and foremost, what sort of bike is it? A 21 speed mountain bike is going to be a lot harder to pedal fast than a 21 speed road bike. Next, exactly what bike are you talking about? I own a professional quality 14 speed road bike built 35 years ago that is easily faster to pedal than any 21 speed bike built today. How strong are you? Extra speeds will not make you faster unless you are strong enough to turn those harder gears. You could take 20 riders and test each one over a specified course and you would get 20 different speeds.

    The bike doesn't pedal itself, it is the rider who makes it go. There is no specific speed that any bike with any number of gears can achieve. The rider is the power source

  • 1 year ago

    They do not move at all unless someone is sitting on it, pedalling.

  • Anonymous
    1 year ago

    Are you really that dumb that you don't understand that the number of gears bears no relation the the potential speed of the bike? Pedalling fast is also irrelevant. It's effort put in that results in speed.

  • 1 year ago

    Depends on the gears and how mobile you are

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