Mountain Bike Gears And Frames

How Mountain Bike Gears Work

The gears in mountain bikes just keep getting more and more intricate. The bikes of today have as many as 27 gear ratios. A mountain bike will use a combination of three different sized sprockets in front and nine in the back to produce gear ratios.

The idea behind all these gears is to allow the rider to crank the pedals at a constant pace no matter what kind of slope the bike is on. You can understand this better by picturing a bike with just a single gear. Each time you rotate the pedals one turn, the rear wheel would rotate one turn as well (1:1 gear ratio).

MTB gears on the rear wheel

If the rear wheel is 26 inches in diameter, then with 1:1 gearing, one full twist on the pedals would result in the wheel covering 81.6 inches off the ground.

If you are pedaling at a speed of 50 RPM, this means that the bike can cover over 340 feet of ground per minute. This is only 3.8 MPH, which is the equivalence of walking speed. This is ideal for climbing a steep hill, although bad for ground or going downhill.

To go faster you’ll need a different ratio. To ride downhill at 25 MPH with 50 RPM cadence at the pedals, you’ll need a 5.6:1 gear ratio.

A bike with a lot of gears will give you a large number of increments between a 1:1 gear ratio and a 6.5:1 gear ratio so that you can always pedal at 50 RPM, no matter how fast you are actually going.

On a normal 27-speed mountain bike, six of the gear ratios are so close to each other that you can’t notice any difference between them.

With actual use, bike riders tend to choose a front sprocket suitable for the slope they are riding on and stick with it, although the front sprocket can be difficult to shift under heavy load. It’s much easier to shit between the gears on the rear.

If you are cranking up a hill, it’s best to choose the smallest sprocket on the front then shift between the nine gears available on the rear. The more speeds you have on the back sprocket, the bigger advantage you’ll have.

All in all, gears are very important to mountain bikes as they dictate your overall speed. Without gears you wouldn’t be able to build speed nor would you be able to pound pedals. The gears will move the pedals and help you build up speed.

There are all types of gears available in mountain bikes, all of which will help you build up a lot of momentum if you use them the right way.

MTB riding shifting gears to get ready to peddle up a gravel hill

What Is A Moutain Bike Frame Made From

The cost of a mountain bike frame is proportionate to its material, as well as the treatment that material has received. Currently, there are five types of material used in mountain bikes – high tensile steel, Chromoly steel, aluminum, titanium, and carbon fiber. Oversized diameters, heat treating, and butting are tubing material treatments that will increase the cost of a frame as well.

High Tensile Steel MTB Frames

This is a very durable alloy that’s found in lower-priced mountain bikes. It offers a high carbon content which makes it less stiff than Chromoly steel, so more materials are needed to make it stiff enough for bicycle frames, which will, in turn, make it that much heavier.

Relatively inexpensive to produce, you’ll find this material in trail bikes, city bikes, and even entry-level mountain bikes. There are some bikes that come with a Chromoly seat tube, while the rest is high tensile steel.

Two children on their MTB with helmets on and BIG smiles too

Chromoly Steel MTB Frames

Short for steel alloy, Chromoly is best described by its major additives – chromium and molybdenum. This is probably the most refined framing material, giving over 100 years of dependable service.

Depending on the type of heat treating and butting, you can find this material in bikes as low as 400 dollars all the way up to 1,500 and beyond. The Chromoly steel material offers very good durability and a compliant ride characteristic.

Aluminum MTB Frames

For the past 15 years, aluminum has been refined in pretty much the same way as Chromoly. There have been various alloys developed, as well as heat treatment, oversizing, and butting. With dual suspension bikes, aluminum is the preferred material as it’s the stiffest and most cost-effective.

Aluminum is stiffer than Chromoly, and therefore it will crack before Chromoly. Of course, this depends on how you ride and how much abuse you give the frame. The advantages of aluminum are that the frame is very light and very stiff through oversizing or butting.

MTB rider on a bike trail in the woods with a tritium MTB bike frame

Titanium MTB Frames

Even though it’s somewhat exotic, the prices for this material have come down over the last few years. Frames made of titanium remain expensive because it takes longer to weld the tubes to the frame.

Titanium is considered an alloy, normally mixed with small amounts of vanadium and aluminum to give it better weldability and ride characteristics. More compliant than Chromoly, it offers better fatigue and corrosion properties.

The material you choose for your bike, all depends on where you ride and what style you use. Almost all materials will last you for years, as long as you take care of your bike and treat the frame with some respect.

3 thoughts on “Mountain Bike Gears And Frames

  1. WOW!  I found your site very professional and comprehensive, and I have to say I am not into bicycling. I never learned to ride. I really would like to though and am toying with the idea. I fancy a comfort bike with a nice basket on it to ride through the parks on a Sunday afternoon. I think that sounds lovely. I enjoy your pictures and I love the fact you tell people up front about cookies. DL


  2. Wow, thanks for this really amazing post. I am fan of cycling but I don’t really know the importance of all these gear packed in a single bicycle. Some time ago around last year i got my son a bike and he complains about having difficulties climbing up high surfaces, now i understand the reason for this. Thanks for this really nice post.

  3. Hi DL! I want to thank you for your kind words and feedback! They are much appreciated! I definitely think you should get a comfort bike or at least try one out before buying one. Comfort bikes are the most widely used style for rentals if that is something that interests you. 

    I think a basket on the front sounds lovely! There are many styles to choose from! I have had my eye on this wicker one for a while now! Take a peek and see what you think here. It is a Nantucket Style and it is FABULOUS!

    I hope you have a FUN and SAFE first ride if you decide to give it a go. Keep us posted!!  

    Please don’t forget to pick up and wear a bike helmet. Here is a  link to the safety tips article for you. 

    Enjoy! Nicole 

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