This post is a beginner's guide to understanding bicycle gears. Yes, you have bought yourself a shiny new bike and wow, it has so many different gear combinations, but how do they actually work? A check on the internet brings up words like derailleurs, cranksets, cassettes and freehubs; Just about enough to put many an unsuspecting newbie into a tizzy. I'll try to explain all there is to know about bicycle gears and shall attempt to keep it as simple as possible. This post, by the way, is dedicated to my good friend and go-to guy in a crisis, , who has just bought himself a new bike and has started bicycling again after a hiatus of twenty years.<div>There are a great many kinds of geared bicycles, but by far the most common type have both front and rear 'derailleurs'. Derailleurs are gear shifting mechanisms, which guide the chain onto differently sized gear cogs. The cogs on the front, which together form what is called the 'crankset', differ a lot in sizes, even when considering cogs which are adjacent. The largest cog, which is on the outside is quite a bit larger than the smallest cog, which is the innermost. The cogs on the rear set, which are often constitute a single 'cassette' are much closer in size to their immediate neighbors, in comparison with the front gear cogs.
A Shimano 7 gear cassette, front and rear derailleurs and wheel with a freehub
So, now that we know the basic differences between the two gear types, let's see what they can do for us. If we have three gears on the front and seven on the rear, there exist twenty one possible combinations once can derive with them; hence the terms 21 gears, 24 gears etc. Not all of these are useful to us at all times. Gear ratios provide limited trade-off points, your currencies being effort and speed. The difference that optimal gear changes can make in the quality of a ride can be quite stunning.
Choosing a smaller cog than necessary on the front leads to inefficient power transfer; If you shift to the smallest cog on the front on a flat road for instance, your legs will windmill uselessly and you don't achieve any speed. Conversely, staying on a bigger cog on a steep incline might mean you slow down to a stop or get completely exhausted.
Gear practicals: rear gears
No amount of reading up about gear ratios can teach one as much as learning handson. The best way to begin is not to choose a course with lots of climbs and descents, but instead, a flattish stretch with the occasional gentle climb or descent, the operating word being `gentle'. An oval track which allows you to maintain a near constant speed is probably the best. If your front derailleur has three gears, simply choose the middle gear and leave it unchanged for the entire session. You may start the bike with rear gear in any position, but switch to highest cog soon. Try to go faster; since the terrain is flat, you should soon reach a point where you are pedalling quite fast but aren't going faster. Now, shift to a lower gear (smaller cog). With each downshift, you'll be able to go faster but with a slight increase in effort. Change up and down as often as you want, to observe the change. For a bonus, if you are not tired, try shifting to the biggest cog in the front and be ready to shift a gear or two higher on the rear, to compensate for the added effort. You should be able to go even faster now! The fastest speeds can be reached when you are in the biggest cog in the front and the smallest, in the rear. You are now ready for lesson two: climbs!
Gear practicals: front gears
Downhill runs in a bike make for some of the most exhilarating experiences, but climbs? Not so much. Climbs are the least enjoyable part of a bike ride, but a biker often has to contend with them and when you need to, gears can be your best friend! Choose a trail with a moderate grade (1.5% to 2%) which is not too long.
Tip: Applications such as Strava can be used to find interesting climb routes and segments.
As you approach the beginning of the climb, quickly shift into a higher gear on the rear. If you find the effort too much, as you start on the actual climb, downshift the front gear. This sounds like a lot of thinking and acting, but with practice, it becomes as easy as breathing. After you crest the climb, savor the sweet feeling of accomplishment and shift to higher gear on the front. Always remember this magic mantra for climbs: shift often and shift early. Don't wait till you are actually climbing and find yourself going blue in the face with strain; shift before you hit the grade. If you want more exercise or cardio, try to engage a lower gear on the rear. This also helps you to move at a faster clip, even while climbing.
Finer points
Higher gear or lower? This is often a question without a definite answer. It depends on your level of fitness and prevailing conditions, but sometimes, extra strain and hence earlier exhaustion when engaging a higher gear in the front outweighs the greater speed you can get. Shifting to a smaller cog in the front and engaging a smaller one in the rear might give you the same speed or better. Just remember that there is no magic gear that allows you to go at record speeds at little or no effort; choice of gears is always about optimizing speed and effort. The more you ride, the more you learn and the better you can get. Happy riding!
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