Bike bits

I thought I’d start a page on parts of a bike.  Why?  Well, have you ever gone to a bike shop, and been completely bamboozled as to what to say when you try and explain what’s wrong?  I don’t know if you have, but I certainly have.

So, I thought I’d put a bit together on the different parts of your bike, and what they do.  Consider this a work in progress.  As I pull apart my bike to do various bits of maintenance/repair (as I break stuff), I’ll update this with more detailed stuff.

So, let’s start with the parts of the frame. The frame is the main part of the bike. It’s the part that the wheels and all your other bits are fit onto. It’s commonly made of steel, aluminium or carbon, but there’s a whole lot of other stuff you can get your frame made of – bamboo, wood and titanium to name a few.

The following diagram shows the major parts of your frame – the top tube, down tub, head tube, seat tube, seat stays and chain stays.


Most frames are essentially made up of two triangles (when you look side on). Your front triangle (apex points to the front wheel), and wait for it… the ingeniously named rear triangle (apex points to… you guessed it – the rear wheel). There are quite a few exceptions to this, however. Many women’s bikes drop the top tube to be parallel to the down tube, to make what they call a “step through” bike. This makes it easier (and to a male designer, more decorous) to get your leg over the bike. They can also be for people with short legs, but long torsos, as often standover height (the height of the bike when you are standing on the ground) can be a bit of a problem.

So, why is all this important? The geometry (the angles and length of those bits have a big impact on how your bike feels. Have you ever wondered what the difference between a mountain bike and a road bike is? Or the difference between a triathlon bike and a beach cruiser? It’s all in the geometry.

For example, a steeper headtube angle (which is the angle the headtube forms with the ground) will influence where your forks lie.  The steeper this is, the twitchier a bike is (it will turn faster), and the faster it will go up hills.  The downside is that it will be less stable at high speeds, or on uneven terrain.

Or, how long your bike is (or the wheelbase) is influenced by how long your chainstays and top tube are.  The longer the wheelbase, the more stable the bike (but the harder it is to turn).  This is great if you are just going down hills, but if you want to get around corners too, it may be a bit hard.

There’s a stack more to this, but you can see that the geometry of the bike has a lot to do with the way the bike rides.

In addition to this, knowing the names of things can help you when you go to the bike store, or want to do your own bike repairs/maintenance.  There are a stack of resources for bike stuff on the web, but knowing what the names of things is important if you want to be able to read and apply it to your bike.


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