The Sped-Web
Triathlon, Running Coaching and Stuff
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The Sped-Web Triathlon, Running Coaching and Stuff
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A very useful link with loads of technical data on wheels, bikes, bike fit, etc etc etc etc How do I choose a bike? 1. Decide how much you want to spend. second hand is much cheaper but new will get you something your size and you have to worry a lot less about fitting on the bike. 2. Find someone who knows about bikes or visit a reputable bike shop and get some advice. There are a number of variables you need to know and find out about in choosing a bike. Go to the beginning pages for some bike shops. a) Inside leg: This will govern the distance between the top of the saddle and the pedal at it's furthest point from the saddle. If you have the saddle at the wrong height it will affect everything about you ability to transmit power on the bike. b) Torso length and arm length this will govern your ability to reach the handle bars from your seated position. c) Women generally have longer inside leg as a ratio to the torso length. For example I am 5'10" with an inside leg of 32". My Wife is 5'4" with inside leg of 31". d) The crank length can also help the inside leg measurement and will also affect the power transferred to the transmission. Think about leverage if you are loosing a bolt. long lever is easier is it not. This has to be weighed up with the length of leg though. 172.5mm is a popular sized crank. 175mm is for the 6 footers and then there's 170 or 165 etc for smaller folk. e) Most bikes are measured in centimetres from the bottom bracket to the top of
the tube below the seat-post. Not all bikes are measured the same though, so a
56cm in one style may not be the right size in another. Some bike manufacturers
make bikes with sloping top tubes and do three sizes: small medium & large.
These are much easier to select as the adjustment in the height of the saddle is
based around a longer seat post rather than frame size plus seat post. Confused,
look at a Giant TCR These are how the dimensions affect your bike. Imagine how you fit the bike.
How do I get the right position on the bike? What do I want from my bike?
We all want to ride faster. To do this we must be in the right position to get the best from our muscles that drive the bike. You need to know you inside leg (or in seam). this is the measurement from the crotch to the floor when you are standing upright (without shoes). measure this in centimetres. multiply this number by 1.09 This will give you a very good idea of what dimensions A+C will be on the picture above. this may not be exactly right but you final position will be within 0.03 -so try multiplying by 1.06 or 1.12 to get a guide if the 1.09 figure does not feel right. These figures are published by the BTA and test they have done on athletes have shown that they all fall within this range. example If you inside leg is 75 cm then if you multiply it by 1.09 you will get 81.75cm. Adjust your saddle to this height. if it not right try the variation above (.03) once you have got your saddle height you need to adjust you reach (measured by D on the diagram). To do this you need to sit on the bike and with help get someone to see if the y can draw a straight line from your kneecap to the centre of the peddle. you can be 2cm from the plumb line though.
If you can do this you are nearly there. Now you need to put you hands on the drop handlebars (most aerodynamic position unless you have a triathlon specific bike). When you are doing this there should be a slight bend in the elbows and the knee should pass within 1-4 cm of each other.
Joe Beer's website JBST offers advice and if you are keen you can travel to Devon and get sized up by Joe, who, by the way is a really nice bloke. Any of the shops listed on the beginning page will also do you a fit on a bike you buy from them.
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and then compared with a TREK 
with standard bike geometry. both bikes will do the business and could set you
back the same ££££'s. 