Riding a bike that doesn’t fit is no fun. It’s uncomfortable and you risk injury from being too cramped or too stretched out. So here's some advice to help you decide on which frame to go for – traditional, semi compact or compact – and find your perfect size.
Getting the right fit means more than just having the right size frame. It also means your bike fits at all the main contact points: saddle, handlebars and pedals. Have a read of our road bike positioning article to achieve the perfect setup.
Of course, we’re not all the same, so use the information below as both a starting point and a guide. After you get the position close using these tips, make smaller adjustments based on what feels better.
Frame components
With experience you will soon find that a correctly sized bike will look in proportion when finally set up. Use this diagram below to help you identify the different tubes used on the frame of a road bike. The effective top tube concerns bikes that use a sloping top tube (road bikes with a semi-compact or compact geometry).
Manufacturers make frames in various sizes to suit the variety of riders. Getting the size right is essential, but this step is only halfway there. The fine-tuning starts when you choose the length of the stem and the width of the bars.
Frame geometries
There are three geometries of frame size to consider when buying your first bike: traditional, semi compact and compact. Traditional frames are characterised by a top tube that runs parallel to the ground. There is a reduced space when standing over the bike, however, so sizing can be more critical here.
Compact frames are meant to look more radical than conventional level top tube frames so expect to see an extra two to three inches of seatpost showing when compared with the horizontal top tube bikes. The contact points should be exactly the same, so be aware of this when buying – a compact should feel exactly like your favourite conventional road bike with respect to riding position.
Compact geometry frames are characterised by a sloping top tube, shorter wheelbase and smaller rear triangle of the frame. The result is more standover clearance than a traditional geometry frame and a possibly stiffer but more responsive ride.
Semi-compact geometry is similar to a compact with the only difference being that the sloping angle of the top tube is not as great so the standover clearance is reduced and the effective top tube distance is slightly longer.
Important lengths
The most important considerations to make as you decide which frame to go for is the effective top tube length: the distance from the head tube to the seatpost on a bike with a sloping top tube, or simply the length of the top tube on a road bike with traditional geometry. Get the top tube length too long and you'll be overreaching to the handlebars, using a flatter riding position akin to a racing position, which could be uncomfortable on longer rides.
If you're looking for a more comfortable riding position then you may wish to go for a shorter effective top tube length. Use the chart below for a rough guide on the frame size to go for.
Once you've decided on your frame size, your bike fit is completed by setting the bar and saddle height. If in doubt, consult a good bike shop or arrange a bike fitting session as decent cycle shops should help with all the steps for a perfect fit. They should get you on a fixed trainer so that your position can be checked once you’re warmed up and riding in your normal shoes, pedals, shorts, etc.
via BikeRadar.com http://ift.tt/1flGfeS
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