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How a bike fits is probably the most important aspect of buying a bike and one where you will ultimately need to take the lead because it is more important to you than anyone else.

Determining the Size to Look For

If your local bike shop uses Accufit, that is great. They will be able to measure you and help you decide on the best size bike. If they don't use Accufit, You can download a copy of Personal Accufit and use it for 14 days to help in the search.

When you have taken your body measurements as prescribed by Personal Accufit and used Accufit to determine the best size bike for you, you are ready to set out on your quest. Print out the Accufit Size Data form and take it along with a tape measure and a note pad to your local bike shop.

Information Gathering

Start by measuring the top tube height of all of the bikes that do not exceed the top tube height recommended by Accufit. You may not want to consider bikes that have a top tube height more than 1" - 11/2" lower than that recommended by Accufit either as they will require a stem rise that may be difficult to achieve. Write down that dimension and the size and model information for all of the bikes that fall in the appropriate range.  While you are at it, measure and record the top tube lengths and bottom bracket heights as well. If the bike shop has the specifications for the bikes they stock, get the seat tube angles as well.  If they don't have the seat tube angles, you can use an angle finder (after making sure that it is on a level surface), check the web site of the manufacturer or armed with a plumb bob and your tape measure, you can take the dimensions as specified in the Personal Accufit help file under Seat Tube Angle Calculator and use the calculator to provide the seat tube angle.

Narrowing the Field

Once you have all of the dimensions that you need, go home and using Accufit, go to the Bike Setup form and enter the top tube height, bottom bracket height, top tube length and seat tube angle in the spaces provided. Now press the Calculate Bike Setup Button. Run the bike setup for each bike that you measured, and print out the bike setup form for each. 

Note: make sure that you set the units to match those that you used to measure the bikes at the shop.

Eliminate those bikes that would require you to use a stem that is either very short (less than 6 cm) or very long (over 13 cm) as this bike will be difficult to adjust if you need to further fine tune your position at a later date. 

If all of your selections are to long in the top tube to let you use a stem length of 6 cm or greater, you may want to go get the dimensions of some smaller bikes and take a look at them. If that doesn't work, you are in for a bit more research. Fear not, somewhere out there a bike awaits that will fit you. Of course, there is always the custom frame route, but that may push you out of your budget range. Do some research anyway, you may be pleasantly surprised. There are plenty of up and coming frame builders out there and you may be able to find one that is in your price range.

Another important thing to look at is the calculated saddle offset. If there is a significant difference between the seat tube angle recommended by Accufit and that on the bike you are considering, a different seat post may be required to place the saddle in the right position. The rails on most saddles have a parallel section of about 3 inches. The clamp on the average seat post is about 1 1/4 inches long. This leaves about 1 3/4 inches of total adjustment so you will want to make sure that the center of the rail can be aligned as specified under Saddle Setback. If this position can not be attained with the stock seat post, you will need to swap it out for one that will allow you to position the saddle correctly. 

Final Selection

By now, you should have a short list of candidates. You can how return to the bike shop and talk to them. They should be able to provide the required stem and possibly seat post change required to set up your bike. 

Please remember a couple of things here. The bike shop needs to make a profit to stay in business. Depending on the price range of the bike you want to purchase and the components it is equipped with there may be a charge for changing these components for both parts and labor. 

For instance, an inexpensive bike typically is equipped with inexpensive parts. It is unlikely that they will have the same brand and model of handlebar stem in stock as there is a limited market for those components. To get the size you need, you may need to pay for the new stem. Additionally clamp style stems are easy to change. There is very little labor involved and they will not have to strip the bars to make the change. On the other hand, "7" style stems will require them to strip at least one side of the bars in order to change the stem. All of this takes time, and the bars will also need to re-wrapped and this may require you to pay for new tape as well as the labor. 

On the other hand, you should expect little or no additional charge for more expensive bikes that come equipped with components that the bike shop probably stocks or will be able to sell.

Most bike shops will be fair when it comes to changing or upgrading parts on your new bike.



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Last modified: July 09, 2014