Bike sizes: metric vs. inches?
371120
If you look at the world at large, only two countries still use the archaic English system of measurement. The British, and the United States. Everyone else uses the metric system.\n\nCycling is still very largely a european sport, and as such, road bikes are measured in centimeters.\n\nEven mountain bikes are starting to use metric measurements with regards to their frames. Bikes are now being marketed as small, medium, large, and so on. However, when you take a deeper look at the frame specs, you'll find nothing but metric measurements.
648027
5 millimetres.  If something is on a scale of 20:1 it means the original version is 20 times the size.  So it's like saying what's one twentieth of 10cm.
972271
It is important to note here that wheel size (20" or 24") really has little to do with the size of the bike except in very general terms.\n\nA bike with 20" wheels will accelerate and handle much quicker than a 24" wheeled bike, while a 24" will be more aggressive in adverse conditions (mud, snow, etc) and be better for longer trips.\n\nA 20" wheeled bike has 3 different frame sizes- Junior, Standard, and XL. A 24" wheeled bike has Standard and XL. This refers to the distance between handlebars and seat.\n\nSo, what size? In a 20" wheel, ask for an XL frame. For 24" wheels, get a standard length.\n\nAll this being said, if you go to a department store you will need to compare and find the right length frame which can be a pain but will provide him with the best fit and longest life... but do yourself a favor and visit a local bike shop.
372062
Metric. Thy still use the same ones.
1137640
For a road bike, look at something in the range of 56cm to 58cm.  For a mtn bike, look at something in the range of 16.5 in to 18 in.
1132272
all metric measurements
965479
12.1 inches is the correct answer here a conversion table for you\n\nhttp://www.dogcraft.com/cmstoins.html
719024
1 inch = 2.6cm\n1 pound is +/- 500gramms
814785
bikesdirect.com has guidelines on the size.
46315
The New Zealand inches are upside down relative to the U.S.A. inches. :-)\n\nIf you define one inch so that one meter is exactly 39.37 inches then you get one length.  If you define one inch as exactly 2.54 centimeters then you get a very slightly different length (do the math).  Both of the above refer to the international standard for the meter, of course.  If there is a difference between the two (besides the upside down thing) then it is probably in which of the above definitions they adopt.
651185
i'd agree with the first answer, it varies a lot from manufacturer to manufacturer.\n\nsome list sizes in inches (15", 17", 18"...) and this refers to the length of the seat tube on the frame, usually from the centre of the bottom bracket (the axle on which the cranks and pedals turn), to the top of the seat tube where the seat post clamp is located. However, a bike with a longer seat tube, will also have other bits that are longer, most importantly the top tube (oddly enough, the horizontal tube running along the top), and also the head tube (where the forks and handlebar stem attach).\n\nOther manufacturers just use a Small, Medium, Large, XL system.\n\nAt 5'5" you probably want to look at 16" or 17" frames, or a small or a medium. The only real way to tell though is to go to a proper bike shop and sit on a few, then ride the ones you like.
535961
Different makes have different sizes that will fit you differently. Im about 6 ft and I a have large scott YZ0 dirt jumper. you will probably want a larger size bike you might hit your knee on the bars if you are turning sharply on a smaller one and that hurts a lot.
549859
It's all in the instruction manual; I assume you've lost it?  The wheel size numbers are odd, I'm not quite sure what it is that determines them.  For my 26" 1.5" wide tires, the number was 2460 ( I don't know why I remember that either. . .).  Generally it is shown on the left hand side what it is that you're to enter.   I don't know if you have the same one that I do, but here's the setup for mine: C1 is the wheel size number, P2 is the pedometer step meter, ignore that if you want to. Then pick km or mi. Then is the maintenence mile picker -- I've ignored this too. Then you should be set.  Good luck!  I've tried e-mailing and finding the Back Trails website, which is no help, so I help that helped some.
226664
Number 1, if Trek spec'd that fork for that bike, they knew that the bike would handle well in both instances.  \nNumber 2, 20mm = 2cm= less than 1 inch.  It is very unlikely that you will notice any difference on how the geometry of the bike has been affected, nor will you see a significant difference of travel.  Most of the additional travel will be eaten up by "sag" or the ammount of  downward pressure exerted on a suspension component with the rider sitting on the bike.  To see a real difference, replace your inner components on the fork, i.e. elastomers/springs, oil, seals...
698218
The simple answer is: the largest size the bike shop stocks. Most manufacturers use an "XL" instead of a measurement for their citybikes / mountainbikes, so that's what you should ask for.\n\nNormally I tell people to get fitted to their bikes before they buy, but that won't work if you want to surprise him. Maybe see if you can come to an understanding w/ the bike shop that after Christmas he can bring the bike in and get fitted, and maybe swap out the bike for the right size if needed.  \n\nAny bike shop bike will be of good quality for those purposes, probably you could go under $500 and be just fine. \n\nGood luck\nScott
724518
Road bikes are measured from the center of the bottom bracket (BB) to the top tube (TT) under the saddle.  This section of the bike frame is called the seat tube.  Trek will have a list of dimensions on their website that you can look at.  They build bike frame proportional to the average riders size.  So as the frame size goes up, the seat tube length and the top tube length will increase in length.  A quality bike shop will be able to fit you properly.  I suggest test driving a few different bikes at a couple different shops to get a good idea of what you like.  Every bike rides and feels different because they use different components or the way the frame is built and they type of material used.
1131192
To determine your proper frame size, you’ll first need to get an accurate inseam measurement . Stand with your back against a wall, your bare feet 6" apart on a hard floor, \nlooking straight ahead.\nPlace a book or carpenter’s square between your legs with one edge against the wall, and pull it up firmly into your crotch, simulating the pressure of your saddle while riding. Have a helper measure from the top edge of the book to the floor, in centimeters. (You can convert inches to centimeters by multiplying inches by 2.54.) Repeat two or three times, for consistency, and average the results to get your inseam length. \n\nSource(s):\nFrame size refers to the length of the frame’s seat tube. Pro frames are measured along the seat tube in one of two ways, center-to-top (C-T) or center-to-center (C-C). C-T measures the distance from the center of the bottom bracket to the top of the top tube or seat lug (See image bellow). C-C measures from the center of the bottom bracket to the center of the top tube. Since C-T measures to a point higher on the frame, a frame measuring 55cm C-T would also measure roughly 53.5–54cm C-C, a difference of 1–1.5cm.\n\nTo size your C-T road frame, we use a guideline of .67 x inseam length. For example, if you have an 85cm inseam, your C-T frame size would be .67 x 85cm, or 57cm.\n\nLeMond’s formula, from his former coach, Cyrille Guimard, establishes C-C size by the formula .65 x inseam length, which yields virtually the same frame size when you add the 1–1.5cm difference between C-C and C-T. \n\nLarger riders (6'0" and up) may find that this formula puts them on a too small, and uncomfortable, road frame. A taller cyclist who wants a more comfortable frame may be better off selecting a frame 27–28cm less than inseam length, C-T.\n\nFor a mountain bike, we start by recommending a frame in the range of 10–12cm smaller than you take in a road frame. For example, if you ride a 55cm C-T road frame, look for a 43–45cm (17–18") C-T mountain frame