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Fitting Your Bike Are you confused about how you should fit a bike to your particular body dimensions? Have you been reading, found the terms Merxx or French Fit, and don’t know what you need? Every style of riding is different- in how you fit the bike to you, and the sizing of the bike itself. It’s more than just measuring your height, reach and inseam. With the help of Bike Fitting, you’ll be able to find the right fit for your frame size, style of riding, and your particular dimensions. Here ya’ go…..the location for everything fit related.

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Old 02-17-14, 01:32 AM   #1
Jackontheroad 
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Question how to calculate reach and stack based on the dimensions of the rider's anatomy?

I guess there is a way to calculate reach and stack by knowing at least the length of arm, torso and inseam; also, there should be a range mainly for the stack dimension depending on if the rider plans to do road racing or endurance.
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Old 02-18-14, 08:06 AM   #2
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There are fit calculators online (you could start with Competitive Cyclist and go from there, for example) but there is a large individual component (your flexibility and core strength, etc.) so that the best you can hope for is a starting point.
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Old 02-18-14, 08:31 AM   #3
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factor in flexibility and comfort, and you're probably better off actually finding what works and getting the measurements from that point, figuring you can move the dimensions some millimeters either way.
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Old 02-18-14, 06:12 PM   #4
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any scientifically found formulas will be useful for what I want, and much appreciated. In the question I tried to make it clear I know there will be a range for stack depending if the rider plans to ride racing or endurance; and the same idea goes if your flexibility is snake, chameleon or bull.
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Old 02-18-14, 06:17 PM   #5
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There simply aren't any. The closest rule I know of is placing the handlebars one cubit from the nose of the saddle, and even then stack and reach vary based upon how high the bar is.
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Old 02-18-14, 07:33 PM   #6
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C.O.N.I http://www.sandcreeksports.com/coni.htm part II chapter 5

Plumb-line thru the BB axis , behind that is setback, in front of that center is reach.

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Old 02-18-14, 08:02 PM   #7
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Thanks for the answers, sorry I was not clear; I am not trying to measure the dimensions on a bike. I want to find a formula or a way to calculate reach and stack based on the dimensions of the rider, length of torso and arm, etc.
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Old 02-18-14, 08:27 PM   #8
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I really don't think there are scientific formulas. There is one rule of thumb, like KOPS, standover clearance, fist of seatpost, heel on pedal etc. That is one cubit, the length from your elbow to the tip of your middle finger, from the saddle nose to the bars, and that will give a range of acceptable stack and reach values. Like the other rules it isn't very accurate and only a starting point. Even with scientifically derived formulas, they're still just starting points.
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Old 02-19-14, 03:10 PM   #9
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Quote:
Originally Posted by Crescent Cycle View Post
I really don't think there are scientific formulas.
Right. Any "calculator" or "formula" has to be based on the fitting principles that the one who derived the formula believes in. For example, let's take Greg LeMond's fitting principles, which include pushing the seat back quite far. That is the definition of increased setback, and this, by definition, must decrease the acceptable reach measurements. Or take the principles of some of the modern fitters, who say that the saddle should be placed so that the knee is 1-2 cm ahead of the pedal spindle. This requires less setback, or even no setback, which would increase the acceptable reach measurements. If someone thinks your saddle should be quite high relative to your leg length, then you'd want higher stack, or at least, more rise in your stem. If you have your saddle quite low, lower stack is probably a requirement. Your question, then, depends on a particular set of assumptions of what constitutes good fit and as such is not a well-formed question.
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Old 02-27-14, 09:50 AM   #10
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where is "stack" measured? from this diagram, there seems to be no definite to location for the dimension, or am I missing something?

http://surlybikes.com/bikes/long_haul_trucker/geometry

thanks
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Old 02-27-14, 02:59 PM   #11
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Look at the horizontal lines above and below the stack line on the diagram

Stack is measured as the height of the center of the top of the head tube minus the height of the center of the bottom bracket. For designs like the Surly, throw in an extra half inch of stack because of the external cup headset.
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Old 03-01-14, 02:03 PM   #12
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thanks. I don't always have the imagination to learn in a vacuum!

since posting my original question, I have finished reading Touring Bikes by Tony Oliver. excellent book and a great learning for me. unfortunately, I took it back to the library this morning so can't reference the page, but his take on "stack" was from the bottom of the fork race to the top of the stem nut (? right hardware term?) - in effect the steer tube & its hardware. maybe that's a dated or English term?

anyway, on a steep learning curve here!
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Old 03-01-14, 03:54 PM   #13
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Quote:
Originally Posted by southpier View Post
thanks. I don't always have the imagination to learn in a vacuum!

since posting my original question, I have finished reading Touring Bikes by Tony Oliver. excellent book and a great learning for me. unfortunately, I took it back to the library this morning so can't reference the page, but his take on "stack" was from the bottom of the fork race to the top of the stem nut (? right hardware term?) - in effect the steer tube & its hardware. maybe that's a dated or English term?

anyway, on a steep learning curve here!
Stack and reach are simply how high above, and how far in front of, the bottom bracket the head tube sits, measured center-to-center of each part. There is no subtraction involved; it's a simple measurement. Probably this diagram is more clear than pic and description above:

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Old 03-01-14, 05:05 PM   #14
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yes; more better. thanks
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