Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I'm stuck in understanding size tables of a bike.

For example this size chart: enter image description here

Am I right in my thoughts? Effective top tube (ETT) is horizontal value so, it's B1 on the chart. BS is the length of line parallel to the frame. But then why BS is less then B1? (if B1 is horizontal, than it's cathetus of the triangle, it should be less then hypotenuse)

Or ETT is not horizontal line, but the line parallel to the frame?

And also, what is A1 on the picture? It looks like the main value (size of those bikes are called by A1 values), but what is the difference with AS value?

share|improve this question
    
B1 is the hippopotamus, not BS. –  Daniel R Hicks Jun 27 at 17:57
    
(Don't ask me, though, to define the other two hides.) –  Daniel R Hicks Jun 27 at 17:58
    
(But the net is that the manufacturer can define any measurement they wish, any way that they wish. Only a few are even halfway standardized.) –  Daniel R Hicks Jun 27 at 18:01

1 Answer 1

up vote 1 down vote accepted

If you look at the full resolution it is clear. BS is center to center (head to seat) along the (sloped) top tube. Since the seat tube is slanted that is a shorter distance. Geomemtry C2C

Cathetus and hypotenuse apply to a right (90 degree) triangle. There is not a 90 degree triangle on the BS.

enter image description here

share|improve this answer
    
Well, there is a 90 triangle involved but BS is the hypotenuse, not a side. B1 is the ETT dimension. A1 is "effective seat tube", ie. how long the seat tube would be on a bike with horizontal top tube. ( A very odd measurement btw ). –  Fred the Magic Wonder Dog Jun 27 at 15:38
    
@FredtheMagicWonderDog That inner triangle is not necessarily 90 degrees. –  Blam Jun 27 at 15:49

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.