Not sure if anybody is reading this but we're does the X-seam measurement come into play when measuring the bike. When I do everything in step 10 I get 32" total when I do my x-seam measurement I get 41". Do I have to make something 41" to fit me
properly. This whole measuring process has become a nightmare for me. I hope to get on the road soon.
The X-seam is just a Fast way to determine if the bit will fit you; xtreme's of short or tall wouldn't
Let's see if I can simplify but leave the necessary details to move you forward.
The Knee Clearance calculation just make it easier to figure out if you will need to cut the boom and let you get it close the first time.
A = top of your knee to the floor in (cm)
B= crank length in (cm)
C= 5cm
Initial Boom Length = A+B+C
IF A = knee to floor 55cm
IF B = 170 mm cranks then 17cm
You get
Boom Length = 55 + 17+ 5 = 77cm
So
- Make your boom 77cm to start with from the handle bar clam to the center of the cranks.
- If you can't get the boom that short you need to cut the end off of the lower part that slides inside the top part.
- That not uncommon and a hack saw or 2.5in pipe cutter will make short work of it.
I use a $8 pipe cutter from the hardware store.
You then put the boom on the bike. If you knees hit the handbear; don't change the length of the boom instead slide the hand bars forward and back (number 3 arrow in the picture below) see if going forward or back resolves clearance; the angle of the boom changes when you do this; and sometimes it resolve the clearance issue. If it does not; then make the boom longer (number 2 arrow) by 5cm ( not millimeters) and repeat the knee clearance check. and move the boom arrow 3 to find optimal.
Once you get a fit this when you will be at a great starting point. Then you have to do some pedaling and see how it feels. You can move the entire boom 5mm (not centimeters) at a time to get it dial in, 5mm adjustments make a big different in arm reach. If the leg reach or leg knee bends isn't right you can lengthen the boom or shorten.
Something like electrical tape on the boom is your friend when marking these initial settings so you know how far you are moving it.
Most beginners like the boom shorter and will lengthen it within 200-300 miles. When you pedal for real you will ankle a bit; because of that is hard to simulate it's not uncommon when fitting to be able to "brush" the handlebars with your legs every so slightly if you can make it happen and make it not happen by thinking about it then you probably have it just about correct; when pedaling in the real world you won't hit the bars un less you choose to when it's set like that. (this is actually true on a correctly setup DF bike but most people never try to do it but knee to palm slapping is actually a training drill.)
