I was doing a bit of calculations. I wanted to figure out if upgrading from a 180mm to a 203mm would make it possible for me to remove the spacers I added.
I’m using the initial drawing from Florian as reference (I did not verify if the final hub is any different)
From middle of left bearing to left flange
E:16+D:17mm = 33mm
Left flange to middle of rim
100mm/2-33mm = 17mm
Note the measurements D+E is to the outside of the left flange.
So let’s add 1mm (even a thin/blade spoke has 2mm thickness at the flange) because we are measuring from middle of the spoke at left flange to middle of spoke at rim
17m + 1mm = 18mm “left-right distance" for the length of the spoke
Using 270mm spokes (likely typical for a 29" wheel build).
Going from 180mm to 203mm disc adds (203-180)/2=11,5mm to the radius.
18mm/270mm*11,5 = 0,77mm added clearance from using a 203mm disc compared to a 180mm
(18mm+3mm)/270mm*11,5 = 0,89mm added clearance from using a 203mm disc and a 3mm offset rim
Personally I’m using a 3mm offset rim but the 0,9mm will only make it possible for me to skip one of the spacers. Maybe grinding a bit more off the corner of the brake caliper would then do the trick. But it seems to me that even a 203mm disc does not make it an easy build without spacers. Or at least the brake caliper choice will be limited (assuming slimmer brake calipers even exists…)
Did I miss anything or are my calculations wrong?