RAD as in Rider Area Distance!
For those who don't know, RAD is the measurement taken from the middle of the BB to the mid-point/intersection of your handlebar grips. Comparing the RAD of your bike against your body RAD aka your knuckle height, basically tells you whether your bike is too big, too small or just right for you. In other words, RAD plus, RAD minus or RAD neutral. There's a useful video about this here:-
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As I chop and change bikes, I often think about frame sizes and top tube lengths, so I thought I'd check this out for myself. Measuring it like they do in that video, wearing my normal riding shoes and standing in a riding stance, with my arms straight down, my body RAD is 72.5cm.
My UB2's RAD is 72cm which means that it is slightly RAD minus. In other words, my UB2 is 0.5 cm too short for me! By way of comparison, I then measured my previous race bike, my Crupi Pro XL, which has a slightly longer, 21.5" tt, though a stem with a shorter reach. My Crupi's RAD is 72.5cm which means that it's RAD neutral and therefore the perfect fit for me. That surprised me because I always thought the Crupi was too long for me, hence adding the shorter stem to it.
So what does all this mean? Do I need to go back to the Crupi? Do I need another race bike? The answer's "no", on both counts. A RAD neutral bike would supposedly be perfect for me but although I liked it, the Crupi was less "chuckable" than the UB2. Having a RAD minus bike makes it easier to manoeuvre and throw around. Not that I do much throwing around, either on the track or elsewhere but I have always felt more confident riding the GT than the Crupi. The RAD measurement doesn't take into account chain-stay length and therefore wheelbase length, so that may also be a contributing factor. In any case, I'm more than happy with my RAD minus UB2, so that will continue as my main race steed for the foreseeable future.
