impact of bond futures conversion factor on calendar spread trading

i have a quick question about conversion factor and his implication in calendar bonds roll trading. I go short on a calendar roll (short front+long back) which has the same cheapest to deliver. The CF is roughly 0.60 for both contracts. The calendar widen +10cts so it negatively impact my position. I realise that the implied repo is pretty much the same than when i enter in the trade 10cts lower because I reckon that this is related to the low CF as the foward CTD is express as: Future x CF, s