Originally Posted by
berlinonaut
You are really running the Brompton on 50 to 60 PSI (3,5 -4,1 bar) and are happy with that? Wow! I pump the Marathons as well as the Brompton Kevelar usually to 6.2 - 6.6 bar (90-94 PSI) and the Kojaks to 7,7 to 8 bar (107-117 PSI). Whenever I feel dragged and slow on my Brommi I check the pressure and if I missed to do so for a couple of weeks the pressure may have gone down to what you are using as a standard. I refill to my standard level and immediately riding feels much easier - like Popey after having eaten his spinach.
It is really a huge and noticable difference for me which I can clearly recognize on my speedometer.
Regarding aerodynamics I am with you. First I think I am too slow to notice the effect of different tires in that aspect and second: Whoever puts a Brompton bag on the carrier block should not be afraid of the negative aerodynamics-effect that may be caused by a tire that is 3mm wider.
hehe... I did one of my usual 15 mile exercise loops yesterday, and although I know I hadn't pumped up my Marathon tires in quite a while, a finger pinch told me it was safe to ride. I just put a gauge to them now and got 38F/41R - it was a comfy ride
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On one hand, I think I should do some time trial runs to see how much air pressure really does impact my pace (and maybe Jan's article is wrong, IDK), but on the other hand, as more of a tourer than a racer, I realize comfort will always out weigh speed/efficiency for me, so I really don't care if lower pressure is a bit slower. I need my minimum level comfort for a given average road surface, and that will define what air pressure I use.
What I DO care about, is how much comfort and efficiency am I willing to sacrifice (vs my gravel bike) for the versatility of a compact folder. I think I've now matched the ergos and aero pretty well, so if my comfort between these two bikes can be tipped by just air pressure, then I think it is fair to assume that any changes in air pressure should equally impact speed/efficiency performance of both bikes, thereby maintaining my same ~3.5% differential. That's good enough for me.