i agree we get to run 23mm with less aero loss and possible better rr but i still dont get it why it is the c2 rim that allows to run lower psi
surely a set psi is the presure in tyre irrelevant of witdh of tyre
why is it the c2 rim makes any differnence to this????people advise 115ish but if c2 rim 95ish????? why

OK ... HERE'S WHY (as explained to me by a HED representative). It's very simple.

Same tire and tube on a 23 mm wide rim will hold a higher volume of air than it does on a 19 mm wide rim. Somehow this is supposed to allow you to run lower pressure and get away with it.

Don't shoot me. I'm just the messenger...

Why is it silly? The tire is the same size from bead to bead, but on a 23 mm wide rim, the total circumference of tire and rim is greater by 4 mm. That would seem to me to be an indisputable fact. Granted, the incremental volume doesn't sound like much, but it IS incremental.

I just did some back-of-envelope math and, unless I'm way off (which I'll acknowledge is possible), I'm coming up with about an 11% increase in area inside a cross-section of a 20c tire on a 23 mm rim compared to a 19 mm rim. I assume that translates directly into an 11% increase in volume. There's some slop in there with regard to rim edge height and how it overlaps the tire bead, but I can't see it changing more than +/- 2 points on the 11%.

That actually seems like a lot of additional air volume to me -- more than I initially expected before I crunched a couple of fast numbers.

edit: Then, contemplate what an increase in internal air volume, given a fixed tire "span", means to how a pneumatic tire operates...

I'd rather contemplate how many angels can dance on the head of a pin.

I feel like I've kicked the neighborhood bully in the shin. I'd like to just run away now. ;-)

Trinole. Do the Hed C2 wheels need special carbon specific brake pads?

I'm debating new wheels and I'm down to Hed Jet C2 60's vs Reynolds Assault/Strike

The Reynolds you def. need carbon brakes or atleast they say the warranty is voided. Whereas, the Hed I think has an aluminum braking surface, so I'm not sure if it needs special carbon brakes?

No - i am using the Swisstop black pads but i have also used the green ones as well. If you decide on the HEDs, I can get you a good price on some slightly used ones....

Tom-
Hold on a second. If you use the same tire on a 19mm and 23mm rim width, the square inches of cross sectional area will be greater on the 23mm rim. PSI is lbs/square in, so if the cross sectional area goes up, psi goes down to get the same amount of load from the tire. Maybe I'm not following your argument, cuz I know your an engineer???

Steve Hed is no Frank Day.

Contact patches will be roughly the same on smooth roads, as in both are really small.

Do lower pressure/higher volume accumulators displace more volume then higher pressure/lower volume ones when subjected to pressure spikes from hitting bumps/potholes? Could this be perceived as providing a smoother ride?

so points for c2 rims
less light bulb effect from tire (apart from using bonty aero tt) now allowing to run 23mm tyre to match rim which should give lower rr
run lower psi due to larger air volume in tyre which should give less harsh ride
??
points against
harder to fit frames
??

bad929 - hit me up witha message and your contact info.