I just posted this in the comments from the tech mailbag, but thought I would put it here as well.
I am sure someone will just say run tubes, but as a mtn biker as well I have been running tubeless for years and it is great, so thought I would test it out now that things seem to have gotten a little better on the road side?
Here is my post:
Late to this article, but I have been trying to figure out what to do since I am getting a set of wheels with 22/27 dimensions and would like to run a 25c tire up front for aero purposes.
It seems that no one in this industry has any idea what is going on with their products:
ENVE lists the same pressure for you (other poster) at 63psi for 130lb rider on 25c tires with 21 ID rims, but lets look at where it just gets bonkers:
They claim a max of 80psi for their AR wheels which is above the ETRTO limits for hookless. However for a 250lb rider with a 28c-30c tire only needs 67psi according to them. Phew.
They say that a 160-170lb rider (me) needs to run 75-79psi for a 25c tire on a 21 ID rim, again above the ETRTO recs. 25-26c tires would be the correct tire for aero for the Foundation series, which is again hookless and 28mm external diameter. In order to meet ETRTO psi specs you would probably need to run a 28c on the wheels and therefor not aero optimized. (Yes I know they have their own 27c tire, but limited choices and also not aero).
So their aero recommended tire of 25c is out of spec for anyone over the weight of 155lbs and running a 28c reduces the whole point of the aero wheels by not being aero optimized.
So lets head over to Zipp:
According to a reputable website: New Zipp 303-S aero wheels are wider, hookless, tubeless, cheaper, disc-only - CyclingTips
The 303s are hookless and therefor follow the ETRTO limits of 73 psi. They claim that riders up to 253lbs can run 25c tires without going above 73psi.
Why am I focusing on 25c tires? Because again these are aero wheels and the 303s are 27mm external meaning they need a 25c tire to have the best aero performance. They also list 25c tires on their chart even though having a 23mm ID is supposedly too wide (according to ETRTO) to safely run 25c tires on hookless rims.
But wait there is more, enter Schwalbe:
Their chart claims that 25c is recommended by them to be on 22-23mm ID rims and they even point out they are going beyond the ETRTO recs.
Lastly why did I mention my wheels in the beginning? Because as noted above I am getting wheels that are 22/27 which means I will need to run a 25c tire for aero gains. But according to Continental (I would like to run GP 5000 S TR) they only recommend 25c up to 21mm ID and 28 for 23mm ID. ETRTO also is in line with that.
So do I follow ETRTO (and Conti) who have been notoriously conservative? Or do I go with Schwalbe and Zipp who seem to say 25 is all good on >21 ID rims?
I am confused, the tire makers seem to be confused, the rim makers seem to be confused, the ETRTO seems confused, are you confused yet?