> >
>

# Hookless Rim Max PSI.. is low

Notices
Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

# Hookless Rim Max PSI.. is low

02-13-24, 02:28 PM
#1
Senior Member

Join Date: Sep 2008
Posts: 781
Mentioned: 12 Post(s)
Quoted: 479 Post(s)
Liked 277 Times in 156 Posts
Hookless Rim Max PSI.. is low

Okay first off, I know. These numbers are for my safety... and the safety of anyone behind me... I know. I would never exceed the max PSI on a tire. Ever.

But let's say someone did. Hypothetically. For example, if I, I mean, a rider finds that the calculated ideal PSI for the width of the hookless rim and the size of the tire is 78 PSI, and the max PSI on that tire (let's say they're 28mm Conti 5000s) is 73 PSI, do we think the engineers factored in a 6.5% margin of error, and that 78 PSI is totally fine. Hypothetically.

EDIT: Hookless... not hooked. datlas

Last edited by Zaskar; 02-13-24 at 05:04 PM.
02-13-24, 04:51 PM
#2
Should Be More Popular

Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 43,019

Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix

Mentioned: 560 Post(s)
Quoted: 22566 Post(s)
Liked 8,902 Times in 4,147 Posts
You mean hookless? Hooked max>hookless.
__________________
Originally Posted by rjones28
02-13-24, 05:05 PM
#3
Senior Member

Join Date: Sep 2008
Posts: 781
Mentioned: 12 Post(s)
Quoted: 479 Post(s)
Liked 277 Times in 156 Posts
Originally Posted by datlas
You mean hookless? Hooked max>hookless.
Yep. Typo.. dammit. Thanks datlas!
02-13-24, 05:06 PM
#4
Senior Member

Join Date: Jun 2021
Location: Australia
Posts: 821

Bikes: 2002 Trek 5200 (US POSTAL), 2020 Canyon Aeroad SL

Mentioned: 1 Post(s)
Quoted: 313 Post(s)
Liked 679 Times in 327 Posts
Potentially yes, but for the sake of simply running 5psi less I wouldn't risk it.
02-13-24, 05:24 PM
#5
Senior Member

Join Date: Apr 2019
Location: UK
Posts: 1,404
Mentioned: 3 Post(s)
Quoted: 682 Post(s)
Liked 452 Times in 338 Posts
Why would this hypothetical individual not want to run 70-73 psi?
02-13-24, 07:05 PM
#6
Senior Member

Join Date: Jul 2009
Posts: 5,912

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Quoted: 3925 Post(s)
Liked 7,231 Times in 2,925 Posts
Originally Posted by choddo
Why would this hypothetical individual not want to run 70-73 psi?
Maybe because the optimum tire pressure for that tire size could be higher, but Continental is capping it at 73 psi (maximum hookless pressure ala ETRTO) for legal reasons.
02-13-24, 07:07 PM
#7
Should Be More Popular

Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 43,019

Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix

Mentioned: 560 Post(s)
Quoted: 22566 Post(s)
Liked 8,902 Times in 4,147 Posts
I think with hookless it’s a shift from the max being based on the TIRE to the RIM.

At this stage, I would be very cautious with higher pressure on hookless. Proceed with caution. I expect with time and even greater tolerances with rims/tires it won’t be as big a concern.
__________________
Originally Posted by rjones28
02-13-24, 07:12 PM
#8
It's carbon dontcha know.

Join Date: Mar 2007
Location: Between the Hudson and East
Posts: 178
Mentioned: 0 Post(s)
Quoted: 21 Post(s)
Liked 18 Times in 7 Posts
Run 30mm Conti's or eat less pies.
02-13-24, 07:12 PM
#9
Senior Member

Join Date: Apr 2019
Location: UK
Posts: 1,404
Mentioned: 3 Post(s)
Quoted: 682 Post(s)
Liked 452 Times in 338 Posts
Originally Posted by tomato coupe
Maybe because the optimum tire pressure for that tire size could be higher, but Continental is capping it at 73 psi (maximum hookless pressure ala ETRTO) for legal reasons.
Sure but that’s not a reason to want to do it though. If 70 felt smoother and was as fast or faster than 80, Conti doing that wouldn’t matter. Curious why the desire to run higher pressures. It’s kind of right in the vicinity of what I use on hooked 25mm.

edit: aha skimmed past your “optimum”. ok so it’s probably slower?
02-13-24, 09:37 PM
#10
I am potato.

Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,099

Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆

Mentioned: 28 Post(s)
Quoted: 1780 Post(s)
Liked 1,619 Times in 926 Posts
If you find yourself at the maximum pressure recommended for a particular tire, it is time to run a bigger tire. It's as simple as that.

If you find the necessary pressure required of a particular tire size exceeds the maximum allowable by the rim, you need a stronger rim.
Here's a fun example of why.

Last edited by base2; 02-13-24 at 09:41 PM.
Likes For base2:
02-14-24, 08:59 AM
#11
Senior Member

Join Date: Sep 2008
Posts: 781
Mentioned: 12 Post(s)
Quoted: 479 Post(s)
Liked 277 Times in 156 Posts
Good point datlas - the 73 (actually, 72.5) PSI is the spec from Syncros on the hookless rim. There's always been that standard 1.5x safety margin in engineering... that a gross generalization for everything engineered. I'm looking for that real world data - you know, that "I've been running 15% over the max for 10 years and... " or "I went 76 PSI and the rim blew apart."

The hypothetical rider is at his optimal weight - eating fewer pies, losing weight isn't in the cards. Going from 28mm to 30mm tires isn't out of the question.
02-14-24, 09:04 AM
#12
Senior Member

Join Date: Aug 2019
Posts: 2,093

Bikes: SL8 Pro, TCR beater

Mentioned: 6 Post(s)
Quoted: 975 Post(s)
Liked 575 Times in 434 Posts
Originally Posted by Zaskar
Okay first off, I know. These numbers are for my safety... and the safety of anyone behind me... I know. I would never exceed the max PSI on a tire. Ever.

But let's say someone did. Hypothetically. For example, if I, I mean, a rider finds that the calculated ideal PSI for the width of the hookless rim and the size of the tire is 78 PSI, and the max PSI on that tire (let's say they're 28mm Conti 5000s) is 73 PSI, do we think the engineers factored in a 6.5% margin of error, and that 78 PSI is totally fine. Hypothetically.

EDIT: Hookless... not hooked. datlas
Why would you need more than 72.5PSI when hookless and tubeless? Don't worry, it won't blow up under you if you go up to 80PSI. They are tested for long duration at pressures a lot higher than that.

FYI, my former hookless rims (Giant SLR1) had a 125PSI pressure limit. Not all of them are maxed out at 5 bar. However, you need to make sure to respect both your wheel and tire maximum pressure ratings.
02-14-24, 09:58 AM
#13
I'm good to go!

Join Date: Jul 2017
Location: Mississippi
Posts: 14,904

Bikes: Tarmac Disc Comp Di2 - 2020

Mentioned: 51 Post(s)
Quoted: 6150 Post(s)
Liked 4,772 Times in 3,292 Posts
I had hookless rims on my old Schwinn Varsity. Back in my less enlightened days, I'd pump them up to over 120 psi. Those were wire bead tires though.

If you are skittish and want no risk, then why even ask? Do you want to live forever?

02-14-24, 10:46 AM
#14
Senior Member

Join Date: Jul 2009
Posts: 5,912

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Quoted: 3925 Post(s)
Liked 7,231 Times in 2,925 Posts
Originally Posted by eduskator
Why would you need more than 72.5PSI when hookless and tubeless? Don't worry, it won't blow up under you if you go up to 80PSI. They are tested for long duration at pressures a lot higher than that.
ETRTO only requires testing to 110% of maximum. Scary.
Likes For tomato coupe:
02-14-24, 01:31 PM
#15
Senior Member

Join Date: Aug 2019
Posts: 2,093

Bikes: SL8 Pro, TCR beater

Mentioned: 6 Post(s)
Quoted: 975 Post(s)
Liked 575 Times in 434 Posts
Originally Posted by tomato coupe
ETRTO only requires testing to 110% of maximum. Scary.
Giant Tire Test Protocol | Giant Bicycles Canada (giant-bicycles.com)
02-14-24, 01:54 PM
#16
Senior Member

Join Date: Jul 2009
Posts: 5,912

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Quoted: 3925 Post(s)
Liked 7,231 Times in 2,925 Posts
It would great if every tire manufacturer did that (or more).
Likes For tomato coupe:
02-14-24, 01:57 PM
#17
climber has-been

Join Date: Dec 2004
Location: Palo Alto, CA
Posts: 7,064

Bikes: Scott Addict R1, Felt Z1

Mentioned: 10 Post(s)
Quoted: 3392 Post(s)
Liked 3,506 Times in 1,768 Posts
Originally Posted by Iride01
I had hookless rims on my old Schwinn Varsity. Back in my less enlightened days, I'd pump them up to over 120 psi. Those were wire bead tires though.
Doubtful. 120 psi on a hookless Schwinn Varsity rim was a blow off waiting to happen.

BITD, I repaired more Varsity bikes than I care to remember. Horrible, heavy things.
__________________
Ride, Rest, Repeat. ROUVY: terrymorse

Likes For terrymorse:
02-14-24, 04:46 PM
#18
Senior Member

Join Date: Aug 2019
Location: SF Bay Area
Posts: 629

Bikes: Lynskey R270 Disc, Bianchi Vigorelli

Mentioned: 1 Post(s)
Quoted: 299 Post(s)
Liked 156 Times in 131 Posts
That's the reason I stuck with hooked rims. I'm biggish and like the ride at ~80psi on my front tire (Conti Ultra Sport 28mm, inflated to 32mm), and 90psi on my rear (GP5k 28mm, inflated to 29mm). I've tried running lower, but always found that it felt squirrelly and squishy.

At least that takes away the want/need to go hookless/tubeless - no real point at the pressures I'm riding.

So I'd throw another option into the mix. If the rider wants to try 80psi on a short section of smooth road, it's likely fine. But if that's what he/she likes, then:
- Getting a fatter tire is likely the better solution
- Going back to hooked rims to allow for higher pressures
02-14-24, 07:36 PM
#19
Klaatu..Verata..Necktie?

Join Date: May 2007
Location: SF Bay Area
Posts: 17,895

Bikes: Litespeed Ultimate, Ultegra; Canyon Endurace, 105; Battaglin MAX, Chorus; Bianchi 928 Veloce; Ritchey Road Logic, Dura Ace; Cannondale R500 RX100; Schwinn Circuit, Sante; Lotus Supreme, Dura Ace

Mentioned: 41 Post(s)
Quoted: 10389 Post(s)
Liked 11,839 Times in 6,059 Posts
Originally Posted by Iride01
I had hookless rims on my old Schwinn Varsity. Back in my less enlightened days, I'd pump them up to over 120 psi. Those were wire bead tires though.

If you are skittish and want no risk, then why even ask? Do you want to live forever?

https://youtu.be/NeOf-tv_YtI?t=3
RMOT. When I watch this, I always imagine someone in the back yelling, "IS THAT AN OPTION?!?"
__________________
"Don't take life so serious-it ain't nohow permanent."

"Everybody's gotta be somewhere." - Eccles
Likes For genejockey:
02-15-24, 05:41 AM
#20
Senior Member

Join Date: May 2021
Posts: 8,350
Mentioned: 12 Post(s)
Quoted: 4379 Post(s)
Liked 4,805 Times in 2,969 Posts
Originally Posted by Zaskar
Good point datlas - the 73 (actually, 72.5) PSI is the spec from Syncros on the hookless rim. There's always been that standard 1.5x safety margin in engineering... that a gross generalization for everything engineered. I'm looking for that real world data - you know, that "I've been running 15% over the max for 10 years and... " or "I went 76 PSI and the rim blew apart."

The hypothetical rider is at his optimal weight - eating fewer pies, losing weight isn't in the cards. Going from 28mm to 30mm tires isn't out of the question.
Just go wider. Too many variables to know what the risk factor actually is for any individual. Let's say 73 psi is safe for 100% of normal use cases, 78 psi might be safe for only X% of use cases. The value of X is an unknown. So just go wider so you don't have to worry about it. Assuming you have tyre clearance of course. If not then just run 73 psi anyway. Running slightly under the "ideal" pressure (which is only an estimate anyway) is better than running slightly over it in terms of rolling resistance.

Note: check your pressure gauge is reasonably accurate too, especially when working close to the max limit.
Likes For PeteHski:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off