The ongoing hookless rims saga

[fa63]

Even though technically the safety margin could be as low as 10%, I doubt engineers at major manufacturers are working with that for normal operating conditions. Enve and Giant are on record saying that they test to at least 150% of the tire rating. I imagine Zipp is in a similar boat.

Whatever caused De Gendt's failure likely falls under the "beyond design basis event" category; I don't think the tires just blew off the rim due to temperature increase or being slightly over-inflated. The question then is, would a hooked rim have held up under the same condition? I don't know the answer, but I will take any additional safety measure I can take when it comes to my wheels and tires, even if it comes at the expense of 15 grams and a little more $$$.

[fourflys]

Originally Posted by fa63

Even though technically the safety margin could be as low as 10%, I doubt engineers at major manufacturers are working with that for normal operating conditions. Enve and Giant are on record saying that they test to at least 150% of the tire rating. I imagine Zipp is in a similar boat.

Whatever caused De Gendt's failure likely falls under the "beyond design basis event" category; I don't think the tires just blew off the rim due to temperature increase or being slightly over-inflated. The question then is, would a hooked rim have held up under the same condition? I don't know the answer, but I will take any additional safety measure I can take when it comes to my wheels and tires, even if it comes at the expense of 15 grams and a little more $$$.

I generally agree, I don't think I would purposely buy hookless.. the Giant I bought happened to have hookless, so I will ride them at gravel pressures and not even think a thing about it.. or I might throw some fatter road tires on there and ride it like that and not think about it.. but I agree, if I bought a set of carbon wheels in the future for road purposes, I would more than likely search out hooked..

[RoosterCogset]

Originally Posted by MikeD

And max pressure according to this chart:

Well that's interesting.
So, if I understand -- Width As Measured is not important -- use the nominal size?
The max PSI for a 28mm tire per this chart is the 73psi amount, and per Silca's calculator, I come up with the max system weight that a 28mm setup can accommodate is about 130lbs.

So, normally the suggestion is 'use a wider tire'. Ok a 30mm tire per this chart can only be inflated to 65psi. Lo and behold, Silca's calculator indicates that roughly the same 130lb total system weight (ie. 110lb rider) is about the most that fits under this ceiling.

[Dave]

Try the Zipp pressure calculator. I put in 140 pounds to cover my weight with shoes, clothes and other stuff. It only suggests 51.3 front and 54.6 rear. Even 240 lbs comes in well below 72.5, unless thin sidewalls are specified. Then it suggest 72.6 psi for 220 pound rider.

[Ewiser]

Would you drive a car that had hookless rims?
All this tubless tire work is like they have never looked at a car tire
And how it is instated on a rim. A tire has to have a bead and hook to
Hold it on the rim wheel. It’s like they are trying to have tubulars without
The glue.

[RoosterCogset]

Originally Posted by Dave

Try the Zipp pressure calculator. I put in 140 pounds to cover my weight with shoes, clothes and other stuff. It only suggests 51.3 front and 54.6 rear. Even 240 lbs comes in well below 72.5, unless thin sidewalls are specified. Then it suggest 72.6 psi for 220 pound rider.

Yes, because Zipp wants to claim their wheels are good for a market with up to 250lb system weights, so only when you get to that weight, will it return a 73psi value. Silca isn't selling tires or wheels.

[Mark McM]

Originally Posted by RoosterCogset

Well that's interesting.
So, if I understand -- Width As Measured is not important -- use the nominal size?
The max PSI for a 28mm tire per this chart is the 73psi amount, and per Silca's calculator, I come up with the max system weight that a 28mm setup can accommodate is about 130lbs.

So, normally the suggestion is 'use a wider tire'. Ok a 30mm tire per this chart can only be inflated to 65psi. Lo and behold, Silca's calculator indicates that roughly the same 130lb total system weight (ie. 110lb rider) is about the most that fits under this ceiling.

Tire pressure affects many properties, including comfort, handling, rolling resistance, safety, rim protection, etc. Any pressure recommendation will have to optimize for a particular balance of all these properties. The Silca pressure calculator primarily optimizes for rolling resistance. Josh Poertner of Silca has stated that most people would probably do better with a little lower resistance, for a little better comfort.

Originally Posted by Dave

Try the Zipp pressure calculator. I put in 140 pounds to cover my weight with shoes, clothes and other stuff. It only suggests 51.3 front and 54.6 rear. Even 240 lbs comes in well below 72.5, unless thin sidewalls are specified. Then it suggest 72.6 psi for 220 pound rider.

We don't know what properties the Zipp calculator optimizes for. But is interesting to note that for the same entered values for rider/bike/conditions/etc, the Zipp calculator recommends lower pressure values for hookless rims than for hooked rims. So either the Zipp calculator optimizes for a different balance of tire/ride properties for hookless vs. hooked, or it applies a fudge factor for hookless rims to keep below a set maximum.

[fa63]

Automobile rims don't usually have hooks... But those tires also use steel beads.

Originally Posted by Ewiser

Would you drive a car that had hookless rims?
All this tubless tire work is like they have never looked at a car tire
And how it is instated on a rim. A tire has to have a bead and hook to
Hold it on the rim wheel. It’s like they are trying to have tubulars without
The glue.

[Mark McM]

Originally Posted by Ewiser

Would you drive a car that had hookless rims?
All this tubless tire work is like they have never looked at a car tire
And how it is instated on a rim. A tire has to have a bead and hook to
Hold it on the rim wheel. It’s like they are trying to have tubulars without
The glue.

I would never drive a car with hookless rims if the tires had flexible corded beads. All the other vehicles with hookless rims use tires with stiff, steel beads. And that includes my old 1974 Schwinn Varsity, with its hookless rims and steel beaded tires. If modern bicycle hookless rims used tires with steel beads, it's likely that there wouldn't be an issue with tire blow-offs and we wouldn't be having this discussion. But instead, the bicycle industry insists on using tires with beads that aren't well suited to hookless rims.

We've actually been through this before. Until the late 1970's bicycle rims didn't have hooks, and clincher tires used steel beads. When so-called "foldable" tires with flexible kevlar beads were introduced, these tires required hooked rims to keep from blowing. There were many cases of people trying to use kevlar bead tires on hookless rims, only to experience blow-offs - even at the same pressures that otherwise identical tires with steel beads would safely stay on the rim.

[dustyrider]

I like checking in on China Cycling’s content and found his recent video interesting: YouTube

The parts related to this thread are that they inflate tires on their rims to 150psi as part of their QC, I guess they’re not hookless, and certain rim manufacturers don’t want the public to know how little they actually pay to manufacture their high priced rims. I also found the entire video to be contrary to so many people’s opinion of poor quality workmanship coming from non-USA manufacturing.

[RoosterCogset]

Originally Posted by Mark McM

I would never drive a car with hookless rims if the tires had flexible corded beads. All the other vehicles with hookless rims use tires with stiff, steel beads. And that includes my old 1974 Schwinn Varsity, with its hookless rims and steel beaded tires. If modern bicycle hookless rims used tires with steel beads, it's likely that there wouldn't be an issue with tire blow-offs and we wouldn't be having this discussion. But instead, the bicycle industry insists on using tires with beads that aren't well suited to hookless rims.

We've actually been through this before. Until the late 1970's bicycle rims didn't have hooks, and clincher tires used steel beads. When so-called "foldable" tires with flexible kevlar beads were introduced, these tires required hooked rims to keep from blowing. There were many cases of people trying to use kevlar bead tires on hookless rims, only to experience blow-offs - even at the same pressures that otherwise identical tires with steel beads would safely stay on the rim.

This seems to be the rationale that Giant/Cadex implies with their wheelsystem and tires for hookless, while at the same time they have no issues apparently ignoring ETRTO guidelines.

In combination, it's interesting to see what what they're doing. One callout, they're ok with 25mm tires run hookless and indicate a minimum inflation of 70psi.

https://www.giant-bicycles.com/us/hookless-technology

https://www.giant-bicycles.com/us/tire-pressure

https://www.giant-bicycles.com/us/tire-test-protocol

[MikeD]

Originally Posted by fa63

Even though technically the safety margin could be as low as 10%, I doubt engineers at major manufacturers are working with that for normal operating conditions. Enve and Giant are on record saying that they test to at least 150% of the tire rating. I imagine Zipp is in a similar boat.

I assume that they are testing new tires. Used tires and ones that have been on the rims for a while, the bead permanently stretches a bit so they don't fit the rims as snuggly. I wonder if that's at play here? My Gravel King tires fit snuggly at first, but looser if I remount them and I need to use a compressor to seat them because of air rushing out under the beads.

[fa63]

Great point. I don't know the answer, but I imagine they would have considered that during design?

Originally Posted by MikeD

I assume that they are testing new tires. Used tires and ones that have been on the rims for a while, the bead permanently stretches a bit so they don't fit the rims as snuggly. I wonder if that's at play here? My Gravel King tires fit snuggly at first, but looser if I remount them and I need to use a compressor to seat them because of air rushing out under the beads.

[Dave]

ETRTO applies to tires manufactured in the EU.

https://en.m.wikipedia.org/wiki/Euro...ing%20bicycles.

[fa63]

Manufactured, or sold in the EU?

Originally Posted by Dave

ETRTO applies to tires manufactured in the EU.