GhostRider62

This isn't a tolerance stack-up between the rim and tire diameter question, the question is how much "stretch" is acceptable on a tubeless tire whether on a hookless or crochet style hooked rim. Some tires stretch a lot and others very little. And, it is not random. Until this mess is straightened out, my tubeless tires are going onto hooked rims and I am riding Compass tires with tubes.

chaadster

I’m not sure the issue (are we still talking about not knowing which tire/rim combos work and at what max pressure?) has to do only with, as you say, “stretch,” by which I assume you mean bead stretch.

Upthread we’ve seen Herse refer to sidewall stiffness as a factor in bead retention, and SimWorks refer to rim design elements, so it seems pretty clearly a multifaceted issue (if, again, we’re still talking about knowing which tire/rim combos work and at what max pressure).

As an aside and as I mentioned upthread, Herse have different casings, and each will perform a little differently on various rims, so talking about Herse tires without specificity isn’t saying much. I run those aforementioned standard casing 650bx48 Herse Switchbacks tubeless at 50/55psi F/R on WTB i23 hooked rims trouble free.

Psimet2001 

Correct - and why I say we will never have what most of us older roadies consider to be supple and well performing and feeling tires in a completely hookless setup. They will steadily get firmer and firmer with less give. The softness we enjoy is what leads to tires blowing off the rim.

Psimet2001 

The softness in the casing (sidewall stiffness) is only a factor if it allows the bead to stretch. The sidewall isn't holding the tire on the rim but it can effect how stress is applied to the bead....but the bead still has to move in order for it to blow off.

it is multifaceted and if you listen to the Nerd Alert podcast linked above and listen to Josh talk about ETRTO standards and how the parts that matter are "secret" and confidential you can get an appreciation for the fact that this isn't going to be solved anytime soon. On the rim side it's tolerance stacking issues which aren't all that hard to address. On the tire side it's tolerancing a molding process that arguable isn't as precise while using materials whose intended purpose requires them to move under stress in an application where movement is very bad.

.....and tires will stretch over time under pressure. All of them to some extent.

Inner tubes were awesome...

Sy Reene

Aren't most beads pretty much made out of the same material -- ie. some variant of Kevlar or somesuch? Why can't there just be standardization on the length of the strip of kevlar that each tire manufacturer will put into each eg. 700c tire?

GhostRider62

How would that help?

Some tires have 2 ply and some have 3 or more ply of various thickness. This material wraps around the bead, doesn't it?

I don't think all mfgs use Kevlar for the beads. All tires stretch a little but some stretch more.

I think a bigger issue with hooked rims is the much more limited margin of safety when airing tires up. I have read reports of 10% and 20% being the maximum over-inflation before a tire blows off. Many pump gauges are not accurate to 10%. Plus, every 10 degree increase in temperature increases pressure about 2%. Bring the bike out from the air conditioned house to hot roads and if you add rim braking.......good luck with that. I have been testing my rim brake carbon wheels on descents to see what kind of rim temps I see.

Sy Reene

You're right I guess -- thought I remembered differently and that all the secret-sauce layers were mostly all laid up everywhere else. This pic is a nice diagram:

chaadster

Do we know bead length is the problem? Do we know length isn’t standardized now? Does a standard preclude +/- variation? Is all “kevlar” the same?

Is bead stretch even the main reason tires blow off? Is bead stiffness a factor? Bead shape? Bead thickness?

lessthanideal

Seems to be some of both.

If you look at the bead on a Continental GP5000 TL, a Rene Herse, Challenge vulcanized TLR, and Challenge handmade TLR and the construction and dimensions of each are clearly different to the naked eye. I remember talking to someone from Kenda (or maybe WTB) about how their bead was molded to allow it to better conform to the shape of the rim's beadhook for tubeless applications. The Challenge handmade tires have a bead that looks like any other "handmade" tire casing to the naked eye but has some secret sauce in the bead material to limit how much it can stretch for tubeless use. Throw some shoddy QC in the mix and it's a recipe for problems.

GhostRider62

Mfgs do not publish tolerances. Processes have variation. The actual measured widths and diameters are all over the place. Who will scrap, rim or tire mfgs? That is why there is no standard and probably just as important, there are patients on the rim lip where the bead seats.

An industry discussion about the all over the place and mess and quagmire.


https://cyclingtips.com/2022/03/nerd...ure-not-alone/

ThermionicScott 

Before this thread, I figured that everything tubeless would work itself out once those new ETRTO standards trickled down to everyone. Boy, did that podcast disabuse me of my naivete. Guess I'll be using tubes a little longer...

GhostRider62

Just considering wearing out of molds and the cost to replace them with tighter tolerances, it makes it feel like there will never be strict standards for the rim and tire interface.

The scariest part of the podcast was Josh's 1.1 safety factor discussion. Whereas tubed tire can withstand 50% over inflation, he found that only 10% over inflation resulted in a blowoff with hookless rims. Tire pressure increases 2% for each 10F rise in temperature. Most bicycle tire gauges are not terribly accurate and virtually none are calibrated to a NIST standard. 10% is not much of a margin.

Personally, I am comfortable riding hooked rims tubeless if the tire fits very snug and does not stretch over time.

smashndash

this is very plausible. Giant (a large brand) sells hookless wheels as OE. any brand specing zipp or enve wheels as OE (are there any?) would be selling hookless. All it takes at that point is someone buying some tire that his friend liked.

also, the tire would be most likely to blow from overpressure in a hard corner

Racing Dan

..Sure, and I cant imagine the salesman mentioning the limitations of hookless in the sales pitch either. Only whatever is perceived to be a benefit. Not to mention the sole purpose of road hookless appear to make carbon rims cheaper, further expanding the market share. Even the wheel manufacturers, Enve, Zipp, etc. isn't very forthcoming about it. Its all there, but you have to look for it and you have to know in advance to look. Usually no obvious links or warnings are given that the 99.9% identical wheel may get you in trouble if you don't know the specifics. Its like if a carmaker designed a wheel the required torqueing to 101nm, but not 100 or 102, or the bolts would unwind or break. - See you in court! :-)

Hiro11

This is an interesting lawsuit because I think it does expose some legitimate issues in the bike industry right now. On one hand, I think the plaintiff was kind of an idiot for trying to run RH tires on a hookless rim as a quick Google would have revealed that this was probably a bad idea. On the other hand I really hate how the industry still just can't get tubeless right and requires consumers to become experts to figure out what going to be safe and reliable.

Compass / Rene Herse is a prime example of the irritating lack of clarity around relatively high pressure tubeless technology these days. RH has always been annoyingly unclear about whether or not their tires should actually be used tubeless at all. They use the wishy-washy "tubeless compatible" rating which is sort of like saying "these MIGHT work tubeless, good luck". I have a set of RH Snoqualmie in normal casing that I personally would be wary of setting up tubeless. Like most RH tires, the casing on the Snoqualmie is ultra-thin and weeped sealant for a few days when I tried them tubeless. Also, the beads are no where near as robust as the beads on something like a GravelKing. I run the Snoqualmies tubed whenever I mount them on my gravel bike. (to be clear: I absolutely LOVE RH tires, they roll and feel like nothing else. However, I just don't like them tubeless).

IMO, taking an already questionable tire for tubeless like an RH tire and trying to set it up on hookless rims is just asking for trouble. There's a reason Enve and others are very clear about which tires they recommend and which they don't for their hookless rims: with hookless, the bead/rim sidewall interface becomes even more important. IMO, the RH beads just don't cut it for hookless.

To me, there's nothing intrisically wrong with hookless as a technology. After all, basically every other tire in the world is hookless. Also, I've been running 32mm GravelKing slicks on a set of Enve SES AR4.5 rims for over a year at about 45-50 psi and it's been a very reliable, tough setup in lots of different conditions. Still, when I bought new tubeless wheels for dedicated performance road use a few months ago, I deliberately went with a hooked design as I don't think hookless is quite ready for prime time on the road yet. I especially don't like the idea of hookless with pressures over ~60psi and I run my 28s on the road at about 77-80 psi.

Overall, this period of tubeless is just annoying. To echo multiple comments above, tire and rim manufacturers really need to do a better job on adhering to standards and running better tolerances if we want hookless to work better.

Paul Barnard

Every now and then I briefly consider going tubeless. Then I encounter information like that contained in this thread. Not being one to lightly suffer the over complication of something fundamentally simple, my decision to stick with tubes is easy.

ThermionicScott 

Sure, and they also use steel beads (not to mention a stiff casing with plenty of rubber coating everything.)

BFisher

Enve's website uses the fact that the motor vehicle industry is all hookless/tubeless as a sort of reasoning for trying to adapt that technology to bicycles.

What it seems to be is a leap backward. If you want that to work consistently, tires need to be stiffer and pressures lower. We won't get super supple folding bead tires to stay on hookless rims at the pressures they perform well at with a high degree of consistency. So, a leap backward to stiff, wire-bead tires run somewhere near 70psi, just without an inner tube. Where is the improvement?

Troul 

has a bicycle wheel & tire manufacturer tried increasing the rims sidewall height as well as the tires sidewall height by a large amount for hookless?
Motorcycle beads appear more robust & the wheel has an inner lip to keep the rubber from deflecting inward.

Polaris OBark

Why not just put a bit of sealant inside tubes with removable valve cores?

Troul 

Tubes are too fragile to quickly self heal with a sealant when used in a road tire setup running higher PSI.

Seattle Forrest

Today I learned tubeless tires are stiff and gatorskins are supple. 🤯

phrantic09

You don’t know that a wire bead is required for this to work consistently or that pressures need to be in the 70s. I’m running 28s 58/62 on hookless rims and it’s glorious, and I’m not small.

GhostRider62

That works well with latex tubes, not very well with cheap butyl one.

Polaris OBark

OK, so why not recommend that to allow people to use sealant and have a layer of solid latex that pushes the tire against the rim to help prevent it from popping off? You would probably need less liquid latex sealant, so the total weight would still be approximately the same.