Agreed, and I expect those lower pressures are reflected in the outputs of the Silca tire pressure calculator.
Thatâs exact, I donât buy ZIPPs anymore. It was a scam decorated in pseudo science.
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Zippâs data doesnât look right though. Final charts just show straight lines, but rolling resistance vs tire pressure should be a j-shaped curve, like they themselves pointed out.
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Question to @rrheisler who I âthinkâ has a legal background ?
@E_DUB is testing blow off pressures. This would give confidence that if I use a pump that is off it wonât result in a blow off.
But if I do a test with someone and I want to try 5.5 and god forbid the tire blows off and the guys sues me, I am hosed ?
Letâs put it another way. @E_DUB does his tests and finds the GP5000TT doesnât blow off until beyond 6Bar. Does ST say itâs OK to ride at 6 bar ?
Does ST have a legal liability by suggesting anything over 5 bar for a hookless tire ?
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I hold a JD. I do not have a license to practice law. So, take the following with a whole container of salt.
Blowoff pressure and manufacturer recommended pressure are two very different animals. Blowoff pressure is really more of a showing of where we sit in the operating window (e.g., if something blows off at 5.5 bar on a given wheel with a max recommended pressure at 5 bar, thatâs probably not a combination weâd be riding).
What this is not is telling you what tire pressure to ride at. Weâre still going to tell you to go to manufacturer recommendations. What this testing might show is that manufacturer recommendations are low for a variety of reasons.
You, on the other hand, directly telling someone to exceed max pressure, yeah, you might have some liability there.
Of course, anybody can be suedâŚI try to keep us out of that as best we can. 
Pretty much what I thought.
I believe even the manufacturers publish they test combinations at higher pressure but they tell you that you must ride them at max 5 bar.
And the manufacturers are pretty much beholden to ETRTO, unless theyâve got a whole lot of data showing otherwise.
You generally donât want to be the first duck fighting against thatâŚitâs when thereâs a tidal wave of manufacturers all showing the same thing that you might see movement.
SoâŚeven though itâs probably likely something in the vicinity of 5.5 or 6 bar is well within the blowoff window, etc., and probably would test wellâŚthat isnât likely going to be recommended any time soon for hookless.
Rather than publish list of tires that blow off at 120PSI, maybe they should publish the lists of those that blow off at 78.
Wouldnât this pressure (no pun intended) the tire manufacturers to do better ?
Or is it not in the hands of the tire manufacturers ?
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For what itâs worth, my personal testing shows 404s will hold a 28 Conti 5k and 100PSI. I did some stress testing/riding at 80PSI (fly weight of 215lbs) and nothing to report. Even with testing catastrophic/instant flats.
Obviously not going to squash any debate here - but good enough for me to not worry about it.
Conti 5000S or TT ?
I find it strange Cadex approves the S and not the TT.
I would love to understand what makes or breaks the compatibility.
TT is what I tested with.
I wonât bore everyone with my nerdy mental appeasement testing on the wheels. But I needed to do it so I could stop thinking about this thread while riding.
Long story short: I wonât worry about this anymore with my 404s
in speaking with CADEX the TT didnt even come close in passing there testsâŚ
Just to make sure weâre talking about the same tire.
Continental Grand Prix 5000 TT TR is what I tested with. Which is on the approved list for 404 Firecrest.
lol, I read Ericâs response and said âwell, there goes Geekâs peace of mindâ
HAHA.
Nah, mine are for Zipp 404s - which are approved by SRAM. I did enough testing to not worry about it. Including hard turns at speed, catastrophic instant flats, and riding while flat.
Different tire (Conti 5k S) but I did have a puncture in a real world scenario a few weeks ago and it was fine.
yea⌠big issue is that everyone has a different testing method⌠Youâre going to start seeing the wheel companies going away from Compatibility charts pretty soon and just putting that on the tire companiesâŚ
just getting off the phone with @marcag.
The tests we are going to do is simply running tires up to 115 PSI and seeing what if any POP.
both Continentals are in our testing pool
Will probably go a little higher on tires that match the wheels for example⌠ZIPPâS Tires on ZIPP wheels we will probably go to 120 be we will see that we find outâŚ
I went up to 140PSI on the Cadex with a Cadex⌠I was waiting for the big blow and luckily for my ears it didnt happenâŚ
This is simply just an experiment to see what is actually happening with theseâŚ
Here is what I didâŚ
I wanted to test 2 things.
1. If I pumped them up to 100 PSI would they blow off the rim. Then if I pumped them up to 80 and rode them, would they stay on. (Note that this is about 10PSI higher than I ride normally)
2. Would the tire stay on in the event of a blowout.
I understood that while testing these I risked damaging the wheel. However, they were useless to me if I worried about it on every ride.
Details
Fly weight of myself and my bike: 215lbs
Tires: Conti GP 5k TT TR 700x28â
Wheels: Zipp 404 disc brake
First I inflated the tires to 100 PSI as measured with my hand pump, then topped it off with my muc-off mini-inflator (my hand pump reads high), then double checked with my Topeak pressure gauge.
Bounced the wheels around, twisted them. All seemed fine. LEt them sit for an hour.
I let out the PSI to 80 and double checked measurement.
Next with normal shoes on (so I could bail out of a crash) I setup cones down a small hill near my house. So I could do hard diving turns between the cones at roughly 15mph. 4x I dove hard into turns and did a steep 180 turn as I flipped around to come back up the hill.
Nothing to report. Tires stayed on.
Next I found an unfilled pothole about the size of a large grapefruit that was about 5" deep. I drover over it 4x at about 10-12mph.
Nothing to report other than realizing I need to wrap my flat kit so it doesnât rattle so much.
Next I wanted to see how the tires responded to sudden flats.
First thing I did was simply let all the air out. The tire stayed on the bead and didnât pancake out.
I thought maybe that wasnât a fast enough deflation. So I pumped the tire back up and put the valve up at 12 oâclock so I would not get covered in sealant. I then removed the valve core. Instant deflation and the tire/bead stayed on. Just to test this further - I tried to remove the tire from the rim and I actually needed a tire lever to break it free.
Finally, I wanted to see what would happen to a tire that was deflated while riding. I wasnât sure how to do this without actually damaging the wheels. So I decided to just deflated the tire as much as would naturally come out of the valve. Then I tried riding at 5-8mph on the road. While not a great test, the tire stayed on and I managed to not scratch up my wheels. I tried twisting the front wheel over some carpet I had in my garage, but aside from being very squishy and behaving like a flat tire - nothing really to report.
Far from scientific, and this is not my argument that âHookless is all good!â However, they came with my bike and I wanted to do my own testing so I could stop thinking about it. For my uses, I will ride these wheels without worry. YMMV
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It would be interesting to hear from Cadex on what they think the technical reason for this is.
I think another interesting test would be to pump them up very slowly (with a precise psi measurement in real time) and keep on going higher and higher slowly with the pressure until the tire blows off, and then noting that real world, ânon scientific,â blow off pressure.
Sounds expensive