My new Giant Propel arrives tomorrow. It comes with SLR1 50mm deep hookless rims. Giant have included the Garvia Course 1 tyres, which are 25mm. They have an 85 psi to 125 psi pressure rating. The wheels apparently, like all hookless wheels, say do not inflate over 73psi to prevent tyres blowing off.
This opens up so many questions for a hookless rim, tubeless Newbie. Please could someone help answer them.
Tubeless can be ridden with lower pressures i.e. 15 psi lower than usual, so I think I could get away with 80 to 85psi, but this higher than the pressure the rims state. What should I do?
Giant say that with the 22.4 inner rim dimension, the tyres are actually 28mm wide once on the wheel. Should I inflate to the recommended pressure of a 28mm wheel i.e. 70 psi?
Giant state the minimum safe tyre pressure for tubeless of 23 and 25mm tyres is 70 psi, but should I treat the tyre as 28mm and ignore that?
Has anyone got the new Giant Propel, and would you recommend an eventual tyre upgrade to either 28 or 30mm GP5000s TRs? I don’t want to spend money unnecessarily, so I’ll wait for these Gavia tyres to be worn.
Many thanks.
James
A starting point is the Silca tire pressure calculator, and importantly you need to know specific info about your total system weight and actual measured tire width (not sidewall size), along with other use info.
And definitely you should NOT exceed the pressure rating of the rim, regardless of what tire you have installed. That is a safety issue and is mentioned in a range of recent podcasts from the last 6 months or so (sparked from tire failures in large pro races for one thing).
Here is a recent podcast that touches on the topic:
Being straightforward: All calculations should be made using 25 as a reference. The fact that the tire assumes a slightly larger surface doesn’t make the tire 28.
Use Giant Calculator for tire pressure and never exceed 73PSI in hookless rins, not even if Jesus himself shows up and asks you that.
Alternatively, there are Zipp and Sylca calculators already mentioned.
My understanding from Giant is that their own brand tyres and rims are designed to work together as a system and are tested up to 150psi, meaning you can exceed the 73psi limit. I think the same tests have been applied to tyres and rims listed in their compatibility chart.
But to caveat that:
their website is far from clear on this! There’s talk of maximum pressures, minimum pressures, it’s all a bit of a muddle. So if going this route I would definitely seek confirmation directly from them, and based on the poor level of knowledge I’ve seen from many LBS staff on hookless I would want a high level of confidence that the person giving me the information actually knew what they were talking about
Those tyres don’t get great reviews, and a 28mm tyre at a lower pressure is going to give you a nicer ride with likely no speed cost unless maybe you’re doing a fast TT on a smooth road
So if it was me I’d probably swap them anyway. Though that’s a very frustrating thing to do on a brand new bike as unless you can get the shop to do a swap and just pay the difference I can’t imagine you would get a good sale price for those tyres.
Thanks for your reply. The tyres are the stock ones.
I like the Silica calculator as it asks for actual tyre width rather than the stated one. Unfortunately, it suggests 76 psi on the rear. Giant state the 25mm tyres should be run above 70 psi so that would mean there’s a 3psi window which can safely be ridden.
Giant sells all their TCRs and Propels with 25mm tyres on hookless wheels from SR1s to Cadexs. Surely they wouldn’t do so unless they were confident in the safety of their tyres run at the recommended pressures. Giant’s own tyre pressure calculator suggests pressures over 73psi. Their website is ambiguous, but it could interpreted that any tyres on their compatibility chart can be run at recommended tyre pressures above 73psi and those not on the list can be run as long as they meet two requirements: that they’re run at under 73psi and they’re not on their short list of incompatible tyres.
I wish it was clearer. I think I might ask the bike shop for some clarification when the bike arrives.
The safest thing to do is just put on some 28s or 30s but I’m loathe to spend more on a bike that’s costing so much.
Never exceed the maximum (MAX) tire pressure indicated on the rim, the tire or the rim tape.
Please note that the stated MIN pressure on many current Giant tires (e.g. 85psi for 25C tire) was originally defined based on a durability test with a 120kg load at 1.5 times the regulated distance. CURRENTLY, for all Giant tires this minimum (MIN) pressure can now be defined as 70 psi (4.8 bar) for 23C & 25C tires, 50 psi (3.4 bar) for 28C tires and 45 psi (3.1 bar) for 32C tires. Never inflate to less than the MIN pressure.
The above pressure values are recommended starting points only.
Please be aware that the load limit of all Giant Road WheelSystems is 129kg. This includes the weight of the rider + bike + luggage. For your own safety, please do not exceed the load limit, and please note that it is never advisable to load the bike to its maximum capacity.
It doesn’t matter if Giant, CADEX or other brands, 72.5 is the maximum pressure for hookless rims. The test conducted at 150 PSI is, as stated, A TEST. The running and recommended tire pressure (maximum) is always 72.5.
If you are in a situation where you are at or above the wheel pressure limit, stepping up to a larger tire is the best & right choice. Small tires require higher pressures for support, while larger tires (and the resulting volume) allow lower pressure for the same support.
Thanks for the reply. I guess I just need to know if the actual width of 28mm is the one I use for calculations or the stated width. Using 25mm, there’s no way I’d get a workable pressure under the 72.5 psi limit. I guess because all TCRs and Propels are sold with 25mm tyres (effective 28mm), I should go with the actual width size. Otherwise, Giant are selling bikes that don’t meet their own safety suggestions.
That’s why I said the website is a muddle! I don’t seriously believe that the largest bike company in the world with a Worldtour team riding their equipment is actually shipping a rim/tyre combo to their customers that has a minimum pressure of 70psi and a maximum pressure of 72.5psi. That would be nuts.
I can’t see anything on their website that mentions a uniform hookless max pressure of 72.5psi (though agree that’s what the ETRTO standard says). The closest they get is point 1 in your list which then begs the question - what is the stated maximum pressure printed on the tyres, rims and rim tape being shipped to the OP?
I’ll be honest I never paid much attention to the minimum tire pressure, and you’re right. It’s a bit weird. 70psi minimum 72.5psi maximum.
I bought my wheels separately, and if I recall, they had a sticker about the maximum tire pressure. I also think that there’s something close to the valve. I’ll check home later.
Brilliant, thanks. My bike arrives in the post tomorrow so I’ll have a look, too. It’s very exciting. I bought the Propel after a bad crash on 23mm over inflated tyres on my old frame - they’re the widest I could run. It’s the low pressure, larger contact area and increased traction that I’m after. Tyres exploding off the rim is something I hadn’t really considered until I started reading about hookless rims.
Do your SLR2 wheels state the 73psi limit? If so so, it’s very confusing. I’ve emailed Giant customer services.
If there’s no mention of it, I think one of the other posters must be right about Giant tyres, which have been specially designed to work with their hookless wheel sets, being safe to run up anywhere between the min and max psi stated on the tyre. Not that the ETRTO standards agree.
Nothing I can see, and as you say, would fundamentally preclude 23 and 25 m tyres being used so…
The 72.5 number mentioned for non-CADEX non-Giant tyres is a red herring. Given we’re using Giant tyres, and I would not extrapolate from it for those reasons.
Giant dealer here. Giant wheels and tires, when used together, can be run at the listed max on the wheel and tire, which is usually 125. Yes, even hookless. So a 25c tire would have a minimum of 70, max of 125, although the calculator pretty much never suggests anywhere close to the max.
A non-Giant tire on their approved list can be run up to max pressure printed on the tire, whatever it is.
A non-GIant tire that does not appear on their approved OR unapproved list can be used up to its listed max as long as its listed max is 72.5 or less and the tire is intended for hookless use.
And a tire on the non-approved list is, well, not approved.
I’ve spent a lot of time parsing that language, so I hope this helps!
