To The Point - UST Rims and Tires
Launched by Mavic, Michelin, and Hutchinson in 1999, the tubeless UST rim and tire system has been used by World Cup racers and weekend riders alike for many years, but the topic is still one that can cause some head scratching from even the most technically savvy of mountain bikers. This is compounded by the large number of "tubeless compatible" tires and rims out there that, while not being UST certified, can also work quite well. With a list of questions in hand, we reached out to Mavic's Zack Vestal for an explanation of how the UST design works, and to clarify some rim and tire compatibility reservations that we had.
What does UST stand for, and what exactly is it?
![Mavic UST]()
And what makes a tire UST-specific?
How does a UST system create a seal?
Do non-UST tires work on UST rims and vice versa?
What are the advantages to running a UST setup compared to a conversion with sealant and rim tape, especially considering that conversions often weigh less?
www.mavic.com
What does UST stand for, and what exactly is it?UST stands for Universal Standard Tubeless, and it refers to a very specific, two-part
system consisting of the rim and the tire. The UST system was developed and introduced
in 1999 as a partnership between Mavic, Michelin, and Hutchinson. On the rim side,
Mavic contributed technical expertise as to the rim shape and keeping the tire bed
airtight. On the tire side, Michelin and Hutchinson developed tires with airtight casings
and beads that would lock into the rim, not unlike a tubeless car or motorcycle tire.
There is a very specific shape and dimension to a UST rim's bead hook (the lipped
inner edge or hook of the rim sidewall that the tire bead locks into), with it having
a square shape rather than rounded profile of a standard rim. Also, there is a “hump” on
the edge of the rim bed that helps lock the tire bead into place. The dimensions of the
bead hook, including its height, diameter, plus the width and shape of the “hump,” are
very closely controlled. The last attribute of a UST rim is that it must be airtight, which
means that any spoke holes must be fully sealed with tape or plastic, or the rim bed is
left intact and not drilled at all. The UST rim shape (particularly the shape of the
bead hook and hump) is patented by Mavic, and Mavic licenses the shape to other
companies, for a fee. An independent lab grants technical approval for any products
from other companies to wear the UST logo.
system consisting of the rim and the tire. The UST system was developed and introduced
in 1999 as a partnership between Mavic, Michelin, and Hutchinson. On the rim side,
Mavic contributed technical expertise as to the rim shape and keeping the tire bed
airtight. On the tire side, Michelin and Hutchinson developed tires with airtight casings
and beads that would lock into the rim, not unlike a tubeless car or motorcycle tire.
There is a very specific shape and dimension to a UST rim's bead hook (the lipped
inner edge or hook of the rim sidewall that the tire bead locks into), with it having
a square shape rather than rounded profile of a standard rim. Also, there is a “hump” on
the edge of the rim bed that helps lock the tire bead into place. The dimensions of the
bead hook, including its height, diameter, plus the width and shape of the “hump,” are
very closely controlled. The last attribute of a UST rim is that it must be airtight, which
means that any spoke holes must be fully sealed with tape or plastic, or the rim bed is
left intact and not drilled at all. The UST rim shape (particularly the shape of the
bead hook and hump) is patented by Mavic, and Mavic licenses the shape to other
companies, for a fee. An independent lab grants technical approval for any products
from other companies to wear the UST logo.
And what makes a tire UST-specific?On the tire side, a UST tire must have a bead that is shaped correspondingly to the
UST bead hook - it’s more square than round, and it has a small flap on the inner edge
to help create an airtight seal. This flap also helps the tire gain an airtight seal against
the rim when it’s first being inflated. The dimension and mechanical characteristics of
a proper UST tire bead are critical. Any variance in diameter or profile, or the bead stretching
under inflation pressure, can cause the tire to not fit correctly and therefore not remain
airtight. Finally, a proper UST tire casing is airtight and holds air over time. Again, an
independent lab certifies the proper bead dimensions, allowable bead stretch, sealing
capability, security of the bead lock even when deflated, and ability to retain air over
time. However, a company that wants to make a UST tire doesn’t have to pay a license
fee. It just has to make the tire such that it passes the certification test.
Note that on the tire side, “UST-ready” systems are ubiquitous. A UST-ready tire has a proper
UST certified bead, but it requires sealant in order to make the casing airtight. Several brands
of tires have sought and achieved UST certification with the use of sealant. Of course the new
Mavic Charge, Roam, and Roam XL tires fall into this category, as do the TCS tires from WTB.
UST bead hook - it’s more square than round, and it has a small flap on the inner edge
to help create an airtight seal. This flap also helps the tire gain an airtight seal against
the rim when it’s first being inflated. The dimension and mechanical characteristics of
a proper UST tire bead are critical. Any variance in diameter or profile, or the bead stretching
under inflation pressure, can cause the tire to not fit correctly and therefore not remain
airtight. Finally, a proper UST tire casing is airtight and holds air over time. Again, an
independent lab certifies the proper bead dimensions, allowable bead stretch, sealing
capability, security of the bead lock even when deflated, and ability to retain air over
time. However, a company that wants to make a UST tire doesn’t have to pay a license
fee. It just has to make the tire such that it passes the certification test.
Note that on the tire side, “UST-ready” systems are ubiquitous. A UST-ready tire has a proper
UST certified bead, but it requires sealant in order to make the casing airtight. Several brands
of tires have sought and achieved UST certification with the use of sealant. Of course the new
Mavic Charge, Roam, and Roam XL tires fall into this category, as do the TCS tires from WTB.
How does a UST system create a seal?The number one aspect of the UST system is the bead hook interface. The precise tolerance between the rim and tire bead, plus its specific square shape, help the tire bead lock securely into place on the rim. Furthermore, the tire bead is controlled for how much it can stretch when inflated, which is very little to not at all. These characteristics create a very safe and secure bead lock. The tire tends to stay in place even when deflated. And, the tire can be run at different pressures with no fear of the tire exploding or rolling off the rim. Of course the valve is a critical component of the system as well - it must be properly mounted in the rim to maintain an airtight seal.
Do non-UST tires work on UST rims and vice versa?Non-UST tires will work on UST rims, but they don’t have the security of the bead
locking securely into the rim channel (bead hooks). And the significant discrepancy
in the shape of the bead will cause trouble with air retention. The tire bead just won’t seal
very well against the rim. Finally, non-UST tires are not as tightly controlled for the tire bead
diameter and stretch, and this means that a loose fitting tire could be more prone to rolling
off the rim or exploding off of it under high inflation pressure.
A person would have more success putting a UST tire on a non-UST rim, but again, the
lack of precision between the tire bead and the rim bead hook would cause sealing problems.
And, a non-UST rim doesn’t have an airtight tire bed. Also, you’d have to find a way to seal
the spoke holes on the rim bed before you could set it up tubeless.
The systems from Stans and other tubeless conversions do work, in that they allow you to
create a mostly airtight tire and rim interface. But these systems don’t have nearly as secure
of a bead lock between the tire and rim. This can lead to inconsistent or at worst, unsafe tire
security on the rim. Of course, this all looks like promotion of Mavic’s patented system, but
other rim and tire manufacturers have clearly tested and seen the benefits of going with proper
UST certification. I’ve spoken to a tire product manager at WTB who was very candid about
the unsafe conditions they found in some “tubeless” systems, and it’s why they created their
rims and tires with proper UST certification. The same is true for other brands like Easton
and ENVE.
locking securely into the rim channel (bead hooks). And the significant discrepancy
in the shape of the bead will cause trouble with air retention. The tire bead just won’t seal
very well against the rim. Finally, non-UST tires are not as tightly controlled for the tire bead
diameter and stretch, and this means that a loose fitting tire could be more prone to rolling
off the rim or exploding off of it under high inflation pressure.
A person would have more success putting a UST tire on a non-UST rim, but again, the
lack of precision between the tire bead and the rim bead hook would cause sealing problems.
And, a non-UST rim doesn’t have an airtight tire bed. Also, you’d have to find a way to seal
the spoke holes on the rim bed before you could set it up tubeless.
The systems from Stans and other tubeless conversions do work, in that they allow you to
create a mostly airtight tire and rim interface. But these systems don’t have nearly as secure
of a bead lock between the tire and rim. This can lead to inconsistent or at worst, unsafe tire
security on the rim. Of course, this all looks like promotion of Mavic’s patented system, but
other rim and tire manufacturers have clearly tested and seen the benefits of going with proper
UST certification. I’ve spoken to a tire product manager at WTB who was very candid about
the unsafe conditions they found in some “tubeless” systems, and it’s why they created their
rims and tires with proper UST certification. The same is true for other brands like Easton
and ENVE.
What are the advantages to running a UST setup compared to a conversion with sealant and rim tape, especially considering that conversions often weigh less?The advantages of a proper UST are several. For starters, the safety and security of
a properly matched tire and rim can’t be beat. The interlocking tire bead and rim bead hook
are a big deal. Airtight UST rims don’t have a weight penalty compared to non-UST rims. On
the tire side, UST-ready tires weigh the same as other tires, but they have a bead that locks
securely into the rim bead hook. Regarding inflation, it should be just as easy to inflate a properly
matched system as it is to inflate a conversion system. True, sometimes the conversion
systems increase the outer diameter of the rim bed and hold the tire bead tighter against the rim
for easier inflation, but the same condition can be created with a UST tire and rim by using a
tire lever to pull the tire bead partially onto the “hump” in the UST rim bed. This instantly creates
a seal and facilitates easy inflation of a UST tire with a normal hand pump.
a properly matched tire and rim can’t be beat. The interlocking tire bead and rim bead hook
are a big deal. Airtight UST rims don’t have a weight penalty compared to non-UST rims. On
the tire side, UST-ready tires weigh the same as other tires, but they have a bead that locks
securely into the rim bead hook. Regarding inflation, it should be just as easy to inflate a properly
matched system as it is to inflate a conversion system. True, sometimes the conversion
systems increase the outer diameter of the rim bed and hold the tire bead tighter against the rim
for easier inflation, but the same condition can be created with a UST tire and rim by using a
tire lever to pull the tire bead partially onto the “hump” in the UST rim bed. This instantly creates
a seal and facilitates easy inflation of a UST tire with a normal hand pump.
www.mavic.com
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The tires, maybe, but the rims are completely unlike a car or motorcycle system as there are no bead hooks on car or motorcycle rims. The new Derby carbon rims look interesting as they have a UST style "hump", but are hookless. Specialized also have hookless rims for 2014.
If only Mavic would make a rim or wheel with a 25mm inner width... *sigh*
But for UST tires, the toleraces are so tight, shouldn't be an issue. I know this much, if I was inflating a non-ust tire on a hookless, I'd have earplugs in, they just blow off the rims.
"Being a bike mechanic for a long time, I've come across different sized beads on standard (non-UST) tires. If it's a larger diameter bead and non UST, a hookless setup has nothing to keep it from rolling off. Hookless is a big step backwards in that case.
But for UST tires, the toleraces are so tight, shouldn't be an issue. I know this much, if I was inflating a non-ust tire on a hookless, I'd have earplugs in, they just blow off the rims."
Pretty much word for word what I was gonna type. Personally cant really see any argument FOR hookless rims. I mean, the hook must add little more than a gram, which I'm sure could be made up for elsewhere, with a slightly less heavy duty tire bead or something, with massive added security in the tire/rim interface...
Hook does one more negative thing than just weight, that is it makes the inner width narrower at same given weight. Maybe raised rim bead like on ZTR rims neutralizes the problems you guys talk about? I'd love to see few more companies like ZTR, Syntace, Specialized, sticking their neck out with developing "weird" wheels
We should be getting this kind of research in wheel department from industry side, not that stupid "intermediatization" and optimization like new wheel diameter.
About the ZTR design, you need a hook to hold the tire in there. The Derby has it on the inside, with a flat inside wall.
Like right now, I'm running a Maxxis 2.5 Minion DHF EXO non-TR tire. It sits a bit loose in my WTB tubeless rims. I haven't tried to run that tire tubeless. I've run some actual tubeless tires or tubeless ready tires in that wheelset. Anyway, my mtb tires take more side loads and off angle pressures than my old bmx rims took. Every other weekend, I had to let the air out of the bmx tire, cuz it would unseat itself. The reason people have been able to run 20-25psi in their 2.5 tires for years is because of the lip/hook on the rim. I'm pretty sure if I threw that tire or my other non-TR Maxxis and Kenda tires in the Derby rims, they would roll off, unseat, blow out. That's a step backward, because TR-UST tires should only be used in that design.
@ katmai, surely if the tyre went on without stretching the bead, it can come off too? I know often you have to push the tyre into the well in the center of the rim to get the other side off, and this is unlikely to happen out on the trail with pumped up tyres, but when I'm running a tyre at 25psi and really pushing the tyres through a g-out corner, well... I'm all for as much security as possible, and if that means an extra few grams of rim weight and as Waki points out, a marginally narrower rim (if the external measurment stays the same), then I guess I'll just have to put up with that.
UST is unnecessary.
Have not had a tire failure(of many different makes) on new and old style Flow rims over the past 6+ years.
Long live Stan's Flows - wide, light, strong.
I may try the Jared Graves "ghetto tubeless setup next year, but tubeless EXO is a bad idea, the sidewall is just not stiff enough, if you burp it just goes completely.
> Have not had a tire failure(of many different makes) on new and old style Flow rims over the past 6+ years.
big proponent of running tubeless as well (2 stans Flow/EX wheels on Trail and DH bike, CB Iodine 3 on Trail) but I have burped the front tire 3 times so far - including 2 hard landing on CB Iodine which caused bad crashes (!) (don't think it was too low pressure) and once on my DH bike (front was pretty low). Tires: TK 2.4 for bike parks, else TK 2.2 and SP ground control 2.1 for trail. On my last Whistler trip I managed to get a 'pinched' flat near the bead (too many fire road section due to tail closing), which sealed right away once I added stans back (was dry) - by comparison my group got about 8 flats tubes so I did much better. Bike also a lot lighter.
Tubeless is not all rosy. Starting to think UST bead an rim might have prevented 2 crashes for me so far.
I had 819 a while back, but never bothered with UST... heavy rims for such a narrow rim. Much happier with Flow EX
Having burped many tyres on 819 and 823 rims, taccoed the rims, stripped out the inserts, I know where my money sits.
Also tbe 823 rim is far too stiff, you need some flex intbe rim when riding hard(ish lol).
I have used dt swiss with conversions, and they were terrible.
The ztr rim just works, even when it is getting old and looks cracked (which is not too hard to do), that is only the outer section, the inneris not cracked and the rim still keeps going.
I run dual ply Minions with DH inner tubes and I cant remember getting a single puncture in recent years.
Don't write it on the rims till you have a full tubeless set up like mavic do.
Mavic UST have definitely found the best way around the tape/rubber floor!
P.S judging by a your other posts do you just come on here to start arguments? I think so judging by your 1 follower.
Second, my main point was that their company is not called Stan's No Tubes because their wheels come ready to go tubeless. The wheels came way after their inception. The name is because they created the first user friendly way to convert non ust wheels to tubeless... hence "no tubes"...
you can take a look here - www.google.com.br/patents/US6257676
no need to read all the text (although I did few years ago). you can look at the pictures and see for yourself that the rim's bead hook is numbered 16 (and 17 at the other side) there is nothing in the patent that limits it to specific shape and dimension nor saying it having a square shape rather than rounded profile of a standard rim.
The patent only describes the dimensions and shape of the inner square tunnel. Here there is another strange thing. the first picture at this article shows Mavic UST rim with rounded inner tunnel instead of square one as the patent dictating.
So I might be missing something but this is my understanding of the patent.
But soon discovered tubeless was real shit because if you ride hard, pointy rocks would go straight through the tire and make a massive hole, the liquid would not block the hole (way too big). this happened so many times (with the proper maxxis ust "dh" tires).
Now use maxxis dh 2 ply tires with (500g) maxxis tubes and have very very rarely punctured ! Who cares about weight ?!?! (even though the wheels and tires are the most important place to save weight...).
this is all riding enduro or dh in the alps (not bikepark stuff, but in the propor mountains).
tubeless is maybe great for xc but as soon as there are rocks and you're not on an xc bike, tubeless is a nono !!
www.youtube.com/watch?v=bGgWYpnztY4&list=PL369BAAB05A5771F5
Mine sure seem to suddenly puncture more easily after using them with sealant for a month or so.
Tubeless setups in general aren't expensive because of Mavic, they're expensive because it's a feature that companies can use to get people to spend more by reserving that feature only for the high-end wheels. Notubes isn't licensing anything from Mavic and they still only sell $600 wheelsets.
Had the same experience with Maxxis: exo where fine, other where more painful to seal.
Yeah as you can see by my profile I don't do that much riding real mountains.
And you have really hurt my feelings about being ugly. Your wife said I was pretty damn hot last time out.