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Deep Dive into the Development of On Cloudultra Pro with Sergi Jansa, Product Engineer
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Jun 28, 2025
Jen Schmidt interviews Sergi who was one of the engineers who designed the Cloudultra Pro, On's new trail supershoe. He takes us behind the scenes of its development, highlighting the data-driven approach to achieve efficiency over varied terrain, and describes key features. Please read our just posted multi tester review here: https://www.roadtrailrun.com/2025/06/on-cloudultra-pro-multi-tester-review-7.html
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i'm john schmidt here with roadt trail
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run and today we're going to be hearing
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about the new on super trail shoot
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so yeah maybe you can tell us who you
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are and what you do at on and and how
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this shoe came to be yeah sure um i'm
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sergy i'm part of the product team at on
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uh live in switzerland based in zurich
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and i've been with on
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6 years um but i transitioned into the
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product team around 3 years ago um there
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was there was a whole reset in the
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organization and they were trying to
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push for a more credible outdoor uh
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vertical um and then they basically
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redid the whole team and that's when i
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came to join this new team great and
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earlier today in the panels you were
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telling us about the outsole so tell us
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about what makes the outsole special and
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and how you developed it i think it's
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interesting because in in the panel i
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didn't really have time to go um deeper
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but maybe we can discuss it a bit more
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in here um so we use one of the road
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running uh technologies called fea which
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is basically what the running team used
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for the cloud surfer to define the shape
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of the cavities but in our case uh we
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were pretty happy with the compound of
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the of the outsole but we didn't do a
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lot of work until then on the outsole
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pattern right so with this software i
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mean fa is sort of an algorithm um it
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helped us to basically track down some
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of the options potential options so we
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looked at the density of the lags the
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geometry of the lags um spacing as well
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right and the orientation even and all
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of these options that we generated
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through a 3d software we made them run
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through this algorithm and then it gave
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us um some idea on on which could
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perform better on which type of terrain
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and then from there basically we took
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those shoes and we went outside on the
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field to test them test them out yeah
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and tell me about that field testing
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process how many athletes do you have
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testing the shoes and what does that
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look like when you work with them and
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get feedback yeah so i mean i don't have
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the the right number in mind but i would
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say around 10 10 athletes at the end we
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are not able to open all the sizes for
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all athletes so for this project we
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started with just two sizes one women uh
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female size um opening mold and then
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another for men's which was a us9 um so
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we tested with um antoine shavealan uh
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jeff gold claudia trems which is one of
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our uh spanish trail athletes um and
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it's basically um i think we've
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mentioned it before during the panel
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talk it it it's a lot about trust uh and
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i think we developed this network with
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the athletes in which there is a lot of
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trust in which they can basically give
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input and feedback without feeling that
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they are you know they are doing their
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job right they are judging a product
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that they need to run on and and we
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basically started with this uh first
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prototypes that we developed in zurich
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so they got the chance to run on the on
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the first races antoan shabalan i think
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he ran marathon mlang 90k marathon de
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mlang on the first prototype made in
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made in durk and we were actually pretty
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afraid because like we didn't know if
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that was going to hold on right and so
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that was a big that was a big day um but
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then obviously the development process
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moves on and then we go into different
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stages that we call well they have a
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name internally but like stage one stage
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two and stage three to make it easier
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and then over these iterations we always
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touch point with the touch base with the
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athletes and we get their feedback and i
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think in this project specifically after
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the stage two the only thing we were
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reworking were basically durability
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details on how to make the radius uh
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maybe a bit browner so that it doesn't
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elaminate or stuff like
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so i i'd say we had something pretty
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special already at the beginning and
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then at lr2 we call it internally lr2
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yeah the shoe was almost ready
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so i want to go back to something you
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said you said you had the men's and the
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women's shoes i've seen a lot of the
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trail super shoes are unisex right now
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so can you tell me a little bit about
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what's the difference i think what i
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meant there is that we open different
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sizes we don't make any difference
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between u male or female shoes yes
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exactly exactly it's the same shoe but
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different sizing yeah and let's talk too
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about the plate because that's pretty
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unique here right that combination of
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nylon and fiberglass versus carbon how
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did you what kinds of materials did you
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test and how did you end up with that
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one yeah i mean this is interesting
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because one of the things we found out
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at the very beginning um when analyzing
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the whole course of utmb was hey people
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are slowing down right so uh at the end
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it was uh it was a matter of efficiency
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not not that much about speed although
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we wanted to do a fast shoe uh we also
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wanted to have the most efficient shoe
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out there and that's why we focused a
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lot on efficiency therefore all the lab
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uh testing that we did was basically
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pointed towards energy consumption and
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oxygen consumption um so we had our
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athletes basically running on the
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treadmill uphill downhill and we tested
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eight different prototypes at the very
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beginning in zurich some of them had
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carbon plate some others a nylon then
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there was a combination with nylon and
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fiberglass uh and then at the end we
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realized that with carbon plated shoes
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especially on the uphill section the
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body was using a lot of oxygen so it was
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really demanding energy wise and that's
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why we went away from from carbon plated
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shoes that's so interesting to think
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about um that it's this really
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datadriven approach to material and
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looking at the efficiency there because
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i think there's so much conversation
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about the carbon plates right now and
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and this is the first one i've seen
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that's really taking that approach to
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figuring out what materials are most
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efficient over different terrain yeah
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and i think what is interesting as well
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is that obviously data points you in the
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right direction but as i mentioned
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before in road with with sport science
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and lab data you can always almost go to
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a final product right but in freya there
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is so much noise and and and i mean the
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terrain is different there's so many
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things happening that you need to test
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also with the athletes outside on the
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field um and especially take that
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subjective feedback as part of the
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basically yeah just how everything ties
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together with the data actually so jeff
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was saying he went through eight
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different versions of history back and
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forth with you to arrive at this one
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well great and what are you most excited
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about that's that's still to come are
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there any other shoes in the works you
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can tell us about well we're already
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working on the next iteration of of this
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yeah for 27 so um that's a long process
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exactly yes and but we are also working
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on on other shoes that are going to come
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up in 26 which i feel like it's going to
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complement really well the quiver of
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shoes that jeff was talking about i
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think at the beginning in 2022 uh
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beginning of let's say this reset that
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we we did with with on right we didn't
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have all the all the tools and i think
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now we are reaching a point in which we
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feel confident with our athletes to have
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like a good quiver of tools for them to
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be equipped uh in in different races
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ultra distance short distance races as
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well i mean we've seen patrick and
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filimon flying down on the on the broken
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arrow curse uh so i'm sure there's going
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to be also i'm sure along uh that
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direction as well mhm and this one was
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designed with utmb in mind right yeah
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it's interesting because this one was i
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mean we basically analyzed the whole
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course of utmb but it at the end what we
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are finding out with all the feedback
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that we're getting and that we've been
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getting with the athletes is that it can
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actually perform as well at western
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states um so i think we have a really
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well balanced uh super show um
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yeah i think we we took the right
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decisions um thinking about that
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efficiency question that i mentioned at
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the very beginning so we did sacrifices
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maybe on on weight or on speed to
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actually meet the the efficiency topic
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that i was discussing with your runs
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very cool well we'll look forward to
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seeing it out on the trails yeah
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hopefully you get to try it as well yeah
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thanks so much i appreciate it