over the last few years bicycle wheels have got wider and wider and the width of tyres that people
are using have got wider as well now in my head a wider wheel and a wider tire would be slower
because surely there's more friction but this is not the case and luckily i have a friend who's an
engineer and who makes wheels who can explain this for us so my first question to dog from parkour
is why are wheels getting wider why are wheels getting wider our wheels getting white it's like
a weird tongue twister so from a wheel designer perspective now that we're no longer using these
and we're moving to disc brakes it's opened up a whole new avenue of design because we're no
longer working with the constraint of having to fit between the braking pads so what that means
is we can start to accommodate wider tires we know that wider tires run at a lower pressure
will reduce rolling resistance and make riders both faster and more comfortable so from a
wheeled manufacturer perspective from a design perspective we want to be able to accommodate
those wider tyres okay that makes sense but what has that got to do with the wheel when we think
about wheel and tire compatibility and performance there's a couple of elements to consider the first
is the inner rim width so the spacing between the sides of your rim where the tire sits now with a
wider tire you need that rim width to be slightly wider so it allows the tyre to open up fully
because otherwise you have a really wide tire which is then pinched together at the bottom by
a nice narrow rim and you end up with a light bulb effect so the tyre won't roll as it's designed to
it needs to be allowed to open out to its full width then from a performance perspective if
you're thinking about aerodynamics the other thing to consider is the outer rim width
whereby you need the wheel or the rim to be wide enough so that when the airflow comes off the
front of the tire the rim can start to recapture it reduce the turbulence and therefore reduce drag
so historically we've worked with a rule of thumb um referred to as the rule of 105 which basically
says that broadly speaking you want the rim to be around about 105 of the width of your tire in
order to maintain aerodynamic efficiency it's not quite that simple there are little nuances to it
but generally speaking if your rim is narrower than your tyre you are going to notice a detriment
to your aero performance so in order to maintain that area performance keep the drag nice and low
you need a nice wide rim externally and in order to maintain the performance of the tire and make
it sit correctly you need a wider internal rim so what's going to happen our wheel's just going to
keep getting wider and wider and frames getting more and more clearance until we're riding like
super moto gp style wheels i mean ultimately we could all end up riding around on fat bikes
um no so there comes a point where the tyre width stops having an impact because what we now know is
that the wider tyre allows more deformation over a rougher surface but there comes a point when
you've reached the max deformation that you need over a surface like tarmac exactly what that point
is i don't know but i know that we're probably getting close to it with a 28 mil tire maybe it's
30 maybe it's 32 but at that point going wider on your tire isn't going to save you on the rolling
resistance so if as a wheel manufacturer we're designing around that width of tyre again there
comes a point where you don't need to go any wider so if you use the rule of thumb you go to 105
then maybe we're looking at 35 36 mil widths but if you suddenly put a wheel that is
40 45 mil into a wind tunnel it's going to come back slower because you've got to the
point where you're no longer helping recapture the air from the tire you don't need to go any wider
you're just forcing a wider object through the air which is going to create more drag
so i think we're we're learning as we go but as an industry we're probably getting
close to the limit of what you would need on the road off-road and gravel is a whole different
ball game we know that there are much wider tires but let's be honest if you look at a gravel tyre
it's going to have novelty tread and that's about the worst thing you can do aerodynamically so
i think from an aero perspective aero gravel wheels is that a thing arguably not um therefore
you're looking at the right width of wheel to suit the tyre in terms of the inner width of
the rim and i think that we're we're getting there that's a much easier thing to define so over the
coming years we may look at going a bit wider but there comes a point of diminishing returns where
you get to too wide so we're getting close well that all sounds good to me i like riding wide
tires because they're more comfortable and to know that they're not any slower is definitely
a good thing these are my uh road wheels that i'm riding at the moment and i'm riding a 30 mil tyre
even though the rim is designed to work best with a 28 so you get a little bit of light bulb effect
but not that much and to be honest if you're not racing i'd rather go for more comfort you can run
really low pressures the british potholes don't feel so bad and yeah they look cool as well as
always a big thank you for watching these videos i hope you enjoyed that if you have any questions
for dov please leave them in the comment section down below and if it's a big topic we can cover
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you