Increasing wheel width--what is best for pure road cycling?

Seems like the width of wheels for road cycling continues to widen every year. I bought some Boyd Carbon Clinchers a few years ago with 19 mm internal width, which at the time seemed to be on the leading edge of wide road wheels. Now, over the past month or so, Flo has increased the width of their wheels from 17 mm to 21 mm, and the new Enve and Zipp wheels are 21 mm and 23 mm, respectively.

Any thoughts on whether these wider widths are being offered because they are better for road cycling speed/comfort, or is this just an attempt to offer a more versatile wheelset for road/gravel/path even though it may cause a slight penalty on the road?

I guess ultimately I am wondering what is the best width for road cycling for those who are not going to be riding on gravel or paths?

I’m also curious if something similar is happening in road that happened in MTB the past 3 or so years. It seemed they were touting the benefits of plus tires in the 2.8in range before relatively quickly scaling back to the 2.4-2.6 range.
On the road side I wonder if there is a sort of race to the widest road rim. Getting a little carried away with the falacy of ‘If 19mm is better than 17mm then 21mm is better than 19mm’ until they realize that they maybe went a little too far and start scaling back.

But what do I know? I’ve never bought aftermarket rims for my road bike. But on the MTB side I definitely felt that going from 27.5x2.8 to 29x2.25 was an upgrade rather than a downgrade.

I think what is happening with wheels at the moment is more a reflection of the market moving to disc brakes. Now the wheels can be shaped more aerodynamically by allowing the widest part of the rim tyre combo to be on the rim (HED) or at the interface. Not saying the whole contact patch argument is moot here. It is clearly a significant driver. We all want to get to the slimmest ‘horizontal’ patch that we can. However there is a limit to that. We all weigh what we weigh so the patch has to X in area to support us and give the suspension, rolling resistance and grip we want. So there is a practical limit. The problem is that the possible combinations are permutating all over the place with no real clarity for us dumb users.


I think you have to back into it based on what tires you ultimately want to run.

And then you need to factor in tire bulge and actual installed width.

And are you trying to be aero optimized? I’m talking about the 105% rule where the widest part of the rim is 105% of the tire’s width.

That said, here is my dream bike / wheelset. I’d love to run fully aero optimized 28mm tires. They will probably stretch to 32mm and I’m not sure if you can stay aero optimized with 28mm tires. A Cannondale Knot 64 wheelset is 32mm wide but a 25mm tires that stretches to 28-29mm is still probably the fastest tire.

Why do I want this wheel? Well, we have some very rough roads around here. I think a higher volume, very aero wheel that can run at 50-60psi would be the fastest wheel on our roads.

The problem for me - my bike will only fit a maximum actual width 27mm tires which is a 25mm tire that isn’t too tall (like a GP5000). My next frame will be one that, at minimum, takes tires up to 30-32mm actual.


Looks like dreams do come true…

The 303 S is among our lightest wheelsets, optimized for top aero performance with a 28mm tire

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At only 27mm wide, that rim is not going to be aero optimized with a 28mm tire that stretches out to 30+ mm. To be aero you’ll still have to use a 25mm tire (27mm actual).

I guess you will have to take that up with Zipp as they see it a bit differently. I don’t have a dog in the hunt as I’m on Enve’s, just passing along their info

*The key innovation is in the 303 S’s rim design. Its 45mm rim depth is the same as its predecessor, the 302 Disc brake. But its external rim width is 2mm wider, at 27mm, and its tire bed is a full 7mm wider, at 23mm internal width. That rim platform is designed to be the fastest with a 28mm tire.

I’ve been following the 105% rule on my road bike, but have been wondering about it for gravel. Is it just not possible for gravel tires, say 38mm, and we just need to go as wide aero wheels as possible?

Not everyone is hardcore, or even the hardcore want wider rims too. Jan Heine has been pushing for wider road tires for a while, and lower pressures, which comes with more comfort.

It goes off on a tangent, but all the info is probably on his blog (somewhere in here

I’ve used his Rat Trap Pass tires, they are nice, and turned an old MTB into a reasonable commuter.

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Along with comfort, the larger tire contact patch leads to better control when cornering and braking, from the improved traction.


Don’t forget it looks cool too :sunglasses:

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I’m thinking that when Zipp says 28mm tire, they mean a 28mm actual width tire. And in most cases that will be a tire marked 25mm.

In any case, I don’t care what their marketing speak says. If the tire is larger than the largest part of the rim then it will not be aero optimized.

Personally, I wouldn’t spend any extra money on deep aero wheels for gravel. A 38mm tire is going defeat any aero benefits.

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What’s your thoughts on that video. I’ve followed the 105% rule, but maybe specialized is saying the penalty isn’t as harsh as previously thought? :man_shrugging:

The problem of potentially having a rim that would obey the 105 with a 38mm gravel tire it it would change the shape of the tire and potentially compromise it’s performance from a grim standpoint. If a tire manufacturer developed a tire so all the lugs were in the right place on a 19mm internal width rim, putting that tire on a 30mm internal width rim could move the lugs so they are less effective.

It will be interesting to see when the new ERTO standards come out what wheel and tire manufacturers will land on in terms of internal width to standardize on (ie a 28mm tire measures 28mm wide on a 21mm internal width)

Anyways, for what it’s worth, Josh Poertner (of Zipp and Silca) said on his podcast a while back he thinks ultimately tire size will land in the 30-32mm range in the US and 28-30mm range in Europe

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Interesting video BUT (without more test details) I’ll say this: Those quoted 40km ITT times are usually based on elite level ITT speeds (40km/hr or 30mph). Who is going to ride their gravel bike with 40mm tires @ 30mph for an hour?

I’m just speculating because we don’t have the test details but the 16/40 seconds saved probably falls to essentially zero savings at normal gravel speeds.

So one can look at their average speeds for gravel and decide what they are trying to accomplish. If I was an elite level rider doing the Belgium Waffle Ride (140miles with a lot of road) on 30/32mm tires then a small aero benefit would probably be worth it. But average joe riding 14-20mph on gravel probably doesn’t need and doesn’t make use of a $2000 carbon aero wheelset.

FWIW, I actually set a Strava KOM on a 10 minute gravel section the other day. My average speed was 19.2mph. What would an aero set of wheels saved me. 1 or 2 seconds?

Here is the Silca blog post on the 105% rule in case anyone is interested:

So are you saying you wouldn’t recommend buying aero wheels on a road bike with say 25mm tires if you only average 19mph? My riding says at that speed aero wheels do provide a noticeable difference.

I’ll have to see if specialized list their test speed anywhere. I believe I remember them saying that their wind tunnel was special in that it was built for bikes allowing for slow speeds and granularity. Compared to normal wind tunnels designed for cars.

I thought we were talking about gravel tires here?

On the road I do think aero wheels are worth it if your goal is saving a few watts.

But in general you can look up any “saves X seconds in a 40k TT” and the speed will be elite level ITT speeds. If they say you are saving 40 seconds then at pedestrian speeds you are saving maybe 1/4 or 1/3 of that.

I think 28mm has a clear advantage with tubeless due to the lower pressures and higher volume.

And since rims 60mm deep and above can be aero optimized for 28mm tires, I think 28mm is the future.

I’m running them on CLX64s.