The new Insta360 Go Ultra might be the action camera that gets me excited about video capture again.

I’m not a connoisseur of action cameras. I used the first few GoPro generations, but was never bowled over by the less-than-user-friendly experience. I also tried Garmin’s long-forgotten Virb, which was easier to use but had less than optimal recording quality capabilities.

After those less-than-satisfactory experiments, I haven’t been impressed enough to step back into the ride-recording fray.

My camera tech experience since then has been limited to having various cameras strapped to me or my bike by our videographer experts over on Bike Radar’s YouTube channel.

• Read more: What are cycling cameras and why should you own one?

Insta360’s new Go Ultra has got me excited about action cameras again. Not just for its clever camera design, but also because of its excellent app with built-in, easy-to-use editing capabilities.

The Go’s super-compact dimensions set it apart from the X series cameras Insta360 is known for.

The Go Ultra camera looks at first glance to have similar dimensions to a GoPro; the clever part is that the camera can be unclipped from its magnetic locator in the base unit, which Insta 360 calls the Action Pod.

The camera is no bigger than an average-sized wristwatch and weighs only 53g.

What’s new with the Go Ultra?

The new super-compact camera comes with a 1/1.28-inch sensor, 220% larger than the previous Go camera. It also gets a new 5nm AI chip, the most advanced yet for a Go camera. Insta360 claims it can deliver “ultra-smooth, ultra-crisp 4K 60fps video”.

This is combined with Insta360’s PureVideo feature, which uses AI algorithms to reduce visual noise and enhance low-light brightness.

The base unit, or Action Pod, connects to the tiny camera via Bluetooth, enabling you to monitor and control recording from a distance on the 2.5in flip touchscreen.

Like the previous Go 3S, the tiny camera element has a magnetic base, although here the magnet is larger and more powerful.

Included with the camera is a magnetic pendant that the camera locks into, meaning on-bike POV video is easier than ever to capture.

Also included is a hat clip with a magnetic base built into a clip that can be attached to a helmet peak, giving another option for POV video.

Action cam mount adaptors are also included in the package.

Plenty of add-ons

Lots of accessories are available at launch, too, with a flexi-strap mount (£13.99 / $14.99) giving lots of bike-mount options and a new angle-adjust cycle mount on the way.

The accessory I find most useful is the new Ring remote (£41.99 / $44.99), a tiny single-button Bluetooth remote that’s attached to a small Velcro strap. Insta360 intends it to be worn like a ring to remotely operate the record function on the camera.

For on-bike users, it’s the perfect size to strap to a handlebar so you can activate the camera while riding, without having to take a hand off the bar.

The Standalone Camera has a claimed run time of 70 minutes on a single charge, and 200 minutes when combined with the Action Pod.

I haven’t managed to get close to 70 minutes, but I’ve only tried the camera on full-fat 4k at 60fps with all the AI stability controls maxed out. So, I’d suggest those claims are for lower resolutions and fewer AI aids in motion.

However, when you do run the tiny camera out, you can simply lock it into the Action Pod and it’ll recharge to 80% after 12 minutes in the base unit.

While the Action Pod isn’t waterproof, the camera is rated to IPX8, so it can be fully submerged down to 10 metres underwater, so it should cope easily on a soggy bike ride.

The Go Ultra also makes the switch to microSD storage; the previous Go 3S only had internal storage. This gives the Ultra Go up to a potential 2TB of storage.

Smart connection and a smart app

The camera connects to the free Insta360 phone app (available on iOS and Android), via a private Wi-Fi connection. The app’s editing software brings multiple cuts, transitions, a wealth of other effects, music and the ability to overlay cycling data from a Strava account in real time.

The user-friendliness of the Go Ultra has impressed me so far, and it could very well be the gateway to getting me excited about action cameras again.

Pricing details

The Insta360 Go Ultra is available now. The standard bundle includes the camera and Action Pod, along with a quick-release safety cord, magnetic easy clip, magnet pendant, USB-C charge cable and a lens guard.

The standard bundle is priced at £389 / $449.99 / €429.

There is also a Creator bundle package, which includes the standard bundle plus a mini two-in-one tripod, quick-release mount and a Pivot stand, priced at £429 / $499.99 / €479.

Key specifications

• Aperture: F2.85
• 35mm equivalent focal length: 14.27mm
• Weight: camera 53g, Action Pod 109g
• Size: camera 46×45.7×18.3mm (1.8×1.8×0.7in), with lens guard: 46×45.7×22.4mm (1.8×1.8×0.9in),
  Action Pod (touchscreen closed): 70.4×48.8×33.3mm (2.8×1.9×1.3in)
• Photo resolution, 50MP: 8192×6144 (4:3), 37MP: 8192×4608 (16:9), 12MP: 4096×3072 (4:3), 9MP: 4096×2304 (16:9)
• Video resolution, highest video quality: 4K60fps, highest video frame rate: 1080p@240fps
• ISO range: 100–6400
• Shutter speed, photo: 1/8000–120s, Video: 1/8000 – to the limit of frames per second
• Battery capacity, camera: 500mAh, Action Pod: 1450mAh

With a number of factors influencing what size tyres you should have on your bike, working out what tyres will fit can be difficult.

Bikes these days come in an array of different wheel-size diameters, from 700c found commonly on road bikes to 27.5in found on mountain bikes.

Width has also changed a lot, with wider tyre sizes on all types of bikes proving more popular thanks to their bump-absorbing nature.

Of course, you can always replace like with like, but if you want to try running a different tyre, or maybe just the same tyre in a different width, there are a few things to consider.

In this guide, we’ll run through everything you need to know about bike tyre sizes and delve into the unique size specifications of road bike tyres, mountain bike tyres, gravel tyres and commuter bike tyres.

How do I find the size of my current tyres?

The size of a tyre should be printed on its sidewall.

The definitive tyre size is the ETRTO number, which will be embossed on the sidewall of all tyres.

It consists of a tyre width measurement in millimetres, a dash and then the tyre bead diameter, also in millimetres. For example, 25-622 means the tyre is 25mm wide and will fit a 700c wheel, while 65-584 means the tyre is 65mm wide and will fit a 650b wheel.

Because ETRTO numbers are not commonly understood, most tyres will have a metric size such as 700c x 25mm, or an imperial size such as 27.5 x 2.60in embossed on them too, sometimes both.

A tyre’s size may be printed in black, and quite tricky to read, so outdoors or under a bright light is the easiest place to pick it out

What defines the size of a bike tyre?

There are two parameters that define bike tyre size:

• Tyre diameter
• Tyre width

The tyre diameter, or to be more specific the tyre bead diameter, is defined by the size of the wheel that it has to fit on. We’ll cover this in more detail.

Tyre width is also a factor to consider. There are more options here, as well as some variability in the width the tyre ends up when it’s mounted on your wheel rim. We’ll come on to this.

Tyre and wheel diameter

Confusingly, there are multiple ways in which tyre and wheel sizes are designated.

Road bike tyres are typically sized using the traditional European measurement system. Usually, a road bike will have 700c rims and fit 700c tyres.

Mountain bikes, on the other hand, usually have tyre and wheel sizes designated in inches, reflecting the US roots of the sport.

Typical mountain bike wheel sizes and tyre sizes are 29in, 27.5in and, historically, 26in.

29in wheels and tyres have the same bead diameter as 700c; 27.5in is the same diameter as 650b.

The 26in wheels that dominated mountain bikes for years are now more-or-less obsolete.

Like road bikes, gravel bikes have metric-sized wheels, but they tend to be either 700c or 650b.

What about ETRTO tyre sizing?

It gets even more complex, because there’s also an ETRTO sizing that’s typically printed on the sidewalls of tyres, defined by the European Tyre and Rim Technical Organisation.

This is controlled by an ISO international standard and ensures that any tyre of a designated diameter should fit on any rim of the same designated diameter.

The ETRTO number is expressed in millimetres:

• For a 700c or a 29in wheel and tyre, the ETRTO diameter is 622mm
• For a 650b or a 27.5in wheel, the ETRTO diameter is 584mm
• For a 26in wheel, the ETRTO diameter is 559mm

With this in mind, there are actually a limited number of wheel and tyre diameters readily commercially available. A tyre of a specified diameter should fit a rim of the same diameter, although, as we’ll come on to, the width of the tyre and rim are also significant factors to consider.

When it comes to tyre size, the wheel/tyre diameter will be combined with the tyre width to give you the full ETRTO number. For example, a 25-622 tyre will have a nominal width of 25mm and a diameter of 622mm (to fit a 700c wheel).

Despite the ETRTO standards outlined above, manufacturing tolerances mean the fit between the tyre and rim can be tighter or looser than expected.

If you need to change a bike tyre fitted with an inner tube, that may just mean the difference between an easy job mounting a tyre and sore thumbs from prising an over-tight tyre onto a rim or off again.

For tubeless tyres, it’s more critical there’s a close fit between the tyre and the rim, particularly for road bike tubeless tyres, where tyre pressures are higher and there’s more risk of a blow-out than with an MTB or gravel bike tyre.

Manufacturers are now making the best tubeless road tyres to much closer tolerances than a few years ago to ensure safety, particularly on the latest hookless rims.

Makers of road bike wheels with hookless rims will often publish a list of tyres recommended for use with their wheels, and it’s best to consult these lists to avoid any mishaps out on the road.

Tyre width

Although there are a limited number of tyre bead diameters to fit discrete wheel sizes, there’s a lot more variation in tyre width.

To start with, mountain bike tyres are a lot wider than road bike tyres. This is one reason why you’ll likely be unable to fit a mountain bike tyre in a road bike frame, although you can in principle fit a mountain bike tyre on a road bike rim.

Road bike and hybrid tyres are typically sized in millimetres, when it comes to width.

Most gravel bike tyres are also sized in millimetres, although super-wide gravel tyres – akin to mountain bike tyres – may be sized in inches.

Mountain bike tyres are typically sized in inches too.

Road bike tyre sizes explained

When it comes to choosing the best road bike tyres for you, width is the key factor to consider.

Almost all road bike wheels are 700c (with a beam diameter of 622mm), although some bike brands fit 650b wheels (with a bead diameter of 584mm) to some of their smaller-sized bikes, so they can maintain a similar road bike geometry to larger frame sizes.

In the past, 23mm was the typical width for most road tyres, and some tyres came in a 20mm width or narrower.

Now, 25mm is the narrowest tyre that typically comes fitted to road bikes and many bikes have 28mm tyres, with clearance on some of the latest bikes for 32mm rubber and beyond.

Wider tyres can offer improvements in grip, comfort and rolling resistance. However, you should check the clearance offered by your frame before committing to a wider tyre.

One final point – while millimetres are often used to measure or refer to the width of a road bike tyre, its actual width when inflated will depend on manufacturing tolerances, the rim width and tyre pressure.

As a result, you may see the width referred to in ‘c’. For example, 25c instead of 25mm.

Common road bike tyre sizes

Here’s an overview of common road bike tyre sizes.

Mountain bike tyre sizes explained

Mountain bikes are now split between 27.5in and 29in wheels. Some mountain bikes have a 29in wheel at the front and a 27.5in wheel at the rear. These bikes are often referred to as mullet bikes, and it’s a popular setup on trail bikes and enduro bikes.

Wide rubber rules the day with the best mountain bike tyres. Typical widths range from 2in up to 2.6in, depending on the type of riding the tyre is designed for. Increasingly, wider tyres are also available.

Common mountain bike tyre sizes

Here’s an overview of common mountain bike tyre sizes, across 26in, 27.5in and 29in wheel sizes.

Gravel bike tyre sizes

Choosing the best gravel bike tyres for your bike often means weighing up wheel size, tyre width and tread pattern, to find an option that suits your riding style and the terrain you’ll be taking on.

Gravel bikes come with either 700c or 650b wheels and you’ll need to choose a tyre that will fit the wheel size you have on your bike.

700c gravel bike tyres start off at around 32mm wide, although most frames can take wider rubber and many riders now opt for 40mm or 45mm tyres. Gravel tyres can reach around 50mm if they fit in the frame.

Switch to 650b wheels and tyres are usually wider, to add extra air volume and comfort. 650b gravel bike tyres typically start at around 40mm wide and travel up towards 60mm, by which point, inches may be used to express the width.

A 650b wheel with a wider (and hence deeper) tyre will have a similar rolling circumference to a narrower tyre on a 700c rim, so many gravel bike frames can take either wheel size.

While gravel tyres may appear to share much in common with cyclocross tyres, UCI regulations for cyclocross racing dictate that CX tyres must be 33mm or narrower for competition.

Common gravel bike tyre sizes

Here’s an overview of common gravel bike tyre sizes for 700c wheels.

Commuting bike tyre sizes

Commuter hybrid bikes have 700c, 650b or 26in wheel sizes, with 700c being the most popular.

Although hybrid bikes tend to have the same-size wheels as road bikes, robustness and comfort are prioritised over speed, so they typically have significantly wider tyres that are heavier and incorporate a more pronounced tread pattern.

Hybrid bike tyres typically start at 30-plus millimetres wide and go up into the high 40s. If you go much wider than this, increased rolling resistance can make for slow progress.

Common hybrid bike tyre sizes

Here’s an overview of common hybrid bike tyre sizes for 700c wheels.

How does rim width affect tyre size?

Although we’ve talked a lot about tyre width, this is only the tyre’s nominal width (i.e. what the manufacturer has stated, rather than the actual width when measured).

A tyre’s actual width will be different when mounted on a wheel. There are two reasons for this:

• First, when inflated, a tyre may plump up wider than its stated width, due to variations in manufacturing tolerances
• Second, the tyre represents only around three-quarters of the circumference of the wheel/tyre combination, the rest is determined by the rim bed

Wheel rims are getting wider both for road bikes and mountain bikes. So, whereas 17mm used to be a fairly standard road bike rim width, many modern road bike wheels have rims with internal widths of well over 20mm.

The Zipp 303 Firecrest wheel, for example, has an internal rim width of 25mm. That adds significantly to the width of the mounted tyre, so a nominally 28mm Michelin Power tyre measured up at 30.9mm wide in our test of the wheelset.

Among the advantages of wider rims, the extra volume of the tyre means it can be run at lower pressure for a more comfortable and possibly faster ride, without any weight penalty. On the downside, you may have clearance issues in your bike frame if a tyre measures up significantly more than the stated width.

I’ve been on a roll lately, racing each week’s ZRacing event on Tuesdays at 12:10pm California time (join me!) in the B group (450-570). While I haven’t won a race in a while, these provide a good challenge with a large and varied enough field to keep things interesting.

This week’s race is on a single loop of Watopia’s Sand and Sequoias, a popular circuit that takes in both the Fuego Flats desert and Titans Grove, two distinctly different sections of road. My event was full of classic Zwift race fun: an overpowered rider staying off the front, an underreading trainer making me work extra hard, praying to the powerup gods, and even a virtual shifting “mechanical” that forced me to improvise a bit to stay in touch! Let’s get into it…

The Warmup

I got on the bike with plenty of time before the race, giving me a full half hour to wake up the ol’ ticker and spin up the legs. I was already one dirty chai and a few pieces of Neuro caffeine gum into my warmup by the time I got on the bike, so I was nicely caffeinated. I had also rubbed PR Lotion into my legs to keep the burning at bay.

My Warmup “Stack”

I rode my Cadex Tri bike during the warmup, since I’m working on upgrading it as we head into ZRL. Gotta get those minutes!

Fuego Flats (the Easy Part)

This route is 22.4km long, and the first ~10km takes you from the desert start pens and across Fuego Flats to Saddle Springs. It’s quite flat, and most racers don’t even attempt an attack here, because the pack chasing from behind is simply too fast.

The Luck of the Powerup

The race was set up to hand out one of two powerups at random at each arch: a feather or an aero. With two arches on the course, the powerups you receive could really affect your race! Everyone wanted a feather as their first powerup, to help them up the Titans Grove KOM. And everyone wanted an aero for the second powerup, to help them in the final sprint.

I got a feather through the first arch. Bingo.

We chugged along, a starting group of 26 riders working at a steady but bearable clip. I averaged 251W for this section, but things started getting spicy near the end as we entered Saddle Springs. One L. Nystrom attacked off the front, and four other riders followed. They soon built a 5-second gap, and seemed to be working hard together as we headed up the Col du Saddle Springs into Titans Grove.

This was gonna hurt. But at least I had my feather!

Titans Grove (the Hard Part)

We hung a right into Titans Grove, and the real work began. One rider from our group put in a hard effort and bridged up to a handful of riders just ahead, but I could see the breakaway had split into two groups. We reeled in the back group at the bottom of the Titans Grove KOM, but there were still three riders up the road.

It helps to know how this KOM lays out. While it’s 2.6km long on paper, the first kilometer is quite flat (less than 2%) and very draftable. So if you want to ride this as efficiently as possible (vs attacking and ripping everyone’s legs off), you want to sit in the pack and draft efficiently for this first bit.

The second portion is steeper, but still only 3-4%. Drafting still helps a lot, so sit on a wheel and just work to hold a good pack position up and over the top.

I stuck to my advice above, and was able to hang with the peloton up and over the climb, triggering my feather with about 600 meters to go. I finished in 4 minutes, 37 seconds with an average power of 330W.

Bad Shifting, Bad Powerup

But as we approached the KOM banner, something odd happened: I shifted (virtual shifting), but the resistance didn’t increase as expected! Instead, it hit… slowly… over several seconds. This odd shifting delay would persist through the end of the race.

I had hoped for an aero powerup through at the KOM banner, but alas: it was another feather. You win some, you lose some.

In contrast to the flat, easy start of the race, the 5.3km section from the start of Titans Grove to the top of the KOM required 308W average for me to stay with the group. Ouch!

The Finish

I tried to recover a bit as we descended from the KOM arch, but my delayed virtual shifting was making things a bit goofy. I also knew there was a sharp little kicker coming up, so I tried to get set into a gear that would work for hammering up and over this rise.

By the time we finished that kicker and began the true rollercoaster descent to the jungle, only two riders were up the road: L Nystrom solo on the front, with B. MacPhee chasing. I didn’t have the legs to chase, so I sat in and hoped our pack of 21 would pull them back.

B. MacPhee got caught with 3km to go, just before we exited Titans Grove. That left only Nystrom, who didn’t seem to be slowing one bit. Just as we all began resigning ourselves to fighting for second place, B. Ruhne, wearing a DIRT kit, jumped hard off the front and got away solo.

I sat in the group, unable to jump hard enough to get away. As we neared the sprint finish, A. Morvan jumped hard with an aero powerup, catching B. Ruhne just before the line. Nystrom won by nearly 20 seconds. And my feather powerup and tired legs proved a poor match against the competition. I crossed the line in 10th.

See ride on Strava >
See results on ZwiftPower >

Watch the Video:

Takeaways

This race basically unfolded the way past Sand and Sequoias races have unfolded for me. Easy on the flats. On the rivet surviving the Titans Grove KOM. And too knackered to sprint to the podium.

Zwift Racing Score

My score increased from 564 to 569 as a result of this race. Looks like I may not be long for the 450-570 group! And neither is L. Nystrom, the rider who jumped off the front ~9km into the race and stayed away to win solo by 20 seconds. He averaged 4.3W/kg for the event, which was his first race since December 2024 according to his ZwiftPower profile. His Zwift Racing Score result for this event was 559, and that includes a seed score upgrade due to some new 90-day power bests.

Generally, I’ve been quite happy with how my Zwift Racing Score-powered races have unfolded in recent months. The algorithm seems to be doing a good job. But today’s race highlights two areas where Zwift Racing Score still needs to improve:

1. Taking a rider’s historic performance into account: Nystrom averaged 4.2W/kg for over 53 minutes in a race in March 2024. He’s clearly got the fitness to be ranked higher than he was heading into today’s race.
2. Upgrading a rider more quickly based on current performance: I’m not sure how much his score jumped due to today’s result, but the fact that he can still race in the 450-570 group is silly, given what he did today, averaging 4.74W/kg for 20 minutes.

Blaming the Trainer

The most annoying bit of information is that I was testing a smart trainer (which shall remain unnamed) during this race, and while it seemed like the trainer may have been reading a bit low as I was warming up, I used it as the power source anyway during the race, while dual recording my Assioma pedals on my head unit.

It turns out that the trainer’s average power was ~15W lower than the pedals for the duration of the race. Ouch. Here’s a chart showing a small portion of the race, with my pedals in blue and the trainer in purple:

The power readings on this chart may look similar at first glance, but the Strava power curve for this race shows that the difference between the trainer’s numbers and the pedal’s numbers is the difference between a ho-hum effort and setting several new PRs for 2025 in the 10-30 minute window.

I’m not saying I lost because of an under-reading trainer, of course. But it certainly didn’t help. Occupational hazard, I guess, when you’re riding in the Zwift Insider Pain Lab!

Your Thoughts

Did you race this week’s Sand and Sequoias ZRacing event? How did it go for you?

See zwiftinsider.com/route/climb-control/

Former Israel-Premier Tech cyclist Jakob Fuglsang has said he feels a sense of relief at no longer wearing the team’s jersey, stating it’s “nicer to ride around without an Israel logo than with it”. 

The two-time Critérium du Dauphiné winner and Liège–Bastogne–Liège champion retired in May and rode his last race, the Frederiksberg Criterium, last Sunday. After the race, he spoke to Danish outlet Feltet and said: “It’s of course nicer to be without. I don’t want to get involved in what’s happening politically, but it’s definitely nicer to ride around without an Israel logo than with it.” 

The 40-year-old Dane added that he had not had any problems with planned protests targeted at Israel-Premier Tech during big races. 

“I haven’t actually experienced that. With or without Israel-PremierTech at the start, there would still have been demonstrations. You also see climate demonstrations during the Tour de France. These are big events where there is a lot of media attention. That said, it’s better to ride without,” he told Feltet. 

Fuglsang’s remarks follow former teammate Alessandro de Marchi stating in July he was “happy and relieved” not to be cycling for Israel-Premier Tech. 

De Marchi, who moved to Jayco-AlUla in 2023, told The Observer he would no longer feel comfortable riding for Israel-Premier Tech due to Israel’s continued war on Gaza.

“I would have really struggled to be there now and been in great difficulty,” said De Marchi. 

De Marchi rode for Israel-Premier Tech between 2021 and 2022. He said the team “gave me a chance to keep riding” and that he was “looking at the house I had to build and my family”. 

“Of course now I am older and able to reflect in a way I didn’t five years ago, and I appreciate that in life there are times that, though it may be hard, it’s better to follow your morals. Right now I would do things in a different way,” he added. 

Fuglsang and De Marchi’s comments come after the Boycott, Divestment and Sanctions (BDS) movement called for peaceful protests at this year’s Grand Tours. 

“As Israel escalates its ongoing genocide against 2.3 million Palestinians in Gaza and its violent military occupation of the West Bank, international sporting bodies have a moral obligation to take all measures to prevent genocide, or risk being held criminally liable,” the BDS movement said. 

Protests were visible at the Tour de France, with those present waving Palestine flags and unfurling banners as the Tour rode through Dieulefit on Wednesday 23 July. 

An activist from Extinction Rebellion was also arrested in Toulouse after running onto the final straight of stage 11 with a T-shirt that read ‘Israel out of the Tour’ while waving a keffiyeh scarf. 

Israel-Premier Tech was founded in 2014 and is co-owned by Canadian-Israeli billionaire Sylvan Adams, who has referred to himself as “self-appointed ambassador at large for the State of Israel”. Adams has described Israel’s invasion of Palestine as “good vs. evil and civilization against barbarism”. 

Ron Baron, the team’s other co-owner, has described Israel–Premier Tech as a form of “sports diplomacy”.

Israel-Premier Tech declined to comment.