Compass 650B x 48 Switchback Hill Extralight TC

How wide is too wide? The 48mm Switchback Hill is the widest 650B tyre that Compass makes, and too wide it ain't. It's super-comfortable, fast-rolling, tubeless-compatible, off-road-capable and light. There's really not a lot wrong here. At a time when people are doing roll-down tests to see if it's worth switching to 28mm tyres from 25s, my advice would be to skip a few sizes and fit a pair of these, if you can. They're great.

• Pros: Light; fast; comfortable
• Cons: Tricky to set up; you'll need the clearance to fit them

Compass has all its tyres made in Japan by Panaracer to its own specifications. I've heard plenty of times that these tyres are just 'rebadged Panaracers'; they're not, although they do share the same facility. The Switchback Hill is a 48mm, 650b road/gravel tyre that's available in a standard or an extralight carcass (the one that we have) that saves 65g.

> Buy these online here

Our test tyres weighed in at 412g either end, which is very light for such a big tyre; lighter indeed than the 40mm Schwalbe G-One Speed tyres that I swapped them out for.

Fitting the Switchback Hill tyres tubeless isn't hard exactly, but it did require a specific workflow to make them seal. If you bung them on the rim and just try to blast them on with a tyre booster or a compressor, you'll be out of luck. Well, I was anyway. In the end I removed the tubeless valve, fitted an inner tube, pumped them up nice and hard to pop both beads in the rim, deflated them, unhooked one bead, removed the tube, fitted the valve and then used an Airshot to pop the unhooked bead back on. Et la.

If that sounds like a massive faff then yes, it's a more drawn-out process than fitting the G-One Speeds that they replaced which you can bung on with a track pump, but those are a bit heavier and more rigid, and keep their shape better when deflated. The carcass of the Switchback Hills – these are the Extralight ones, after all – is a lot more flexible and doesn't pop out to the bead on its own. Anyway, bottom line: you need an hour, but it's not hard.

> Buyer's Guide: Tubeless tyres

I was fitting them to a set of the excellent Reynolds ATR 650b wheels, and I stuck them on my first-generation Tripster ATR. That's as big a tyre as that frame will take; there's about 2mm of grace either side. Most modern gravel bikes will squeeze them in. More road-orientated adventure bikes will struggle.

Once they were up, they went down. The first time, anyway; that was because I was a bit stingy with the sealant. I needed 60ml in each tyre (I used Orange Seal, which is what Compass recommends) to make them stay up. You need to use latex sealant as they don't have a buytl liner; the lack of a liner is what makes the carcass of the tyre so light and flexible, but it's not airtight off the production line and the sealant needs to find all the little holes. The best thing to do is get the bike in a workstand and keep spinning the wheels from time to time to slosh the sealant around.

> How to fit tubeless tyres

With an eye-watering 40psi in the Switchback Hills it was time to take them out on the open road. And what lovely tyres they are. I've completed plenty of riding on the Switchback Hills, including a 300km weekend to and from North Devon on a Sven Pathfinder (with lightweight tubes), and lots of shorter rides on my Tripster ATR around Bath (running tubeless).

They're massive, and they only weigh 412g a piece; the extralight casing is super supple and they thrum along on tarmac with no obvious penalty over something much, much narrower. I've checked my Strava times; that's not conclusive, but there's no trend to suggest I'm slower, and they don't ever feel slower. They really are quick, these tyres. Compared to the same bike, on the same routes, with 'wide' 30mm Schwalbe G-One Speed tyres, I can't discern any meaningful difference. I'm a bit quicker on my race bike (on 28s), but that's my race bike. It's 3kg lighter.

> Buyer's Guide: 27 of the best road cycling tyres

Take this ride for example: going fairly hard up a 10-minute back-lane climb I was only half a minute off my best time, and that was set on my race bike in a group, rather than on my Tripster, on my own. Further into the ride I bagged fifth overall on a short, punchy fire road climb, for which the prerequisite for a good time is basically to be able to carry plenty of speed on the preceding gravel descent. The Switchback Hills are exceptional at that.

Compass doesn't recommend the tyre for 'truly technical terrain' and indeed I'd be wary of chucking the thin sidewalls at anything that was especially rocky, but on gravelly unsurfaced paths they're almost as quick as they are on the tarmac, floating over imperfections with aplomb, especially if you drop the pressure a bit.

On the road they allow you to be a lot less choosy with your line, and in a group you have to remember to point out holes and other imperfections that you can glide over on 48s but might easily pinch-flat a 25. Grip is exceptional, with the tyres deforming around imperfections and hugging the tarmac on steep climbs and tricky descents.

They really come into their own on any surface that's less than smooth; that can be gravelly back lanes or a main road with a surface in need of repair. Basically, round here, it translates as: nearly any road.

Those are the main reasons to fit a tyre like this: versatility over a range of surfaces, grip, and comfort. Compass recommends a maximum pressure of 55psi. My sweetspot was about 38 in the front tyre and 40 in the rear; I'm about 92kg so lighter riders will be going lower. That's a bit above what the all-knowing Berto chart of tyre width vs. optimal pressure would suggest is ideal for a 15% compression of the tyre (36/28psi), but it felt good to me on a bike that's predominantly used on the road.

> How to choose your tyre pressure

Overall, I'm really impressed with the Switchback Hills, as you can tell. We've tested the Steliacoom TC and the Barlow Pass TC previously, and both of those tyres received high praise from reviewer Mike Stead and these are no different. Aside from the fact that they're a bit of a pain to fit, there really is no downside to a big tyre like this if you're doing anything other than racing.

Verdict

Exceptional, super-light, big chamber tyres that roll fast on tarmac and gravel alike