Tyres are getting bigger, and the Continental Grand Prix 4000S II 28mm (let's just call it the GP4000S from now on, eh) is a great example of why this is A Good Thing. Assuming you can fit these tyres into your frame, there's plenty of reasons why you should. They're excellent.
The GP4000S is Conti's top racing clincher; they call it the "Undisputed market leading race bike tyre", and while we wouldn't go that far it certainly has a big following. It's been available in 23mm and 25mm widths since the update from the last incarnation, but the 28mm is a new departure for Continental in the racing sphere.
At 266g per end (claimed 260g) it's heavier than the 25mm (claimed 225g) and 23mm (claimed 215g) but the plus side is that the air chamber is much bigger than the smaller tyres, and you can run it at a lower pressure. Continental suggest 110psi for the 23mm and 25mm, and 95psi for their big brother. Construction is the same: Black Chili compound tread, Vectran puncture strip, three-ply 110TPI carcass and a kevlar bead. The 23mm tyre you can have in a variety of sidewall colours, Pantone-matched to your Fizik bar tape. But if you want 28s, it's black or black.
Out on the road they feel extremely smooth and fast. Continental (http://www.conti-tyres.co.uk/conticycle/ti_GP4000SII.shtml) point to a recent Tour Magazine test that found that the 28mm GP4000S not only had lower rolling resistance than its narrower siblings, but also the lowest of any tyre on test. We're only talking a few watts but it all counts, right? Anyway, the take-home message from that is that big doesn't necessarily mean slow. It certainly doesn't here. I didn't notice the extra bulk of the tyre when accelerating, and once up to speed they do have a very supple feel and excellent all-round grip. Continental's Black Chilli rubber is predictable in both the wet and dry. I've used these tyres for everything up to a 300km cross-country day trip and I've never found them to be wanting for grip.
As for comfort: well, I'd only normally put 95psi in a 25mm tyre so I immediately knocked these down to 85psi and they give excellent cushioning at that kind of pressure without sacrificing any speed that I could discern. If you want them even plusher then they're fine at 75psi too; once you get down to 60psi you're starting to risk a pinch flat and on narrower race rims they start to lose their composure a bit in the turns. They're best on a wider rim, 23mm or more, which flattens out the profile a touch and means you can run them softer because they're not quite as tall. A wider rim will make the whole package more aerodynamic as well, as the tyre won't bulge out from the rim as much.
Continental's Vectran breaker does a pretty good job of resisting any unwelcome intrusions. I had one puncture during about 800km of testing, so they're not infallible, but for race-spec rubber they're pretty hardy. Adding extra protection adds weight and reduces the suppleness of the carcass. They wouldn't be your first choice for winter conditions but they're a good all-rounder for summer and autumn conditions. There are a few cuts in the tread now, but nothing serious.
Assuming you can live with the 70g weight penalty over 25mm tyres, and you can squeeze them into your frame, there aren't really any downsides. These are big tyres that feel like race tyres, only more comfortable. And comfort is a performance advantage, don't forget.
Excellent big-chambered race tyre with a fast and smooth feel
road.cc test report
Make and model: Continental Grandprix 4000s II 28mm
Size tested: black 28mm
Tell us how the product performed overall when used for its designed purpose
Very well, a fast and smooth tyre.
Tell us what you particularly liked about the product
Comfortable, fast, puncture protection is decent.
Tell us what you particularly disliked about the product
A bit tall on narrow race rims.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
The legendary GP4000S tyre has been updated to include a broader range of sizes which now also benefit from the latest cutting edge rubber compounding available in the bicycle tyre industry - BLACKCHILI. This technology is constantly evolving and what better way to introduce our latest version than to update the tyre that launched the compound back in 2007. Featuring lower rolling resistance, higher mileage and maximum wet weather grip, riders who already use the GP4000S will continue in the knowledge that they are riding the best all-round performance road bike tyres that money can buy. Newbies to the Continental brand will gain from all the factors that make countless professional riders insist on riding Continental tyres. The coloured versions of the tyre now also feature a BlackChili compound with the colour coding moved to the sidewall. The wide range of available colours are Pantone matched to the Fizik saddle & bar tape range for those riders who love to colour coordinate their machines. The new sizes of 23-571, 20-622 and 28-622 cover a broader range of customer requirements, with 28mm now a genuine race tyre size thanks to the availability of the new GP4000 S II 700x28. This size is in fact, the lowest rolling of all the sizes available. Don't belie ve us? Read the independent test report from TOUR magazine below... Vectran™ breaker for unsurpassed puncture protection
About the tester
Age: 42 Height: 189cm Weight: 91kg
I usually ride: whatever I'm testing... My best bike is: Kinesis Tripster ATR
I've been riding for: Over 20 years I ride: Every day I would class myself as: Experienced
I regularly do the following types of riding: road racing, commuting, club rides, sportives, general fitness riding, fixed/singlespeed, mtb, Mountain Bike Bog Snorkelling, track
Dave is a founding father of road.cc and responsible for kicking the server when it breaks. In a previous life he was a graphic designer but he's also a three-time Mountain Bike Bog Snorkelling world champion, and remains unbeaten through the bog. Dave rides all sorts of bikes but tends to prefer metal ones. He's getting old is why.