The older version, not the Evo, particularly a small frame.

Thinking of buying one secondhand, local back roads are pretty appalling, a roadie mate says 28c minimum through the winter, & maybe 25c in summer, 23c is risky.

Google foo seems to have differing opinions as to whether you can squeeze a 28c in (front AND rear).

Ta

Nobody else biting so:

Large frame (although may not make any difference as would not think rear triangle would be any different due to physical size required for wheels) 25c continentals (measured at 26mm fitted) 4mm clearance each side at tightest point. All other points slightly more clearance. Front forks about 5mm each side.

I realise not answering question but gives a real world example of clearances.

I have the small version, there is no chance of fitting 28mm in
I fitted 25 once and they rubbed under power
I’ve gone back to 23 now

I have a large with 25mm Conti 4000s which fit fine once the wheel is in. However it is really difficult to get the rear wheel in/out so IMO a 28 would be just too big to get the wheel back in. Tyre jams in the frame between the chainstays and bottom bracket before the axle is near the dropouts – requires a firm thump to fit! 28mm would also be very very tight with the chainstays if you did manage to get the wheel in.

requires a firm thump to fit!

Or you could just pump the tyre up after fitting the wheel. Far more mechanically sympathetic.

28s don’t fit, simple as that. 25s on mine (when I had it) had about 1/2mm clearance from top of the tyre to the bottom of the fork crown. Grit from the road ground the crown away, so I’d say 25s are pushing it as well.

These days tyre width standards are completely up the swanny, when you have 25mm Conti GP4000S IIs for example measuring ~27mm in the real world and the 28mm variant measuring ~31.5mm. GP5000s are much closer to spec, ~26/29mm respectively.

28s would be tight under the rear brake on any frame. Ive just fit some Schwalbe One tubeless on Stans alpha 340 rims to my cannondale and the flashing down the center catches on the brake and those are only (allegedly) 25mm. Conversely hutchinson 25mm tubeless fit under mud guard brackets in the same frame.

Victim of Conti sizing here – bike came built with 28mm 4 Seasons and mudguards fitted, couple of years on I bought a new pair of 28mm 4 Seasons and they were nowhere near fitting

Not a chance.

You might squeeze the right tyre/wheel combo in but its going to rub in the even slightly gritty conditions.

And its pretty brutal on 24c tyres.

Large here with 25C tyres (Conti GP4000?) – no real issues, but 28c tyres are a non-starter – tried a pair off a pal and were just too big.

I’ll just add that I use 25c Conti GP4000s on my nice roady on (pretty much) the same roads you’re looking to ride and I’ve not had an issue. I shouldn’t worry about it too much.

I really rate the pro carbon as a spring summer autumn ride but I realised pretty early on after purchase it was unsuitable as a winter machine. I have always ran 25s no problem (Conti grand sport/Vittoria Corsa G+) however once u had even the slightest layer of grit/debris which Is inevitable on wet and dirty roads there is an issue with clearance and that’s on 25s. Basically I would say it is only great for good conditions, as you say if desperate for use in winter to drop to a thinner say 23 would give that but more clearance but do you really want thinner tyres at the time of year, for me definitely not so I would not recommend as a winter option. Ashame as they are great, comfortable bikes but the clearance is it’s achilles heel I’m afraid.

If I was buying a bike specifically as a winter bike, then yes 28mm is a nice to have, but I’d also want full length propper mudguards, which no race bike will take as you need taller brake callipers to clear them.

It isn’t the be all and end all, and TBH most of the roads aren’t any better in the summer. The difference between my bike in the winter and summer is a set of SKS raceblade longs which are an OK compromise and fit over narrower 25mm tires (i.e. that actually measure 25mm). Summer tyres were either 23 (that came up big) or just lighter 25mm tyres. The recently fitted ‘big’ Schwalbe one 25c weren’t intentional, I was happy with the true-ish to size hutchinsons.

If you’re on a budget, look for anything with long drop rim brakes (easy to spot, they wont’t be 105/ultegra, they’ll be labeled R-550 or similar) , they should allow proper full length mudguards to fit under the caliper and still get 28mm of clearance. Disk brakes obviously solve this problem in a much neater way, but a disk braked bike with 28mm+ clearance is going to be quite a bit more £££, although you might get lucky if you can think of/find something unfashionable on ebay (Eastway frames often go cheap despite getting good reviews for example).

If you just want “a road bike” for clubruns etc I’d get the planet X, it’s a good enough road bike, and should fit (actual) 25mm tyres and raceblade-longs as a good-enough compromise. Obviously “real” roadies will have n+1 road bikes for every eventuality. And obviously MTBers like to pretend they’re not real roadies by trying to differentiate themselves with poorly thought out, or over thinking component choices. It’s “reliability trial” time of year, which magically means everyone’s summer bike and 23mm tyres comes out and the mudguards are off for one weekend of the winter and somehow no one dies.