recommendations for tubeless ready 28mm road tyres ideally for 3/4 season riding

Hutchinson Sector 28s are a good 4 seasons tubeless tyre. If you can't quite fit the Schwalbe S-One/G-One speed tyres then the Sectors are what I would recommend.

How have you found going tubeless on the Synapse?

I have ordered a set of Hunt AeroDisc wheels (not the carbon ones) to replace the Mavic's that came with them, and toying with the idea of going tubeless.

Schwalbe S-One now called G-one.  30mm has the same profile as the Pro 28mm. 

Get either one.  Both excellent.  Currently I am using the S-one at 50 PSI.  

One of my top three upgrades together with Di2 and Disc Brakes.

If you can't fit the Schwalbe S-One tyres (G-One speed) then the Hutchinson Sectors would be a good shout. Tubeless, robust, 28mm, reasonably fast and comfortable. Not as fast as the s-ones, but still very good and designed for rough surfaces

I have the S-ones and at 30mm I would very much doubt they would come up larger than the 28mm Contis. The Schwable tubeless are on the small side compared to the equivalent Conti GP4000s.

The S-ones ride smooth and not at all like an off-road tyre but they do feel better on light mud than the 25mm Pro-ones I use on another bike. If you're after a pure road tyre then the a 25/28 Pro-one tubeless would certainly be worth considering. I was worried about reports of high wear but I've not found that to be the case, although they are softer than the GP4000s for sure.

Both the S-one and Pro-one were very staightforward to fit and inflate. I did use plastic levers for both (onto tubeless specific rims) but just a normal trackpump with a little soapy water got them pumping right up.

schwalbe s-one ( I have them, they are great) which may be now called G-One Speed or something odd (not sure the same needed changed honestly...).  Fast and tubeless and 4 seasons.

schwalbe pro-one is also good too, though more spring-summer-autumn I would suggest.  Though I have not used them.

specialized turbo is good but wears quickly, and gets some deep cuts even though it seems not to puncture, I even did a whole CX route on them and the grip is astonishing for such so not off road tyre. It does pick up clay type mud though, but in the sloppy stuff and rocks and roots I had to take my hat off to the specialized turbo.  The roubaix wears better and is tougher than even the conti, but only in a 23/25 casing, but is big enough IMO for my winter purposes as is super subtle (180tpi) and run it as low as 60psi at 80+kg. Grip however is limited due to hard centre shoulder, and have even spun on wet roads when standing up, as I have on bonty aw3. Scwalble pro one is other option, but I do not like the look of the tread; its neither a slick nor a tread, no idea how its supposed to work and cannot see any data anywhere to say what the on-off tread is supposed to do.

I know people who are happy with the Bontragers, but they never veer off tarmac and is very much a slick so would keep speed down in full on wet. I have had various hutchison tyres and they are OK, but the sidewalls start cracking way before they should on all the atoms, intensives and fusions I have tried over the last 7 years or so and you can see the tyre loses its compliance in the process. Do not know if its the salt or what but they do not like british roads, maybe ok off -road??.

Sadly there is nothing like the conti gp4000s2 or the amazing tt tyre in tubeless world, and they are the only tyres I can be bothered using a tube with but the specialized are as good as tubeless tyres get IMO for versatility, the Scwalbe pro one offers you the best size options and hopefully the tread works for you.

I do wish Scwalbe would launch the s-one in 28 and 25 and the tubular only TT tyre in tubeless version as it looks like the perfect tyre for triathlon / TT, and an s-one in 25 or 28 would nver be off my other road bikes.

if you cant fit 30mm. Which I cant.

then my LBS has directed me towards Bontrager AW3

http://road.cc/content/review/94811-bontrager-aw3-hard-case-lite-tyres

S-One is very quick and comfortable at the same time. It's not an offroad tyre, it was designed for races with cobbled sections (look up Paris Roubaix) which makes it ideally suited for UK roads (IMO).

It IS 30mm though so you're probably right to be wary of fitting it under your 'guards.

But if you can find a Schwalbe S-One, it's the same tyre as the G-One Speed, older stock and maybe a bit cheaper, you will soon be finding out how expensive tubeless tyres are!

Dave's proposal is good. That tyre is magnificent. Hutchinson Fusion 5 models are apparently great - I think they have a 4season model in its range. Also check for Panaracer tubeless ones...they have couple of models which are also very good.

If you can fit a 30mm Schwalbe G-One Speed in your frame, get them.