Bike tire advice for Clydesdale

I'm a big clyde, 5'11'' 274lbs and I ride a 700 X 23 Continental Grand Prix 4000s and they ride awesome.  Really smooth and just fine for us big fellas.

It may be just my experience, but I don't buy Continental tires any more.  I had them for about a season and a half.  They would ALWAYS get flats, and worse, a lot of sidewall cuts.  Granted, I didn't have the best version.  I used to think it was the roads causing the problem until I got some Vittoria Rubino Pro Slicks and the incidents of flats went WAY down.  Still get the rare puncture due to glass or wire, but no more cuts...

I personally look for tires I can run at at 120 psi, 700x23, and max them out.  I am about 235 on a good day.

I don't care for Conti's either. Everyone has their own opinion though. I like Michelin tires FWIW. I don't think your weight is a factor. Best thing you can do is keep them inflated properly. I keep mine pretty tight and luckily I never get a flat unless I pick up debris (screw, little piece of metal, etc.).

While I'm not as big as most of you guys here, I wanted to chime in on this topic.  I too, am not a fan of Conti tires.  Could have just been my bad luck, but I put on a brand new pair of Conti GP 4000S tires on my bike last fall...the very next day at 30 miles into a ride, I took a direct hit into my front sidewall that left a gapping hole in that tire.  I was lucky to make it back home (thanks to a dollar bill!!)...but was not pleased throwing out an expensive brand new tire with only 30 miles on it.  I immediately put on my OLD and WORN Vittoria Rubino Pro Slick's (which had 4,500 miles on them!) and didn't have a single problem for the rest of the riding season.  I have since put on a new set of Vittoria Diamante Pro's and couldn't be happier.  So far, I have been extremely impressed with the quality of Vittoria tires.  

I am love/hate with conti.. I think they feel the best.. and are fast.. but they wear quick and cut up quickly.

I am 300lb.. which would be a factor. my favourite set of tyres I have ever had were the attack/force combo. The attack (front tyre) is 22, the force is 25. The bike felt amazing with these tyres. The force did not last long before it starting flatting every second ride.. the attack lasted a long time, but eventually failed on the sidewall. 

I must ride through barbed wire roads cause my Vittoria Rubino Pros get cut like crazy. Still working on the front tire of the first pair close to 2000 miles - the rear died around 1700 miles mostly due to trainer wear (before I got a dedicated trainer tire). They are a pretty comfortable and fast ride which is why i'm sticking with them for racing/training - good value too.

Conti Gatorskins and Pasela tourguards on the commuter though - they are both bombproof.

I along ride the Conti 4000s its a good blend of performance and duribility and at a decent price. I have never flatted them. Of course this means I will flat then next time I ride but oh well.

To the OP...no, you won't have any problem going to the smaller wheels.