Ogsarg

Due to getting a flat every few hundred miles, I decided to go tubeless on my 19 Roubaix. I still had the original Specialized Turbo28C tire in the front and the rear had been changed to a GP5000 28C. I got 30C Schwalbe Pro One tires and mounted them today. My first experience with tubeless and I had some issues but sorted them out without too much trouble.

I have a DIY bike stand that holds the bike upright at the front tire. It was a snug fit with the original tires so I expected i was going to have to modify the stand to use it with the new tires. Much to my surprise, the front slid right in and in fact there is about 3-4mm gap between the tire and the stand. Measuring the width I see the tire is 29mm wide. I never measured the Specialized tire but it must have been really wide for a 28c.

Well. I'll ride these and see how it goes. Next time around maybe go to a 32.

WhyFi

Many older tires are sized with narrower rims in mind. The current generation Schwalbe tires are made to match their nominal size on 19mm internal width rims, so you'll have to size up/down depending upon your rims.

surak

I've a '19 Roubaix as well, and there was plenty of clearance for larger than nominal 28mm tires like the GP4Kii and Pro4E that measure over 31mm on the OEM DT Swiss rims (21mm internal, I think?). Haven't switched to tubeless of them yet, though I suspect the 32mm GP5K to fit easily.

Pizzaiolo Americano 

I have GP5000TL 32s mounted on my wife's 2020 Roubaix. Plenty of clearance on 25mm internal width rims.

Princess_Allez

I've been wanting to try out 28c tires too, but I keep finding deals on 25; 28 are out of stock everywhere, unless you're willing to pay full retail.