Originally Posted by
tFUnK
I don't disagree that weight alone would not explain the difference. The only bikes in my stable that can fit wider tires are my gravel bikes (albeit, they are similar to regular road geometry apart from the slightly longer chainstays), so I'm not comparing the same performance road bike with wide vs skinny tires. But I suppose that is the unanswered question in my mind: how would my nice road bikes ride with slightly wider tires (though several have noted here that they would be just as fast and nice riding even if with a slight weight penalty).
I think it depends on the condition of your local roads. If the roads you ride are super smooth pristine tarmac, then it probably wouldn’t make much difference. But if they are rougher then it could be the best upgrade you could possibly make, both for speed and compliance.
Tyres make a lot more difference to the ride quality than say frame compliance. I currently run tubeless 30 mm Conti GP5000S TR on my main road bike at relatively low pressure (<4.5 bar), which I find ideal for fast century rides on mixed roads. Along with a compliant carbon seat post and bars, the ride quality is excellent and I’m faster than ever on routes I’ve ridden for years. On smoother roads, maybe slightly narrower tyres would be fractionally quicker, but that’s a moot point for me.