Just bought a CX bike with 35mm road tires that is around 1-2lbs heavier than my road bike with 23mm tires. I set PRs with it every time out so I disagree
. The catch is I did almost nothing but mtn bike last year and am in better shape than I've been. I'd probably set PRs left and right on the road bike as well but I greatly prefer the ride of the CX bike and its soft squishy tires, roads suck here. I'm getting rid of the road bike and when the 35mm tires on the CX bike wear out I probably won't go a whole lot smaller, maybe 32s. I already bought a set of gravel tires but I want to keep the option open to go off road even with my road tires for short bits.