Generally, worn tires roll faster, but probably not so much as to mitigate the increased risk of flatting. There are faster options, but GP4000s broken in for 50 miles are still a top shelf selection. Especially when you consider the aero benefit they provide on many race wheels.... but of course then you have to consider that that aero benefit will diminish pretty quickly as the tires are worn in and lose their original hump shape.

This seems plausible but I have never seen it evaluated. Do you know of wind tunnel data on this? Probably would only apply to the front tire since the rear leading edge would be shielded except on beam bikes. Fronts seem to me to wear in a way that preserves their shape whereas rears of course get a flat area.
Anyway, its a really interesting thought and I'll love see data.
Cheers,
Jim

This was a Tom A. hypothesis IIRC. I'll dig around on his site one of these days. It was fairly well established with data, again IIRC.

Some good data here: https://silca.cc/...ure-and-aerodynamics

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Perfect, thank you.
Still seems odd to me. That is a rear tire wear pattern. The leading edge will generally be shrouded. Would love to see a worn front tire. I suppose it might influence the wake on the trailing the rear tire's trailing edge.
Cheers,
Jim

So is a case of new tires are better aerodynamically, but broken in tires have less rolling resistance? Is there a comparison of these points? Is it met neutral?

From data collected by Al Morisson on rollers:

When combining rolling resistance and drag, I leave you decide if it is neutral or not, according yaw.

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The one tire I've seen that seems to visually show front tire wear is the GP4000S with higher miles. I've always assumed it is the extra tread depth and elongated tire shape. Plus they do tend to allow for higher miles. The other factor that Josh Porter and TG have brought up previously is that the used tires tend to expand in size over time. This may contribute quite a bit to the front tire aero reduction. In addition to the Al Morrison data posted above, a good example is the Conti Supersonic testing in TomA's Crr spreadsheet. Crr on a well worn SS (600-1000 miles), yielded a watt or two over a newer SS. While tire width difference was 22.8 new to 23.6 used. This is testing on the newer versions of the old SS.

For OP, one approach is to rotate your front GP4k to the rear and run a new front tire. This can yield more mileage out of each tire.

Thanks for sharing, great info.