Yup, there's a reason why the pros tend to ride the widest tyres that will clear their frames, and why the 19-20mm tyres of old are now seen as indoor only tyres (they still work on smooth wood boards @200psi). Just a few years ago bike frames were only designed to clear 23mm tyres. Pretty much all frames are designed for 25mm today and there are a lot of 28mm frames out there.
Most Pro teams are now running 25mm, the extra 2mm of width (over the old school 23mm's) had a massive impact on RR, jumping up another 3mm doesn't have as much impact on RR (and at an ever greater aero and weight penalty).
For now the second
widest tyre is seen as ideal for the Pro Peleton.
Quote:
|
Originally Posted by Continental Tyres
Remember that wide tyres of the same type and with same air pressure run better and more lightly than narrow tyres.
|
That's translated from German, but I think what they're saying is clear.
https://roadcyclinguk.com/gear/using...ad-bike.html/3
etc, etc, etc. Use a search engine, all the data says wider tyres= lower RR. Bicycle data is easier to find than car data, as cyclists are more interested in saving a few watts than car enthusiasts.
BUT
That's not to be confused with 'better' economy. I've personally switched from Fiat's OE 195's to OE 175's and their lower weight & better aero had a massive benefit, even if the RR was unlikely to be any better. The switch also meant going from heavy open faced alloys to light weight steelies with hup caps. That's a lot of variables. RR got worse, but everything else got better, making it easy to assume that everything got better. Traction also got worse so again it's easy to think RR got better.
On older cars, say 90's back, the bodies widest point was at the height of the plastic rub strips (roughly the top of the guards). On my Proton with 205's, the top of the tyre is easily within the guard, however, just a few inches lower the tread is already exposed to the airflow. Newer cars do a much better job at enveloping the tyre, so there's potentially less aero gain from going to a narrow tyre.
Would I fit wider tyres to improve economy? No. I doubt the RR gains would ever offset the other losses.