Taller, narrower tyres for your next car?

BMW i3 takes advantage of taller, narrower tyres
Credit: BMW/The Telegraph

Recently, a few trends in cars have been:
• wider tyres
• larger diameter wheels
• improved fuel efficiency

All other things being equal, & within reasonable limits, for each centimetre increase in tyre diameter, rolling resistance reduces by 1%. This happens because the tyre suffers less deformity in the contact patch (the part of the tyre in contact with the road) & sidewalls, as it rolls.

Increased tyre diameter is consistent with the other current trend toward improved fuel efficiency.

Odd man out in this equation is wider tyres, which increase rolling resistance & aerodynamic drag. Taken together, these two factors reduce fuel efficiency of a vehicle.

Wet weather performance of a tyre is substantially determined by it’s ability to displace water. A tyre which displaces more water, effectively drives on a drier road. As the tread rolls into contact with the road, it begins to displace water sideways, to be expelled from the sides of the contact patch.

A narrow tyre has a relatively long, narrow, contact patch. On a wet road, water has a shorter distance to travel to be expelled at the sides of the tyre. A long contact patch has more patch-length in which to displace water. The rear edge of a long, narrow contact patch has more contact patch ahead of it to dry the road, & so has more grip.

Wide tyres have the reverse situation: a short, wide contact patch, which displaces less water.

Taller, narrower tyres offer a range of advantages, but raise a question about grip in dry conditions. At least in part, this will be compensated for by an increase in the length of the contact patch in the larger diameter tyre.

http://www.drive.com.au/motor-news/skinny-tyres-the-new-fashion-20141004-10qelg.html?utm_source=outbrain&utm_medium=cpc&utm_campaign=outbrain_amplify / tyre design larger diameter skinnier tyres bigger wider narrow narrower tyres larger large diameter reduce fuel use carbon dioxide CO2 emissions Damien Hallez Michelin head technical communications improve energy efficiency use less fuel internal resistance slows rolls reduce rolling friction improved improve improves aerodynamics reduces rolling resistance increasing diameter rolling resistance security aspects wet dry grip less deformation tyre compact patch touching road at any time less deformation side walls gain in energy efficiency narrow narrower skinny skinnier tyres dissipating water aquaplaning aquaplane more efficient efficient Renault design boss Laurens van den Acker larger diameter skinnier more energy efficient tyres designers big wheel engineers aerodynamicists narrow wheels less resistance braking performance aesthetics technology tyre manufacturers BMW production car i3 electric vehicle EV performance luxury cars concept cars Citroen Cactus 18 inch tyres /