Efficiency gain from 21" to 19" w Michelin Energy

[JimmyB]

At the end of June, after destroying two 21" tires on a pothole, I switched to 19" Slipstreams and Michelin Energy tires. I've now put nearly 1,000 road trip miles on them and had a feeling the new combination was proving considerably more efficient, but I didn't have a sense of how much. So I filtered my journey data on Grafana to give me all journeys over 25 miles and 50mph average speed, and took a look at the consumption figures.

According to my math, my average energy use has gone from from 360.60Wh/mi with the 21" Turbines and whatever Hankook tires came from the previous owner, to 303.49Wh/mi with the new combination - an improvement of 15.84%. Plus the new setup is considerably quieter and more comfortable.

This seems like a significant number, to the extent that I'm questioning my own calculations. But real world experience backs it up - I drove from DC to Philly yesterday, 132.8 miles at highway speeds (AP1 set to 75 but we did hit some traffic), and my battery went from 98% to 49%.

Anyway. Might be interesting data for someone contemplating a similar switch. I'm not a statistician, and while I was good at math in high school it was a while ago ... so if anyone wants to check my work, here's a google sheet.

Cheers

JB

 

[Dave EV]

This seems like a significant number, to the extent that I'm questioning my own calculations. But real world experience backs it up - I drove from DC to Philly yesterday, 132.8 miles at highway speeds (AP1 set to 75 but we did hit some traffic), and my battery went from 98% to 49%.

Absolutely believable - you went from huge wheels and sticky tires to smaller wheels and high efficiency tires. Most of the gain on freeway is from the wheels, but I've seen people report 5-10% just from high efficiency tires alone, so the combo seems realistic.

As good as the slipstreams are, I wonder if the new Tempest wheels are even more slippery...

 

[JimmyB]

As good as the slipstreams are, I wonder if the new Tempest wheels are even more slippery...

I’m sure they are, with the covers on. I was initially looking at Rotiform RSEs with the Aerodisc covers for long trips, but I got a good deal on the Slipstreams. I wonder how much more efficient the Aerodiscs would be?