I’ve been advised brevity is the watchword on this forum. This is like prison for me but I will try. I noticed my newly-bought gen 3 Prius here in 2023-land, of the 2010 variety that you must never, ever buy, seemed to limit my EV-only use a bit tightly. IE it cut me off, long before in my estimation, I hit 31mph. Then I got into tyre and wheel sizes, because I really hate the huge things that are Pirelli whatevers the car’s booted with, and I began to look at what I call ‘comfort wheels’ or 15” shod with 195 65 R15, as like the ‘standard’ against which I will judge others ie for rolling radius. The wide, huge but low profile Pirellis are ‘not recommended’ on ‘Alloy wheels’ comparison calculator for tire sizes. They come out 1.4% different, ie smaller diameter. This explains why the car seems faster than I expected maybe. EDIT I mean, accelerates more rapidly - QUICKER as Starsky used to say. So, am I correct in thinking, that in fact if you wanted to do a better EV-only top speed, that the ‘taller’ gearing larger rolling radius/diameter tires like the tall, skinny 195 65 R15 give, is higher at maybe the ‘true’ 31mph? It’s my theory that this is the case. But I have a ramp up to my drive, and the electric motor really doesn’t like it as it is, so I wouldn’t want to go ‘taller’ gearing by using bigger-diameter setups than certainly the 195 65 R15 has. I suspect it might have saved my bacon though - while fiddling with the controls in wonderment, I shot through a speed trap higher by a margin than the 30mph allowed (36/37 is the trigger apparently, and that’s high enough to lose your licence in the UK as it exceeds 20%). So this also makes me think, it’s reading probably added to the usual manufacturer speed-inflation (‘needle-thickness’ as-was), allowed me about 4mph of latitude in total. I have lived here 25 years and NEVER sped in that section, but one guy got caught twice in an hour, and wasn’t happy. Anyway, any experience out there of EV-only speed-limiting, seeming to be elevated or lower, affected by tyre size? Or is it my imagination.
The 1.4% difference in tire size won't have much effect. Playing with "EV-only top speed" isn't good for either the battery or overall fuel consumption, assuming we're talking about a non-plug-in Prius.
That middle number of 65 is the tire aspect ratio or as you say the "tall" measurement part of the tire... In my Gen2 Prius with Gen 3 wheels I bought 60 instead of 65 because they had a big discount on them and the tires are for my project Prius where I try out these kind of things. While these were lower profile tires by only the tinniest bit, the difference was hugely beneficial on back road twisty turns... Felt way more solid like a sports car rather than usual Prius handling that feels more like driving a top heavy couch that makes me drive slower than the person behind me would prefer. The drawback of course is the speedometer said I was going 1 or 2 mph faster than I was going at freeway speeds and my MPG dropped to upper 40's instead of lower 50's. You can read more about our discussion of it all here: Alternative Wheel and Tire Sizes | PriusChat
