Wheels (Smaller is better)

[The Atomic Ass]

Originally Posted by CapriRacer

What you want is the largest diameter tires that will fit in the body - and the smallest diameter rims (Yes, yes, but "wheels" is sometimes confusing and I want to be clear that I am talking about the metal part, not the rubber part!)

Then a check for load carrying capacity.

My guess is that you'll find out that this results in a 15" diameter rim, and a small 75 series tire - and this will probably also result in much more load carrying capacity than you need.

Just for reference, current practice seems to be to total up the maximum load each tire will be carrying (worst case), then add 15% - then that is the MINIMUM load carrying capacity needed for the tire at the pressure selected.

For load capacity, we'll figure on just north of 2 tons gross. Perhaps as high as 2.5 tons.

As for fitting it into the body, the point of the downsizing exercise is to reduce the space in the body consumed by the tire, reduce the opening in the lower portion of the body, and eliminate any need for a wheel opening in the side of the body. So not really a matter of fitting the tire to the body, but actually of designing the body around a smaller diameter tire.

As for a 15" rim with a 75 series tire, I used to own a final-gen S-10, so I'm familiar with how BLOODY HUGE this combination is. Good god I don't even plan to have my hood that high off the ground!

[The Atomic Ass]

Originally Posted by basjoos

All else being equal, rolling resistance is lower with a larger wheel diameter since the rubber isn't flexing as sharply where it contacts the ground. That's the reason you see large wheel diameters on racing bicycles dispite their greater aero drag.

I was afraid that would be the case.

[Frank Lee]

Finding out how engineering is just a constant series of compromises?

[SVOboy]

You can buy some 9 lb aluminum 4x100 13" wheels from me

[Ryland]

you can get 145/80R10 tires that the Honda N600's use, same tires the old Minis use, you can get 145/70R13 tires that NEV use, that is what I have on my electric car, they are a LRR (low rolling resistance) tire, you can also look on tirerack.com and see what is out there and the load rang of them.
if you go to small the you limit you brake rotor size, so I would stick with 13" or so.

[blueflame]

Originally Posted by The Atomic Ass

I've been thinking on my electric car design again...

(And for those that do not worship the ground I walk on and thus have no idea what I'm talking about, (heathens), my electric car design is a ground-up build, with 4-wheel hub-motor drive, 4-wheel steering, 50KWh battery capacity, seating capacity of 6 AND a huge trunk, all wrapped in an aerodynamic shell with a planned curb weight of ~2,500 lbs. Yes, it is still a twinkle in my eye, bite me).

Anyway, I got to thinking about wheels. Looks will be a non-concern on this vehicle, as the wheels and tires will be hidden inside of the bodywork. So I got to thinking about using the smallest wheels possible, for weight reduction as well as altering the ratio on the direct-drive hub motors.

Now my design calls for high-performance, so occasionally I'll be launching off at 150KW, and reaching speeds well into the triple-digits.

How small can I go? I'm thinking there are still some viable tire options at 13", but I'm thinking of going even smaller. How about 10? 8? Is anything made other than low-speed trailer tires at these sizes?

At 100mph high speeds with 2500lbs you will need serious rubber just for safety, let alone required high performance. Minimum would be 185 13" 's I'd guess. How far will a 50kwh capacity battery travel with these power and weight demands?

[The Atomic Ass]

Originally Posted by Ryland

if you go to small the you limit you brake rotor size, so I would stick with 13" or so.

I won't have brake rotors, so that's not an issue. I'll be downsizing my hub motors, but I don't believe that to be an issue either, as my estimated 65mph cruise will be 10KW. Acceleration can be dealt with through water cooling.

[The Atomic Ass]

Originally Posted by blueflame

At 100mph high speeds with 2500lbs you will need serious rubber just for safety, let alone required high performance. Minimum would be 185 13" 's I'd guess. How far will a 50kwh capacity battery travel with these power and weight demands?

I estimate a 100% DOD range at 65mph of 250-300 miles, level ground. That of course is just an estimate, and my goal is a minimum of 150 real-world miles.

Of course, hypermiling techniques will be employed.

[The Atomic Ass]

Originally Posted by Frank Lee

Finding out how engineering is just a constant series of compromises?

Compromise? That sir, is a vulgar profanity in my vocabulary.

[Frank Lee]

Good luck with that!