4 donut spares for hyper miling

[Zenehet]

Has anyone tried running, say Nissan Altima donut spares in a set of 4 on their leaf to try and increased efficiency?

I would think with the higher PSI on the tire (60) and the smaller contact patch (135/90/16) that it would be like running on train wheels with very low rolling resistance? Any thoughts on if it would improve range? Has anyone put it to the test?

Thanks,

 

[RonDawg]

You'll have low rolling resistance alright. You'll also see much poorer handling, braking, and acceleration. Also, most donut spares are not rated for speeds above 50 MPH, so if you repeatedly drive at freeway speeds you are looking at a rather high risk of a blowout at those speeds. You can expect to replace the tires very frequently.

I don't know about you, but when I see a car on the freeway driving on a donut spare, especially if it looks like it's been on that spare for a long time, I stay FAR away from it. Seeing one with 4 donut spares driving at freeway speeds would warrant me calling the Highway Patrol to report an unsafe vehicle.

 

[TomT]

Donuts are also not supposed to be used for more than 50 miles and 50 MPH. Using them as regular tires is an idea fraught with danger and disaster!

 

[DaveInAvl]

Being smaller in diameter, the donut spares would also raise the engine RPM, which might put the motor in a more-efficient part of its operating characteristics at some speeds. But for anything other than testing in a controlled setting, I'd stay far away from the notion.

I've been driving for 50 years, and one of the spookiest things I've seen was several years ago - an old Chevette running donut spares on both front wheels, and no front damping at all. The front end was bounding up and down like anything. On an Interstate. The young man driving it looked highly entertained, but like the locally-popular bumper sticker says this is "Asheville - Where Normal Is Weird" :mrgreen:

 

[dhanson865]

https://www.youtube.com/watch?v=HPh90yNX-mY

Mercedes 480bhp C63 AMG coupe, with optional power upgrade, already has more than enough power to trouble its rear tyres. What happens when you remove some of that grip?

Stock tires are 235mm 18" front, 255mm 18" rear.

Test tires are 125mm front and rear.

Not safe for general use but you can see the effects quite clearly.

Now if we could just get tire manufacturers to make a 25.5" diameter 15" or 16" tire for the Leaf with a corresponding 155mm or 165mm width we'd have something hypermiling friendly that is much safer than a space saver spare.

 

[minispeed]

It's been done over at ecomodder on 13s
[/http://ecomodder.com/forum/showth...diameter but that will also lower the car 1".

 

[MattInAkron]

(Former tire engineer here)

Most temporary spare tires are bias-ply tires, which means they will have considerably more rolling resistance than a conventional radial tire. This is caused because there is a great deal more flexing of the tire carcass as it rolls. This flexing generates heat, wastes energy, and is why they're only rated for 50mph.

As the test data posted above shows...just because a tire is small doesn't make it LRR.