spacesaver steel wheels - Page 4 - Fuel Economy, Hypermiling, EcoModding News and Forum

Christ · 04-19-2011, 07:46 PM

Quote:

Originally Posted by rmay635703

In the real world you may find that its basically a wash.

I typically run much higher load tires for the harder tread compounds, higher presses, and longer life when used on lighter applications. Traction is reduced, but that's a moot point for most of us, imo.

Frank Lee · 04-19-2011, 07:51 PM

Quote:

Originally Posted by Christ

I've had that thought about valve springs, as well... But I've been "corrected".. Not that I believe it.

Well that is the difference between steel and rubber; deform spring steel and when it returns to original shape it does it with little internal "friction" or energy loss, while rubber behaves quite the opposite.

Christ · 04-19-2011, 07:57 PM

But the spring is pushing against a rotating object, which, at speed, is probably rotating away from the spring close to the same speed that the steel spring can return to original form, not to mention the lack of force application, since the force of the spring is pushing back against the can at close to the cams center line, or with rocker type valve trains, pushing against a lever which rides near the center line of the cam. Applying linear force to a rotating object without leverage in the direction of rotation? Sore, that's a winner...

Frank Lee · 04-19-2011, 07:59 PM

Non dimensional, non linear concept here, only concerning material properties...

if we had rubber valve springs and steel tires I would expect them to behave the opposite of what they do now as far as energy losses.

Christ · 04-19-2011, 08:01 PM

Material properties, I agree.

gocamgo1 · 04-20-2011, 12:16 AM

Wow,I never thought this thread would go on this livley and this long. I may end up getting the altima wheel and a 145 tire combo. I weighed the spacesaver for the civic and it's a bit heavy at 26 lbs. with the tire and it's just butt ugly. I suspect honda did this to shame you in to not running them any longer than necessary! The altima wheel is descent looking for a steelie and the suave honda wheel covers (HAHAHA) may even fit them.

zonker · 04-20-2011, 12:55 AM

Quote:

Originally Posted by gocamgo1

Wow,I never thought this thread would go on this livley and this long. I may end up getting the altima wheel and a 145 tire combo. I weighed the spacesaver for the civic and it's a bit heavy at 26 lbs. with the tire and it's just butt ugly. I suspect honda did this to shame you in to not running them any longer than necessary! The altima wheel is descent looking for a steelie and the suave honda wheel covers (HAHAHA) may even fit them.

The RX7 spare wheel and tire (4x114.3 bolt pattern, with a 40mm offset) is 21 lbs

CapriRacer · 04-20-2011, 08:16 AM

Quote:

Originally Posted by justjohn

Hahah. I read it. I just don't get the part about load capacity going up by a greater percentage than tread and how that translates to lower RR.

The load carrying capacity of a tire is directly tied to the internal volume of the tire.

If we take the example of a tire with a 100% aspect ratio (because the cross section is a circle and that's easier to visualize), then the volume of the torus (the shape of a tire) is a function of its cross sectional area.

The area of a circle is pi* r-squared. If the radius is increased one unit, the the area is pi* (r+1) squared = pi* (r+1)*(r+1) = pi*(r squared + 2r +1).

It's that 2r term causes the area to go up faster than the increase in r.

Tires are oval in cross section, but that only makes the formula more complex. It doesn't change the fact that the width is squared to get the volume.

justjohn · 04-20-2011, 11:11 AM

Well I think the volume formula would actually have a pi^3 in it, but okay I get that part then.

What I still don't completely get is how increased load capacity... wait a second. Unless you're saying that this means there is actually less tire in contact with the road. Which seems counter-intuitive to me, but would definitely give a reason for decreased RR.