driving on 4 narrow spare tires (or similar) to reduce rolling resistance

[mwebb]

yes

Originally Posted by mans

mwebb, does that still apply if my skinny tire has 50 psi?

[mans]

Originally Posted by mcrews

Since the skinny tires have a SMALLER OD, then that is a mute point.

He is reducing his ability to react in an emergency to absolutely ZERO.

mcrews, in all respect why do you write that the skinny tires have a smaller od?

have you seen the links I provided?
this is a quite negative-sounding post.
I said earlier my stock tire is 195/60/R15 with a od of 23.75".

I provided a link where there is a choice of a 125mm tire and a 135mm.
the 125 is 23.00 od and the 135 is 23.57" od. the difference in od between the fat tire and the skinny tire is tiny.

you do raise a good point about stopping in an emergency. that seems to be a very valid point in my opinion, however we must explore how true it is, since many vehicles in europe have tires that are skinny like "euromodder" says above.

[mwebb]

mcrews is correctly telling you that there is nothing to be gained from the path you are on in terms of improving fuel economy and
you will be decreasing the stopping and handling capabilities of your car if you continue .

do you suppose that
with the CAFE values that are being imposed by our government that any current auto manufacturer that sells cars in the USA would install tires that hurt the CAFE # of the car ?
do you see any current cars with tiddley wink wheels / tires offered for sale today ?
no

get some Michelin Harmony s in 196 60 15 .

[DKaz]

One thing you can do is downsize the wheel to 14" if your brakes allow it, go with a lightweight wheel at that, and possibly go to say a low rolling resistance 175/65R14 tire which is common on an older Corolla. Just make sure the tire meets your car's speed and weight rating.

I highly advise against going with the old VW tires for all the reasons already mentioned.

[Ryland]

I'm not finding any 14" tires that are close to the right size that are also LRR, there are however a handful of 15" 175/65R15 tires that are.

Tire Search Results

And they are only 1/4" taller then stock on your car, so a really close fit, slightly narrower and LRR, I would call that a good match.

[abogart]

Originally Posted by mans

Hi guys,
while driving on the street I see the car in front of me with a doughnut on his rear wheel.
I can't help but notice how narrow the doughnut spare tire is, it looks like 1/2 the width of the normal tire.
At the minimized ground contact + the higher pressure of doughnut tires I thought to myself there should be way less rolling resistance if you were driving on 4 of these... tho you'd need to find ones that have the same outside diameter of your full size tires so you don't decrease your engine rev's.

I had the same thought when I got a flat and had to put the doughnut on my rear wheel. I guess great ecomodders think alike!

However, I also noticed that having that one spare tire on resulted in some slipping around turns and I think the anti-lock even kicked in once during braking, all on dry ground. And that was only driving 1 city block at less than 30mph to the tire store.

It sounds like a good idea, but I don't think that it's worth compromising traction and safety when the gains probably aren't going to be much more than you would get with a good set of LRR tires of the same size as you have now. Remember that the doughnuts are only rated for 50mph MAX speed.

My opinion is to spend that $400-some dollars on a good set of LRR tires. That way you still have traction and braking when you need it AND decreased rolling resistance. My guess is that doughnuts probably wouldn't get you much better economy that LRR tires.

[oil pan 4]

$400 for tires that handle like garbage, are speed limited to 50-55mph and have their load rating nearly maxed out by an empty vehicle really sounds like a waste of $$$.

Tire weight isn't as much of a factor as every one claims it is.
Taller tires with less rotations per mile (lower cruise RPM) seems to be where the real savings are found.
The only time taller heavier tires might hurt you is if your vehicle is so under powered it has trouble turning the size factory tires and maintaining or picking up speed.

[mans]

Originally Posted by Ryland

I'm not finding any 14" tires that are close to the right size that are also LRR, there are however a handful of 15" 175/65R15 tires that are.

Tire Search Results

And they are only 1/4" taller then stock on your car, so a really close fit, slightly narrower and LRR, I would call that a good match.

is it ok to mount 175 tires on rims that were made for 195's?

[Ryland]

Originally Posted by mans

is it ok to mount 175 tires on rims that were made for 195's?

If you are looking at the Tire Rack web page and are looking at an exact tire, click on the "Specs" link and it will give the range of rims that they will work on, 5-6" rims for those.
They will also give rotations per mile, tire weight, tread wear, traction and other useful info.

[Frank Lee]

Originally Posted by oil pan 4

Tire weight isn't as much of a factor as every one claims it is.
Taller tires with less rotations per mile (lower cruise RPM) seems to be where the real savings are found.
The only time taller heavier tires might hurt you is if your vehicle is so under powered it has trouble turning the size factory tires and maintaining or picking up speed.

Big Dave and I and countless others have found that bigger heavier tires on pickups don't lead to fe gains.

I think that's especially true on trucks with overdrive. Some of the real old school stuff with slushboxes and no overdrive could maybe benefit though. I think my a/t Tempos benefitted from going up in diameter ONE size.