If two snow tires, where on 4WD Expedition?

Someone kindly donated three F-150 wheels for our medical transport SUV. (He damaged his fourth wheel and replaced all with custom wheels.)

(The SUV takes blood and components, etc. to hospitals on highways and interstates closed due to snow and blizzards.)


Three 17-inch wheels (F-150)

One 17-inch spare (Expedition)

Four 18-inch M&S-tired wheels on the vehicle.

If we can obtain two very aggressive snow tires, is it best to place them on the front wheels? (As with the 17-inch spare on the SUV, they would match the diameter of the 18-inch tires.)

(As funds allow, we would mount snow tires on the third F-150 wheel and remove the spare tire and mount a snow tire.)

Thank you for your advice.


If I could only use two, I’d put them on the back to keep from spinning out, but I would MUCH rather find some way to put 4 on it, much more stable.

You always want the tires with the best traction on the REAR axle. If you only have two snows, put them on the rear. Otherwise you’ll spin like a top.

I wouldn’t mount them until I had four, preferably matching, winter tires.

Thank you, both.
My thoughts were front because they would be in drive, pulling, and would be creating a track, when heading straight, in which the M&S tires would follow.

Yes, we hope to obtain enough funds to purchase 4 tires. But until then we may have only two.

If you can not afford four proper winter tires, then you can not afford to be driving. You would not drive without insurance or registration, would you? Think of winter tires as insurance you use every day.


Winter driving without winter tires:

Not a grand idea to put two snow tires and two all-season tires on a vehicle at the same time. I also wouldn’t put different sized wheels on it either, Just because the diameter is the same it doesn’t mean that the tire will behave the same as the 18 inch tires, as the sidewall will be more prone to flexing which could upset the handling of the vehicle.

The obvious solution would be to get four snow tires for the 18 inch wheels or get a matching 17 inch F-150 wheel and get four snow tires for them. Seems to me that it would be foolish to try to pinch pennies on a vehicle that has an important use and that apparently sees triple digit speeds on occasion.

How often do you see emergency vehicles with mismatched wheels and tires?

Make sure you watch these videos all the way through. At about 1:30 or 1:40 each video shows a demonstration of a vehicle with two winter tires and two so-called “all-season” tires. Basically, with only two winter tires, you you are just as well off as if you had no winter tires. In true winter conditions, you might as well be driving 100 MPH downhill on skis.

Here is the same test with FWD vehicles.

I hope seeing is believing.

Must we get another F-150 17-inch (aluminum?) wheel?
Or can we remove the spare tire from the 17-inch steel Expedition spare and mount the fourth snow tire on it?

Before a blizzard or big snow storm is expected to arrive, we would put on the 17-inch snow tired wheels.
After a few days when conditions have improved, put the 18-inch M&S wheels back on.

(Would never attain high speeds with snow tires, even if clean, dry pavement.)

So what do we do?:
At 90 mph on clean, dry, level rural highway. We slow (coast) when approaching the few vehicles encountered.
Hospital calls and asks us to speed it up.
100 mph OK?

These are not SNOW tires. They are WINTER tires. You should install four WINTER tires and leave them on all WINTER.

Thanks, Whitey.

Damn. - Now we’ll have to shell out even more money to get four tires.
(We are just unpaid volunteers.)

OK, what’s the difference between SNOW tires and WINTER tires?
What is best for the worst conditions?
(Whenever couriers and cabs can’t move, that is when hospitals call us.
Last blizzard I was up digging out at 0350. Almost done when hospital called at 0500.)
Thank you.

Snow tires are what we had in the 1970s and 1980s for winter driving. They were very soft low tech tires to improve driving on snow and ice, but on dry pavement, even below freezing temperatures, they wore out pretty quickly.

Winter tires are what we have now. A lot of technology goes into the design, both in composition and with tread patterns. They are made for driving in all winter conditions, including frozen but dry pavement. They last longer than snow tires of yesteryear, and they do a better job of helping you maintain control.

In terms of which is better, the obvious choice is winter tires since what you think of as “snow tires” are not readily available anymore.

Considering where you live and how you drive, four winter tires are a good idea anyway. Don’t see this as an additional cost. While you are driving on winter tires, your summer tires are being stored and spared wear and tear. Tire costs are usually incurred on a per-mile basis. There will be an initial cost outlay, but per mile, the cost of operating your vehicle should not go up, unless you buy yourself a second set of rims for your winter tires, which I think is a good idea.

It’s a 4WD. Use the same wheels all around, and the same tires. If you put new tires on two wheels and leave the old tires on the other two wheels, you’ll end up damaging your car.

On 4wd, all the tires should be the same. If you do this kind of work, and carry blood supplies in need, do it correctly or not at all. There has to be some liability involved. Do it by the “book” and no book recommends anything but 4 tires of the same.

watch these videos

Thank you, everyone.

Yes, I’d like to do it correctly with the same winter tires on the same wheels.
Wondered if a compromise of two winter tires would be better than only M&S tires.

We will work on getting the same winter tires.
The F-150 aluminum wheels are nice.
Maybe someone will trade them for three 17-inch steel wheels like the 17-inch spare.

Thank you.

“If two snow tires, where on 4WD Expedition?”

On eBay.

4WD and AWD should have 4 of identical tires - identical meaning same size, make, model, and state of wear. To do otherwise is to risk drivetrain failure - very expensive!

Agree, you need 4 matching snow tires. The reason most posters have given is about traction to go.

The real reason to match the tires is to have the same traction on all 4 wheels to STOP. ABS brakes and traction control are calibrated for matching tires. If you have mismatches then the tire with the least traction is the wheel that slips and kicks in the ABS brakes that kills braking pressure to the other 3 wheels; meaning your stopping power is only as good as the traction you get from the worst tire on the vehicle. Assuming you have to go up the mountains then you have to go down as well and you need effective ABS brakes to do it safely.

The Expedition has P255 70R18 Bridgestone Duelers and I believe a P265 75R17 spare.
I was hoping they were all the same so that I could include the spare in rotation with the rest of the tires.
If I had a flat in the rear, I would put the spare in the front and front tire in the rear.

Bottom line; traction differences between axles on non specialized vehicles are not recommended. This point has been made many times when people ask where the “best” tire should go. The common response is the rear. But on drive pavement, the snow tire on the rear is no longer the “best” traction tire and when mounted on the front is not on snow and ice. A loose-loose situation.

Went to Big O tires.
They suggest mounting Cooper “Discoverer” tires with studs on the three alloy F-150 wheels, remove the Expedition spare tire and mount a winter tire on the Expedtition’s steel wheel.