2023 - Prius or Prime - spare tire?

Not all rubber ages at the same rate. The OEM Michelin tires on my 2012 Prius v had really cracked sidewalls at 6 years,

My 2005 utility trailer tires are still serviceable after 17 years. I lent it to a friend who used it for two years for his pressure washing business. The tires have been exposed to the outdoor environment since new. Whenever I use it, I carry two brand new spares for security.

 

You have probably come across 'dry rot' on tires. That cracking is from exposure to air and sunlight. 6 to 7 years seems to be the point at which the degradation requires replacement for tires in service on cars.

The spares go longer because they are shielded from the sun, but they are still in contact with air. The pressure of a filled tire can cause the reaction to go faster on the inside. A spare that looks fine can have 'dry rot' on the interior surfaces. A spare that can't hold air, or quickly fails, doesn't help.

Few people do replace the spare tire. Few even check the spare's pressure. Having the spare is because it is a better solution in an emergency. Why skip on the maintenance of it, and increase the likely hood a flat tire becomes an even bigger hassle?

 

You’ve sold me.

 

* Compact spares ("donuts") come with a warning that they're safe to use for only a limited number of miles (e.g., 70 to 100) and only at limited speed (typically 50 mph max).

* Not only is speed impaired, but also handling including braking distance.

* Car makers advise that if you get a flat on a front tire, you must move a good back tire to the front and put the donut on the rear axle only. When you get a front flat, you have to change TWO tires.

* Also, any variance in the wheel diameter can stress out some AWD systems when the wheels try to turn at different rates.

* Take a little ride out into the middle of Wyoming, or Highway 50 across Nevada and ask yourself if you'd like to get stuck with a flat in the middle of nowhere in 115F heat. Or just drive anywhere in the snow and ice. You'll wish you had a full size spare.

 

I don't know if I'm allowed to include a link yet, but I'll try. I think this is what I saw: EPREL Public website This is the European rating, and the "Fuel Efficiency Class" is the equivalent of rolling resistance. Either the tire has been updated, or there's some confusion based on geography (which jurisdiction is publishing the rating). I don't really know much about these metrics, however, it may be that rating depends on the tire width. So the same model of tire in a different width would have a different rolling resistance rating and that's why you're seeing some FE-AE30 model tires with a B rating.

 

Haven’t seen it in any Owners Manuals; any specific instance you can quote?

When I measured our temp and full size (stacked and aligned with a carpenter square), the temp spare was within 1/8” of full size, for diameter; so 1/16” on the radius.

 

i agree in extreme circumstances, but in most urban areas, getting to a dealer or garage shouldn't be a problem with a donut.
if i were driving across country, i'd probably take a full size spare

 

I had a blowout in NJ on Mother's Day a while back and put on the donut. It made it 1/4 mile, hit a pothole that dented the rim (NJ may be a worst case test) and we were stuck. Luckily a local knew that there was an open tire shop nearby and they had an off brand tire that would fit my Prius rim so we got home. Be careful when driving with your donut as they are not robust tires/rims.

JeffD

 

Caution is my middle name.
How fast were you going?
How old was the tire?
Was it at correct pressure?

 

There should be warnings on the tire itself about speed, and maybe distance. It's likely in a fine print, like manufacturing date, so easy to miss though.

 

30-40 MPH on Rt 46

about 10 years, but it was the rim that failed, not the tire

Yes, I checked it when I put the donut on my Prius

JeffD

 

It's not in the two Prius manuals I quickly checked(2010 & 2023), but I've seen versions of it in other manuals. It's not something you have to worry about if you're doing a short run home or to the tire shop in good weather conditions, but I've seen it advised to move the compact spare to a rear wheel(on a FWD car) if you're forced to drive a decent distance in poor conditions(weather or terrain). The front wheels are just put under so much more stress with steering, power application, and primary braking.

 

I have a 2017 Subaru Impreza. The owner's manual includes the warning:

"When replacing or installing tire
(s), all four tires must be the
same for following items.
(a) Size
(b) Circumference
(c) Speed symbol
(d) Load index
(e) Construction
(f) Manufacturer
(g) Brand (tread pattern)
(h) Degrees of wear
For the items (a) to (d), you must
obey the specification that is
printed on the tire placard. The
tire placard is located on the
driver’s door pillar.
If all of four tires are not the same
for items (a) to (h), serious mechanical
damage could occur to
the drive train of your car, and
affect the following.
— Ride
— Handling
— Braking
— Speedometer/Odometer
calibration
— Clearance between the body
and tires
It also may be dangerous and
lead to loss of vehicle control,
and it can lead to an accident."

I've been advised that the max allowable variance in the tread depth is 2/32" for otherwise identical tires, although I don't see that number in the manual. Subaru uses symmetrical full time awd, so that's much different than the e-AWD setup on a Prius or Corolla or Rav4 hybrid, so I don't think the Toyotas will be as finicky about replacement tires since there's no physical linkage between the front and rear.

 

Our old Subaru Outback had a fuse that, if installed, turned off the AWD and a mismatched tire would not cause difficulty. I learned that when the clutches were burned by my spouse driving home from Boston on the Donut. The burnt clutches in the transfer case made it fee like there was a bad tooth in the differential when in a tight turn. Putting that fuse in eliminated the symptom. We had the transfer case rebuilt for $750.

JeffD

 

T145/9016106M

 

9 bucks. All I needed in the past 20 years. You can thank me later.

 

Needs a portable air pump to complete the kit.
The goo pump that came with the car very likely can't be used as an air compressor alone.

 

Got this:


BV Bicycle Ergonomic Bike Floor Pump with Gauge & Smart Valve Head, 160 psi, Automatically Reversible Presta and Schrader

 

Vast majority of tire issues come from nails and screws. They almost always cause a slow(er) leak. When I'm at home, I jack the vehicle, find the nail / screw, pull / screw it out, clean the hole with the tool, use one of those rubber patch strips with some glue, and inflate with the compressor in my garage.

When I face a leak on the road, there is usually enough time to find a gas station with air. The tire monitoring system gives enough room. Instead of jacking the vehicle I just rolled it to a point where I can access the nail / screw. Same process, takes me 3 minutes.

I live in a part of Florida with a huge influx of people moving in from up North. We have new residential communities being build EVERYWHERE. That ongoing construction comes with a ton of... nails and screws laying on the roads. I catch one every few months.

Been using those rubber strip patches for a long time. Never replaced a tire after patching, I just keep driving until the thread is toast. Never had a blowout.

 

You can't rely on the air pumps at gas stations around here. Those that still have them tend to be in poor shape. Last one I tried couldn't seal the stem, so just let more air out as it pumped.

I noticed the local Lowes has an air pump.