Total Load Capacity Doesn't Seem to Match Interior Room

Manufacturer load limits are also related to the tire ratings. Probably more that you think. Prius, with it's LRR tires, can surpass the GVW fairly easily. The car itself is relatively heavy for it's size. And with the light weight tires, can be marginal with 4 adults in the car. Safety is the key word, not so much as what the car is capable of carrying.

 

The GY Assurance Fuel Max tires on my Gen III are rated for 1279 lb ea or 5116 lb total. That is close to 2,000 lb over the empty vehicle weight.

 

The following is from a Prius E-mail group and the author is a gentleman named Mike Bridges. He has obviously done his homework concerning dynamic tire loading.
I
take no credit for any of the quoted material.



"I am considering replacing my 2003 Prius OEM
I am considering replacing my 2003 Prius OEM Potenza's (pretty worn
@35K) with:

Uniroyal Tiger Paw Touring T
P185/60R14 82T
908 rev/mile
1047lbs @44psi load rating
11/32 inch tread depth
22.9 in diamter
"A" Traction
"B" Temp
660 Treadwear
80k warranty
$66.40/tire


Any comments on noise or handling etc.?

I have read all of the posts on load ratings and have the following
question:

The Gross Vehicle Front Axle Rating for O3 Prius is 1970lbs. Now
assume the car is loaded and the weight distributed such that this is
the ACTUAL STATIC front axle weight. The resulting tire load is 985lbs
and I am using 94% (= 985/1047 x 100%) of the Tiger Paw tire load
capacity (6% margin). Similarly I would be using 89% of the Potenza
load capacity (11% margin).

When braking and cornering the actual load experienced by the front
tires can actually exceed the static load. Is the extra 5% margin I
get from the Potenza absolutely required to handle the dynamc loading?
The Toyota engineers put that 11% margin in for a reason so I guess I
am really asking how far would people feel comfortable deviating from
that margin?"

Thanks!

Mike





(pretty worn
@35K) with:

Uniroyal Tiger Paw Touring T
P185/60R14 82T
908 rev/mile
1047lbs @44psi load rating
11/32 inch tread depth
22.9 in diamter
"A" Traction
"B" Temp
660 Treadwear
80k warranty
$66.40/tire


Any comments on noise or handling etc.?

I have read all of the posts on load ratings and have the following
question:

The Gross Vehicle Front Axle Rating for O3 Prius is 1970lbs. Now
assume the car is loaded and the weight distributed such that this is
the ACTUAL STATIC front axle weight. The resulting tire load is 985lbs
and I am using 94% (= 985/1047 x 100%) of the Tiger Paw tire load
capacity (6% margin). Similarly I would be using 89% of the Potenza
load capacity (11% margin).

When braking and cornering the actual load experienced by the front
tires can actually exceed the static load. Is the extra 5% margin I
get from the Potenza absolutely required to handle the dynamc loading?
The Toyota engineers put that 11% margin in for a reason so I guess I
am really asking how far would people feel comfortable deviating from
that margin?

Thanks!

Mike

 

What's the email group address?

Thanks,
Mike

 

static vs dynamic tire loads

toyota-prius : Hybrid Toyota Prius E-mail Group

 

That's a Yahoo Group. I see I was already a member

Mike

 

Note that this load rating is likely valid only when the tires are inflated to the rating pressure molded into the sidewall.

The car maker's recommended pressure on the door placard is lower, requiring that the tire load ratings also be reduced (de-rated).

Now, many of us ignore the door placard number and use something closer to the tire sidewall pressure number, so the tire load rating is more valid.

 

I run 'em at the sidewall psi Down 2 psi for the rears.

Mike

 

Nope, max load rating marked on passenger car tires in the US is usually at 35 PSI.
Tire Tech Information - North American Load and Pressure Markings

 

I hadn't seen that, but this is my first car with a 35 psi door placard. Previous cars in this household have (or had) lower ratings, two as low as 26. The wording on one particular set of replacement tires was far more clear than others that the load rating was not valid at the lower placard pressure on the car.

 

True.

I wasn't able to find much on the topic, but this paper talks about different variations on determining load ratings for tires inflated to less than their max load pressure.
http://www.dawsengineering.com/linked_files/tirepressureatreducedloads.pdf

 

Yep.

It's not necessarily a Japanese thing. See Exterior & Cargo - Consumer Reports.

Yep on the defunct Element. I even brought it up at 810 Pounds Maximum Weight | PriusChat.

 

re: It's not necessarily a Japanese thing. See Exterior & Cargo - Consumer Reports.

Agreed. It just seemed so given the vehicle placards that were available for my inspection.