C rated vs E rated

[Seanm26]

Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.

https://m.tirerack.com/tires/tiretech/techpage.jsp?techid=55

 

[JCWages]

Interesting discussion, especially since I need new tires on both my trucks. :)

In my experience tire failures on the trail are extremely uncommon. In 20 years of offroading I can think of one, and in that case it was a large branch straight through a sidewall. All of my tire problems have been nails and other crap (half a pair of pliers) picked up on paved roads. I've always run C rated tires on my trucks and have never had a failure on the trail, perhaps I've just been lucky.

Anybody else had first hand experience with on-trail failures? If so, do you happen to know the load rating of the tire?

Slim stick through the sidewall. Wildpeak AT3W uses 2ply with a high turn up. Unfortunately I believe the extra turn up ply stops before it reaches the upper sidewall area. LT285/70/17 E

A single plug fixed it up and it held air for the next 200+ miles (75 of which were offroad)

 

[Dilldog]

Interesting discussion, especially since I need new tires on both my trucks. :)

In my experience tire failures on the trail are extremely uncommon. In 20 years of offroading I can think of one, and in that case it was a large branch straight through a sidewall. All of my tire problems have been nails and other crap (half a pair of pliers) picked up on paved roads. I've always run C rated tires on my trucks and have never had a failure on the trail, perhaps I've just been lucky.

Anybody else had first hand experience with on-trail failures? If so, do you happen to know the load rating of the tire?

Only real failure I have had was actually the wheel, a rock hit my sidewall caught the wheel and peeled the wheel off of the tire. Tire was a 28x8.50r14 TSL bias ply, I think the load rating was a C.

 

[tjZ06]

Which is exactly what the hilux needs.

Basically,
C is for light, 1/2 ton trucks
D is for 3/4 ton truck capacity
E is for 1 ton and dually loading

I know you said "basically" so I agree.

FWIW I run a F-rated tire on my 3/4 ton '11 Silverado 2500 HD. Of course, I also pull a 16k lbs 5th wheel with ~3k lbs of pin-weight with it (let's please not get into a GVWR debate).

I went C-rated on my WJ because I never intend to tow much of anything with it (at most it'd be my RZR on my little 10' trailer, under 2,500 total weight) and I wanted the smoother ride and better conformity to rocks and stuff offroad like @JCWages mentioned.

-TJ

 

[tjZ06]

Slim stick through the sidewall

We always think it's going to be a rock that slices a tire... yet it's ALWAYS wood that gets 'em.

-TJ

 

[JCWages]

We always think it's going to be a rock that slices a tire... yet it's ALWAYS wood that gets 'em.

-TJ

Stupid little rock destroyed a lame P-metric tire on our work Canyon. Otherwise I agree. lol

 

[MidOH]

Paper thin sidewall. lol.

Wait until you see how thick an STT is.

 

[Big Blue]

Do you air down a C rated tire the same way you would an E rated tire?

 

[tjZ06]

Do you air down a C rated tire the same way you would an E rated tire?

Yes and no. I go for about the same amount of sidewall flex and increase in footprint (which is totally unscientific)... which generally will mean less of a decrease in air pressure on a C vs. an E. In other words, on the exact same vehicle (loaded the same way) you'll probably keep a higher air pressure in the C than the E and achieve the same amount of flex and improved footprint.

-TJ

 

[JCWages]

Yes and no. I go for about the same amount of sidewall flex and increase in footprint (which is totally unscientific)... which generally will mean less of a decrease in air pressure on a C vs. an E. In other words, on the exact same vehicle (loaded the same way) you'll probably keep a higher air pressure in the C than the E and achieve the same amount of flex and improved footprint.

-TJ

I agree with this.

 

[Horosha]

Thanks to all for sharing experiences and the different points of view.
I will probably give a try on the st maxx 255/75.
But can one confirm/disprove the following? If I air down by 50%, do I lower the load capacity by 50%?

 

[bgenlvtex]

Possibly more, possibly less, but load capacity is entirely dependent on two factors:
Air volume
Air pressure

A reduction in either equals a reduction in capacity irrespective of load range/load index/ply rating but not necessarily in linear fashion.

Thanks to all for sharing experiences and the different points of view.
I will probably give a try on the st maxx 255/75.
But can one confirm/disprove the following? If I air down by 50%, do I lower the load capacity by 50%?

 

[Fletcher8969]

I know almost nothing about tires/ load rating and pressures. I've read the technical page at tire rack and think I understand it generally. One question I have is... If a tire is rated for 3195 lbs does that mean that your combine the 4 tires to stay under the GVWR? Another question is... I cannot find E rated tires in the size I want for my vehicle. I'm currently running:

LT 40X13.50R17 121Q C BSW

39.8"

13.6"

8.5-11"

11"

21/32"

C

3195 lbs

35 psi

86 lbs

523

But the stock tires were:

LT 37X12.50R17 124Q D BSW

36.8"

12.5"

8.5-11"

10"

21/32"

D

3525 lbs

50 psi

73 lbs

566

I'm using the bigger size on the recommendation of a shop that's been working on my truck but I don't understand why the same type of tire changes from D to C rating when I go up 2 sizes (diameter wise). Also, the max load is 330lbs less per tire. My truck has a 10.300 GVWR though I typically don't run it over 9500lbs.

Can anyone explain this to me? I'm so unfamiliar with this topic and I'm worried about the recommendation of the shop. I'm I running tire that isn't rated high enough? I do drive it off road and have run tire pressure around 20psi without a problem so far. I do have bead-locked wheels. I'd rather have more tire (91 octane in a 87) than not enough (87 octane in a 91) if you know what I mean. Thanks in advance for any advice.

 

[Billiebob]

I know almost nothing about tires/ load rating and pressures. I've read the technical page at tire rack and think I understand it generally. One question I have is... If a tire is rated for 3195 lbs does that mean that your combine the 4 tires to stay under the GVWR? Another question is... I cannot find E rated tires in the size I want for my vehicle. I'm currently running:

LT 40X13.50R17 121Q C BSW

39.8"

13.6"

8.5-11"

11"

21/32"

C

3195 lbs

35 psi

86 lbs

523

But the stock tires were:

LT 37X12.50R17 124Q D BSW

36.8"

12.5"

8.5-11"

10"

21/32"

D

3525 lbs

50 psi

73 lbs

566

I'm using the bigger size on the recommendation of a shop that's been working on my truck but I don't understand why the same type of tire changes from D to C rating when I go up 2 sizes (diameter wise). Also, the max load is 330lbs less per tire. My truck has a 10.300 GVWR though I typically don't run it over 9500lbs.

Can anyone explain this to me? I'm so unfamiliar with this topic and I'm worried about the recommendation of the shop. I'm I running tire that isn't rated high enough? I do drive it off road and have run tire pressure around 20psi without a problem so far. I do have bead-locked wheels. I'd rather have more tire (91 octane in a 87) than not enough (87 octane in a 91) if you know what I mean. Thanks in advance for any advice.

Looks like either tire has plenty of capacity. The main reason the C Rated tire has less capacity is the lower inflation pressure it is built for. I'd sooner run 35psi than 50psi with a bit more capacity. If you air down that D Rated tire to 35psi I doubt it will have any more payload capacity than the C Rated tire at 35psi.

That said, Hummers are built for peak performance stock, I doubt a taller tire will enhance the Hummers capabilities.

 

[Fletcher8969]

Looks like either tire has plenty of capacity. The main reason the C Rated tire has less capacity is the lower inflation pressure it is built for. I'd sooner run 35psi than 50psi with a bit more capacity. If you air down that D Rated tire to 35psi I doubt it will have any more payload capacity than the C Rated tire at 35psi.

Ok. That's helpful to know. The shop gave me an explanation that was probably something along those lines but I didn't understand at the time.

 

[bgenlvtex]

Load capacity is a function of volume at pressure.

As volume increases requisite pressure decreases to support the same load.

Load range/ply rating is an indicator of the ability of the tire to contain higher pressures (higher or lower) .

Generally speaking a higher load range/ply rating does not indicate additional actual plies,but it may in some cases.

 

[Fletcher8969]

Load capacity is a function of volume at pressure.

As volume increases requisite pressure decreases to support the same load.

Load range/ply rating is an indicator of the ability of the tire to contain higher pressures (higher or lower) .

Generally speaking a higher load range/ply rating does not indicate additional actual plies,but it may in some cases.

Ok. That helps to explain it!