Developing a HATE for my Load Range E Tires

[BroncoAZ]

The 315s should be on a 9.5" wide wheel; yous look too narrow for the tire section width.

Ford disagrees with that advice and sells Broncos/F-150 Raptors with 315 tires on 8.5” wheels for over a decade. On the 87 Bronco I ran 35x12.5R15 tires on 8” wide wheels without issue and my spare was a 7.5” wide wheel.

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[GmaninAZ]

Ford disagrees with that advice and sells Broncos/F-150 Raptors with 315 tires on 8.5” wheels for over a decade. On the 87 Bronco I ran 35x12.5R15 tires on 8” wide wheels without issue and my spare was a 7.5” wide wheel.

Just because Ford does it, doesn’t make it right. A 315 has a section width of 12.5” and the OP has 8 ply E load range 315s, not OEM C rated. Check out what the tire manufacturers of 315 E rated tires recommend…..

 

[BigGarnet]

‘Cuz ‘E’ range tires do not belong on small trucks. Period.

Sure they do, if you want very durable off road. Lot's of Jeep guys run them no problem, because the benefit off road outweighs all else. I ranE's on my FJ for a while, which is lighter, and it wasn't a big deal...I just ran low PSI and it rode fine. The OP's problem is that he runs way too high PSI. Drop that and he'll be more than fine.

 

[BroncoAZ]

Just because Ford does it, doesn’t make it right. A 315 has a section width of 12.5” and the OP has 8 ply E load range 315s, not OEM C rated. Check out what the tire manufacturers of 315 E rated tires recommend…..

Toyo doesn’t seem to have any issues with 8.5” wide rims on anything except their F rated 33x12.50R17. Their chart specifies 8” in the approved rim width range. Running a wider rim in the rocks results in more rim strikes. I noticed a significant difference in rim damage when crawling going from 8” to 9” wide wheels running a 35x12.5R17 MTR aired down to 15 psi. Ford’s choice of 8.5” is not accidental.

 

[22OBX]

I put these Terra Grappler G2's on about 10,000 miles ago, and I am ready to get rid of them. Love the look, offroad they are great, but this thing doesn't ride anywhere close to as good as my F150 did on the road, and I am thinking it is the E rating on the tires. Any input/advice would be greatly appreciated. It is a Badlands Non-Sas. Thanks.

I have the same tires in 275/70/18 Load Index 125 and ride smooth on stock Bilstein shocks using between 32-35 psi.

My Non SAS OBX came stock with 113 Load Index tires with 35 psi recommended for MAX LOAD.
Looking at load index of 113 @ 35 psi ETRTO standard load chart shows 2458. Moving to a LT you can remove the 10% safety load from the calculation leaving 2234 as the actual load rating.

Moving to the 275 79 18 G2’s that are load E LT tire indexed rated 125, I had to use the TRA LT tire rating chart and 40 psi supports 2270. BUT....even with that said, the Bronco GVWR is around 6,100 pounds for most models. So if you take 6100 GVWR/4 = 1525# per tire, so I think Ford engineers are accounting for the fact some will choose to air down for off road. You still need adequate pressure to support the load when air downed.

Depends on your tire markings what you should run as optimal, along with GVWR, and whether you are riding fully loaded or not.

 

[IwannaGOfast]

Toyo doesn’t seem to have any issues with 8.5” wide rims on anything except their F rated 33x12.50R17. Their chart specifies 8” in the approved rim width range. Running a wider rim in the rocks results in more rim strikes. I noticed a significant difference in rim damage when crawling going from 8” to 9” wide wheels running a 35x12.5R17 MTR aired down to 15 psi. Ford’s choice of 8.5” is not accidental.

Also a narrower rim is harder to lose a bead. I ran 15x7 on my 33x10.5 ko's and 15x8 on 35x12.5 and would air down to about 12 PSI and never had any issues.

I run the bronco about 30 psi and it rides really nice. Only problem is both times it has gone back to the dealership they fill the damn things back up to 40 and I have to air down again when I get home. Asked them not to the second time to no avail.

@dankeller13 unless your stuck on running a MT, I would look for someone selling f150 raptor take offs. 315/70r17 load C ko2's. People are constantly selling brand new sets on OfferUp, usually at very good prices. I picked up a set of 5 wheels/tires, sold the wheels and basically scored 5 new (800 miles) tires for $600.

 

[Knownman]

Tire pressure makes all the difference in ride and performance.

Actually it won't effect the ride enough with those tires in particular. I had them on my Ram 2500 set at 45/40 pounds which is what was recommended by Carli suspension. The additional weight and stiffness that an E rated tire adds just makes them much less compliant. Here you have a load range E tire on a Bronco that weighs 5K pounds versus my Ram at 8K as built. It'd be a really crummy experience and the performance hit comes from the added rolling weight which is significant IMHO.

 

[dgorsett]

Can't stress enough how valuable an inflation table like this is worth:
Application of Load Inflation Tables Version 2020-7 (toyotires.com)


Assuming those are 35X12.50s, your 40psi is good for a vehicle weighing 6500lbs. If you aren't rolling anywhere near that weight, you need to go down. 30psi is for around 5400lbs. I'd definitely not be running those tires at 40psi.

Thanks kodiak for linking this chart. It confirmed life ex[erience which was looking contrary to data i found elsewhere and also confirmed my faith in paper maps, and analog clocks, they (and your chart) show relativity.

Using some of the online calculators where you input existing tire and new tire spit out that I needed to run 47 to 50 psi in my load range Es to get them same load capability as my factory C;s at 35. These calculators assured me this what right even though it looked wrong. I have always run at or under door sticker when running bigger LREs on my rigs.

Looking at your linked chart I realized the issue. They other calculators assume you need the Max load rate of your existing tire (in my case 2400 lb) and give you the equivalent recommendation. By looking at the linked chart I could see I did not need that max load rate for my under 5000 lb Bronco. So it confirmed my choice to run 35 in my LREs still giving me 1800 lb per tire capability.

Now considering that most Broncos spend most of their off road time on three wheels (by the photos in this forum), I may need to reconsider.

 

[Tony4x4]

I have been running 40 psi. I wasn't comfortable any less. 32psi? Seems really low but at this point, it is give it a shot or shell out $1500 for new rubber...

OMG 40 PSI!

That is WAY too high. I would go with 30~32psi tops.

 

[Kaumi808]

I run my falken wildpeak a/t3 E rated on my base steelies at 28 psi rides smooth, max speed here is 60 I would won't be worried much, I inflate them when I'm running my small trailer. My second choice for a C rated tires for my base steelies would be Toyo open country C/T but these are a bit heavier than my E rated Falken.

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