Are you guys sure about tire pressure?
- Thread starter CybrSlydr
- Start date
Running a 31/10.5r15 Kelly Edge AT load range C on my SE 4.0 auto. Max pressure 50psi. Obviously not stock rims or tires, but currently running at 33psi which matches the manufacturer's specs on the door jamb (down from 40 and definitely feels better).
Any specific recommendations for air pressure for this set up - both on and off-road? Other than on sand, I've never 'aired down' any of my trucks when off-road - and even then, not to the extend I see many mention here. I certainly get the concept of the larger, 'grabbier' footprint on rocks, loose surfaces and mud, as well as better ride quality, but am concerned about rolling a bead. How low is too low for non-bead lock tires?
10psi is about as low as I usually go (I dont have beadlocks) but if you’re more nervous about rolling a bead shoot for 15!
10-12 is fine for offroading with appropriate size wheels. I regularly ran 8 psi without a problem on my previous non-beadlock 15x8 wheels with 35x12.50 tires mounted on them. Most experienced offroaders don't even consider 15 psi to have been aired down on a Jeep-size tire.
Head Lice
TJ Addict
What you refer to as a 'truck' may be different than what a truck really is. 'C' may be perfect for your 1988 Toyota running empty.Because all "LT" tires are truck tires.
'C' is a truck tire too . . .
'E' is a truck tire . . .
Semantics aside, whether or not a Jeep might be called a "truck" by some, both D and E load range tires are designed for vehicles that are significantly heavier than a TJ is. A Load Range C tire is appropriate for a vehicle with the weight of a TJ.
D and E rated tires are made stiffer to support heavier vehicles which can reduce traction on tough offroad trails when mounted on a TJ. Being stiffer than necessary means the tire won't flex as well around rocks, obstacles, etc. to conform to the obstacle's shape for improved traction as well as a Load Range C tire can.
D and E rated tires are made stiffer to support heavier vehicles which can reduce traction on tough offroad trails when mounted on a TJ. Being stiffer than necessary means the tire won't flex as well around rocks, obstacles, etc. to conform to the obstacle's shape for improved traction as well as a Load Range C tire can.
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To my understanding an e range tire is a 10 ply tire intended for three-quarter ton and 1 ton light-duty trucks and is directed toward commercial use
I have always ran them on my work vans and work trucks
I would be a little surprised they worked well on a Jeep but I'm not saying they don't. ... And I don't know how the sidewall thickness factors in.
I did notice a tremendous improvement when I dropped to 26 PSI in ride and handling.
We run trials tires on Enduro bikes exactly for the same reason that load c range tires work well on Jeeps.. they flex and grab like a tennis shoe.
I have always ran them on my work vans and work trucks
I would be a little surprised they worked well on a Jeep but I'm not saying they don't. ... And I don't know how the sidewall thickness factors in.
I did notice a tremendous improvement when I dropped to 26 PSI in ride and handling.
We run trials tires on Enduro bikes exactly for the same reason that load c range tires work well on Jeeps.. they flex and grab like a tennis shoe.
What you refer to as a 'truck' may be different than what a truck really is. 'C' may be perfect for your 1988 Toyota running empty.
'E' is a truck tire . . .
C load ratings for all of my previously owned pickups and SUVs; Datsun pickup, Ford Bronco, Toyota 4Runner, Chevy Silverado, Ford F150 and Chevy Tahoe.. E load rating for the Sierra 2500 HD I currently own.
Back in the days of bias ply tires one did use 4 or 6 ply tires on a 1/4 ton vehicle such as a jeep or small pickup, 8 ply tires for 1/2 ton pickups and 10 ply tires for 3/4 ton pickups, etc.
The alpha load rating system for radial tires, i.e. P, C, D, E, etc., does not correspond to the number of plies in the tire. It replaced the previous system of "10-ply rated, 8-ply rated, 6 ply rated, etc. which also did not correspond to the actual number of plies in the tire, but was designed to be familiar to consumers used to bias ply tires where the load capacity did correspond to the number of plies.
One can get quite an education by using the Rim and Tire Association Load & Inflation Tables to compare actual load capacities at lower air pressures such as the 24, 26 and 28 psi frequently suggested for 33" or 35" tires on a jeep. There is less difference in load capacity between similar size C, D and E load rated tires at these lower pressures than you may think.
https://www.toyotires.com/tires-101/tire-load-and-inflation-tables
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Thanks for this. I've been stuck with Es on my Rubicon for as long as I have owned it. While I'm sure there is an improvement in comfort with C's, I have never felt like I was driving a buckboard wagon.
As mentioned above in an earlier post, the benefit to running Load Range C tires is not just a comfort thing where offroading is concerned.
As mentioned above in an earlier post, it's not just a comfort thing where offroading is concerned.
My previous set of Goodyear Duratracs felt a little bit softer than my current Cooper Discoverer ST Maxes. Both are Es, so there might also be differences between manufacturers beyond the letter code.
This is 8 psi on LR E, 285/75r16. I've always thought they sat high for that low of pressure.
I hope to switch to 15" on the next set of tires so I can run Cs.
Wow that's 8 psi? Yowsa that almost looks like street pressure! That's a great illustration of why E's on a TJ suck for offroad traction on tougher trails.My previous set of Goodyear Duratracs felt a little bit softer than my current Cooper Discoverer ST Maxes. Both are Es, so there might also be differences between manufacturers beyond the letter code.
This is 8 psi on LR E, 285/75r16. I've always thought they sat high for that low of pressure.
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I hope to switch to 15" on the next set of tires so I can run Cs.
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You have hit the nail on the head and your example illustrates why overgeneralized subjective opinions about tire load ratings should not be relied upon as gospel, e.g., statements such as "E's on a TJ suck . . . ." There is much more to it than load rating and not all E load rated tires are constructed the same way or have the same ride on the street or compliance (or lack thereof) over rocks and obstacles.
The Cooper ST/Maxx, ST/Pro and Mickey Thompson Baja MTZ and ATZ tires share the same tire carcass with 3-ply sidewalls. However, Goodyear Duratracs can have either 2-ply or 3-ply sidewalls depending upon the size and manufacture date. Industry literature also suggests that the Duratracs use lower denier thread in the sidewalls and less of it than the Coopers. That, and the construction of the treads has a tremendous effect on the stiffness of the tire, how it rides, and how well it might conform to obstacles at very low pressures. This may explain why your perceptions of the ST/Maxx and Duratrac are so different. I've used both ST/Maxx and Duratrac tires, albeit not on a jeep, and my impressions of the two tires are not dissimilar to yours.
Another problem with focusing on load rating alone is that the weight of a jeep has an impact on how a D or E load rated tire rides at common street pressures of 24-28 psi. Not all TJ's are built in the relatively lightweight style one poster on this or another jeep forum coined as a Southern California fairweather rockcrawler, which as one might imagine is a jeep that may be armored and equipped with built-up axles and big heavy tires, but is stripped of all gear and weight unnecessary for a day run. The reality is that there are as many if not more jeeps built for camping or multi-day trails that regularly carry more passengers and weight and on which tires with of a D or E load rating will perform differently.
If I were running a lightweight jeep I would try to find a C load rated LT tire as my first choice, but those of us who own Rubicon's and run 16" wheels have very few of those to choose from and none in the larger sizes. Moreover, those of us who own LJ's frequently upgrade to 16" brakes, the size frequently recommended for LJ's by Black Magic Brakes, which prevents us from downsizing to 15" wheels in order to buy C load rated tires. The reality for many is that C load rated tires are simply not an option.
I may have to air down my E load rated Mickey Thompson Baja ATZ P3 tires installed by the previous owner lower than I would have to air down a tire with a lower load rating in order to get the same flotation or deflection, and my current tires may be a bit too stiff even when aired down for some trail somewhere, but thus far I have been able to wheel on moderate and difficult trails alike without ever once thinking, "Gee, I wish I had C load rated tires instead." I have certainly not found sufficient downsides to my E load rated tires to justify getting rid of a perfectly good set of wheels and tires just to get some C load rated tires instead.
Bottom line, load rating is certainly a consideration, and given the choice a C or D load rated tire on a jeep is generally better matched to the weight of the rig than an E load rated tire, but it really isn't as big a deal for most jeepers as some would have us think.
Endnote:
When my current tires wear out I am likely to purchase new 17x9 wheels and 315/70R17 or 35x12.50R17 tires, many of which have a D load rating. I'm not going to lose any sleep over the limited availability of C load rated tires in those sizes.
@Mr. Bills great summary and very well written.
I bought my 16" MOABs used before I knew the nuances of tires and load ratings and air pressure for street/off road use and all that you've written explained so nicely. I wish I had read something detailed like yours instead of the blanket "run at ___ psi" recommendation so prevalent in the all the forums.
I'm currently running 265/75R16 Duratracs (C rated, FWIW) and once these wear out, I'm switching to 15" rims so that I have more choice in tires. I'm happy with my Duratracs but don't like being stuck with limited options. For street use, I keep them at 28-30 psi and they've been wearing well and the ride is comfortable for me.
I bought my 16" MOABs used before I knew the nuances of tires and load ratings and air pressure for street/off road use and all that you've written explained so nicely. I wish I had read something detailed like yours instead of the blanket "run at ___ psi" recommendation so prevalent in the all the forums.
I'm currently running 265/75R16 Duratracs (C rated, FWIW) and once these wear out, I'm switching to 15" rims so that I have more choice in tires. I'm happy with my Duratracs but don't like being stuck with limited options. For street use, I keep them at 28-30 psi and they've been wearing well and the ride is comfortable for me.
The reason that I try to avoid real General statements on tire threads is because tires very so much from manufacturer to manufacturer.
Rubber compounds ,sidewall stiffness and handling characteristics vary from manufacturer to manufacturer and also vary with different load ranges and sizes.
at the same time I know tires cost a pretty good chunk of change so if someone ask me I'm going to tell them to get load range c tires and air them up to 26 psi.
Rubber compounds ,sidewall stiffness and handling characteristics vary from manufacturer to manufacturer and also vary with different load ranges and sizes.
at the same time I know tires cost a pretty good chunk of change so if someone ask me I'm going to tell them to get load range c tires and air them up to 26 psi.
OlYellerTJ
New Member
OP, I run my KO2s, load range C (33x10.5x15) at 27-28 psi. Over 28 gets a bit rough, and they're wearing well across the tread. But if you're happy with what you're running, more power to you.
I've been thinking about this thread title
Yes we are sure about everything.
Except women.
Jkowners.
Women who own JK's.
Politicians and TV evangelist.
Other than that we got you covered.
Yes we are sure about everything.
Except women.
Jkowners.
Women who own JK's.
Politicians and TV evangelist.
Other than that we got you covered.