Best 315/75R16 All-Terrain tire?

[Steel City 06]

Anyone have a 35" load rate E tire they can measure the effective rolling radius at street pressure for me? How much less is that then the (listed mfg spec dia)/2?

I currently have a 2006 LJ with Cooper ST/MAXX in a 35 x 12.5 x 15, load rating C. Mfg spec shows dia = 34.45. I set the pressure at 23 psi for on-road, using the oh-so-accurate 'chalk line even wear off test'.

After about 1/2 tread depth loss and running at 23psi my rolling radius is 16".

I'm moving to a load rate E tire Cooper ST/MAXX 285 x 75 x 17, mfg spec says dia = 34.06. and wondering if I might see a rolling radius closer to 1/2 the mfg dia because of the stiffer tire. I don't know how much of the additional stiffness comes from the sidewalls and how much from the tread.

I am regearing to 4.88 and trying (with grimm jeeper calculator) to get an idea of my resulting rpms at highway speeds with the new tires.

thanks in advance

I don’t have my new tires yet, but the best way to estimate the RPMs is to use the revolutions per mile. Each manufacturer is supposed to list a certain number of revs per mile for each tire, which is based off of the effective rolling radius.

Grimm has a section for you to input that number instead of the tire size. That will give you a far better estimate of the actual RPMs and how much you’ll need to adjust the speedometer

 

[Mr. Bills]

Anyone have a 35" load rate E tire they can measure the effective rolling radius at street pressure for me? How much less is that then the (listed mfg spec dia)/2. . . ?

315/75R16-E Mickey Thompson Baja ATZ P3 with 13/32" tread at 27 psi on 8" wide wheel, with front axle scale weight of 2,180# (1,090# per front tire, weighed 7/19/19) = 16.5" rolling radius. The MT Baja ATZ, Cooper STT Pro and Cooper ST/Maxx all share the same tire carcass with 3-ply sidewalls.

Manufacturers specifications list tread depth at 18.5/32" with a diameter of 34.5" when inflated to 65 psi on a 8.5" wide wheel. Mickey Thompson does not publish revolutions per mile.

I'll let you do the math.

Just for fun I ran the Grimm Reaper calculator for my jeep using the 34.5" published diameter and also the actual rolling radius of 16.5" x 2 = 33.

@ 75 mph the difference using 34.5" vs. 33" = 123 rpm

@ 65 mph the difference is 107 rpm

@ 55 mph the difference is only 97 rpm.

Can you really discern a 100 rpm difference at Interstate speeds? That's barely a needle width on the tach.

It seems to me that using the published tire diameter gets one close enough most of the time. If the result points between two possible gear ratios then use other factors to determine which is optimal, i.e., do you live at altitude and regularly drive mountain roads - lower ratio might be better. Live in Kansas and can't remember the last time you saw a hill, the higher ratio might work. Heavier rigs can benefit from lower gears to get that weight moving. You get the drift.

 

[Ron Hall]

Yeah, I have a Super 16 kit. Haven’t installed it yet, but I’m relatively set on keeping the stock rims. The color and style matches the silver TJs well in my opinion. I also want the better braking performance, especially since I live in a hilly area and plan on loading the Jeep up and towing.

Did the load range D give you too harsh of a ride?

I have put my 33x15 ko2 C through sone very eroded and rocky Colorado jeep trails this past month with very good results. My wife drove it 1000 miles coming out while I pulled out trailer with the truck. I would not want an E tire on the tj. For all the miles you drive getting to 4 whel.

 

[Steel City 06]

I’m actually currently leaning towards D-rated Goodyear MT/Rs in 315/75R16 at this point. Maybe not the best on-road tire, but they come in D and are slightly oversized compared to the metric tire specifications

 

[bluejeep]

315/75R16-E Mickey Thompson Baja ATZ P3 with 13/32" tread at 27 psi on 8" wide wheel = 16.5" rolling radius. The MT Baja ATZ, Cooper STT Pro and Cooper ST/Maxx all share the same tire carcass with 3-ply sidewalls.

Manufacturers specifications list tread depth at 18.5/32" with a diameter of 34.5" when inflated to 65 psi on a 8.5" wide wheel. Mickey Thompson does not publish revolutions per mile.

I'll let you do the math.

thanks, a little bit surprised it's not more, but it is what it is.

 

[Steel City 06]

I ended up with the E-rated Duratracs.

I had a chance to check them out before they were installed on the rim, and I was surprised how flexible the sidewall was, even as thick as they were.

I decided the slightly harsher ride over a D was an acceptable trade for snow performance. So far they're good. Good on-road grip, although I have spun them a few times because I'm driving in front wheel drive.

Still have them at 32 psi though...