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Old 09-18-2010, 10:07 PM   #11
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Re: Advice On Replacement Tires

Quote:
Originally Posted by Silver350
it has nothing to do with the weight of the tires.

Tire weight is also closely tied to rolling resistance. Heavy tires take more power to get spinning and keep in motion. Obviously a 44-inch Super Swamper is harder to get moving from a dead stop than a 33-inch all terrain tire. The more power needed to keep a tire moving, the worse the gas mileage and the harder the engine strains to get it moving and keep it at speed.

It is also commonly known in the bike world the lighter the tire the faster you go uphill as it is directly related to kinetic energy and joules burned to get the rolling mass moving. Also it takes more energy to stop a heavier tire as well.

however, the reality is that small of a weight difference probably doesn't matter between a 33" or a 35" for a V-8.

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Old 09-19-2010, 12:55 AM   #12
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Re: Advice On Replacement Tires

I can reccomend these tires. http://www.coopertire.com/html/products ... overer_stt

Click on tire specs in bottom right blue box, for sizes-dia-load range-tread depth-ect... .
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Old 09-23-2010, 12:28 PM   #13
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Re: Advice On Replacement Tires

Went to local Les Schwab today as they are having a sale on Toyo's through the end of Oct (about $25-$30 off per tire approx).

Here is some useful information on the Toyo MT which is a 10 ply tire (E rated).

The 285/75/16 (stock size from SMB)
33.0" tall
11.6" wide
and has 3740# per tire load

The 305/70/16
33.0" tall
12.2" wide
and has 3525# per tire load

The 315/75/16
34.9" tall
12.9" wide
and has 3860# per tire load

The interesting thing to note is the 285 size has higher load ratings than the 305 size even though they are both E rated 10 ply.
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Old 09-25-2010, 01:26 PM   #14
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Re: Advice On Replacement Tires

Now you guys got me looking at the Toyo MT - looks like a heck of a tire and one of the few with E load range.

No I'm trying to decide which size:

Toyo Open Country M/T
35x12.5R17 E10 - Max Load 3640 lbs @ 65 PSI, 81 lbs/tire

These would be pretty much a swap with my BFG AT 315/70R17 that came with the rig as the overall diameter and width is very close, but boy are they heavy, my old BFG are 66 lbs/tire vs the Toyo at 81 lbs tire - the other size in the Toyo M/T that I'm considering is the:

LT295/x70R17 E10 - Max Load 3970 lbs @ 80 PSI. 73 lbs/tire

With these tires I would give up 1" in overall diameter, and a bit of width, but are about 8 lbs a tire lighter (for what ever that is worth). It would seem at 80 PSI one would have a pretty harsh ride, but I was wondering if you dropped down the PSI to say 65 PSI, wouldn't the max load per tire come down also, that is to say at least at highway speed you would be best to run them at 80 PSI?
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Old 09-28-2010, 08:05 AM   #15
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Re: Advice On Replacement Tires

Quote:
Originally Posted by stikine
Now you guys got me looking at the Toyo MT - looks like a heck of a tire and one of the few with E load range.

No I'm trying to decide which size:

Toyo Open Country M/T
35x12.5R17 E10 - Max Load 3640 lbs @ 65 PSI, 81 lbs/tire

These would be pretty much a swap with my BFG AT 315/70R17 that came with the rig as the overall diameter and width is very close, but boy are they heavy, my old BFG are 66 lbs/tire vs the Toyo at 81 lbs tire - the other size in the Toyo M/T that I'm considering is the:

LT295/x70R17 E10 - Max Load 3970 lbs @ 80 PSI. 73 lbs/tire

With these tires I would give up 1" in overall diameter, and a bit of width, but are about 8 lbs a tire lighter (for what ever that is worth). It would seem at 80 PSI one would have a pretty harsh ride, but I was wondering if you dropped down the PSI to say 65 PSI, wouldn't the max load per tire come down also, that is to say at least at highway speed you would be best to run them at 80 PSI?
No, running them at 80psi would not be good unless you van is servery overloaded.
Taking a 10,000 lbs van with a 40/60 weight distribution. (kind-a ok-ish assumption without getting your vehicle weighed)
You would want to run :-
rear 60psi and front at 40psi on the 295's
rear 54psi and front at 35psi on the 12.5's

You should add 10% to each of those psi figures and use that as a starting point. But, it's the ballpark you will be in.

Calculation, (for rear is) 6000 lbs, 3000 per tire.
So for the 295's
80 / 3970 * 3000 (max PSI / max load * real load) Then add 10%. Again this is just a close starting point.
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Old 09-28-2010, 10:05 AM   #16
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Re: Advice On Replacement Tires

I've reached 33K miles on my 315-75-16 BFG AT's, and am getting a new set today. Chunks missing from tread edge resulting from trying to drive back onto a raised roadbed from soft sand. I know they are D rated, but that has not been an issue at all. No flats ever. Some minor sidewall tears and minor bulging, but they provided good service. I looked at a lot of tires thinking of going to E rating, but I have no real reason to. This model of tire has been on my previous four 4x4's for decades with excellent results. My Range Rover Sport runs Terra Grapplers, and they are great, too.
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Old 09-28-2010, 01:59 PM   #17
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Re: Advice On Replacement Tires

Quote:
Originally Posted by SheepShagger
Quote:
Originally Posted by stikine
Now you guys got me looking at the Toyo MT - looks like a heck of a tire and one of the few with E load range.

No I'm trying to decide which size:

Toyo Open Country M/T
35x12.5R17 E10 - Max Load 3640 lbs @ 65 PSI, 81 lbs/tire

These would be pretty much a swap with my BFG AT 315/70R17 that came with the rig as the overall diameter and width is very close, but boy are they heavy, my old BFG are 66 lbs/tire vs the Toyo at 81 lbs tire - the other size in the Toyo M/T that I'm considering is the:

LT295/x70R17 E10 - Max Load 3970 lbs @ 80 PSI. 73 lbs/tire

With these tires I would give up 1" in overall diameter, and a bit of width, but are about 8 lbs a tire lighter (for what ever that is worth). It would seem at 80 PSI one would have a pretty harsh ride, but I was wondering if you dropped down the PSI to say 65 PSI, wouldn't the max load per tire come down also, that is to say at least at highway speed you would be best to run them at 80 PSI?
No, running them at 80psi would not be good unless you van is servery overloaded.
Taking a 10,000 lbs van with a 40/60 weight distribution. (kind-a ok-ish assumption without getting your vehicle weighed)
You would want to run :-
rear 60psi and front at 40psi on the 295's
rear 54psi and front at 35psi on the 12.5's

You should add 10% to each of those psi figures and use that as a starting point. But, it's the ballpark you will be in.

Calculation, (for rear is) 6000 lbs, 3000 per tire.
So for the 295's
80 / 3970 * 3000 (max PSI / max load * real load) Then add 10%. Again this is just a close starting point.

I'm a bit slow and not following you here. How/why does this formula work and why is it not advisable to run the tires at max (80psi) or near max (75psi) pressure for normal driving?
Thanks
R
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Old 09-29-2010, 07:05 AM   #18
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Re: Advice On Replacement Tires

Quote:
Originally Posted by EMrider
I'm a bit slow and not following you here. How/why does this formula work and why is it not advisable to run the tires at max (80psi) or near max (75psi) pressure for normal driving?
Thanks
R
Under inflation will make the tires heat up too much, in turn increase pressure, and will result in failure. Over inflation means less of the tire is in contact with the ground, tire will not heat up to "operating temp", and won't do it's job of sticking to the road. Obviously with over and under inflation there are other things, like ware, MPG, traction, ride quality etc, but they are the main ones.

Max PSI is just that, the max load and pressure the tire can work at. The recommended PSI that you get on every vehicle door is not the max PSI the tire can take. It's the recommended PSI for the vehicle axle weight and that tire it came with.
So it's just applying the same rules to aftermarket wheels / tires. As I said that's just a gauge/point to start at.
It works by using the max PSI and Load of the tire and changing the PSI to the real load the tire will be under.

To do it correctly, you should inflate tires while cold to a figure. Drive to bring the tires up to temp, if the PSI increase is 3~4psi your starting / cold PSI is correct. If it's more than 4psi, your starting/cold psi is too low, if it's less than 3psi your starting/cold psi is too high.
The 3~4psi may be wrong, but it's something like that.
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Old 09-29-2010, 09:17 AM   #19
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Re: Advice On Replacement Tires

Quote:
Originally Posted by SheepShagger
No, running them at 80psi would not be good unless you van is servery overloaded.
I'd always thought there was nothing wrong with inflating to the max allowable, not that I do, I run 62-65 all around usually, but apart from ride quality, is there any reason NOT to inflate above the load (but not overinflate past the max pressure)?
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Old 09-29-2010, 09:51 AM   #20
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Re: Advice On Replacement Tires

Quote:
Originally Posted by SheepShagger
Quote:
Originally Posted by EMrider
I'm a bit slow and not following you here. How/why does this formula work and why is it not advisable to run the tires at max (80psi) or near max (75psi) pressure for normal driving?
Thanks
R
Under inflation will make the tires heat up too much, in turn increase pressure, and will result in failure. Over inflation means less of the tire is in contact with the ground, tire will not heat up to "operating temp", and won't do it's job of sticking to the road. Obviously with over and under inflation there are other things, like ware, MPG, traction, ride quality etc, but they are the main ones.

Max PSI is just that, the max load and pressure the tire can work at. The recommended PSI that you get on every vehicle door is not the max PSI the tire can take. It's the recommended PSI for the vehicle axle weight and that tire it came with.
So it's just applying the same rules to aftermarket wheels / tires. As I said that's just a gauge/point to start at.
It works by using the max PSI and Load of the tire and changing the PSI to the real load the tire will be under.

To do it correctly, you should inflate tires while cold to a figure. Drive to bring the tires up to temp, if the PSI increase is 3~4psi your starting / cold PSI is correct. If it's more than 4psi, your starting/cold psi is too low, if it's less than 3psi your starting/cold psi is too high.
The 3~4psi may be wrong, but it's something like that.
Thanks, that helps me understand the concept. Max psi is not necessary the recommended or ideal psi for all situations.

With the SMB, I'm always pretty close to max GVW. For that reason, I've tended to inflate my tires to 75-80psi for most highway driving.

R
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