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Old 05-23-2013, 09:02 PM   #1
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Yet another tire thread

Just brought home new (to me) and my first SMB. 2005 with SMB 4wd, 38k miles, all SMB factory...springs / ome shocks, etc.

Previous owner had it shod with BFG A/Ts 285/75/16 D load range.
So my first plan of action is getting new tires in E rating.

I giving thought to a size increase to 315/75/16s both for the slight increase in diameter (gearing) and for the fact that the E rated tires I am looking at in that size have that rating at 65lbs tire pressure rather than 80 lbs for 285s.

Two questions...

Question 1) is...is there any downside to the 315s. This van seems to sit as tall as any of that year range. Is tire clearance a possible issue or a "no problem"?
I know that the 316/16 ave basically the same dimensions as the 315/17s on the 2008 and newer SMBs but I believe those vans site a little higher on the later spring pack.

Question 2) is this...I am looking at both Goodyear Duratrac and Toyo AT2s as both come really highly reviewed here and abroad.
Road manners, noise, handling and rolling resistance have a voice in this and thus the AT2s have a lead in common sense way, though the Duratracs seem well spoken of in those areas as well.
However I would go with the more aggressive Duratracs if I thought they had a clear advantage in the mud or snow...conditions I will not frequently be in but want to have the gear to handle them when I am.

Real world opinions appreciated.
Thanks in advance!
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Old 05-23-2013, 10:12 PM   #2
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Re: Yet another tire thread

At least with my 06, 285's required the fenders to be cut or the bushwackers catch on mud terrain tires. I added about an extra 2" of lift after I had Deaver springs installed and thought 315's would fit but I had to trim the fenders back even more.

I found the 315 MT Toyo's were not all over the road like the smaller 285's and I don't know why. I never have had any dealings with AT's other than BFG's.
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Old 05-23-2013, 11:54 PM   #3
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Re: Yet another tire thread

For road manners you can't beat the BFGs. I have no complaints about mine, on or off road.

Quote:
I giving thought to a size increase to 315/75/16s both for the slight increase in diameter (gearing) and for the fact that the E rated tires I am looking at in that size have that rating at 65lbs tire pressure rather than 80 lbs for 285s.
Can you explain what you mean about pressure? I can't see a reason to run 80 PSI in a 285...

And yes, you should get E rated tires. Make sure you inspect your wheels too, look for cracks between the lug nut holes.
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Old 05-24-2013, 03:11 AM   #4
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Re: Yet another tire thread

"Can you explain what you mean about pressure? I can't see a reason to run 80 PSI in a 285...

And yes, you should get E rated tires. Make sure you inspect your wheels too, look for cracks between the lug nut holes."


Goodyear, Toyo and BFG list following ratings...

size weight rating at pressure
LT285/75R16 E 3750 80

LT315/75R16 E 3860 65

In 315 the BFG is not avail in E, only D rated at 3195 at 50lbs
And FWIW the BFG 285 in E states "not rated for sever snow" on Tirerack website list of specs

And thanks for the reminder to inspect wheels, good advice!
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Old 05-24-2013, 07:19 AM   #5
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Re: Yet another tire thread

I find the 315 Duratracs a bit better in snow than the E rated 285 BFGs. A bit more road noise as well. They rub the sway bar in a hard turn but I can live with that. I didn't have to trim the fender wells any more that what was done by SMB. I also have the 2005 era SMB suspension.
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Old 05-24-2013, 11:52 AM   #6
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Re: Yet another tire thread

Quote:
Originally Posted by rarrace
Goodyear, Toyo and BFG list following ratings...

size weight rating at pressure
LT285/75R16 E 3750 80
LT315/75R16 E 3860 65
Are you really carrying ~3800 lbs on each tire? How much does your van weigh?

If your tire load is less than the maximum for your tire, you should be running a pressure less PSI than maximum, right?

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Old 05-24-2013, 04:02 PM   #7
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Re: Yet another tire thread

Quote:
Originally Posted by geoffff
If your tire load is less than the maximum for your tire, you should be running a pressure less PSI than maximum, right?
Yes, that's right.
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Old 05-24-2013, 04:51 PM   #8
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Re: Yet another tire thread

Yes, there is a correct inflation pressure for load for each tire per manufacturer, its actually covered pretty well in other tire threads on this board luckily / conveniently.

I would agree and add to your comment that I doubt anyone has as much as 3000lbs on any single corner (not towing/or massively loaded).
That said / acknowledged, however, the chatter here is (and this being a pretty well informed / experienced group I put some faith in that as a pretty good real world sample) that the frequency of tire failures is mostly with D rated tires. Which in stock size for these usually rate around 32-3300 lbs at max pressure.

So in going with an E rated you get more load rating / safety margin for same pressure.

And the point I make about tire pressure and size is simply that in going from 285 to 315 you get roughly equal load rating at lower pressure.
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Old 05-26-2013, 06:59 PM   #9
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Re: Yet another tire thread

When I bought my Van new in 2005, I ordered it with BFG 285/75r/16's "D" series. I didn't know from tires at the time, but after reading the Forum, found that given the weight of The Van, (9,900 lbs +/-), the tires should have been "E" series. After about 35k miles I replaced them with BFG 285/75r/16's"E" series.

When I asked the tire guys what the inflation should be they said 80 lbs, and pumped them up to the max. I immediately took off for a little fishing trip (Kelly Creek in North central ID). To get to Kelly Creek, go to Superior MT, and head South on a marginal forest service road for 60 miles. 60 miles of bad road with tires inflated to 80 psi did not make for a pleasant trip.

So, long story short, I like the BFG All terrain, and I run them at 63 psi. I think they're fairly quiet, and have about 30k miles on this set, with very little apparent wear.

Maybe there should be a thread on why SMB's (that usually weigh more than an E 350 chassis is designed for) are delivered with tires that are not rated for the weight they're carrying?

Tom
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Old 05-27-2013, 10:39 AM   #10
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Re: Yet another tire thread

Quote:
Originally Posted by flyfisher
When I asked the tire guys what the inflation should be they said 80 lbs, and pumped them up to the max.
Most tire techs don't understand the placard number is for the stock tire size. They should know better. Actually these days they go by their computer, and don't look at the tire or placard at all.

I wouldn't run more than 60PSI at the back on a 285/75-16.
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