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Old 06-04-2013, 07:40 PM   #1
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Proper air pressure for 235/85/16?

I have a 1996 535S Dolphin with new BF Goodrich Commercial T/A's 235/85/16? Americas tire recommended running max pressure which is 80psi. Seems high to me, any opinions?
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Old 06-04-2013, 07:49 PM   #2
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To set the correct pressure for your tires and rig you need to weigh all four "corners", then take the highest weight on an axle and then consult the weight/pressure charts for your tire.
Until then the best answer is, as you were told, use the highest pressure you can.
BTW, the pressure on the tire sidewall is NOT the maximum it should eve have, it is the MINIMUM cold pressure to support the MAXIMUM rating of the tire.
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Old 06-04-2013, 08:13 PM   #3
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Quote:
Originally Posted by lbaker5644 View Post
I have a 1996 535S Dolphin with new BF Goodrich Commercial T/A's 235/85/16? Americas tire recommended running max pressure which is 80psi. Seems high to me, any opinions?
I couldn't find a Goodrich table specifying axle-end weights; you might be forced to extrapolate an inflation based on load range as opposed to your actual loads.

Of course, that is a dangerous game. Look at Michelin and Goodyear tables, see how they are affected by weight. You can assess your choice on the road by scanning for core temps: 120F is a great target on a 60F day.

While it is obscene to adhere to sidewall values -- they are the recommended pressures for max rated load -- at lighter weights, you want to shrink away from those pressures cautiously.
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Old 06-04-2013, 10:41 PM   #4
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10 ply? if so 80 would be my choice
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Old 06-04-2013, 11:19 PM   #5
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I would think that if you were to come close to what is on the tire side wall it should be good enough
Just a thought..
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Old 06-05-2013, 12:24 AM   #6
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80 lbs. These tires are running close to or overloaded so run the max. My coach is 900 lbs over weight so I run 80 lbs and they seem happy and run pretty cool.
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Old 06-05-2013, 12:33 AM   #7
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Should I run 80 lbs on the tag axle and steer axle as well?
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Old 06-05-2013, 12:17 PM   #8
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I am in the same spot. I have not had a chance to weigh my RV and have been told to put in the max air pressure on the tire when cold which is 80 psi. I've done that on all 8 tires (includes the tag axle). However, after a short 30 mile drive, it seems like the RV needs constant corrections at the steering wheel while going 60 mph. I haven't driven the RV much since I bought it, so I don't have a good comparison to say if the 80 psi caused the issue. The tires were all around 70 psi when I bought it.
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Old 06-05-2013, 02:27 PM   #9
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You folks REALLY need to get your coaches weighed all the way around. My 36' Coachmen single-slide is the same chassis as yours, 460 Ford with the tag axle. After doing a full weight check, I know the load on EACH tire and used the load charts from Toyo (my tires) to set the correct pressures. They will differ side-to-side so just use the higher value for both sides of each axle.
I am at 75 front, 70 duals and 50 on the tag. Rides like a Caddy and needs minimal steering corrections going down the road. BTW, you won't get the straight axle F53 to track like a car but you shouldn't have to fight with it either.
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Old 06-05-2013, 02:54 PM   #10
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And those weights can change with each trip. For simplicity sake simply inflate to max on the sidewall. If you are a bit over inflated it will show up in center tire wear in a few thousand miles. Just the opposite of under inflation which shows up as edge wear. But since 90% of RV tires are replaced due to age what's the big deal?
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Old 06-05-2013, 04:45 PM   #11
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If you haven't weighed the rig and gotten axle (or better yet individual wheel) weights, then assume the axle is at it max load (GAWR) and each tires carries a bit more than half that (because the weight is rarely equal on both sides). If you can't figure out the axle GAWRs, then I would agree with the tire shop - run the tires at their max load capacity until you have data to justify some lower number. I doubt if it is going to be much lower, though, cause those 16" tires are working hard to hold up that coach.

At worst, a bit of overinflation gives a harsher ride than necessary and maybe wears the center of the tread a bit ore than the outer edges. Much better alternative than running even a few pounds underinflated, which can lead to tire failure quite quickly.

yes, run the steer axle at that psi as well. Tag is more of a question mark, since tags on that type of coach rarely carry more than around 5000 lbs and probably less. Still, 80 psi isn't bad for that either.
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