Marshmellow tires during towing
#22
Yeah, if you go too low you start to lose sidewall flex and on 20s there isn't much there to start with. Which is why I stated earlier not to go too low.
Well you really can't have it both ways. You could have gone with LT tires in a C range, but 8000# is a pretty good load on a 1500 and you're much better off with a D. You want that stiffer sidewall when you tow. 17" wheel/tires would have given a good bit more sidewall flex for a bit softer ride and still give the higher capacity in a D (not to mention 1000# higher tow rating over 20s) but then you would have had to buy wheels. For the extra towing capacity over a P(assenger) car tire in daily driving, your truck is just gonna feel like a truck instead of a car...
Well you really can't have it both ways. You could have gone with LT tires in a C range, but 8000# is a pretty good load on a 1500 and you're much better off with a D. You want that stiffer sidewall when you tow. 17" wheel/tires would have given a good bit more sidewall flex for a bit softer ride and still give the higher capacity in a D (not to mention 1000# higher tow rating over 20s) but then you would have had to buy wheels. For the extra towing capacity over a P(assenger) car tire in daily driving, your truck is just gonna feel like a truck instead of a car...
#23
The OEM P tires are more than capable of handling the max payload of the truck when inflated at 35 PSI. You will exceed the axle capacity before you exceed the tire capacity.
2200 lbs times 4 tires comes out to 8800 lbs. The truck payload limit is around 6800 lbs.
#24
No, because you use GAWR not GVWR.
Using those 2000# rated P tires, we'll take a 8800# GVWR truck. That truck has a front GAWR of 4800# and a rear GAWR of 6084# (yeah I know, they add up to more than 8800 but that's how it works, total on the two combined can't be over that 8800).
A pair of 2200# tires means the tires are only rated for 4400# on the rear axle, well below the axles capacity of 6084#. While 4400# for the front isn't significantly less than the 4800# limit...
Using those 2000# rated P tires, we'll take a 8800# GVWR truck. That truck has a front GAWR of 4800# and a rear GAWR of 6084# (yeah I know, they add up to more than 8800 but that's how it works, total on the two combined can't be over that 8800).
A pair of 2200# tires means the tires are only rated for 4400# on the rear axle, well below the axles capacity of 6084#. While 4400# for the front isn't significantly less than the 4800# limit...
Last edited by HammerZ71; 09-13-2015 at 09:22 PM.
#25
So here are the real numbers on my 2009 Ram CC 2WD SLT.
From the door
Front GAWR = 3700 lbs
Rear GAWR = 3900 Lbs
Vehicle GVWR = 6800 lbs => this is the number the manufacturer recommends not to exceed.
Stock OEM tires Goodyear SRAs with a load index of 115 @35 PSI are rated at 2679 lbs
2679 x 2 = 5358 lbs, plenty of margin for either front or rear GAWR
edit, although I'm running p tires with a LI of 115, the P275/60-20 SRAs have a load index of 114 (2601 lbs). You can also find the General Grabber HTS tires in the P275/60-20 in a LI of 119 (2998 lbs)
From the door
Front GAWR = 3700 lbs
Rear GAWR = 3900 Lbs
Vehicle GVWR = 6800 lbs => this is the number the manufacturer recommends not to exceed.
Stock OEM tires Goodyear SRAs with a load index of 115 @35 PSI are rated at 2679 lbs
2679 x 2 = 5358 lbs, plenty of margin for either front or rear GAWR
edit, although I'm running p tires with a LI of 115, the P275/60-20 SRAs have a load index of 114 (2601 lbs). You can also find the General Grabber HTS tires in the P275/60-20 in a LI of 119 (2998 lbs)
Last edited by Pedro Dog; 09-13-2015 at 11:25 PM.
#26
Yep, I don't think they can legally sell the truck where the tires don't at least meet the axles limit.
The numbers I gave were simply to show how you come up with the rating. They were from a 2001 Ford F250 gasser which you obviously shouldn't use a P tire on.
For 90% of 1500 buyers passenger car tires are fine and will offer a smoother ride, better fuel economy and cost less. Which is why they use them at the factory . In the OPs case however, he's pulling 8000#. Even though his original P tires could technically handle it, they are not a good choice for his use...
The numbers I gave were simply to show how you come up with the rating. They were from a 2001 Ford F250 gasser which you obviously shouldn't use a P tire on.
For 90% of 1500 buyers passenger car tires are fine and will offer a smoother ride, better fuel economy and cost less. Which is why they use them at the factory . In the OPs case however, he's pulling 8000#. Even though his original P tires could technically handle it, they are not a good choice for his use...
#27
he's worried about the feel of the tires so he may be better served with stiffer sidewalls. Since he's running 33" tires on 20 " wheels, E rated tires may be too hard for everyday use. Probably a good compromise would be 33" tires on 17" wheels.
Some of the way the truck feels could be due to the way the weight distribution hitch is set up. Many folks, including some in this forum, under appreciate a properly set up hitch. The first thing they do is put on air bags or timbrens as a solution to their improperly set up hitch.
The OP's truck is probably around 5,600 lbs with approximately 56% of that on the front tires ~ 3100 lbs and the rest (empty) ~ 2500 lbs on the rear axle. He and his family add up a few hundred more Lbs distributed to the front and rear so the front wheels are up to about 3,250 lbs and the back to about 2,650 lbs,
Once he hooks up the trailer (800 lbs TW) plus all of the other stuff (hitch itself is about 100 lbs) he's got about 3,700 lbs on the rear axle.
He should be able to move off 200 to 300 lbs of that off the axle with a properly set up WDH. So, basically with the OEM tires with a LI of 114 (2601 lbs ea), he's got plenty of safety margin. he's got 5,200 lbs tires carrying a load of 3,500 lbs. The load is only 67% of the capacity, not bad in my book.
Some of the way the truck feels could be due to the way the weight distribution hitch is set up. Many folks, including some in this forum, under appreciate a properly set up hitch. The first thing they do is put on air bags or timbrens as a solution to their improperly set up hitch.
The OP's truck is probably around 5,600 lbs with approximately 56% of that on the front tires ~ 3100 lbs and the rest (empty) ~ 2500 lbs on the rear axle. He and his family add up a few hundred more Lbs distributed to the front and rear so the front wheels are up to about 3,250 lbs and the back to about 2,650 lbs,
Once he hooks up the trailer (800 lbs TW) plus all of the other stuff (hitch itself is about 100 lbs) he's got about 3,700 lbs on the rear axle.
He should be able to move off 200 to 300 lbs of that off the axle with a properly set up WDH. So, basically with the OEM tires with a LI of 114 (2601 lbs ea), he's got plenty of safety margin. he's got 5,200 lbs tires carrying a load of 3,500 lbs. The load is only 67% of the capacity, not bad in my book.
Last edited by Pedro Dog; 09-14-2015 at 12:05 PM.
#28
Originally Posted by dwaldmann
f you put on some passenger car tires rated for 2200# at a maximum of 35PSI will now lower your capacity to 4400#
While I agree with just about everything you said about tire inflation and size, this statement is completely wrong.
The OEM P tires are more than capable of handling the max payload of the truck when inflated at 35 PSI. You will exceed the axle capacity before you exceed the tire capacity.
2200 lbs times 4 tires comes out to 8800 lbs. The truck payload limit is around 6800 lbs.
The OEM P tires are more than capable of handling the max payload of the truck when inflated at 35 PSI. You will exceed the axle capacity before you exceed the tire capacity.
2200 lbs times 4 tires comes out to 8800 lbs. The truck payload limit is around 6800 lbs.
Interestingly, my son just bought a '13 1500 Ram, and it's door sticker says 35 PSI (for P275/60R20, same as mine), but my '15 1500 says 39 PSI. What's up with that? My guess is, a way to improve MPG rating for CAFE.