Why do tow vehicles "sag" in the rear, under a load they were designed to accommodate
08-28-2015, 11:09 AM
#11
Registered
I have an Avalanche 2500 as well and tow my 32 with it. I'm guessing it is around 10k fully loaded. I added a Curt class V hitch and a matching stinger and ball since after reading the specs on the OE hitch I wasn't too impressed and the previous owner of my boat that had a 3500 dually said his OE hitch broke when towing it. My Avalanche is lifted 9" and I am running 35" tires. The way my lift is set up it is a little nose high when not towing and when I add the weight of the boat and trailer it sags in the rear 2 or so inches but nothing major. I do not have any weight distribution system either. My rear suspension leaf pack has the two factory leafs with the factory overload spring and an aftermarket lift "helper" spring added in between. It has lift blocks and Bilstein shocks also. I have been very pleased with the way it tows so far.
08-28-2015, 12:14 PM
#13
Registered
Added the Air Lift bags to my Excursion years ago and wish I would have done so from day one. They can level 5000 pounds of tongue weight at max 100psi, which I will never see, but they sure are nice to have with the heavier boat I have now have. Went from the 30 Outlaw to the 35......Run about 70psi in them loaded. 40 not loaded.....
08-28-2015, 02:45 PM
#14
Registered
The new Denali's have the Magnetic fluid shocks and air adjustable shocks for ride height. I have a Yukon Denali towing 6000lbs and with 6 passengers coolers and a full boat it sits the same as empty. The 6.2 LT1 8 speed automatic pulls like a diesel too, can barely tell your pulling 6000lbs when passing. The new oversize brakes are a big improvement as well. FWIW they have a Denali HD, but I would look at the MAX tow package if your looking at Gas, the 6.2 LT1 has great torque.
VIP Member
08-30-2015, 02:02 PM
#20
Registered
Got a truck that does not sag much under a lot heavier load than a boat trailer tongue, but will loosen internal organs when empty. It's an old grain truck. You learn to prefer a bit of sag unless you are always running under a load. Keep in mind even OTR trucks today have air ride suspension instead of leaf springs, so put some on your truck and be thankful for your comfortable ride when empty.
The light front end is not a matter of rear sag, btw. It's simply due to the teter totter effect of adding 1000+ pounds of tongue weight on the hitch to counter the engine weight on the front axle. I've run my truck over scales with and without trailer, and know there is still about 3000 pounds on the steering axle even with 1000+ on the WC hitch. That should be enough to keep the tires attached to the ground.
The light front end is not a matter of rear sag, btw. It's simply due to the teter totter effect of adding 1000+ pounds of tongue weight on the hitch to counter the engine weight on the front axle. I've run my truck over scales with and without trailer, and know there is still about 3000 pounds on the steering axle even with 1000+ on the WC hitch. That should be enough to keep the tires attached to the ground.
