Tow Vehicle Bounce

Okay, one more question from me (I promise I'll figure this TM thing out eventually!)...

I've noticed a rather disconcerting bounce while towing the TM and I hit a small bump. I'm guessing I have some weak rear suspension in my Silverado 1500 and that the TM has a rather heavy tongue weight.

As far as I can tell there are two things that might help me out:

1) Beefing up the rear suspension

2) A weight distributing hitch

I'd be curious about people's experience.

(next summer is the new truck - so I don't really want to spend a fortune, but I do want something that is drivable and safe)

With a Silverado, I wouldn't jump into "beefing up" the rear suspension until after I tried a WDH. We have a GMC Jimmy and it has a real squishy rear suspension - the WDH takes care of that and makes it all ride level. Our WDH is from U-Haul and it's made by Valley. You can get more expensive WDHs, but they work the same basically, so why spend a lot more money? That's my opinion any way - others may not agree. (I've only been a mechanic since 1966, so I don't know everything!)

I have a Silverado 1500HD. When I brought the TM home I noticed a bounce that was rather surprising. So I spent countless hours reading these TMO forums as well as the rv.net forums.

All I needed was more air in the rear tires of the truck. I run about 55 psi when unloaded but put 75 in the rear tires when towing. Try that first, the cost is free.

While speaking with the factory on one occasion we discussed the need for a WD hitch. For my truck they suggested that a WD hitch was not necessary. After a little more than 2 years of towing I have found no reason to add a WD hitch. On the one occasion when I performed a near panic stop, it stopped faster than I had anticipated and it stopped dead straight.

My HD, being a crew cab with 3/4 on suspension/brakes etc. may be a little larger than your truck if you have the standard 1500.

[Bill]

I've noticed a rather disconcerting bounce while towing the TM. I'm guessing I have some weak rear suspension in my Silverado 1500...

A heavy tongue weight should be pretty much like a heavy load in the bed. They both might depress your rear suspension, but neither one should cause the suspension to bounce. Try increasing the tire pressure first, but if the bounce continues, could it be worn out shocks? How old is your tow vehicle?

Bill

I'll look at the air pressure in the rear wheels today when I get back into town (I'm dry camping up at a national forest campground, with a handy satellite internet connection - it and my boss let me telecommute from anywhere). It would be wonderful if it was that easy of a fix. Looking at the tire, my max pressure is 44 PSI - I'll fill them to that (I've got 35 in them now).

As for age of the vehicle, it's a 2003 with about 80,000 miles on it. I've got a friend that runs a tire shop - I'll be asking for his opinion on both tires and shocks. It seems to ride fine without a trailer, if not a bit stiff. They way I've always tested these is to push down on a corner of the vehicle and observe whether or not it bounces after it comes back up - but I'm sure there's a more sophisticated method (they pass my method).

Definitely want to get this fixed before the 5000 mile cross-country trip!!! I feel much better now that I have a proportional brake controller - it actually stops properly when I hit the brake - so that exposed the next problem.

I, too, noticed that "bounce" when I first got my TM. Taking my rear tires from 35 to 40 psi helped a little, but a WDH pretty much stopped it. That being said, there are road sections that have lumps or ridges at intervals that seem to make my Sport Trac bounce even without the TM behind (I've seen other sections that even do that to my Mercury Marquis), and these same sections will sometimes still give me a little bit of that bounce (resonance?), but otherwise the WDH made a BIG difference in handling -- suddenly I didn't really notice the trailer behind me, except on rare occasions.

The rig combo even seemed to not be as sluggish on acceleration, though I'm sure that was psychological, due to the more comfortable ride and vehicle angle, rather than any actual change in rate of acceleration.

I forgot that not everyone has an oversized TV like I do. I don't need a WD hitch, but anyone with a TV much smaller than mine likely would want a WD hitch even if they didn't actually need on. I still say check the tire pressure in the TV tires first, because it is free and looks can be deceiving. Check all four TV tires and also the TM tires.

I wouldn't guess about tire pressure. Get a good digital gauge and measure them.

I measure the pressure of all TV tires and TM tires at the beginning of each trip. If it is just a few days I just visually inspect them before driving home. The one time that I went camping for a week, moving every other day, I checked the pressure mid week and then again for the trip home.

I have been reading a lot over the past few years about trailers and tires. It appears that the number one cause of premature tire failure is excessive heat build up due to under inflated tires. I run my TM Marathons at the pressure indicated on the tire, which I belive is 50 psi. I carry about 3380 pounds on the TM axle, which is very close to the documented limit of 3500 pounds. I have never weighed left to right. Gotta do that one of these days.

My guess is that if your tires are under inflated then increasing the pressure to spec will help, but may not be enough. After that check the shocks on the TV. If they are due to be replaced then I would replace them. Ultimately you may end up with a WD hitch, but I would never recommend that with a WD hitch that you ignore tire pressure and condition of the TV suspension. You gotta keep an eye on the tire pressure and susension no matter what, so start there.

If it turns out that you need or want a WD hitch then be aware that you won't need sway control if the TM is loaded to properly distribute the weight.

I'll let someone else discuss WD hitches and sway control as that is not an area that I have any experience with.

fwiw, when I hitch the TM onto the truck, the rear bumper of the truck sags about 3/4 inch. If you have a lot of sag then I am pretty sure you need a WD hitch.

[Bill]

It appears that the number one cause of premature tire failure is excessive heat build up due to under inflated tires.

I've seen this statement a lot, too. And I always wonder how anyone knows it to be a fact. After all, if you knew BEFORE the failure that the pressure was low, you would fix it and the tire wouldn't fail. And AFTER the failure - well, the tire is just a hunk of shredded rubber. How do you figure out what caused the problem? Is there some way of doing post-failure analysis that I am unaware of?

When I see this statement, I always read it as the tire manufacturer saying "It must have been your fault, not ours, so we won't be liable for anything."

But then, I am a skeptic on a lot of these things ...

Bill

[Bill]

It appears that the number one cause of premature tire failure is excessive heat build up due to under inflated tires.

I've seen this statement a lot, too. And I always wonder how anyone knows it to be a fact. After all, if you knew BEFORE the failure that the pressure was low, you would fix it and the tire wouldn't fail. And AFTER the failure - well, the tire is just a hunk of shredded rubber. How do you figure out what caused the problem? Is there some way of doing post-failure analysis that I am unaware of?

When I see this statement, I always read it as the tire manufacturer saying "It must have been your fault, not ours, so we won't be liable for anything."

I agree that tire pressure is extremely important, and that low pressure will cause failure. But it is a long way from there to concluding that most failures are caused by low pressure. But then, I am a skeptic on a lot of these things ...

Bill

[Denny_A]

Originally Posted by Bill

............snip.......
I agree that tire pressure is extremely important, and that low pressure will cause failure. But it is a long way from there to concluding that most failures are caused by low pressure. But then, I am a skeptic on a lot of these things ...

Bill

At least not as skeptical as Sen. Byrd, who repeats his skeptical observations thrice!!.

BTW, running with tire pressure closer to mfr's printed sidewall limits a)improves traction, b) decreases sidewall flexing (ergo heat buildup), c) decreases rolling resistance, d) improves handling and, e) makes for a rougher ride. I like a) thru d).

Denny_A (just hangin' out)