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Old 08-20-2015, 10:39 AM   #1
Uncle Shelly
 
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Tow vehicle performance after change in TV cargo

Just returned from a trip to Arkansas. While there decided to replace TV tires. I was very happy with my setup and performance that I just tried to replace with identical tires. Tires were replaced just prior to returning home.

Data: TV - 2010 Grand Cherokee hemi with towing package. Trailer 2001 25ft Safari AS sleeper6. Original tires Goodyear Fortera HL 245/60r18. New tires are Goodyear Wrangler SR-A 245/60R18 Load/Speed rating 105T. OEM tire pressures suggested 33lbs. Put 38lbs. in new tires. Max tire pressure on tire sidewalks is 51lbs. Reese hitch with trunnion style WD bars. No sway control. Ball is set 3/4" above coupler before load. After load front measurement at front TV axle does not drop. After load rear TV axle drops 1.5".

So immediately after leaving with new tires I noticed a dramatic difference in sway. Not only did large semis suck me in but small pickups also caused a pull. This was a dramatic change. Completely rechecked my hitch settings since I had new tires. All measurements were the same. Decided to increase tire pressure to 44lbs as my original tires were maxed out at 44lbs. After driving about 50 miles on freeways, I felt that the sway was somewhat better but internet advice from various websites reiterated following OEM suggested pressures. I stopped at a rest area and dropped the pressure back to 38lbs. So I fought the swaying all the way through Atlanta.
As we got north of Atlanta, I realized that there was another change in my TV. I did not bring my Toolbox. I needed the room for a number of boxes of china. And those boxes were now gone. They went at the same time we put on the new tires. So at the stop for lunch I grabbed our trays of canned goods stored under the dinette and moved them into the TV.
The result was just as dramatic. Gone were the scary semi truck pulls. Gone were the pickup truck pulls. Now I could start to enjoy the drive.
We have been traveling the Eastern U.S. For the past year and a half. I just realized that I always have brought a toolbox.

So my question is this. Why would 50-75lbs in the back of my Grand Cherokee make that much difference? And what can I do about it for the future? If I shorten the WD hitch with one less link and nose down the front of the TV help?

Your advice will be greatly appreciated.
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Old 08-20-2015, 10:56 AM   #2
CLOUDSPLITTER "Tahawas"
 
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Question Confused....

"Reese hitch with trunnion style WD bars. No sway control."

75lb shouldn't make that much of a difference.....no sway control would?

The reviews on those tires are 3 out of 5....why were they chosen?

Bob
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Old 08-20-2015, 11:04 AM   #3
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I had a similar experience with new TV tires. Solid as a rock before and squirrely after. It had nothing to do with load in our case. It took time for the new tires to square themselves off. It was like the truck was on the "balls of its feet". After about 300 miles the truck was back to normal, but wow that 300 miles was rough!
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Old 08-20-2015, 11:20 AM   #4
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Why were they chosen? They were suggested by the tire dealer. I was away from home. Not an excuse just a reason. The change that occurred was dramatic. I felt the change within five miles from the rest area's on ramp. It only took a couple of truck passes to to tell my wife that things were better.
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Old 08-20-2015, 11:31 AM   #5
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On my 2011 JGC Hemi I went from the OEM stock tires to Bridgestone Dueller H/L, P265/50R20. Really dramatic improvement in handling and feel. I run them at 39lbs. These tires are highly recommended on the Jeep Forums for towing and all around use.
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Old 08-20-2015, 03:39 PM   #6
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Concentrate on the tires when there is no sway control?.....

Just what I would do, set PSI to the max sidewall value or just a bit less, add sway control and visit the scales to get the proper WD set-up.

But that's just me.....

Bob
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Old 08-20-2015, 05:12 PM   #7
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Take the TV tires up to 50 psi and see what you think.
Our F250 is squirrely when the tires are low.
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Old 08-21-2015, 06:59 AM   #8
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I plan to increase the tire pressure to 50 psi and test drive our local freeway. I will report back here with the results.
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Old 08-21-2015, 11:01 AM   #9
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Is your dinette in the front or rear of your trailer. I recently had about 100# extra in the rear of our trailer an it felt similar to how you described. Weight out on the next trip and all was cool. In my case I believe we are on the edge of low tongue wt. I haven't checked with a scale.

I'll second the tire wear in as well. Last time I got new treads they were particularly squirmy for the first week or so. Then settled right in.

Add the canned goods back to the trailer and see if you can repeat.
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Old 08-21-2015, 01:02 PM   #10
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One thought - You may have selected the wrong load range for your usage of the vehicle. I noticed that the tires you bought are 105T load rating, or SL. Take a look at your sidewall to see the maximum load capacity for this tire. My guess is that you are running near that load on the rear axle when you have the trailer attached. 50PSI will help, and I recommend running the fronts at 50 as well for weight transfer during braking.

The last tire change on our tow vehicle (horse trailer, not camper) I went with XL rated tires for the higher load rating. My wife's initial complaint was that the TV drove more like a truck. That was true - the stiffer sidewalls did not absorb little bumps as well as the p-metric tires that were previously on her SUV, but the load rating per tire went from 1600 to 2200 lb. I like having 1200 lb of safety on the rear axle when the TV is used as a truck.

Good luck, and I hope running at 50psi helps.
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Old 08-21-2015, 07:10 PM   #11
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Thanks, I will look at my options. If the increase in psi fixes the problem and I am not exceeding load capacity of the tires, I will let you know the results. If I made a $1000 mistake, I will fix it.
I thought I did things right.
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Old 08-21-2015, 07:18 PM   #12
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Widget, the dinette is in the middle. My heavy weight is almost directly over the axles. I will be trying the movement of the weight.
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Old 08-21-2015, 08:18 PM   #13
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"50PSI will help, and I recommend running the fronts at 50 as well for weight transfer during braking. "


I'm not sure you want to run front tires at max. You need max pressure on rear for load and running cool but front tires at max unless you really transfer a ton of weight forward will give you poor steering control. High pressure without weight will round out the tire and wears center faster....so less foot print under the front suspension. Certainly there is some dive under hard braking, but the equalizers tend to keep the truck even front to back even under heavy braking.

JCW
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Old 08-21-2015, 09:04 PM   #14
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I wouldn't run without a sway control myself. The risk is always there for a good side wind, whether from a large semi or winds.

We run an F150 with a 31' 1979. I can tell the difference when I move 40# from the trailer center to the bed of the truck. I have gotten the load down now to where I can tell whether we are light in the truck bed or front of the trailer and will stop at the first rest area and shift a little. Have you put the box back in the TV and tried out that additional weight with the new tires?
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