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Old 11-27-2013, 05:54 AM   #1
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Handling Questions '14 Thor ACE 29.2

Hi all fellow rv's

I have a question regarding the handling concerns I have on our 2014 Thor ACE 29.2. The SAFE T Plus has been installed and I have had the toe adjusted. Ford tells me that that is the only adjusted that can be made.


Is there a general rule on tire pressure if MH is not at max weight? 5 psi less than max, 10 psi les etc.

When being passed by a tractor trailer I'm being pushed pretty hard to the right. Should I slow down or speed up slightly as the larger rig approaches?

I know the MH won't drive like my Expedition, but I'm not comfortable in it yet.

Thanks for any feedback

Nick
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Old 11-27-2013, 06:09 AM   #2
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Originally Posted by Newbie58 View Post
Hi all fellow rv's

I have a question regarding the handling concerns I have on our 2014 Thor ACE 29.2. The SAFE T Plus has been installed and I have had the toe adjusted. Ford tells me that that is the only adjusted that can be made.


Is there a general rule on tire pressure if MH is not at max weight? 5 psi less than max, 10 psi les etc.

When being passed by a tractor trailer I'm being pushed pretty hard to the right. Should I slow down or speed up slightly as the larger rig approaches?

I know the MH won't drive like my Expedition, but I not comfortable in it yet.

Thanks for ant feedback

Nick
it seem's like everything I have done make's a difference now it's one more tweak and I think that will be all I can do .

try and get a 4 corner weight done if you can't get that goto to a truck scale on highway or truck stop and weigh the coach and set tire pressure to weight of coach .
my max pressure is 120 psi and I run 90 psi in front and 100 psi in back , handle's better now, I will say that never owning a rv before they do not drive like a car you are driving a sail down the road and when wind hit's it you will get a push. here is something i put on another thread .


Josams did my alignment and did a great job . but it seem's to good " maybe "

when on flat road the coach drive's perfect " steering wheel straight " now when driving on a road with a crown to the left or the right the coach will have some pull either way the crown is , and I would say that 90 % of the roads in Florida have a crown to the right for rain drainage so there is a pull to the right most of the time " small pull " I was thinking of getting a " Truecenter " or a " safe T plus with trim kit " to help with this .

any other Palazzo owners have the same problem with crown's in the road ?
again first Rv so don't no if this is normal or not , very small pull to left or right depending on the crown or pitch of road .

even in my car driving down here in florida when holding the wheel straight she drive's straight but when you let go it will 90 % of the time drift to the right a lot slower then the Rv but still drift's

thank's
mike
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Old 11-27-2013, 07:12 AM   #3
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As stated: weigh all 4 corners of your coach loaded as normal. If you can't weigh the corners then at least weigh the entire coach. Then you should have in your chassis manual a chart that tells you what to set your tire pressure at. If you can't find that go on the web and find the tire pressure chart for your tires and set the pressure to what it tells you for front and rear. I have an 03 Class C and my max is 80 psi and based on weight I run the fronts at 60 and the rears at 65. When I had my Class A the previous owner had them at max and I was struggling to stay on the road. Once I weighed the coach and set the pressure correctly it handled great.
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Old 11-28-2013, 04:40 AM   #4
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To avoid the pushing to the right by a tractor trailer , its best to keep as much possible distance sideward when passing. So keep as much possible to the right , and then if the trailer keeps as much as possible to the left, there is as less possible suction between the 2 vehicles.

About the tire-pressure , I think empty for an RV is not that much weight less then fully loaded. But can be wrong there , going from the European situation , where much motorhomes of under 3500kg/7700lbs and no heavy things like boats and motorcicles on or behind it.

If you use 85% of the loadcapacity that belongs to the pressure, there is still acceptable comfort and gripp.
Example: fully loaded 2000lbs on the tire , use pressure calculated for 2200 lbs, to cover a reserve for things like , pressurelosss in time, misreadings of pressure and weight schales,etc. Then the weight on the tire can drop to 85% of 2200lbs= 1870 lbs before confort and grip gets to much lost.

So most lilely you can keep one pressure for all situations.
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Old 11-30-2013, 04:01 PM   #5
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Handling Questions

Thanks guys for the replies. My scale ticket shows

Steer Axle 6200 lb

Drive Axle 9160 lb

Gross Weight 15360 lb

I had full tank of gas (80 gal) no other additional liquid weight, but most of personal travel weight

Does this mean 3100 steer (divided by 2) and 2290 axle (divided by 4) for tire load pressure limits.
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Old 11-30-2013, 05:15 PM   #6
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Thanks guys for the replies. My scale ticket shows

Steer Axle 6200 lb

Drive Axle 9160 lb

Gross Weight 15360 lb

I had full tank of gas (80 gal) no other additional liquid weight, but most of personal travel weight

Does this mean 3100 steer (divided by 2) and 2290 axle (divided by 4) for tire load pressure limits.
YES , those are the #s , also add some weight to the front and the rear as if you had a passenger in the seat next to you and also in the back as in water in the tank and people , clothes food ect,

I would estimate 10 % more for both steer and drive wights and then divide

steer 3410

drive 2510
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Old 12-01-2013, 08:51 AM   #7
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The steer axle wont be getting much more, because most things are stored on the rear,
but you have to keep in mind a weightdifference between Right and Left on both axles.
So front 10% adding for reserve is yust fine to keep both sides above 85% of the load the pressure is calculated for ( futher called loadpercentage L%).
Back is a different thing , there mayby even add 18% to make in case of even weight R/L L% 85%.
This would give the rear axle as much possible reserve .
And because passenger and drivere are in front the front axle is most important for comfort.

Then you have to use the dual load maximum load for rear .

You mention scale weights so you weighed per axle.
But what are your GAWR's , wich are mostly on the same plate as the pressure advices in America.
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Old 12-01-2013, 09:11 AM   #8
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My Tires are Goodyear 245/70R19.5G GAWR front is 6500 and rear is 11000. Here is the latest recommendation from Goodyear. What would you say is a good starting point for tire psi to aid in the handling.
http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
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Old 12-01-2013, 09:34 AM   #9
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My Tires are Goodyear 245/70R19.5G GAWR front is 6500 and rear is 11000. Here is the latest recommendation from Goodyear. What would you say is a good starting point for tire psi to aid in the handling.
http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
if im reading right it look's like 80 lb's minimum in all tire's .
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Old 12-01-2013, 02:30 PM   #10
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My Tires are Goodyear 245/70R19.5G GAWR front is 6500 and rear is 11000. Here is the latest recommendation from Goodyear. What would you say is a good starting point for tire psi to aid in the handling.
http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
In that list 2 tires with that sise in G load and H load but both with a to small difference between single and dual. In Europe Dual maxload is 92,5% of single and in America sometimes dual =91% of single.
In this newer list of goodyear the H load is larger difference between single and dual.
http://www.goodyeartrucktires.com/pd...dinflation.pdf
So look at the sidewall of the tires to get the right given maximum load or loadindex for single and dual.

So I cant fill in my calculator if I dont know for shure the right maximum loads.

Calculated with the right formula you can go lower then 80 psi but the calculation used for those lists is inadequate.
American TRA swiched over to the calculation of European ETRTO in 2006, but only for standard load/P-tires and XL/reinforced/Extraload, wich calculation was realy bad. But for C-load and up TRA stil uses a formula that leads to to much deflectionn of the tire at lower pressure/load.
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Old 12-02-2013, 08:12 AM   #11
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Found an European list of Goodyear with your sises and there the dual is 94% of single. This is because the calculated maximum load is rounded down to the first lower maximum load that belongs to the loadindex. Here li 136 /134 and if you caculate the dual back to single , that single is yust to low to call it a 137 Loadindex, so rounded down to 136.
The dual though is calculated back to 92.5% of the original and unrounded single maximum load.
Worldwide the maximum load is calculated this way in Kg and kPa ( kiloPascal, 100kPa is 1 bar = 14.5 psi.
After that it is conversed for the American marked to LBS and PSI, and sometimes again rounded.

Also mind that in this European list there are no different loadratings ( H,G,Fetc) in one list as is done in American lists.
http://www.fleetfirst.eu/ff_nl_nl/Im...1465-89659.pdf

Calculated back that they used the European calculation for it wich leads to lower load-capacity for the same pressure then the American still used calculation for C-load and up.
Also mind that in Europe the axle loads are given ,so you dont have to devide by 2 or 4 yourselfes to get it per tire.
8.5 bar of the tire here is 123 psi so its a H load tire in the list.

Thougt I give the link here to show what the differences are in the American and European system.
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Old 12-03-2013, 05:16 PM   #12
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I was always taught to use the tire pressure listed on your data plate, which you should be able to find on the drivers side wall somewhere near the drivers window. It's the same for a car use the pressure listed on the door jamb. One trick you can do when a truck passes as well as keep to the right is to give it a little gas when the truck comes in line with you rear bumper. Don't try to outrun him just, it seems to cut down on the push. The size of your coach has a great deal to do with it as well. Happy and safe travels
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Old 12-04-2013, 03:02 AM   #13
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Reaction to above from rvbunz.

The advices given on RV.s are for the original tires and fully loaded , calculated with the "American" formula, wich leads to to low pressures.
For that reason also , the pressure-advice is kept to the high side , sometimes behind even maxloadpressure of tire.
But also often there are other tires placed with higher maximum load and pressure for that, wich need higher pressure for the same load.

So if comfort and grip gets important, and the loads are lower, it has to be calculated . And its always better to recalculate, for the reasons given here.
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Old 12-04-2013, 07:35 AM   #14
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Goodyear truck tires service shop has recommended 95psi on front and 100 on back. Test drive back to storage was extremely favorable. I will take on highway this w/e and see how it is at higher speeds.

Tires are rated 120
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