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08-20-2017, 11:47 AM
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#1
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Junior Member
Join Date: Apr 2016
Location: NH
Posts: 5
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Tire size?
We have a 1993 Winnebago Brave 27' motorhome. Last year, after getting a blowout on the road, we had 6 new 235/85/16 10 ply tires put on. We now notice a lot of sidewall roll and it is very hard to handle driving now. My question is this: Would a different size tire ( 265/75/16 ) or a larger rim size help with the problem?
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08-20-2017, 11:51 AM
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#2
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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What tire pressure are you running? You may just need more air.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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08-20-2017, 10:02 PM
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#3
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Junior Member
Join Date: Apr 2016
Location: NH
Posts: 5
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Thanks for the reply but the tire pressure is maxed out so that isn't the problem.
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08-20-2017, 10:25 PM
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#4
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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Do the new tires have a lower ply rating or are they not steel sidewall and tread? Those would allow more sidewall flex.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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08-21-2017, 04:24 AM
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#5
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Senior Member
Join Date: Jul 2016
Posts: 3,284
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I see potential for two common issues with new tires. One of course is rim width. If the recommended rim width of your new tires is more than your old rims then you will get exaggerated tread squirm. You won't be riding on the full tread patch. You will be riding on the middle of the tire because the tire pressure.
Then there's plain old fashioned tread squirm. You get this with new tires, especially on trucks, and the cheap Chinese brands. What is happening is the tread is deep enough that it is moving between the carcass of the tire and the surface of the road.
Performance tires for cars when used in racing conditions will have the tread shaved off, down almost to illegal conditions for street use to eliminate tread squirm and increase contact surface area.
I would check out rim width first. Then you have to decide if you want to drop down in tire size for your rims or buy new rims appropriate for your new tires.
It can be very disconcerting when you make a turn and you feel the vehicle reacting afterwards. Tread squirm can feel just like underinflated tires on too small rims.
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Life is Good
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08-21-2017, 08:32 AM
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#6
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Junior Member
Join Date: Apr 2016
Location: NH
Posts: 5
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Thanks for the info!
After reading these replies I believe that we may have it figured out. Since we were on the road when we had the blowout, we had to have whatever the garage had on hand installed. After checking them out further we have found out that they may not be the right tires. They are Wild Trail Commercial LT 235/85/R16 M+S straight rib Load range E. Tread measures 7/16 deep Max load single 1380 lbs. at 80 PSI. Tread plies are 2 polyester plus 2 steel plus one nylon. Sidewall 2 polyester. The rims are steel accuride and they are marked " mas load 2440 lbs at 80 PSI ( 16" X 6" ) After reading the rims I am wondering if that means not to ever go over 80 PSI? My son insists that going up to a 265/75/16 on wider rims ( which is what he uses on his truck ) will help. I believe we need new tires to correct the problem! Thanks for all of your input!
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08-21-2017, 08:40 AM
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#7
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Senior Member
Join Date: Apr 2017
Posts: 199
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>"Wild Trail Commercial LT 235/85/R16 M+S straight rib Load range E"
IMHO: Those LT tires are typically rated for 80 lbs max pressure.
Are your tires rated for more? Max pressure should be on the sidewall.
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08-21-2017, 08:55 AM
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#8
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Junior Member
Join Date: Apr 2016
Location: NH
Posts: 5
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Tire pressure
Yes, they are rated for 80 lbs pressure and I have them maxed out.
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08-21-2017, 10:14 AM
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#9
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Senior Member
Winnebago Owners Club
Join Date: Jan 2014
Location: North Central Alberta
Posts: 193
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Quote:
Originally Posted by yamahaxv920
We have a 1993 Winnebago Brave 27' motorhome. Last year, after getting a blowout on the road, we had 6 new 235/85/16 10 ply tires put on. We now notice a lot of sidewall roll and it is very hard to handle driving now. My question is this: Would a different size tire ( 265/75/16 ) or a larger rim size help with the problem?
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The thing to look at would be the GAWR for the front and rear axles.
The tire you have currently installed is quite a tall tire with a 85% aspect ratio.
The tire's maximum load capacity is 3086 lbs at 80 psi.
That only gives you a maximum of not even 6200 lbs for the front axle.
My guess would be that your Brave is heavier than that and if it is, you are not safe going down the road...
__________________
2004 Winnebago Journey 36G 330Cat
2004 Grand Cherokee BlueOx towbar
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08-21-2017, 03:28 PM
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#10
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Senior Member
Join Date: Nov 2016
Posts: 165
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Guessing your 93 is the same as my 97 F53 Winnebago. Recommended tires are 235/85/16 E tires with a max rating on the tire of 80psi and recommended rating from Ford/Winnebago of 80psi. Doesn't leave much room.
Not sure if changing tire or wheel size would make a dramatic difference and kind of an expensive experiment.
Have you checked condition of your rear sway bushings and shocks? I went with new shocks and poly sway bar bushings. Also weighed all 4 corners and set pressures accordingly. It feels like a slot car compared to before.
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08-21-2017, 05:15 PM
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#11
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Senior Member
Join Date: Jan 2011
Posts: 1,740
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I have a 96 F53 36 Bounder with same size tires .
Mine are Firestone Transforce HT, it drives great & I notice no odd wear
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08-22-2017, 07:04 AM
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#12
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Junior Member
Join Date: Apr 2016
Location: NH
Posts: 5
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More specs
The spec tag calls for 7:50X16 65 PSI Front axel GAWR is 4880 and the rear axel is 7500. I've been told that the 235/85/16 were the equivalent size, but now I am questioning that. I installed all new poly bushings 2 years ago. The reason I suspect the tires is because when I push the rear of the RV by hand I can see the front tire sidewall roll sideways.
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08-22-2017, 02:00 PM
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#13
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Senior Member
Winnebago Owners Club
Join Date: Jan 2014
Location: North Central Alberta
Posts: 193
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Quote:
Originally Posted by yamahaxv920
The spec tag calls for 7:50X16 65 PSI Front axel GAWR is 4880 and the rear axel is 7500. I've been told that the 235/85/16 were the equivalent size, but now I am questioning that. I installed all new poly bushings 2 years ago. The reason I suspect the tires is because when I push the rear of the RV by hand I can see the front tire sidewall roll sideways.
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If that's what the tag says... 7.50 inches would be the width of your rim.
16 inches is the rim diameter and 65 PSI would be the maximum pressure the rim can handle...
The max pressure to which the rim should be inflated to will be stamped on the inside of the rim. Are the rims original?
Having said all that, your son is on the right track. A wider tire with a shorter aspect ratio, ie 255 or 265/70 16, preferably a tire that can carry somewhere between 2600 and 3000 lbs at 65PSI will give you a more stable ride. In theory. All else being equal, shocks, springs torsion bars etc.
__________________
2004 Winnebago Journey 36G 330Cat
2004 Grand Cherokee BlueOx towbar
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08-26-2017, 01:06 PM
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#14
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Senior Member
Join Date: Aug 2017
Posts: 224
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Do you know what the tire size was that you took off after the blowout? You could try something like a 265/75 tire, they are the same overall height, meaning the sidewall will be just as tall as what you have now, but with a wider tread section. The other problem you have with dual rear wheels is making sure the rear tires do not rub each other. If you are going to change tire sizes, I would look at going to a LT225/75/16. It is a slightly narrower section width than what you have on now, but a shorter sidewall.
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