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Old 08-29-2012, 07:18 AM   #1
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Join Date: Jul 2012
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Newbie, first mh need new tire question

Hi all, picking up my 1st MH today! 2000 gulf steam sun voyager DP. It needs new tires. The current size is 245/75/22.5 gawr front 9000 back 16750 on the MH sticker. Went down to the local shop and they have toyo m154 in same size available. On toyo website it said max load 4675 lb single 4300 lb dual.
So do I just take 4675 x 2= 9350lb max for the front? And take 4300lb x 4 for the back?

If so why would I want to put these tire on since it max is only 350 lb over my front gawr? Would you go with different size so it could handle more weight? Or my understanding of weight is wrong?


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Old 08-29-2012, 07:47 AM   #2
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Newmar Owners Club
Spartan Chassis
Join Date: Apr 2012
Posts: 6,129
A couple thoughts if I understand your situation...

First, make sure you get all 4 corner weights. You will need to make sure any wheel or set of wheels isn't individually overloaded for your tires. So, you need to make sure you do not exceed 4675# on either of your front wheels or 8600# on either of your rear set of wheels.

Second, use the highest weight on each axle to determine the air pressure to use for all wheels on the same axle.

Third, make sure the tires you are looking at are properly rated for your weight and speed.

I believe you could go a bit bigger on your tires but there are some factors to consider. The most important is the space between tires on duals. There are others here that have done that so I will let them comment on that since I have never done that myself and only have a basic understanding that it can be done.

The advantage of the bigger tires would be you can run your max axle weights and use a little lower tire pressure. For a gas chassis like mine, that can really help in ride comfort but for a DP with air suspension I'm not so sure such a change would be as noticeable. It would also give you some extra cushion if you find it hard to get your L & R sides weights nearly equal.

I would recommend that you get it weighed before you pick it up if you can talk the dealer into full water, fuel and LP. That will let you know just where you stand and whether or not there have been modifications after the RV was manufactured that affected its REAL weight. That could also help you in your decision of tire size/make.


Don, Sandee & GSD Zeus. Guardian GSDs Gunny (7/11/15) & Thor (5/5/15)
2006 DSDP 4320, Spartan MM IFS, 2013 CR-V, Blue Ox Avail, SMI AF1, Samsung 197R Refer.
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Old 08-29-2012, 10:22 PM   #3
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Thank you. I will do what you suggested.
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Old 08-30-2012, 06:50 AM   #4
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Location: Silver Springs, FL. USA
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You did the arithmetic correctly. The 245/75's are adequate for your rig but don't have much extra capacity. They will have to be run at/near their max load psi, which might mean a slightly harsher ride.

I suspect your axles are actually loaded less than their max (GAWR), though. You may have more margin their than you think. A trip to the scales would be a good thing. Then you will know rather than guess about your safety margins.

If you feel you want extra capacity, you may be able to find the same size tire with a greater load range rating (more weight capacity), or you may be able to go up a bit in size. However, changing the tire size is not something to be done casually. You need in investigate a number of potential problems, e.g. front wheels might hit wheel well when turning, rear duals may be too close together, speedometer & odometer accuracy will be affected, tires may not fit properly on the existing wheels, etc.
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
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