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Old 12-28-2017, 09:05 PM   #1
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Default Tire question for RV 1984

Hello,

I have a 1984 Horizon the Chevy G20 chassis with the 318 engine. The vehicle weighs around 6000 lbs. I purchased it used 2 years ago. It came with tires: LT 235/75/R15. I'm unsure what tires to put on it.

The official plate on the door suggests: P235/75/R15. I'm unsure to trust the plate because this could be from when the vehicle transferred to the RV manufacuturer. I'm pretty sure the plate was not updated to take into account extra weight and such.

I'm inclined to go with LT 225/75/R15 with a Load Index of say 100 since the weight is probably not evenly distributed. I don't trust what is on the vehicle since the previous owner took a lot of 'fun'/dangerous short cuts.

Any thoughts or suggestions?
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Old 12-28-2017, 09:43 PM   #2
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I would recommend tires of the original size on the door (chassis) plate.

Look at getting tires with the highest load index if possible. Research tires at Discount Tire or Tire Rack, paying attention to customer comments and ratings.
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Old 12-28-2017, 09:47 PM   #3
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Originally Posted by gadman View Post
Hello,

I have a 1984 Horizon the Chevy G20 chassis with the 318 engine. The vehicle weighs around 6000 lbs. I purchased it used 2 years ago. It came with tires: LT 235/75/R15. I'm unsure what tires to put on it.

The official plate on the door suggests: P235/75/R15. I'm unsure to trust the plate because this could be from when the vehicle transferred to the RV manufacuturer. I'm pretty sure the plate was not updated to take into account extra weight and such.

I'm inclined to go with LT 225/75/R15 with a Load Index of say 100 since the weight is probably not evenly distributed. I don't trust what is on the vehicle since the previous owner took a lot of 'fun'/dangerous short cuts.

Any thoughts or suggestions?
Aside from the rating plate and tires that are on it, you may want to look at the wheels to see what width they are. If the previous owner was oblivious of what might be considered safe, it could have tires that are too big for wheels on it.

My guess is that the van came with 225-75-15 tires on it, but that is only a guess at this point.
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Old 12-28-2017, 09:52 PM   #4
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Here is a link to what allegedly came on the van

https://www.sizemytires.com/vehicle/1984/chevy/g20#15

It will be different based on GVWR so you need to check the door sticker.
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Old 12-29-2017, 12:25 AM   #5
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Van has LT 235/75 and chassis tag says P235/75. Why go smaller? Are tires rubbing somewhere? If not, I would never go smaller than the factory recommended because that will just reduce your load capacity. BTW P=Passenger and LT= Light Truck - LT will usually be a bit stronger/more plys (for load capacity) than the P where they are looking for a nice smooth ride. IMO stick with the LT and 235/75.
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Old 12-29-2017, 05:35 AM   #6
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Thank you for the advice so far. I made mistake in my original statement.

"The official plate on the door suggests: P235/75/R15"

It should have been:

The official plate on the door suggests: P225/75/R15
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Old 01-12-2018, 04:16 AM   #7
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I have a 1993 GMC G30. Here in Florida it is registered as a Short Heavy Bus as it weighs over 7000 lbs as I'm sure your conversion does. The door tag was pre-conversion!!! You must, for safety sake use LT tires and I would look for 115 -118 load range to carry the weight.
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Old 01-12-2018, 11:14 PM   #8
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Default Michelin Defender LTX

I just put Michelin Defender LTX All-Season tires, 235/75R15 with a load rating of 109T, on my Roadtrek 170P . They match the original tire size and fit the Dodge van chassis very well. The 109T load rating makes them stiffer than a passenger tire, which is really necessary on a heavy van.

Unfortunately, the tire vendor, Costco, and the local alignment shop only inflates them to the door label's specification: 35psi Front/41psi Rear. But they are rated at 50 psi. Does anyone know if it's a good idea to run the rear tires at a higher pressure, and who can advise on this?

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Old 01-13-2018, 12:23 PM   #9
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Quote:
Originally Posted by Nic7320 View Post
I just put Michelin Defender LTX All-Season tires, 235/75R15 with a load rating of 109T, on my Roadtrek 170P . They match the original tire size and fit the Dodge van chassis very well. The 109T load rating makes them stiffer than a passenger tire, which is really necessary on a heavy van.

Unfortunately, the tire vendor, Costco, and the local alignment shop only inflates them to the door label's specification: 35psi Front/41psi Rear. But they are rated at 50 psi. Does anyone know if it's a good idea to run the rear tires at a higher pressure, and who can advise on this?

Wouldn't a 10 ply rated load range 120 be required? What is the actual weight or stated capacity on the rear axle?
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Old 01-13-2018, 01:23 PM   #10
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10 Ply tires come in a wide range of load ratings, 120 would be excessive. 100 load range will carry 1800 lbs per tire, 115 will carry 2679 lbs you x's by 4 = that's a lot of van.As for pressure, you must remember the door plate is put there by the vehicle manufacturer and those pressures are for the smoothest ride (so you'll buy another veh from them). I always read the tire... if it says max load 2675lbs at 60 psi - I run 60 psi. Tire lasts longer and wears better. The GMC 20 came with 6.5 wide rims.
Take your van to a metal scrap yard or feed lot and get it weighed.. that will tell you how much tire you need... just my two cents
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Old 01-13-2018, 06:17 PM   #11
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Load range 109 tires are good for 2271lbs, for a total of just over 4500lbs on the axle. Good enough for a 170?

My RT requires load range E or a 120 load index using 245 tires, but it is on a 3500 Chevy chassis.
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Old 01-14-2018, 12:37 AM   #12
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Get the Gross Vehicle Weight and divide by 4, this will tell you how weight each tire must carry. My load range 115 tires will carry 2,679 lbs each or 10,716 total - load range 118 will carry 2,910 lbs or 11,640 total. Just found this for Roadtrek 170
Gross Vehicle Weight Rating 8,600 lbs.
Occupant & Cargo Carrying Capacity 1,250 lbs.
Gross Combined Weight Rating 13,000 lbs.

That tells me you need a 10 ply with a load rating of 122 minimum - that will support 13,200 lbs total.
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Old 01-14-2018, 12:40 AM   #13
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Load range E will support 3,640 lbs each or 14,560 total.
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Old 01-14-2018, 12:46 AM   #14
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Load range E will support 3,640 lbs each or 14,560 total.
What size tire are you talking about? The SRW class b most used tire seems to be the 245-75-16 size in an 80 psi load range E, and it has a rating of 3040# per tire.

Our 265-75-16 load range E tires aren't even 3600# per tire.
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Old 01-14-2018, 02:28 AM   #15
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Quote:
Originally Posted by john.orourke View Post
Get the Gross Vehicle Weight and divide by 4, this will tell you how weight each tire must carry. My load range 115 tires will carry 2,679 lbs each or 10,716 total - load range 118 will carry 2,910 lbs or 11,640 total. Just found this for Roadtrek 170
Gross Vehicle Weight Rating 8,600 lbs.
Occupant & Cargo Carrying Capacity 1,250 lbs.
Gross Combined Weight Rating 13,000 lbs.

That tells me you need a 10 ply with a load rating of 122 minimum - that will support 13,200 lbs total.

Gross Combined Weight Rating (GCWR) is the vehicle weight plus tow weight,

not the vehicle weight alone.
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Old 01-14-2018, 02:34 AM   #16
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.

Gross Vehicle Weight Rating is the MAXIMUM weight your vehicle is designed to operate.

This is the total weight of the following...
the dry weight of your vehicle,
plus fuel and oil and coolants,
plus all the interior,
plus the occupants,
plus all the supplies. ie food water clothes and whatever.

THIS IS THE WEIGHT YOU SHOULD NOT EXCEED when you are driving on the road.
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Old 01-14-2018, 03:10 AM   #17
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What tire capacity you need is easy to figure. Forget all the gross, combined, weights and look at the axle weight maximums on the sticker. Divide by 2 and add safety factor if you are cautious like I am.

Chevy Roadtrek, has rear axle max of 6080# or 3040# per tire which is what a 245-75-16 load range E is, so perfect match. As an example.

YOU CAN'T GET A TIRE'S CAPACITY FROM THE VEHICLE WEIGHT OR CAPACITIES NO MATTER HOW YOU DO IT.

YOU CAN ONLY GET THE TIRE'S CAPACITY BY LOOKING AT THE TIRE'S SPECIFICATIONS.
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Old 01-14-2018, 03:27 AM   #18
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Default Michelin LTX ratings

The 17-foot Roadtrek 170P was built on a "3/4 ton" Dodge B2500 van, not the larger "one-ton" B3500 19-foot Dodge van.

The Michelin LTX "Extra Load" tires are rated for 2271 lbs.

Last time the vehicle was weighted (by RVSEF) on all four wheels, the weight totaled 6550 lbs, with the following distribution:
1500 lbs front-left,
1550 lbs front-right,
1900 rear-left,
1600 lbs right-rear.

So a 2271 lb rated tire provides some margin for a 17-foot Roadtrek, but would not be appropriate for a 19-foot version. "One-ton" Dodges have 16" tires to accommodate a larger tire and larger load.

The weight difference on the rear axle corresponds to the kitchen cabinetry on the driver side. If I add extra house batteries, they should go on the passenger side.

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Old 01-14-2018, 03:56 AM   #19
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john.orourke, don't include total trailer weight into a tow vehicle's tire loads. Receiver-type tow hitches are usually limited to about 500 lbs of tongue weight.
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Old 01-14-2018, 04:58 AM   #20
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Quote:
Originally Posted by Nic7320 View Post
I just put Michelin Defender LTX All-Season tires, 235/75R15 with a load rating of 109T, on my Roadtrek 170P . They match the original tire size and fit the Dodge van chassis very well. The 109T load rating makes them stiffer than a passenger tire, which is really necessary on a heavy van.

Unfortunately, the tire vendor, Costco, and the local alignment shop only inflates them to the door label's specification: 35psi Front/41psi Rear. But they are rated at 50 psi. Does anyone know if it's a good idea to run the rear tires at a higher pressure, and who can advise on this?

Quote:
Originally Posted by Nic7320 View Post
The 17-foot Roadtrek 170P was built on a "3/4 ton" Dodge B2500 van, not the larger "one-ton" B3500 19-foot Dodge van.

The Michelin LTX "Extra Load" tires are rated for 2271 lbs.

Last time the vehicle was weighted (by RVSEF) on all four wheels, the weight totaled 6550 lbs, with the following distribution:
1500 lbs front-left,
1550 lbs front-right,
1900 rear-left,
1600 lbs right-rear.

So a 2271 lb rated tire provides some margin for a 17-foot Roadtrek, but would not be appropriate for a 19-foot version. "One-ton" Dodges have 16" tires to accommodate a larger tire and larger load.

The weight difference on the rear axle corresponds to the kitchen cabinetry on the driver side. If I add extra house batteries, they should go on the passenger side.

Sounds like you have it handled. Happy travels.
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