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Old 05-17-2013, 04:49 PM   #1
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Just Weighed Grand Star---Comments?

Dont you hate it when you have a post all typed and it is lost when you time out? ARGH...re-keying it from memory:

Any comments, concerns, or suggestions?
The following is for a 2009 Newmar 3752 Grand Star FRED with a full fuel tank and empty water tanks. Groceries and more gear will likely add another 1,000 pounds.
GVWR is 26,000#

Tires are Cooper Roadmaster RM 120's 255/70R 22.5 Load Range H, 6 plies tread, 1 sidewall (all steel). Load rating on the side of the tire is 5,510 pounds per tire at 120# of air..I have been running 105# of nitrogen. For two tires the rating shows 5,070 each.

Total motorhome: 24,040 (4,007 per tire)


Front axle (both front wheels): 8,780 (4,390 per tire)
Just left front: 4,520 (4,520 per tire)
Just Right Front: 4,560 (4,560 per tire)

Rear axle (all 4 wheels): 15,260 (3,815 per tire)
Just Left Rear: 7,860 (3,930 per tire)
Just Right Rear: 7,820 (3,910 per tire)




Your thoughts?

Thanks!!

Curt
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Old 05-17-2013, 05:02 PM   #2
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A little hard to read the way it's laid out , but I don't see your GVW; FAWR & RAWR any where, and no tire rating for duals ?
Funny the post lay out changed while I was typing.????
Maybe others can comment on this but your corner weights don't add up to your axle weights ?
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Old 05-17-2013, 05:12 PM   #3
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Skip426...my apologies, I tried to put a "table" into the thread and it didnt work so I was saving and resaving until I got it to work in text form, plus I added the GVWR and dual tire limits...how's that look?
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Old 05-18-2013, 05:42 AM   #4
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What tires came with the FL chassis from Newmar?
The RM-120 Cooper is a trailer tire not used for drive or steer tire.
Would say you may need one of these type tires.
If you had Michelin tires what was wrong with them they still had good wear on them.
If you had the Michelin tires 255/70R , front tires 95 psi, rear duels 85 psi.
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Old 05-18-2013, 05:57 AM   #5
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I'd say your weight is very evenly distributed, much more so then mine.

You could, maybe lower your pressure to 95-100. But I think you might want to call Cooper Tire (not the dealer) and ask about those tires.

Their web site says they'll work for RVs, but then says their not for steering.
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Old 05-18-2013, 07:50 AM   #6
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Quote:
Originally Posted by PDR John View Post
I'd say your weight is very evenly distributed, much more so then mine.

You could, maybe lower your pressure to 95-100. But I think you might want to call Cooper Tire (not the dealer) and ask about those tires.

Their web site says they'll work for RVs, but then says their not for steering.
The proper tire pressure should be set according the tire manufacturer's tire pressure charts. Most tire mfrs have their tire pressure charts for each model tire on their websites. The tire pressure is determined by the actual weight on the tire. Tire pressures need to be the same in each tire on each axle - and that should be the tire pressure required for the tire position with the greatest weight it is carrying.

Make sure your tires are rated to carry those weights - the tire's maximum weight carrying capacity and air pressure for that weight will be listed on the tire's side wall. Proper tire pressure for weights less than that maximum will have to be on the tire's inflation chart.

Tire pressure should be checked often; we check ours each morning before we drive the MH. inadequate tire inflation is the most common cause of tire failure.

Happy travels

Al
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Old 05-18-2013, 08:16 AM   #7
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Hi MoonchaserTX,

Per the Newmar brochure, I do not see a chassis with a GVWR of 26K.
Ford and Workhorse ratings are:
Front GAWR 9K
Rear GAWR 15.5K
GVWR 24K

Freightliner
Front GAWR 10K
Rear GAWR 17K
GVWR 27K

The individual tire weights should add up to the total for the axle. The numbers in the OP do not add up. Depending on the chassis and getting the number totals (axle weight) correct, you could be okay, close to GAWR or over the limit.
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Old 05-18-2013, 10:56 AM   #8
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Quote:
Originally Posted by MoonchaserTX View Post
Skip426...my apologies, I tried to put a "table" into the thread and it didnt work so I was saving and resaving until I got it to work in text form, plus I added the GVWR and dual tire limits...how's that look?
No apology required, the easier the post is to read , more members will comment, and I see you have a few already. Look into the tire use issue right away and re-check your chassis GVW , and axle ratings.
Were you getting your weights at a cat scale, or were they done with a 4 corner scale set up ?
Placement of the RV on the scale for the corner weights could explain why your 2 corners total differs from your axle #. Even a slight ground slope towards the scale could put you off by the 3/400 lbs.
If , your GVW is 27,000, as per Gary's post, you have a nice cushion for loading, but you should set your tire pressure for your axles loaded to max until you have a travel weight. Do you plan on traveling with water on board ?
BTW. If your DW , packs the way mine does, your going to need all of that 2960 lbs CCC.
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Old 05-18-2013, 11:20 AM   #9
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Once again, IRV2 members provide great info, thanks all!

Steer/Trailer tires? When I bought the tires I saw that these tires are shown as non steer tires so I called Cooper at the time and they said this particular size is actually a steer tire even though it does not indicate that on the web, but I will be calling them Monday morning to double check and even get it in writting in a reply to my onliine message if I can. If they say it's not a steer tire than that opens a whole new discussion with the Cooper dealer where I got them!

Tire pressure: Good idea to let Cooper tell me what pressure I should be running based on the weights measured...will do that Monday too.

Coach GVWR: I will check the numbers again and maybe even call Newmar Monday to get all the data I possibly can.

Corner weights: The scale is a certified one (only one for two counties around these rural parts) but it is true that the scale operator had never heard of weighing the corners separately so we may not have done it correctly but we just did it 4 times where I manuvered the coach so that only one corner was on a very corner of the scale. Oh, also there was not room beside the scales to weigh one entire side at a time and (yes) when we weighed the two front corners the back of the coach was a few inches lower than the front.

thanks again!! I appreciate it!

Curt
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Old 05-19-2013, 06:29 PM   #10
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Thanks again for the comments!!
OK, I dont know where I got 26,000, but here is the corrected GVWR plus the axle ratings:

GVWR: 27,000
GAWR Front: 10,000
GAWR Rear: 17,000

Here are the actual weights in bold:

Total motorhome: 24,040 (that's 4,007 per tire)
(GVWR: 27,000)
27,000 - 24,040=2,960 (What is that number called?)

Single tire rating: 5510
Just left front: 4,520 (4,520 per tire)

Just Right Front: 4,560 (4,560 per tire)
Two front corner weights added together = 9,080
Front axle (both front wheels on scales): 8,780 (4,390 per tire)
GAWR Front: 10,000
Front corner individual weights are 300 shy of total front axle weight but the rear of the coach was a few inches lower for this weighing.
10,000-8,780=1,220 (What is that number called?)

Dual tire rating: 5,010
Just Left Rear: 7,860 (3,930 per tire)

Just Right Rear: 7,820 (3,910 per tire)
Two rear corner weights added together = 15,680
Rear axle (all 4 tires on scales): 15,260 (3,815 per tire)
GAWR Rear: 17,000
Rear corner individual weights are 420 shy of total rear axle weight but coach was slanted to get just a corner on the scales.
17,000-15,260=1,740 (What is that number called?)

I usually drive with a quarter to half tank of fresh water (let's say 150 lb) and empty black and gray tanks. The weighing was done with a full fuel tank and I usually drive with a half to full fuel tank so that cancels out the fresh water sort of.

Even though it's a 2009 model year coach, the original tires were date stamped early in 2007 (thus why we got new tires before we take off for a few months). They were Goodyears same size and also load rating H. The weight rating on the old Goodyears (best I can read on the tires) was the same as the new Coopers (5510 single at 120 and 5,010 dual at 120).

I should mention that we also tow a Honda Element (about 3,500 pounds). Does that factor in to any of this?

It appears the rear tires have much more room for more weight (actual weights compared to tire rating) than the front does so it's a good thing most of the weight we will add in groceries etc will be mid-ship and to the rear. And it appears both front and back have room for some weight as compared to the GAWR's. So, from my understanding of all this, I am good to go for both tire and chassis capacity to add another 1,000 of gear, eh?

-->So, I need to call Cooper about these showing to not be steer tires, and based on the actual weights (plus some for clothes/groceries), what air pressure to run.

Any other comments or things I need to check out?

There should be an app to calculate all this eh?

Thanks again very much for the comments, this is a learning experience for me!
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Old 05-19-2013, 06:53 PM   #11
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Corner weights are the ideal! But not being level when weighing corners . . . not so much! I woulda thunk there were lots of grain elevator scales in your area, but I guess not, eh?


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Old 05-20-2013, 08:31 AM   #12
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Hi MoonchaserTX,
It looks like you are in good shape (weight wise). Just do not tell the wife. If she is like mine, she will quickly find stuff to max out what you can carry. If you are towing 4 down, GCWR is the only number you need to consider. The GCWR for your chassis is 30K lbs. You need to weigh the Honda. I know it is a PITA but it is the only way to get an accurate calculation.

Based on the info in the past post, you should be okay. Coach at 24K and Honda at 3.5K = 27.5K for your GCW. That being said, there is a caveat. Like people, motor coaches gain weight over time. Towing this car, your GVW can be only 26.5K. Over time, you will need to watch the GVW.
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Old 05-20-2013, 08:37 AM   #13
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Your tow bar adds weight to the rear axle ; and like Gary says the rest of the calculation is for GCVW.
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Old 05-20-2013, 08:57 AM   #14
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The 2960 number would be considered the excess cargo carrying capacity, which means you could safely put 2,960 more lbs in your rig, mostly toward the rear axle. Your are not exceeding your weight ratings at that weighing.

You need to get the tire inflation chart for your tires - Cooper should have them. You should set your tire pressure in both front tires for the 4,560Lb weight number - refer to the tire inflation chart for your tires. Equal tire pressure in the front tires will help alleviate the rig steering straight. The air pressure in the rear tires for all four tires should be the amount on the chart for the 3,930 weight number.

If your fresh water tank is a 100 gal. and you carry half a tank - water weighs 8,34 lbs per gal 50 x 8.34 = 417 lbs of water weight. Diesel weighs about 7.2 lbs per gal, so a 100 gal tank would weigh 720 lbs. Propane weighs 4.2 lbs per gal. Those variable weights need to be considered in your rig weight management plan so you do not exceed your GVWR.

Happy travels.
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