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Old 04-05-2013, 06:21 AM   #21
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Re: Tire Pressure ?

Quote:
Originally Posted by Ford_6L_E350
Uprating the capacity is up to the upfitter. Salem-Kroger had the engineering talent to rerate my conversion. And to list it on the tag they placed on the van.

Mike
Be careful. Ford crash tested the their vans at 7,900lbs to establish FMVSS certification. In order for a manufacturer to build a unit that exceeds that weight they would have to do their own crash tests. A 6 figure investment. Once a unit has been sold it is the responsibility of the owner to adhere to the weight ratings established for the vehicle, which in the case of the Ford E-350, would be 9,500 lbs. Exceeding that weight leaves the owner open to litigation when involved in an accident. It is more involved than just putting a label on the door.
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Old 04-05-2013, 11:12 AM   #22
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Re: Tire Pressure ?

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Originally Posted by geoffff
but I don't see how it would *hurt* gas mileage.
I think Pschitt simply meant that your tires will wear quicker (i.e., less miles per tire). Note that he didn't say gas mileage.

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Old 04-05-2013, 11:21 AM   #23
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Re: Tire Pressure ?

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Originally Posted by vwteleman
I think Pschitt simply meant that your tires will wear quicker (i.e., less miles per tire). Note that he didn't say gas mileage.
Yes, sorry for my poor English...
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Old 04-05-2013, 12:51 PM   #24
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Re: Tire Pressure ?

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Originally Posted by Larry Yates

Be careful. Ford crash tested the their vans at 7,900lbs to establish FMVSS certification. In order for a manufacturer to build a unit that exceeds that weight they would have to do their own crash tests. A 6 figure investment. Once a unit has been sold it is the responsibility of the owner to adhere to the weight ratings established for the vehicle, which in the case of the Ford E-350, would be 9,500 lbs. Exceeding that weight leaves the owner open to litigation when involved in an accident. It is more involved than just putting a label on the door.
That probably explains why there's no change in weight rating on my door; there's the Ford one, and a SMB one, both with the same weights. I'd say the capacity has changed, but it was the certification of such I was curious about. Thanks for the explanation (kind of ironic though, since at the time Ford vans were flipping cuz of a lousy front end; Craig at Salem Kroger had actually been consulted on design defects).
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Old 04-05-2013, 08:16 PM   #25
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Re: Tire Pressure ?

Can someone explain to me why there is more weight on the rear axles than the front. I am assuming this based on the string of comments and the fact that rear tires are being inflated at a higher amount than the fronts.

I would have thought that with the engine of front, there would be more weight on the front tires?

If this is true, that is more weight on the rear tires than front, will the rear brake pads wear faster than the fronts?
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Old 04-05-2013, 11:44 PM   #26
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Re: Tire Pressure ?

Not in my case. The front brakes have always gone faster. My van is mid-11K Lbs. Lets just say to keep on topic, if the tires are at full tire pressure it will roll easier and be harder on the brakes.
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Old 04-06-2013, 08:20 AM   #27
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Re: Tire Pressure ?

Quote:
Originally Posted by silvett1
Can someone explain to me why there is more weight on the rear axles than the front. I am assuming this based on the string of comments and the fact that rear tires are being inflated at a higher amount than the fronts.

I would have thought that with the engine of front, there would be more weight on the front tires?

If this is true, that is more weight on the rear tires than front, will the rear brake pads wear faster than the fronts?
Im kinda wondering the same thing. More pressure in rears makes sense if your pulling a trailer, but day to day without a big payload, are we still supposed to runs higher pressures in the rear?

As far as rear brakes wearing faster than fronts, it typically wont happen. I cant say what the ratios are on the vans, but i was told most cars only direct 10-15% of thier braking to the rear wheels.
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Old 04-06-2013, 11:05 AM   #28
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Re: Tire Pressure ?

A one ton van is rated to carry 2000 lbs (one ton).
You put one ton of weight in the cargo area, and the weight will be more over the rear wheels than the front, thus higher rear air pressure. Running in SMB version you may still have more weight at the rear, a good reason to run your van over some scales to see where you are at.
An empty cargo van may not need extra psi at the rear.
I have always applied extra psi to the rear for the reason being, I would rather have the rear tires break loose first vs the front and the resulting front end push (understeer). Not that 4x4 van tires are going to break loose on dry pavement!
I apply this this to cars, trucks and motorcycles.

You can see semi-regularly a pick-up loaded with logs, or dirt/rock sagging in the rear with bulged out tires.
You can pretty much expect they did not bump up to max inflation, or their tires are under rated for the weight they are carrying. Different psi needed for different loads required.

I am glad to hear Larry Yates response, as I have never felt you can just throw in a set of upgraded axles and or springs, and in turn uprate your gvwr.
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Old 04-06-2013, 11:27 AM   #29
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Re: Tire Pressure ?

Quote:
Originally Posted by Larry Yates
Be careful. Ford crash tested the their vans at 7,900lbs to establish FMVSS certification. In order for a manufacturer to build a unit that exceeds that weight they would have to do their own crash tests. A 6 figure investment. Once a unit has been sold it is the responsibility of the owner to adhere to the weight ratings established for the vehicle, which in the case of the Ford E-350, would be 9,500 lbs. Exceeding that weight leaves the owner open to litigation when involved in an accident. It is more involved than just putting a label on the door.
Thanks.

My real concern was being over GVWR and getting caught at a weigh station and not being allowed to continue. I was weighed once in Canada in 2004 (less equipment then and underweight). At least with the uprated ID plate from Salem-Kroger I would probably be ok.

Many of our vans come out of Sportsmobile over the GVWR before we add our gear in it. I doubt anyone is removing stuff from their van to get under GVWR. It is a problem for many SMB's.

Mike
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Old 04-06-2013, 12:38 PM   #30
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Re: Tire Pressure ?

I agree with Mike; I'm wondering if people have asked SMB about it. My van is relatively unencumbered compared to some, and people add even more stuff on. There's a little RV worksheet in my documentation working out how much you can carry. I don't recall SMB telling me, in effect, "well, with your chosen layout you only need an E250" but maybe they did. I'm under, but I couldn't really add much without topping out. Never been weighed by the Authoritays, even off the backroads

As to tire pressure, since it does relate to weight, I expect most vans, even diesels with their heavier engines, are biased to the back in real weight. And they're designed that way, as noted, as load carriers. Those of us who've driven empty pickups are well aware of that, and how you sometimes have to ADD weight back there to get a decent ride if you're not laden. Bags o' sand in winter.

I add extra pressure to the rears on some of my vehicles as maxacceleration; many (most?) cars these days are designed with understeer built in (pushing, for NASCARites). It's generally easier for your typical crappy driver to recover from than oversteer (or looseness). But sometimes you WANT oversteer (watch a video of a rally driver, or an ATV turning) since it helps induce a turn more quickly. And most cars are weight balanced to the front anyway.

And the weight of your vehicle is dynamic. That stuff bouncing on your hitch? It's like a long lever with the rears being the fulcrum, lifting your front end, esp with an EB. But braking is the opposite: the weight pushes forward, and now you've got much more on the front. Again, this is helpful in steering: performance drivers brake not only to slow a vehicle, but to push the weight forward, induce grip in the front tires, loosen grip in the back, and allow the vehicle to turn quicker. In fact every driver does it, most just are unconscious of it.

So altering your tire pressures can affect that as maxacceleration noted. Indeed, if I leave mine highish and I get going on washboard, the rear can start asking to swap with the front. Time to lower pressure back there.
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