Why 65psi max for dually rims?

[Cubey]

This post is mostly just me complaining, why are the old Ford dually rims only spec'd to 65PSI max?

This was brought to my attention today by someone on a classic RV Facebook group today. Upon inspecting my spare rim, it does in fact say 65psi max. Is 65 considered all that's needed so that's what they say, or they actually incapable of standing up to more?

Not knowing this and going by my 87 F250 HD (3/4 ton truck with 1 ton rear) I bumped the RV's rear tires up to 80PSI many hundreds of miles ago. Thankfully I didn't have any problems. I will be lowering them to 65PSI to comply with the rim's spec of course, I just found that odd.

 

[The_Josh_Bear]

That's interesting, does it say that for dually only or does that go for the fronts as well?

Same tires as the pickups right? Load E?

If it's for dually only, then I'd be certain it's because 65psi accross 4 tires meets the rated GWR of the axle. But I don't know for sure of course.

 

[Cubey]

That's interesting, does it say that for dually only or does that go for the fronts as well?

Same tires as the pickups right? Load E?

If it's for dually only, then I'd be certain it's because 65psi accross 4 tires meets the rated GWR of the axle. But I don't know for sure of course.

They don't specify front vs dually pressures, just max pressure period. They are dually style rims so naturally they would also be used on the front.

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The old spare in the picture is load D, but the new Chinese tires I got from Walmart are E. The RV conversion tag doesn't spec which to use. Nor does the Ford one.

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These Load Range Es I got are spec'd at 2,680lbs at 80psi. The site doesn't say that, I checked the sidewall myself. That's normal for an LT215/85R16 tire, based on other tires online for sale.

But what is the weight capacity of Load Range E at 65psi?

Based on Load Range D of the same size (I only found one on TireRack, BFG Commercial T/A Traction), the max weight is 2,335lbs at 65psi, so maybe that's about the same for E at 65?

The Dana 70 axle is most likely spec'd a 7500lbs, or 1875lbs per tire if perfectly evenly loaded, which it's not on an RV of course, with a 4000W generator on one side and a grey water tank on the other. The driver's side bears much more weight.

 

[IDIBRONCO]

I have no answer on the air pressure question. Just a comment or two about your door plate. I'm fairly sure that El Dorado is no longer in Minneapolis, KS. It's in Salina, KS (about 12 miles south of Minneapolis) and is now called El Dorado Bus. That's where I've seen most of the incomplete vehicles that I've seen. And I mean incomplete as in Cab and chassis only. I'm.not sure if they still do RVs or just small busses.

 

[Cubey]

I have no answer on the air pressure question. Just a comment or two about your door plate. I'm fairly sure that El Dorado is no longer in Minneapolis, KS. It's in Salina, KS (about 12 miles south of Minneapolis) and is now called El Dorado Bus. That's where I've seen most of the incomplete vehicles that I've seen. And I mean incomplete as in Cab and chassis only. I'm.not sure if they still do RVs or just small busses.

I think they were bought out or something. It could be a different company making the buses.

 

[IDIBRONCO]

I think they were bought out or something. It could be a different company making the buses.

That could be. It would explain some things.

 

[FoolhardyIDI]

In my 1991 DRW 7.3IDI I ran 80psi on all 6 tires when hauling

 

[Tumbleweed210]

The short answer...is that those rims marked 65 psi were spec'd, and manufactured for the Automotive and RV industry to the then current standard. They were marked as such to belay any legal issues that might arise from any unforseen misapplication. And are ONLY intended and engineered to meet a D load rating at 65psi. Anything beyond that you're risking personal liability for any failure.

NOT TRYING TO BE A PARTY POOPER...BUT...HAVING WORKED FOR MANY YEARS IN THE RV; AS WELL AS THE TIRE INDUSTRIES...I HAVE SEEN THINGS GO VERY, VERY WRONG.

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Of course times have changed, so has the availability of certain sizes with certain load ratings. Just try to find a 9R-20, they used to be a common size for heavy trucks (including the duece-an-a-half)...And now-a-daze its 11R22.5 or 11R24.5

 

[IDIBRONCO]

Of course times have changed, so has the availability of certain sizes with certain load ratings. Just try to find a 9R-20, they used to be a common size for heavy trucks (including the duece-an-a-half)...And now-a-daze its 11R22.5 or 11R24.5

When I worked for a Goodyear store back in '06 and '07, they used to keep a few 9r and 10r20 tires on hand. There was a lot of old farm trucks around these parts that still ran them.

 

[Cubey]

The short answer...is that those rims marked 65 psi were spec'd, and manufactured for the Automotive and RV industry to the then current standard. They were marked as such to belay any legal issues that might arise from any unforseen misapplication. And are ONLY intended and engineered to meet a D load rating at 65psi. Anything beyond that you're risking personal liability for any failure.

NOT TRYING TO BE A PARTY POOPER...BUT...HAVING WORKED FOR MANY YEARS IN THE RV; AS WELL AS THE TIRE INDUSTRIES...I HAVE SEEN THINGS GO VERY, VERY WRONG.

Well, I'm not trying to overload the rims weight wise. I dropped the pressure to 65ish yesterday, so everything should be good in regards to that.

I found one of the extensions rubbing against the chrome cap with a very slight wear cut in it. I slipped some 5/8" vinyl tubing over it as a thin layer of protection until I can address it properly. The extension on the other side is different and it isn't an issue at the moment.

Any suggestions on where to buy good extensions, including holders to keep the extensions from rubbing against the outer wheel hubcap? Does O'Reilly carry them? I'm leaving where I am too soon to order any online now, unfortunately. Plus with stuff like that, I want to be able to return them if they are junk.

 

[Cubey]

Well, I could probably get these in time, based on the estimated delivery day. Who knows what quality they are though. But at least I'd have the wire holders for keeping the stems from rubbing, even if I don't use the extensions it comes with.

https://www.ebay.com/itm/6-Phoenix-...Stem-Extension-for-Dually-Wheels/302110614506

 

[Tumbleweed210]

Well, I'm not trying to overload the rims weight wise. I dropped the pressure to 65ish yesterday, so everything should be good in regards to that.

I found one of the extensions rubbing against the chrome cap with a very slight wear cut in it. I slipped some 5/8" vinyl tubing over it as a thin layer of protection until I can address it properly. The extension on the other side is different and it isn't an issue at the moment.

Any suggestions on where to buy good extensions, including holders to keep the extensions from rubbing against the outer wheel hubcap? Does O'Reilly carry them? I'm leaving where I am too soon to order any online now, unfortunately. Plus with stuff like that, I want to be able to return them if they are junk.

Without knowing your budget...I can honestly say that, in my experience, the most reliable extenders I've seen have been the cross-fires, haven't priced them in a few years. I've put them on fire trucks, ambulances, and school busses...my boss didn't like redos or comebacks for any customer, with special regard to those.

No matter which ones you end up with...don't just throw them on and "call it good". Get some dish soap in your favorite flavor, 3 or 4 Tablespoons to a quart in a squirt bottle, give 'er a spritz over the stem and core on your rim first, then install the extenders finger tight (if they don't seal send 'em back), and then check the entire length of the extenders (crimps, hose, and fittings). And for those out there with Aluminum Rims...rinse after (yes dish soap can damage some aluminum finishes).

 

[Cubey]

Without knowing your budget...I can honestly say that, in my experience, the most reliable extenders I've seen have been the cross-fires, haven't priced them in a few years. I've put them on fire trucks, ambulances, and school busses...my boss didn't like redos or comebacks for any customer, with special regard to those.

No matter which ones you end up with...don't just throw them on and "call it good". Get some dish soap in your favorite flavor, 3 or 4 Tablespoons to a quart in a squirt bottle, give 'er a spritz over the stem and core on your rim first, then install the extenders finger tight (if they don't seal send 'em back), and then check the entire length of the extenders (crimps, hose, and fittings). And for those out there with Aluminum Rims...rinse after (yes dish soap can damage some aluminum finishes).

Napa has some with the holders for $13.50 each that I may try.

https://www.napaonline.com/en/p/NTH90329

Or maybe I'll spring for these, where all are easy to reach for routine pressure inspection.

https://m.northerntool.com/shop/tools/product_200741184_200741184

I hate trying to reach the outer tire valves, they have no extensions right now and even with a double sided gauge, i can't get to it very well with the chrome rim covers.

I might eventually buy a cheap $100 tire pressure monitor with 6 sensors so I can monitor pressure without doing so manually.

 

[Tumbleweed210]

WARNING: THIS IS NOT A PRODUCT OR ANY OTHER KINDA ENDORSEMENT....

I saw some from Summit online...they seem reasonable, Summit's CSR's are usually very helpful...and they got a good return policy.

The problems I've seen with the "less expensive" extenders...namely leaks...have been at the crimps to the fittings, and the O-ring seals (yes, technically they are gaskets).

 

[Cubey]

WARNING: THIS IS NOT A PRODUCT OR ANY OTHER KINDA ENDORSEMENT....

I saw some from Summit online...they seem reasonable, Summit's CSR's are usually very helpful...and they got a good return policy.

The problems I've seen with the "less expensive" extenders...namely leaks...have been at the crimps to the fittings, and the O-ring seals (yes, technically they are gaskets).

Yep that's why it's something I would rather buy at retail price, so they can be exchanged/returned if needed without return shipping hassles. I might wait until January to change them, when I will have access to a paved driveway and my 3 ton floor jack for removing the wheels. Naturally, its impossible to reach the inner stem with the outer wheel on.

Vinyl tubing over the existing stem extension as a protector will have to suffice until then.

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