Hi CapriRacer, Finally getting this this response. Thank you for your thoughts on the tire bulge. I’ll comment below on the loads.
CapriRacer wrote:
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I am also going to take issue with your math - AND EVERYONE PAY ATTENTION!! I have seen others do this type of math and I think there is a hidden pot hole there.
The principle is that for tire loading you want the absolute WORST loading. The load an individual tire experiences is NOT the average. Tires don't average out the load and neither should you.
Yes, you are correct. I made an assumption, bad this I know, that I had enough reserve and I may not. I will correct this. A take away on my part is to get actual individual wheel position loads. I will do that this weekend as I need to hook up the truck to get the WD effects on included.
CapriRacer wrote:
First you said the axle loads were 7660, but added that the water tank adds 266# more axle load. Why didn't you add that to the axle loads? Why did you use the 7660# for your calculation as is when you already know the side to side loading is different? What about the front to rear loading difference?
There is a slight misunderstanding from my post based on your response. Sorry I was not more clear. I stated this.
JBarca wrote: - Axle weight scaled at 7,660# with no water. When I fill the fresh tank over the front axle it adds 266 # more axle load.
My statement was meant that I have a weight slip at 7,660# which includes WD transferred from the truck. Not included is when I carry fresh water which is over the front axle which adds 266# more. The equalizer moves some of this but I do not know yet what that is.
I then stated this which you may have missed:
JBarca wrote: - LRD tires have 2,540# load at 65 psi. X 4 tires = 10,160# of tires against a scaled axle weight of 7,926#. Or 2,234# of reserve capacity.
Here I did include the water weight. 7,660 + 266 = 7,926# as I expressed above against 10,160# of tires. So yes, I did include the water. However regardless, I do not yet have individual wheel location weights and I need to rectify this.
CapriRacer wrote:
OK, so I'm going divide the axle loading by 4 to get 1915#. Add 133# for the water = 2048. I estimate that there is a 15% variation in loading by wheel position, so the worst case is 2409# - and I recommend a 15% reserve, so the tire should be capable of 2834#
That mean an ST225/75R15 Load Range D is about 12% under that value.
I'd recommend going up to a Load Range E and 80 psi as the inflation pressure.
I need to get actual weights and go from there. If this camper setup needs an ST tire capacity of 2,834# or 11,336# total for all 4 tires, there is a large miss in the design. And this is then an industry wide problem.
This is what I had prior thought, correct or not. This camper is at least built from the factory to have the running gear that will support the entire GVWR of the camper. The GVWR is 10,000# and the tire capacity at max is 10,160#. The truck holds 15% of this weight on the tongue. And if I ever had a 10,000# GVW and 15% is on the tongue, then the running gear should have 15% extra capacity.
I was loaded to 7,926# on the axles and my tongue weight is 1,375# for a GVW of 9,301#. So I made a bad assumption I still should have had reserve as I should be able to add still 699# more cargo to reach the 10,000# GVWR. Some split on the tongue, some on the axles.
I am not contesting the fact I need to get individual wheel loads. I will do this and report back. However my camper is at least built with running gear to handle the entire GVWR. Many brands cheap out and declare the truck is going to hold part of the GVWR so they install lighter running gear. If my setup is over, those poor folks do not have chance of not being into issues with ST tires.
In my case you have accurately pointed out a miss in my assumptions and I need to base this on actual wheel loads. Again, I will rectify this. Thank you for showing me this. I see the light!!
Question: Where does the 15% variation in loading addition by wheel position thought come from? You added the entire water weight to the front axle not accounting for any of it to be spread by the equalizer. I could not follow how you came up with this. This is like an additional 15% extra. Maybe I will figure this out this weekend when I weight each wheel location. I have a force jack and can do this here in the yard. With and with out water.
CapriRacer wrote:
JBarca wrote: ......Before I buy anything new, I need more research into why my tire failed and what to buy to help not have the same problem then next time.........
To do that you'll need to take the tire off the vehicle and PAY a tire forensics specialist about $2K. That's the going price.
But if you are willing to accept educated guesses that are worth the price you paid - tire is too small (based on my analysis earlier)
Yes, I know the cost of lab work. I buy forensic metallurgical analysis along with FEA failure analysis often and your $2K is a lot cheaper… LOL However on the private sector $2K is a lot and I can buy a few sets of tires for that cost. Me being me however, I have to at least search this out to make sense of it in my own head before I buy new anything.
Did I understand this correctly, you are thinking the tire loads are what caused the tire bulge? I respect your opinion and I’m trying to understand that I have not somehow else created a situation other then weight to cause this failure. When a tandem axle TT turns the tires are doing some really strange twisting in the side walls. My thought was that somehow this twisting may have upset the inside of the tire in the tread area or would side turns more affect the side wall construction?
Thanks for your time on this. Greatly appreciated.
John
John & Cindy
2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10
CC, SB, Lariat & FX4 package
21,000 GCWR, 11,000 GVWR
Ford Tow Command
1,700# Reese HP hitch & HP Dual Cam
2 1/2" Towbeast Receiver
2004 Sunline Solaris T310SR
(I wish we were camping!)
ExRocketScientist wrote: John -- Unless you have only 3" of clearance in your wheel wells, if you don't mind getting new wheels, you might consider the BFGCTA in LT225/75R16 Load range E. It is about 29.6" in diameter. Your current tires are about 28.3 inches. If you have about 3 and 3/4 inches of clearance now, these would probably work for you. You could get a tire and wheel package from trailertiresandwheels.com in Edon -- the shipping shouldn't be too bad for you since you are in the Columbus area.
Hi Ex,
Another forum member tipped me off on these. I wish they would work.
Sunline built this camper as a low rider. Even with a flush floor slide and a 10" wide frame. I have 2 1/2" tire to wheel well clearance and this is on a rubber equalizer. So 2 1/4 to 2 1/2" is what I have. I am at the limit.
Another hit is I have the shorter springs. I'm on 32" axle spacing not 33 like many other brands in this size TT. This one will not get me as bad as the wheel well but still a concern with this rubber equalizer.
Long term I can deal with the 5 new rims cost and 5 new tires. I will soon be buying a 10,000# GVWR flat deck trailer to haul equipment on here locally and it uses these same tires I have now on the camper. This is a private trailer maker and he may make me a deal for me to bring my own wheels and tires so I can reuse these with new ST's on them. Running ST's on a flat bed use for 1 hour hauls not often is a lot better then the TT that gets a lot of towing and in 6 to 8 hour stretches some times.
If coming out of this I end up needing new wheels and tires my options are not many. So far I have the ST E range that Capri Racer suggested and that is about it. I have not found any LT tire that fits the diameter and at least a 2,500# max load rating. If some one knows of a 28.3" OD tire with that load rating in a LT please point it out.
Doing an axle flip to gain 4" more inches is not great in my case. DW already does not like the 4 steps I have to get in, going to 5 steps to get in is a concern. The extra wind drag does not help either. This truck sucks enough fuel now...
Thanks for the info, If I can come to grips and work in 16" tires then the options open up.
Before I buy anything new, I need more research into why my tire failed and what to buy to help not have the same problem then next time.
Here're a couple of links that I think very informative...much of the research has been conducted on over-the-road big trucks, but the principles/conditions described are often much the same as those encountered by any highway tires. No brand recommendations, of course. But diagnosing the cause ought to make the choice of new tires easier, especially if as it sometimes turns out the culprit is something other than the tire itself.
ExRocketScientist wrote: What do you think of replacing it with the LT225/75R16 LRE BFGCTA?
From a load perspective, it's OK, but there are clearance issues that have to be considered, plus definitely a new wheel. I think there are suitable alternatives without having to deal with the last 2 items.
JBarca wrote: .......A take away on my part is to get actual individual wheel position loads.......
Exactly!
JBarca wrote: .......I need to get actual weights and go from there. If this camper setup needs an ST tire capacity of 2,834# or 11,336# total for all 4 tires, there is a large miss in the design. And this is then an industry wide problem.......
This is the conclusion many have reached.
JBarca wrote: .......This is what I had prior thought, correct or not. This camper is at least built from the factory to have the running gear that will support the entire GVWR of the camper. The GVWR is 10,000# and the tire capacity at max is 10,160#. The truck holds 15% of this weight on the tongue. And if I ever had a 10,000# GVW and 15% is on the tongue, then the running gear should have 15% extra capacity.......
I have made a conservative estimate that individual tire loads vary up to 15% - and if that is the case, then the worst loading on a tire would have NO reserve capacity
JBarca wrote: .......I was loaded to 7,926# on the axles and my tongue weight is 1,375# for a GVW of 9,301#. So I made a bad assumption I still should have had reserve as I should be able to add still 699# more cargo to reach the 10,000# GVWR. Some split on the tongue, some on the axles.
I am not contesting the fact I need to get individual wheel loads. I will do this and report back. However my camper is at least built with running gear to handle the entire GVWR......
That's not good enough if the individual tire load vary - which we know they do - and that should be factored into the design.
JBarca wrote: .......Many brands cheap out and declare the truck is going to hold part of the GVWR so they install lighter running gear. If my setup is over, those poor folks do not have chance of not being into issues with ST tires.
In my case you have accurately pointed out a miss in my assumptions and I need to base this on actual wheel loads. Again, I will rectify this. Thank you for showing me this. I see the light!!
Question: Where does the 15% variation in loading addition by wheel position thought come from?.........
I tried to find some data to back this up, and only found a smattering. It's based on a guesstimate on my part - a conservative one, such that I will be on the safe side. I could be wrong and the actual value could be lower, but until I find solid data that contradicts it, I'm sticking with the value.
JBarca wrote: .......You added the entire water weight to the front axle not accounting for any of it to be spread by the equalizer. I could not follow how you came up with this.....
Again, I was being conservative. I really really don't want to give advice that contains a fatal flaw just because I underestimated some value.
Besides, if I over estimate the size needed, then it's just a bit more expensive - as opposed to a failed tire and the damage that it makes.
JBarca wrote: ....... This is like an additional 15% extra. Maybe I will figure this out this weekend when I weight each wheel location. I have a force jack and can do this here in the yard. With and with out water......
Yes, definitely do that. Actual values always trump estimates.
JBarca wrote: .......Yes, I know the cost of lab work. I buy forensic metallurgical analysis along with FEA failure analysis often and your $2K is a lot cheaper… LOL However on the private sector $2K is a lot and I can buy a few sets of tires for that cost. Me being me however, I have to at least search this out to make sense of it in my own head before I buy new anything.
Did I understand this correctly, you are thinking the tire loads are what caused the tire bulge?......
There are 2 different questions here. What caused the tire to fail and what can be done to revent a reoccurance. I'm asnswering the second one.
To answer the first one, I would really want to closley examine the tire in question.
JBarca wrote: ....... I respect your opinion and I’m trying to understand that I have not somehow else created a situation other then weight to cause this failure. When a tandem axle TT turns the tires are doing some really strange twisting in the side walls. My thought was that somehow this twisting may have upset the inside of the tire in the tread area or would side turns more affect the side wall construction?.........
If I were confronted with the tire in question, the first thing I would do is have the tire examined with a Shearograohy unit.
Shearography is a non-destructive test where the tire is placed in a sealed chamber and phtotgraphed in an unmounted, un-inflated state. Then a small vacuum is applied to the chamber and the tire is photographed again.
The photos are superimposed over each other (in a computer) and areas of movement are identified. Any area that moves is an area with air trapped inside the tire - a separation. That gives a clue as to what areas are failing.
The normal follow up is to cut the tire in the separated areas to see what components are involved. This might reveal the starting point of the separation.
Typically radial tires fail at the edge of the belts and not the center of the belt.
You mentioned the turning action that takes place in trailer tires and I don't think this would cause any issues with the sidewall - and I'll explain why.
There is a test that the company I work for uses to evaluate belt edge durability. It consists of heat aging a tire (placing a tire in an oven for a period of time) then tesing the tire on a pulley wheel (standard tire tesing equipment), then cycling the tire with varying degrees is slip angle. This stresses the belt edges.
Without the slip angle cycle, the tire doesn't experince belt edge separations, but the varying slip angle does.
So I think this is more a belt edge phenomenon.
I haven't seen anyone report any sidewall failures - except for those normally associated with run flat (air loss) situations.
ExRocketScientist wrote: John -- Unless you have only 3" of clearance in your wheel wells, if you don't mind getting new wheels, you might consider the BFGCTA in LT225/75R16 Load range E. It is about 29.6" in diameter. Your current tires are about 28.3 inches. If you have about 3 and 3/4 inches of clearance now, these would probably work for you. You could get a tire and wheel package from trailertiresandwheels.com in Edon -- the shipping shouldn't be too bad for you since you are in the Columbus area.
Hi Ex,
Another forum member tipped me off on these. I wish they would work.
Sunline built this camper as a low rider. Even with a flush floor slide and a 10" wide frame. I have 2 1/2" tire to wheel well clearance and this is on a rubber equalizer. So 2 1/4 to 2 1/2" is what I have. I am at the limit.
Another hit is I have the shorter springs. I'm on 32" axle spacing not 33 like many other brands in this size TT. This one will not get me as bad as the wheel well but still a concern with this rubber equalizer.
Long term I can deal with the 5 new rims cost and 5 new tires. I will soon be buying a 10,000# GVWR flat deck trailer to haul equipment on here locally and it uses these same tires I have now on the camper. This is a private trailer maker and he may make me a deal for me to bring my own wheels and tires so I can reuse these with new ST's on them. Running ST's on a flat bed use for 1 hour hauls not often is a lot better then the TT that gets a lot of towing and in 6 to 8 hour stretches some times.
If coming out of this I end up needing new wheels and tires my options are not many. So far I have the ST E range that Capri Racer suggested and that is about it. I have not found any LT tire that fits the diameter and at least a 2,500# max load rating. If some one knows of a 28.3" OD tire with that load rating in a LT please point it out.
Doing an axle flip to gain 4" more inches is not great in my case. DW already does not like the 4 steps I have to get in, going to 5 steps to get in is a concern. The extra wind drag does not help either. This truck sucks enough fuel now...
Thanks for the info, If I can come to grips and work in 16" tires then the options open up.
John
Something doesn't add up here John. My fiver came with 28.3 OD tires and has a 9.5 inch tall frame. After we adjusted the suspension so it would tow level with our truck, we had about 5 inches of clearance in the wheel wells, which is just the flat bottom of the floor. It is a triple step camper, and the first step up was about an inch more than the rest. So we have to step up four times to get in, just like you. Your camper sounds very similar to my fiver, I would only expect the bottom step to be about a half inch higher off of the ground because your frame is a half inch taller. I would think you should have about 4 inches or so of clearance in your wheel wells.
The other option you have if you want to do the LT upgrade without doing an axle flip is to have a commercial truck frame shop put a 2" subframe on it (oh wait a minute -- you weld and would probably do that yourself). I know you ended up reinforcing your frame and doing the equivalent of the Mor Ryde X-Factor -- the subframe would preclude the need for that.
One of the things I have never posted is pictures of the "thing" I put in front of my door and throw a mat on. We started out using wooden pallets so we could have a mat that did not sit in the mud. Then we progressed to nice little platforms of 5/4 deck boards attached to 2x4s laid flat (gives a 2.5 inch high platform). I got on a weight reduction kick and wrapped some 1" think extruded polystyrene in epoxied fiberglass biaxial mat (I made saw cuts almost a half inch deep 1" apart on both sides with the direction perpendicular from one side to the other and put in some fiberglass there as stiffeners). This gives me a 1.25" platform for the mat and evened up the step heights getting into my fiver.
Thanks for your reply. If the weather cooperates this weekend I will get wheel position weights and report back.
A question on the E range ST tire you suggested. In my case the load will not be that high as Max of the E range tire at 80psi. Is there a concern of high center tread wear running 80 psi? Or is it in this case that the tire will age out mostly like before it wears out providing good axle alignment. Sort of like where I am now.
I can tell on the D's I have now the center is wearing slightly more then the outer threads. Granted I'm measuring with a dial caliper to see this. I attributed this to running 65psi verses the load on the tire. On the E's this might be more pronounced. I do not see this as a show stopper, more of a curious question.
Another question is a thought of harder bounce due to the E range tire? On a truck/car this shows up for sure, on a TT, well I do not know. In my case I have a rubber equalizer and shocks to help the cause.
Thanks
John
PS. I will need new rims to go to E range. Mine do not list a PSI, only a load weight that lines up with a D tire. I'm not going to attempt 80 psi in a rim intended for a D. I know enough about pressure vessels not try that. No 80 psi stamp means, no.
Something doesn't add up here John. My fiver came with 28.3 OD tires and has a 9.5 inch tall frame. After we adjusted the suspension so it would tow level with our truck, we had about 5 inches of clearance in the wheel wells, which is just the flat bottom of the floor. It is a triple step camper, and the first step up was about an inch more than the rest. So we have to step up four times to get in, just like you. Your camper sounds very similar to my fiver, I would only expect the bottom step to be about a half inch higher off of the ground because your frame is a half inch taller. I would think you should have about 4 inches or so of clearance in your wheel wells.
The other option you have if you want to do the LT upgrade without doing an axle flip is to have a commercial truck frame shop put a 2" subframe on it (oh wait a minute -- you weld and would probably do that yourself). I know you ended up reinforcing your frame and doing the equivalent of the Mor Ryde X-Factor -- the subframe would preclude the need for that.
Hi Ex,
I only have 2 1/4 to 2 1/2" worth of clearance. Here see.
This is on the original setup when I had Maxxis tires
Here is the max suspension travel for my loaded weight. I am at the limit.
After I added the hanger stiffing and the 1 1/4" lift due to the loss of the EZ flex height and shocks. I now have 6 1/4" effective hangers.
Odds are high on your 5er you had a piece of 2 x 2 tube welded to the frame and then the hangers put on it. Lik this. This is off an old Jayco
Here is a side shot the day I put these Denmans on. Gee, 3 years and here I am....
I really do not want to do an axle flip on this setup. Yes I can build something to raise the camper 1" or 1.5" but boy, moving all 6 hangers down again....
If coming out of this I end up needing new wheels and tires my options are not many. So far I have the ST E range that Capri Racer suggested and that is about it. I have not found any LT tire that fits the diameter and at least a 2,500# max load rating. If some one knows of a 28.3" OD tire with that load rating in a LT please point it out.
John
Take a look at the very last item in this reference. Can you make a 29.3" tire work?
JBarca wrote: .......When we are talking "trailer" wheels what is an acceptable run out (total indicator reading) of the rim where the tire bead seats against?.........
Wheels? Mmmmmm. First, my expertise is in the rubber things. When it comes to wheels, Ihave limited experience and expertise.
But I will tell you I don't like TIR (Total Indicated Runout). The important value is the first harmonic - the best fit to the curve of a sine wave. I can't remember if a Hunter GSP9700 gives that value for the wheel or not - I'm thinking probably, because the machine does do matching.
The other half of this is that it is easier to make round wheels than it is to make round tires - and wheel's affect is greater - so the values has to be pretty small.
I'm thinking on the order of - rim only - 0.020" for the first harmonic and 0.030" for total (what Roger and I would call composite).
The question stemmed from the 0.040 TIR I measured on the stamped bore of a trailer wheel I measured the other night.
I keep hearing folks using wheel weights for balance but they do not talk about the lug centric rims we have on a trailer. My tire dealer wanted to spin balance mine using this wheel bore when I bought the Denmans. I told him it was a stamped bore, not machined like autos in relation to the lug holes. He did not understand. I asked if he had an adapter to balance it by the lugs holes and he said he thought so. However the one he had did not fit. They saw no problem balancing off this stamped hub.
I cannot see how on purpose balancing a tire by a bore that is 0.040" TIR (0.020" off center) with the center of rotation as being correct when I am supporting and rotating it by the studs. But then again I do not know the tolerance of balance for a tire.
All I could measure here is the rim which stemmed the question as if I have a dealer do this, it will be by the center hole. I have since gone to balancing beads as I cannot find someone with a hub to fit trailer wheels.
Any idea if this 0.040 TIR will matter or not?
Thanks
John
* This post was
edited 04/25/12 08:08pm by JBarca *
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