Tires...Tires...Tires

[Bob Thompson]

Part 1:
All the recent posts about tire failures got me thinking. This whole idea of blowouts is very unappealing. Besides the danger issue, I hate the potential damage to the wheel well. So, I've committed time and money to solve the problem. My '97 Excella 25 weighs about 6000 lbs. at travel weight. I've made numerous alterations to get the dry weight down to about 5400 pounds. The 5400 lbs. is roughly the weight supported by the tires or 1350 lbs per tire. The other 600 lbs. is supported by the hitch and truck. At 1350 lbs of load, you wouldn't think Load Range D tires would blowout when carrying less than 60% of their rated capacity of 2350 lbs, but my Goodyear Marathon did!

After some research, I have found the problem is the lack of credible manufacturers making quality 15" ST tires. Goodyear Marathons, Carlisles, Coopers, and (I think) Titan are about the only US manufacturers, the rest are Asian. None have a good reputation for making durable products. Google it and see what comes up! What I want is the reliability of Michelin or BFG.

So you're supposed to use ST (special trailer) tires instead of LT (light truck) tires because the sidewalls are stiffer to reduce sway! The ST tires on my trailer are rated 8 ply Load Range D, but when I read farther on the tire, I see the tire sidewall is actually constructed of 2 polyester plies, not 8! So you shouldn't believe the bull out there about ST tires being made with extra stiff sidewalls to reduce sway. Go read your tires! If the tires were actually 8 plies, there would be fewer blowouts.

[Bob Thompson]

Part 2: The solution

To get high quality tires, you have to move up to 16" wheels, and for them to fit into the wheel wells, you have to pay close attention to the wheel width and backspacing. For Airstreams like mine, you'll need 16x6 to 16x7 wheels with a backspacing of 3.5" to match the stock wheels. You can go as high as 3.75" on backspacing. Next, you need to choose a commercial LT tire with a diameter and load rating matching or slightly higher than your original tires. The tires currently on my trailer are 28.5" in diameter and Load Range D. The tires I chose are BF Goodrich Commercial T/A All Season LT225/75R/16/D. Their diameter is 29.4" and they have a Load Rating D of 2335 lbs. @ 65 psi. This should work fine for my trailer and they are warrantied to last 50,000 miles. I Googled them several times and couldn't find a single case of blowout caused by tire failure either on the tow vehicle or on the 5th wheel being pulled.

For wheels, I went with American Racing Outlaw II clearcoated aluminum wheels which have a 2450 load rating. If I wanted a larger safety factor, I would opt for a Load Range E tire (3000 pounds), and wheels also rated for 3000 lbs. The LR "D" tires are usually 65 psi and LR "E" are usually 80 psi. I chose the aluminum wheels to reduce weight (about 65 pounds less than steel) and because they come with factory clearcoat so I won't have to polish them.

It is important to note, commercial LT tires are required by DOT to safely carry 15% more load than their rating. This is not the case with ST tires. Commercial LT tires are the tires you see everyday on service and delivery trucks as well as SuperDuty Fords and HD Chevys, and 3500 Dodge trucks pulling 40 foot 5th wheels. They are every bit up to the task of carrying my Airstream. Some of the other top choices for commercial LR "D" and LR "E" tires are Michelin XPS Rib, Yokohama TY213A, Cooper SRM II, and Toyo.

Anyone wanting to reduce tire problems might consider the path I've taken.

[Steve Heywood]

Originally Posted by Bob Thompson

My '97 Excella 25 weighs about 6000 lbs. at travel weight. I've made numerous alterations to get the dry weight down to about 5400 pounds.

For Airstreams like mine, you'll need 16x6 to 16x7 wheels with a backspacing of 3.5" to match the stock wheels. You can go as high as 3.75" on backspacing. Next, you need to choose a commercial LT tire with a diameter and load rating matching or slightly higher than your original tires. The tires currently on my trailer are 28.5" in diameter and Load Range D. The tires I chose are BF Goodrich Commercial T/A All Season LT225/75R/16/D. Their diameter is 29.4" and they have a Load Rating D of 2335 lbs. @ 65 psi.

Bob,

You definitely got my attention but of course I have a few questions.

First: What did you do to reduce the weight of your trailer by 600 lbs?

Second: The wheelwells of your 97 25' Excella should be nearly identical to the wheelwells on my 97 30' Excella. I consider them a tight fit with my current 225/75-15 Goodyear Marathons. How are you for room? Any chance you can either post a picture or email me one?

Last: Have you had a chance to tow your trailer with the new tires and wheels yet? If so any change in handling?

Thanks,

[Steve Heywood]

Originally Posted by Bob Thompson

For wheels, I went with American Racing Outlaw II clearcoated aluminum wheels which have a 2450 load rating. If I wanted a larger safety factor, I would opt for a Load Range E tire (3000 pounds), and wheels also rated for 3000 lbs. The LR "D" tires are usually 65 psi and LR "E" are usually 80 psi. I chose the aluminum wheels to reduce weight (about 65 pounds less than steel) and because they come with factory clearcoat so I won't have to polish them.

When I looked on The American Racing website I couldn't find an Outlaw II wheel in 16X6 or 16X7 with the backspacing you mentioned. Do you happen to have the part numbers, this wouldn't be the 1st time their site didn't mantion all the wheels they make.

Thanks again,

[joatmon]

Originally Posted by Bob Thompson

If the tires were actually 8 plies, there would be fewer blowouts.

I used to be concerned about ply count. Check this thread and you can read more about this quote:

Originally Posted by Action

Actual plys vs ratings changed when manufactures could develop tires that had the same strength with less plys. Less plys less heat. And heat kills tires. If one could make a one ply tire with the load capacity of 2000 #'s per tire they would do it. And it would be easier and cheaper to build. (The material may be more $)

[87MH]

Don't forget the (rubber) tire stems as being problematic.....

It's amazing how frequently the rubber stems seem to factor into tire failures and how difficult they are to obtain.

None of the "small" tire centers I have been to have carried metal stems, the only place I found them was the local NAPA store (catering to farms and ranches).

I know several of the tire failures here on the forum have been attributed to rubber stem failures, and I lost both the (brand new - about 200 miles) duallys on the driver's side of the E-350 a couple of years ago - Ford owners take note! I speculate that I lost one, and when that one lost it's tread it threw the other one also.

The metal stems are only a few bucks each, but with the heavier sidewalls you need air powered tire tools to replace the rubber stems, and then rebalance.

One thing for sure, if I EVER get into tires running more than 50 psi I WILL spend the bucks to replace the rubber stems with higher rated metal stems.

[Bob Thompson]

Hi Steve, The AR part number for the Outlaw II 16x7 wheels is: 62-67764, but I understand they are no longer produced under that number, but under a different number (because of a different clearcoat) that isn't listed on their website. I don't have the new number, but it was a question I asked in case I damaged a rim and needed to replace it. I had to look long and hard to find the set of wheels I purchased. At one point I was considering the American Eagle 055 wheel which is very similar and has matching numbers, but none of the American Eagle wheels have clearcoat.

As for removing 600 pounds from the trailer, it came from many many sources. I think of weight reduction just like the wheels. I opted for aluminum wheels because they are in total about 60 pounds lighter. Do this sort of thing 10 times and you have 600 pounds. I removed the sofa, side tables, twin beds, rear nightstand cabinet, passenger side upper cabinet, and carpet/pad. I replaced the sofa with Ekornes chairs, replaced the Univolt with an Intellipower, replaced the twin beds with a pedestal RV queen replaced the carpet/pad with sheet vinyl, didn't replace the side tables or other cabinets, etc, etc. Another way I've taken out weight is to remove excesses like wire length. Everywhere I seemed to be working to renovate my trailer there was excess wire. I would shorten those wires removing the excess. I probably took 20 pounds of wire away just in the area of the batteries and Univolt when I combined the batteries into one area and put in the Intellipower. In the refrig service area, there was a coil of wire for, I presume, a solar panel. I cut the wires so they were only about 8" long, but removed the other 16 feet or so. Multiply these weight reducing attempts by a factor of 2 or 3 and you get to where I am now. I removed the rear drapes and put in day/night shades, rebuilt the valences to make them lighter, rebuilt the upper cabinet soffits, etc. etc. Many of these things make the trailer seem more spacious. Did I give up something? I don't think so. I've even been told by some Airstream owners that my trailer has the most beautiful and usable interior they've ever seen. I guess it is the architect in me.

The tire and wheel package will be swapped with the original wheels this week, so I haven't towed with it yet. I will be sure to take Dennis's advice and get the metal valve stems installed.

As for tire fit, the cross section of the new tires has the same aspect ratio as the tires already on the trailer, but the new tires are about 1" larger in diameter. There is room to fit the very slightly larger diameter, and since the backspacing and cross-section are the same there will be no issues with fitting in the wheel well.

[Bob Thompson]

Similar info on another website: http://www.motorhomemagazine.com/for...pging/1/page/1

[Rog0525]

Originally Posted by Bob Thompson

Part 2: The solution
To get high quality tires, you have to move up to 16" wheels, and for them to fit into the wheel wells, you have to pay close attention to the wheel width and backspacing.

Before anyone switches to 16" tires, I think this caution from Inland Andy has to be considered:

Originally Posted by Inland RV Center, In

CAUTION

Use extreme caution when increasing wheel diameters.

Most trailer models "DO NOT" have enough wheel well clearance to accept larger wheel/tire combinations.

To do so, especially if the axles show signs of settling, and the trailer is loaded for travel, will allow the tires to rub on the plastic wheel wells, usually resulting in a fire that you won't see until it's way too late to put out.

Then, the fun really begins when you deal with your insurance company, and they find out that "YOUR" modification was the cause of the fire.

If Airstream felt that 16 inch tires were better than 15 inch tires, they would have installed them.

Again, use extreme caution.

Andy

source: http://www.airforums.com/forum...ion+and+wheels

[Torii]

Another thing to consider is the "ride" It is my impression that the Radial Marathons provide a softer ride for the Airstream. Wouldn't that be a good thing?

[85MH325]

Bob, all brands and makes of tires can and do fail. I was a victim of "D" rated Firestones on my Excursion and literally watched the sidewalls fail as I drove it on a single trip from being overloaded for weight with my 34' Airstream in tow. We got them replaced with "E" range tires, and fortunately we averted catastrophy on that trip.

Every failure I've had on trailers, as it turns out, have been radial car/truck tires. I've not yet lost an ST tire on a trailer that was properly inflated and in good condition. I DID, however, on a single trip lose TWO new car radials (out of four) on a boat trailer I used to tow. I had put new tires on it, and didn't know about ST rated tires in those days...

Since then, I've had several tire folks tell me that car/truck radials fail on trailers because of sidewall overheating. Apparently there is some dynamic that causes car radials to fail that ST radials manage better in a trailer application. I'm not a tire expert nor claim any special knowledge in the area, but I'll stay with the STs.

Roger

[Bob Thompson]

The Marathons, Nankangs, Carlisles, etc. are 2 ply sidewall just like the BF Goodrich tires. That and 50-65 psi tire pressures should produce similar rides.

As for clearance, yes, it is a good thing to check clearance in the wheel well. However, if your tire/wheel well situation is so close that a tire sticking 1/2" farther into the wheel well will rub, then you've already got serious axle problems and should have them fixed. My current tires have 4.75" clear at the top of the wheel wells. The new tires will reduce that to 4.3". There's still plenty of vertical travel room.

[Steve Heywood]

Originally Posted by Bob Thompson

Hi Steve, The AR part number for the Outlaw II 16x7 wheels is: 62-67764, but I understand they are no longer produced under that number, but under a different number (because of a different clearcoat) that isn't listed on their website. I don't have the new number, but it was a question I asked in case I damaged a rim and needed to replace it. I had to look long and hard to find the set of wheels I purchased. At one point I was considering the American Eagle 055 wheel which is very similar and has matching numbers, but none of the American Eagle wheels have clearcoat.

As for tire fit, the cross section of the new tires has the same aspect ratio as the tires already on the trailer, but the new tires are about 1" larger in diameter. There is room to fit the very slightly larger diameter, and since the backspacing and cross-section are the same there will be no issues with fitting in the wheel well.

I wasn't worried about width but overall diameter. I'll glue an 1" thick piece of foam above my current tires and see if I have any contact on my upcoming vacation.

[Coloradobus]

Bob Thompson,

I just found out today, that Carlisle Tire, (www.carlisletire.com) has ST225X75X15 trailer tires (10 ply) Load range "E" available at Discount Tire. They are about $85.00 a piece. We are putting a 6,000 lb axle on our '67 Globe Trotter, removing the Load Range "C" Carlisle 205X75X15 the PO put on. After our rennovation, our Globe Trotter weighs a more. Originally, from the factory trailer weighed 3,091lb. Now loaded it weighs 3,980 lbs. These LR"E" tires have a capacity of 2,830 lbs.per tire max inflation of 80 psi. Our current tires can carry 1,820 lbs. We barely make it. Of course, if you subtract 600+ lbs tongue weight off the tires we are a bit better. I'm going to go for these "E" tires after we put the axle on next month. Might as well go all the way and get all the beefy-ness we can get.

[uwe]

Originally Posted by Coloradobus

Bob Thompson,

We are putting a 6,000 lb axle on our '67 Globe Trotter, removing the Load Range "C" Carlisle 205X75X15 the PO put on. After our rennovation, our Globe Trotter weighs a more. Originally, from the factory trailer weighed 3,091lb. Now loaded it weighs 3,980 lbs.

I would strongly advise against a 6000lb axle on a Globetrotter.
I firmly believe that going over the factory rating by more than about 500lbs makes Airstream trailers ride very poorly.
Too stiff an axle is as bad as a worn out axle.
If it weighs 4000lbs loaded, you will be fine with a 4000lb axle, because you can deduct the tongue weight from the axle weight. ( assuming you weight the trailer as a whole, not just the axle weight)
So theoretically, you'll have and axle only weight of about 3500lbs or so, plus 500 lbs tongue weight, give or take few.

[Coloradobus]

Uwe, Too late, the axle is in. We will be weighing the trailer at our rally this weekend. With all we have loaded since the last weighing, the Globe Trotter is going to weigh more than four thousand pounds. We are also thinking of re-enforcing the frame to accomodate a bike rack for 2 bikes. We saw a Bambi at the vintage rally last year that had an additional steel run the length of the frame to carry more weight. R

[Inland RV Center, In]

Coloradobus.

Remember before you proceed with a bike carrier as you proposed, that the Airstream shell holds the frame "up".

Therefore you will increase the stresses on the shells ability to hold the frame "up", which is the big cause of rear end separation, along with lack of proper running gear balance.

Andy

[Chuck]

Andy, what would you recommend as a reinforcement to support such a modification? (bike-rack or other weight added to the bumper/rear-end).

I've seen this description before, about the shell holding up the frame; seems to me that adding steel to the frame would actually be counter-productive. it would just add more weight, which would pull away from the shell even more. unless something around the wheel area, like those plates made for repairing the frame-sag problem would counteract such forces in the rear....

[Coloradobus]

Andy,
Point taken, however let me add this. We already suffered from rear-end separation from rotton wood in the floor. While repairing the separation, we ran a 2 inch square steel re-enforcing beam under the house. Then attached bolts thru the "C" channel of the house thru this beam that is attached to insides of the main frame rails, making sort of a box end at the bumper. The Globe Trotter came to us with a spare tire carrier. I believe that's what helped the rearend separation with the tire vibrating. After our completed reapairs, the spare tire carrier was "rock solid" and didn't move. Even with this carrier at the rear, our tongue weight is 600 lbs.
What your saying, is nothing can be done to help the structural integrity of the airstream to carry anything canti-levered over the bumper, including a grey tank?

[Rog0525]

Coloradobus, just let me stick my nose in long enough to say that those stiff 10 ply tires will increase the shock impact to your GT and could result in more damage.
I 'm sure that I'll be corrected if I'm wrong, but I don't think Airstream has ever condoned tires more than 8 ply.
If the intent of using bigger and stiffer tires is to avoid blowouts, why not use solid rubber tires instead? That would be ridiculous of course, but sometimes we have to carry theories out to the extreme to understand the equation.