16" wheels/LT tires

[Ag&Au]

Originally Posted by TinTin

18 wheelers are truck and trailer (with hitch). Sideways scuffing would probably be similar to our Airstreams, scaled up by a big weight difference factor. Pretty sure they use tires designed for the application.

I'm not talking about the trailer portion of the semi. I am talking about the tandem axles on the rear of the tractor, or even a clearer example are the rear tires on a tandem axle Van, dump truck or motor home.

The thought behind this is: I am beginning to believe that the "sideways scuffing" of the tandem axle trailer tires in a turn that has been used as a reason why LT tires need to be "derated" is a non factor. In my analysis, the rear and probably even more so the front tires on a truck would be subject to more scuffing than the tires on a trailer in a turn.

Ken

[Inland RV Center, In]

Originally Posted by Ag&Au

I'm not talking about the trailer portion of the semi. I am talking about the tandem axles on the rear of the tractor, or even a clearer example are the rear tires on a tandem axle Van or dump truck.

The thought behind this that I am beginning to believe that the "sideways scuffing" of the tandem axle trailer tires in a turn that has been used as a reason why LT tires need to be "derated" is a non factor. In my analysis, the rear tires on a truck would be subject to more scuffing than the tires on a trailer.

Ken

Ken.

Try this out.

Using the truck, make a tight of turn that you can, and stop in the middle of that turn. Then observe the twist in the truck tires.

Then make a tight of turn that you can with the tandem trailer, and stop in the middle of that turn. Then, look at the twist in the trailer tires.

These tests should only be done on concrete or asphalt.

Andy

[dkottum]

Originally Posted by slowmover

The short of it is to keep max load at 85% for LT tires in trailer service and to keep pressure at sidewall maximum.

This is the reasonable starting point.

I don't think it's reasonable to keep pressure at sidewall maximum, which is 80 psi for my 16" Michelin LTX.

Andrew Thomson of Can-Am and Inland Andy, both long-time Airstream repair shop owners, say the rough ride will eventually damage the Airstream. For our particular trailer 65 psi is working well and leaves plenty of margin above load charts for the tire (depending on who is defining plenty of margin).

And yes Slowmover I understand your concerns about sway and somebody else's concern about tire rollover in turns, but am not seeing that as an issue, at least no more than if they were mounted on our truck and probably less.

[BoldAdventure]

Why is the sky blue?

Personally I have appreciated the advice os Switz and Dkottum in this thread which are steering me in my decision. CapriRacer helped me understand some things. So thanks guys.

I am pretty set on the 16's now. The personal evidence is in about a dozen threads. I even think we could survive on 15's presently, because we are not full timing yet, and travel very lite since we're only 4 night camping at most right now. But April isn't too far of, so I might as well just pass for the better investment. That's my plan.

Now to off to research weather or not I really want to do that disc brake conversion.

[slowmover]

The short version is a place to start. A minimum load index for a given TT.

I notice there are are those who overinflate TV tires and underinflate TT tires. The wrong direction for things.

As with WDH setup have a starting place. Use the recommendations. And if moving away from them be aware of trade offs. Establish the numbers and make small changes, if that.

Combination rigs -- especially with trucks -- are stable until they are not. The transition is abrupt. Often without warning.

[Gene]

When you change from 15" to 16" tires, the trailers is raised one half inch, not an inch as was previously stated. The tire is half an inch bigger on all sides, thus adding up to 16". The difference is so little that I never bothered to reset my hitch to the added height.

Pressure is endlessly debated. We converted to Michelin LTX M+S LR E years ago. I calculated 68 lbs. initially, but can't remember how I came to that number. After a couple of years and probably 15-20,000 miles, I found a little more tire wear with a tire tread gauge on the outside of the tread indicating under inflation. I then increased pressure to 72 lbs. So far, so good.

I think the tire tells you what makes it happy in a particular application. A tread gauge costs around $10-15 and translates to English what the tire is trying to tell you in tire language. It tells you when and where to rotate tires and whether they are wearing evenly or not. It can clue you in to bad balancing or improper pressure.

Over the years I have read a gazillion tire posts and know more about tires than I ever wanted to know. Some times I can't make much sense of some of the posts, but that may because it is beyond my knowledge or expressed poorly. But I've tried to sort it out and hope to learn more, though I am not sure I am at this point. Roll on….

Gene

[Action]

The previous 11 posts about disc brakes were moved outr of this discussion about 16" Wheels and LT tires, to the brake forum under "Disc brake discussion" should you wish to continue the brake discussion.

Please stay on topic as other users will not benefit from this discussion in years to come.

>>>>>>>>Action

[gecko]

Andy--
Is there a place in Southern California that you recommend for wheel balancer installation?
Thanks.

[blkmagikca]

Originally Posted by gecko

Andy--
Is there a place in Southern California that you recommend for wheel balancer installation?
Thanks.

Look at Wheel Balancer 200-221_Special from Centramatic - that's what I put on my AS. They are dynamic balancers, so you never need to spin-balance your wheels. I also put hem on my TV, and the ride is smooth.

[Msmoto]

Sideways scuffing of trailer tires is probably not an issue. On my 41,000 lb Tiffin Allegro Bus with tag axle, there was no difference in tire wear between the duals or tag axle tires in the rear after 51,000 miles. Pressures were set in the tires at about 100 psi road side, 103 psi curb side. Tire size was 295/80R on 22.5 inch wheels. The weight on the six rear tires was about 27,000 lbs, the front or "steer axle" was about 14,000 lbs.

By far the front or "steer axle" tires showed more wear than the rear, but still had 10-20,000 miles remaining if the tread depth were measured.

Thus, my conclusion that the scuffing of trailer tires is inconsequential unless one is continuously driving around corners.


Ms Tommie Lauer
Greensboro, NC
2015 Serenity 30 RB / 2008 Dodge Cummins 4 X 4
WBCCI #4165 AIR #31871

[m.hony]

Sideways scrubbing would be a little more of an issue with a 3 axle trailer, but still not enough to worry about or dissuade me from buying a 34' Airstream-

[Phoenix]

We have a lot of tire scrub when backing our triple-axle boat trailer through a 90-degree turn into it's parking spot.

Tire scrub is easily reduced by just wetting the backing path with the garden hose or spreading a little dirt or sand. This allows the tires to slip a little and reduces the scrubbing.

In addition, this marked path can also help the driver in backing; because it provides a guide to follow when making wide sweeping turns.

[dznf0g]

Just a bit of a side note: I don't agree that you will never have to balance the tire/wheel with Centramatics. ....Maybe not RE-balance. IIRC, Centramatics are capable of offsetting a 3.5oz imbalance. I have seen some WILDLY out of balance drums/hubs on trailers. It is possible to exceed the Centramatic capability if hub, drum, tire and wheel are mounted with additive (relative same point) heavy spot. I still balance the tire and wheel when new tires are installed. You at least take out much of the imbalance of tire and wheel that way, and shouldn't have to re-balance for rotations, etc.

[Gene]

Originally Posted by dznf0g

Just a bit of a side note: I don't agree that you will never have to balance the tire/wheel with Centramatics. ....Maybe not RE-balance. IIRC, Centramatics are capable of offsetting a 3.5oz imbalance. I have seen some WILDLY out of balance drums/hubs on trailers. It is possible to exceed the Centramatic capability if hub, drum, tire and wheel are mounted with additive (relative same point) heavy spot. I still balance the tire and wheel when new tires are installed. You at least take out much of the imbalance of tire and wheel that way, and shouldn't have to re-balance for rotations, etc.

Absolutely.

Trailer tires wear differently than truck or car tires. On those the drive tires wear faster than the steering tires, but on a trailer they wear the same. There's less reason to rotate trailer tires because of that, but I do rotate to get full use of the spare. We've had Centramatics on the trailer wheels for years and they have never worn unevenly.

Gene

[Tireman9]

Originally Posted by TinTin

Wading into tire threads is never wise. However, regarding de-rating of tires for trailer use, this is what would appear to make sense to me (hopefully I'm not just repeating what others have said:

LTX tires (P metric): de-rate by 10% due to mis-application
LT tires: de-rate by 10% due to mis-application
ST tires: no need to de-rate (no mis-application)

In addition to the above, it would be great to leave an adequate safety margin of an additional 10-15% for perfect peace of mind.

Passenger tires must have their load capacity derated by dividing by 1.10 when being used in trailer application.
No such de-rating need be applied to LT tires.

Now a 15% reserve load i.e. the actual load is no more than 85% of the load capacity of the tire when inflated to a specified level.

I have posted the technical reasons for Running multi-axle trailer tires at the inflation on their sidewall.

Fictional example with made-up numbers

Measured loads on a trailer
RF 3200 LF 2700
RR 2900 LR 3100

1, Front axle use 3200# consult Load Inflation table and confirm the tire can carry at least 115% of 3200 or 3680 when inflated to the tire sidewall max
2. Rear axle use 3100# so can the tire carry 3565# ?
3. You confirm your 345/65R17 LR-E tires are rated for 3700# at 80 psi
4. You are good to go when you inflate all your tires to 80 psi.


BUT lets say your tires are 300/75R16 LR-D at 65 psi which are only rated for 3000#
If you were your brother in- law who refuses to learn the actual individual tire loading you might think all is OK as the CAT scale weight reading is 11,900 or 2975# per tire. He also doesn't think any reserve load is needed and he also doesn't like the rough ride he gets with 65 so reduces his inflation just a bit to 60 psi as that is "close enough".
Is it any surprise that late in the summer after never checking his tire pressure he has two tread separations? Of course the failures are the tire's fault.

[Msmoto]

11,900 lbs on four wheels suggests a trailer weight of over 13,000 lbs. What AS weighs this much?

My ST trailer tires are rated for 2640 lbs each or 10,560 lbs. De-rating by 10% gives 9,500 lbs capacity and as my AS crosses the scales about 7200 lbs loaded, it would seem the standard factory wheel/tire combination is entirely adequate.

[slowmover]

Originally Posted by Msmoto

11,900 lbs on four wheels suggests a trailer weight of over 13,000 lbs. What AS weighs this much?

My ST trailer tires are rated for 2640 lbs each or 10,560 lbs. De-rating by 10% gives 9,500 lbs capacity and as my AS crosses the scales about 7200 lbs loaded, it would seem the standard factory wheel/tire combination is entirely adequate.

In principle, one will know adequacy once a TT has been weighed at each wheel position.

Not otherwise.

[r carl]

Originally Posted by Msmoto

11,900 lbs on four wheels suggests a trailer weight of over 13,000 lbs. What AS weighs this much?

My ST trailer tires are rated for 2640 lbs each or 10,560 lbs. De-rating by 10% gives 9,500 lbs capacity and as my AS crosses the scales about 7200 lbs loaded, it would seem the standard factory wheel/tire combination is entirely adequate.

On paper but on a camper I would De-rate a ST tire 20%.

[CapriRacer]

Originally Posted by Msmoto

11,900 lbs on four wheels suggests a trailer weight of over 13,000 lbs. What AS weighs this much?

My ST trailer tires are rated for 2640 lbs each or 10,560 lbs. De-rating by 10% gives 9,500 lbs capacity and as my AS crosses the scales about 7200 lbs loaded, it would seem the standard factory wheel/tire combination is entirely adequate.

As pointed out, the problem is that the loading on each tire is different - that is, there is side to side and front to rear variation.

For trailers, I use a conservative 15% variation, so while you think 9500# is plenty of capacity for a 7200# trailer, the worst tire could be seeing 2070#, which is a lot closer to the derated 2376# than you think.

In other words, you have to be careful with the math.

[Msmoto]

I suspect what I need to do is measure each wheel on some friends race car set up. I am somewhat mystified how the wheel loads could be so varied in view of their location and the type of suspension employed.

But, discussing the theoretical is good, I simply need to weigh each wheel individually. Gosh, this thread could get expensive....