View Full Version : Any tire guru's here?

Scott Shepherd
07-31-2010, 10:10 AM
I'm trying to help a friend solve an issue. They have a 50 foot lift made by Genie that tows behind a truck. Two tires. Weighs about 4,000 lbs. Everytime they use it, they blow a tire or both tires. They have put about 15 sets of tires on it over the last few years and no one can resolve the issue.

When towing it, the tires will get so hot, they will actually blister and bubble. It has breaks on it, but you can touch the tire and it's smoking hot, but the hub, the break drum, and everything else in the area can easily be touched.

They have spent a small fortune trying to get it fixed and no one seems to know what's wrong with it. They had new hubs put on, new bearings, new brakes, new hitch, new hitch brake (not sure what that thing is called, but when it senses pressure, it applies the trailer brakes).

They even flew Genie people in to correct it. They aligned it and said it was in perfect alignment and went through the entire thing and could not find any issues with anything being wrong. Yet, it will still melt the tires off of it when you tow it at 60mph.

Genie says it's the only one they have ever seen with this problem and they can't help. I've seen it happen myself. Pulling it for 15 miles at 60mph, the tires were so hot you couldn't hold your hand on them.

The tires called for by the manual are something along the lines of supporting 1,200 lbs each, but the tires on it are 8 ply rated for 3,100 lbs each.

If you pull it at 45mph, it will not blister the tires. They are hot, but not smoking hot.

Any ideas or things to look for? Might take me a day or two to respond with questions, since I have to get in contact with him and find out answers.


Gordon Harner
07-31-2010, 10:16 AM
What is the air pressure in the tires? It sounds like flexing and friction on the tires are causing the problem.

Scott Shepherd
07-31-2010, 10:40 AM
I think it was 60psi, but I'll have to check. I know they have taken brand new tires, right from the tire company installing them, hooked them up to the trailer and they were blown within 30 minutes. It's not a new, one time problem, it's happened, they tell me, at least 15 times now. So much so that they don't move it any more. They use it at one location and that's it.

They have used numerous tire companies, brands of tires, etc, and all have the same result. That's why they called genie factory people in, to align it all, but the problem hasn't changed.

I will get the exact tire numbers on it and what's recommended some time later today.

Dan Hintz
07-31-2010, 10:42 AM
I'm with Gordon on this one... too little pressure and flexure of the tread/sidewall is going to create a lot of heat. What's the pressure in the tire after it is blistering hot?

If the trailer weighs 4,000 pounds, It doesn't make sense that the manual suggests 1,200 pound rated wheels... you should use tires rated for your max load + 20% or better.

Phil Thien
07-31-2010, 10:45 AM
Two axles? Are the axles flexing with the weight?

Scott Shepherd
07-31-2010, 11:02 AM
Single axle. I don't think it can be air pressure related. Someone over the years would have figured that one out. The factory guy also put new tires on it when he was here, so I'm sure that didn't get by him too. He verified it's making the tires very hot, but said he had no fix for it and had never seen it before.

Glenn Vaughn
07-31-2010, 11:09 AM
To the best of my knowlege there are only 2 ways for the tire to heat up:

1. Excessive flex of the tread and sidewayy.
2. The tire is rubbiung on something.

I have a dualy that weighs 6000+ pounds empty. The minimum recommended tire pressure for the tire on it is 65 psi. I would suspect that 60 psi for 2 wheels and 4000 lbs is quite a bit low.

Dan Hintz
07-31-2010, 11:09 AM
Well, if the experts can't find the problem in person, I have little hope of coming up with a solution from here...

Scott Shepherd
07-31-2010, 11:21 AM
Awww, come on Dan, sure you can!

Keeping in mind, the "experts" have been 1/2 dozen tire stores (are they really experts?), and 1 guy from the factory. I'm hoping someone can offer up something that these people are missing.

I'll post the air pressure and tire info later when I can get him to check it.

Ed Hazel
07-31-2010, 11:28 AM
Heat is caused by friction. If the tire pressure is correct and the tires are rated fore the load. That just leaves three things in my opinion.

1. Tire is rubbing on trailer, I would think this would be easy to detect.
Is it poss the tire is hitting the trailer on bumps ect.

2. There is an alignment issue, toe in or out possibly a camber issue. Bent Axel or misaligned axel would be my bet

3. Something is causing the tire to turn hard. Brakes possibly, I would try towing it with out the brakes hooked up.

Scott Shepherd
07-31-2010, 1:02 PM
Thanks Ed, I'll have him check the rubbing issue on bouncing. The factory guy said he aligned everything with the tongue of the trailer. He actually removed the brakes completely off the unit and ran it without the brakes and the tires still got overheated. The time I rode with him, I got out, touched the tire and it was really hot. I'd say well above 120 degrees. I leaned in, under it, saw the brake drum, and touched it (expecting to leave my fingerprints behind), and it was cool to the touch. So doesn't seem like a brake is causing it.

I don't know if the fenders come off of it or not, I'll have him look at that and see if it's something to try as well.

Scott Velie
07-31-2010, 1:27 PM
There is a load rating on the tire somewhere. It is a letter B, C, D up to N.
The higher the letter the more weight the tire is designed to carry. You did not mention the size what size rim are they on? What type of tire? passenger (P) light truck (LT) special tire (ST)? It should be on the sidewall.
I think you are using tires not rated for the weight they are carrying.

Pat Germain
07-31-2010, 3:09 PM
Clearly it's time for a priest and generous amounts of Holy Water.

Jim Koepke
07-31-2010, 3:43 PM
The "we have never seen this before" line is one that is very common. As a tech, I was often chewed out for not using it.

But, if Gene has never seen this problem before, they should be happy to exchange the trailer for another so their engineers can go over this one to figure out how to keep it from happening again.


Cliff Rohrabacher
07-31-2010, 5:11 PM
Pressure is the problem.
A 50 foot crane weighs a bloody ton.

Why don't you check with any Truck-Stop mechanic. I am more than certain that such an inquiry will straighten it all out.

Walt Nicholson
07-31-2010, 6:19 PM
Couple of things to try if they haven't already; put the trailer on a scale (weigh station, truck stop, etc.) and get the exact weight (not what the manual says) and see if the tire rating is sufficient for the exact weight of the trailer. Overloading will destroy a tire in a hurry. Do a simple check of the toe-in/out. On the front edge of the tires, measure (as precise as possible) the distance from the outside edge of the left tire to the outside of the right tire, then go to the back of the tire and take the same measurement at the same relative spot on the tire. If the measurement is off even a little the tires will scuff going down the road similar to doing a "snow plow" maneuver on skis that is used to scrub off speed. Then do the same type of check with the top and bottom edges of the tires to see if they are leaning in or out at the top. Also have someone follow the trailer at speed and see if the tires are leaning in once the trailer starts to roll. This will also have a detrimental effect on tire wear. You said they checked the alignment of the axle with the tongue but I would check it again making sure the trailer frame, tongue and axle are square and parallel with the tow vehicle. Another simple test is to pull the trailer slowly through soft dirt or mud that will leave a good tread imprint. Look at both imprints and if the tread imprint is not clear and distinct but is sorta smeared looking the tires are no rolling right (alignment problems above). Just some thoughts from past experience.

Dan Hintz
07-31-2010, 7:19 PM
If caster was changed by the load, I would expect that to be obvious from the tread wear... and I wouldn't expect it to affect heat unless it was so extreme you could see it bow off to the side. Even a few degrees of camber is pretty obvious.

Toe in/out, however, is a definite possibility (though I thought quick tread wear would make that obvious, too, so I didn't bother suggesting it).

Scott Shepherd
07-31-2010, 7:50 PM
I'm not sure I understand the load ratings, but it's not my problem, so I guess I'll go back to stupid about it all......

I went by and looked at another brand, sitting at a job site close to me, and it was a JLG lift, about the same size. The tag on it said it weighed about 5,000 lbs, but it called for tires rated at 1,100 lbs. That's the same information that's listed in the manual for the this one- here's what's listed :

Weight is about 5,000 lbs (can't find it in the online manual, but that's what I'm told)
Tire size 225/75R15
Load range D (Range D is about 1,800 lbs)
Lug nut torque, dry 80 ft-lbs
108 Nm
Tire pressure, maximum (cold) 65 psi
4.48 bar

Here's what's on it :

Hi Run 8.14.5LT LQ225 14PR, max load is 3,100 lbs @100psi 6 inch wheel. Load rating is "G".

So it's rated almost double of what it specified.

When I saw it happen, the tires were brand new, still had the little nibs on them. Drove it at 60mph for about 15 minutes, and both tires were VERY hot.

Scott T Smith
07-31-2010, 9:44 PM
I would hazard a guess that the spring mounts were welded in an incorrect position on the axle, causing either a toe-in or toe-out situation which is creating the heat.

Trailer axle's are usually manufacture with a slight amount of camber in them. If the axle tube had rotated slightly before the spring mounts were welded on, the problem that you describe could result due to the friction of the tires scuffing on the pavement. This is not an "alignment" problem, and the typical task of checking the distance from the spring hangers to the trailer coupler is not applicable.

To check, place a very long straight edge from front to rear on each tire, and compare the side-to side distances between the front and back of the straight edges. It should be the same. If it's not, you've found the root cause.

Dan Hintz
07-31-2010, 9:54 PM
Shouldn't there be at least a minor degree of toe-in (half a degree, maybe?) to prevent wandering?

Gary Max
07-31-2010, 10:35 PM
Heck I would jack the thing up and cut the axle off it and install two axles using new hangers, watch the balance of the weight. That will put a stop to your problem.

Scott T Smith
08-01-2010, 11:33 AM
Shouldn't there be at least a minor degree of toe-in (half a degree, maybe?) to prevent wandering?

Dan, I've never seen any toe-in on a trailer axle. For that matter, I have not seen it on the rear axle of a vehicle either. I do understand the concept though.

Re the weight of a 50' lift, I own a 60' articulating JLG self-propelled manlift, and it weighs 20,000 lbs. However, the trailer-mounted lifts are built much lighter, as they have to be able to be towed by the average renter with a pickup truck. If the manufacturer's tag states that the weight is 5,000 lbs, then one would think that they know the weight of what they built.

Jerome Stanek
08-01-2010, 12:03 PM
On my tandem trailer there is a toe in. I would look at some truck tires or some implament ag tires A freind of mine has a crop service and the tires on his 10 ton running gears hold up good he tows them pretty far at times.

Chris Parks
08-02-2010, 9:57 AM
I know you don't want to entertain the idea because it is so simple but as someone who is involved in the trucking industry I will say categorically it is pressure related. The industry is moving to onboard pressure sensors because over 90% of tyre problems are pressure related and this stands out as a classic example. It is a simple thing to inflate the tyres to a much higher pressure and see what happens and as you are already destroying tyres that is the worst that can happen. Note the maximum pressure and inflate to that.