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Tires cupping
I have a Blue Ox tow bar and have had a cupping problem on two different vehicle one a Jeep Wrangler an now on a GMC Sierra. I talked to Blue Ox to ask if because the tow bar is well broken in could this cause the peoblem,they said no and that maybe I need to have the caster changed. Has anyone heard of this or know of a fix? I pulled a H3 and didn’t have this problem.
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7 Replies
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Greg, I pulled a number of vehicles quite a few miles and it was only recently I noted unusual tire wear on my H2.
I got to checking and found the hub bearings were failing, and replacing the hubs cured the problem. What I learned was the hubs on an H2 Hummer seem to have an 80,000 to 100,000 mile life. Even though my odometer read mileage in the mid 20’s I realized we had towed it 100,000 miles or so.
Before you chase problems with the tow bar, check for misalignment or worn bearings in the front hubs.
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Thanks Jon,
Im going to the dealer in the morning for a recall ill have it checked.
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Greg,
Let us know the outcome because this might be an issue owners of certain toads might want to be aware of. I can tell you the problem with the hubs took me by surprise and it was only after repairing it that I realized the miles that show on the odometer do not reflect the amount of wear and tear on the drive train.
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Dealer said everything was ok, so I’m not sure what ill do next.
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Ditto with Jon on hub bearings.
Another problem with towing.
This picture shows the correct horizantal position of the tow bar, flat and level.
Tie rod ends checked for wear.
Front shocks or struts. This I learned on the Saturn we pulled for estimate 60K miles.
When I installed a new set of tires we replace both struts. No parts issue just plain worn out.
Mileage on the Saturn was 42K but well over 100K towing.
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Greg I had to replace the hub bearings on my pickup as will due to cupping. I had checked the front end off the ground and everything seemed ok. I replaced the bearings anyway and the cupping problem ended. Rick
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Caster is the degree to which the front hub does not rotate on a perfectly vertical axis. You can tell if a car has much caster by looking at a parked car that has its wheels turned. If the wheel lays over like a road grader then it has much caster. German cars are more aggressive on this and have about 2.5 degrees of caster. This is needed for tracking on any vehicle in order to be flat towed. Generally, street cars have no adjustment capability for caster. If we try to flat tow a car with insufficient caster, it will go to full lock either left or right. I think a vehicle will track or it does not, no in between. So I would guess that caster is not the answer.
Cupping could however be related to toe-in/out adjustment. This is adjustable on all cars. With the suspension in a static state the toe-in on rear drive cars (and the tow-out on front drive cars) is set at about one thirty second of an inch.
What can happen if you carry weight in the back of your dingy or on the receiver, such as a scooter, is that tow-in is no longer in spec. The weight in the back of the vehicle causes the front to be elevated. This is called bump steer. Now the distance between the chassis mounted steering rack and the hub is different than it was when the toe was set. So if you carry weight in the back, this might be causing cupping. We carry two bicycles on a receiver rack with total weight of maybe a hundred pounds without any front tire affects. Good luck, let us know what fixed it.
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