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#61
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On Oct 16, 4:46 am, Eric Greenwell wrote:
Dan G wrote: On Oct 12, 3:57 pm, "01-- Zero One" wrote: So to say that "Towing is simple. Follow these rules, and your rig will be stable in all conditions and not need stabiliser hitch." is in my experience a gross oversimplification. Think we'll have to agree to disagree - but I'd like to know of examples where these guidelines were met, but the rig was still unstable. My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is stable at 60 mph. At 70 mph, it's starting to quiver, and I've never dared go faster. So, is the rig "stable" or "unstable"? What's the speed limit for a towing vehicle in the US? In the UK it's 60, so your rig would be "stable", though of course it would be preferable to have a higher safety margin in the event of cross-winds etc. Let me try and explain this another way: *if your trailer is trying to lift the rear of your tow vehicle when hitched, it will have reduced stability than if it's pressing down. *If your trailer has a heavy mass at the far end, it will have reduced stability compared to if it had that mass in low down over the axle. *If your trailer has underinflated tyres, it will have reduced stability compared to if it had correctly inflated tyres (and they might go "bang", too) *If your trailer weighs more than your towcar, it will have reduced stability compared to if the towcar was heavier than the trailer. I hope that's clearer. The Bath University guidelines were also developed using average Euro cars - I would not expect an tall, unstable American SUV or pickup with ancient suspension to be particularly stable in many circumstances, even when not towing. More recent models with relatively modern suspension should, of course, fare better. Dan |
#62
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![]() "Dan G" wrote in message ups.com... On Oct 16, 4:46 am, Eric Greenwell wrote: Dan G wrote: On Oct 12, 3:57 pm, "01-- Zero One" wrote: So to say that "Towing is simple. Follow these rules, and your rig will be stable in all conditions and not need stabiliser hitch." is in my experience a gross oversimplification. Think we'll have to agree to disagree - but I'd like to know of examples where these guidelines were met, but the rig was still unstable. My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is stable at 60 mph. At 70 mph, it's starting to quiver, and I've never dared go faster. So, is the rig "stable" or "unstable"? What's the speed limit for a towing vehicle in the US? In the UK it's 60, so your rig would be "stable", though of course it would be preferable to have a higher safety margin in the event of cross-winds etc. Let me try and explain this another way: *if your trailer is trying to lift the rear of your tow vehicle when hitched, it will have reduced stability than if it's pressing down. *If your trailer has a heavy mass at the far end, it will have reduced stability compared to if it had that mass in low down over the axle. *If your trailer has underinflated tyres, it will have reduced stability compared to if it had correctly inflated tyres (and they might go "bang", too) *If your trailer weighs more than your towcar, it will have reduced stability compared to if the towcar was heavier than the trailer. I hope that's clearer. The Bath University guidelines were also developed using average Euro cars - I would not expect an tall, unstable American SUV or pickup with ancient suspension to be particularly stable in many circumstances, even when not towing. More recent models with relatively modern suspension should, of course, fare better. Dan On our USA Interstate Highways, speeds tend to average 75mph. Speed limits are lower, but not usually enforced until above 80 mph or more. Even the Semi trailers (18 Wheel trucks) are doing 70-75 or more. If you drive 65, you are continually passed by these trucks, each producing "bow waves" that induce more sway. So stability up to 80 mph is highly desirable. The above noted points all contribute to stability, but I tried them all, and then some, one at a time, and in combinations. There was no dramatic improvement until I changed vehicles. The Tahoe and the Avalanche weigh about the same. The Avalanche has a longer wheelbase. They both have live rear axles and use the same tires. IMO the best way to improve a tow vehichle is with "helper springs" to stiffen the rear, and if needed, the front, suspension. These are easy to add, relatively inexpensive, and can improve the handling even without the trailer. Of course, this is after bringing the suspension up to "specs" first. Shortening the distance between the hitch and the rear axle, where possible, helps too. Two inches can make a difference. Hartley Falbaum "KF" USA |
#63
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Regarding safety in collisions:
Linked bellow is a report from the institute for Highway safety that shows that a car colliding with a heavy SUV favors the occupants of the SUV enormously. These are death statistics. However, in Solo acciddents, like spin outs and collisions with immovable objects, the car is far better and the statistics support this. Because in cars, 42% of deaths are in solo accidents. In SUVs, 63% of deaths are in solo accidents. So basically, don't loose control of an SUV or hit anything. In cars, only 27% of deaths occur when cars are involved with something bigger than themselves, including buses. The report concludes that by far, the most deaths occur in solo crashes in both cars and SUVs. This speaks against SUVs being safer overall. Overall, except for slow city driving, I doubt the SUV is safer and I personally don't feel safer in one cruising on a country road or freeway, especially towing something. Report: http://www.iihs.org/sr/pdfs/sr4005.pdf |
#64
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Dan G wrote:
My '89 Dodge Caravan and ASH 26 E trailer meets all your rules and is stable at 60 mph. At 70 mph, it's starting to quiver, and I've never dared go faster. So, is the rig "stable" or "unstable"? What's the speed limit for a towing vehicle in the US? The highest speeds are on the Interstates. In California, it's 55 mph; in Montana, it's 75 mph. Other states are between these two. In the UK it's 60, so your rig would be "stable", though of course it would be preferable to have a higher safety margin in the event of cross-winds etc. So, the study investigated relatively short, wide, and tall trailers towed no faster than 60 mph. It doesn't seem likely to have much to offer the typical glider pilot! The point I'm trying to make is most of the glider towing combinations can go fast enough to become unstable, and following the "rules" doesn't ensure stability at even legal speeds, much less at the speeds many pilots want to tow. Let me try and explain this another way: *if your trailer is trying to lift the rear of your tow vehicle when hitched, it will have reduced stability than if it's pressing down. *If your trailer has a heavy mass at the far end, it will have reduced stability compared to if it had that mass in low down over the axle. *If your trailer has underinflated tyres, it will have reduced stability compared to if it had correctly inflated tyres (and they might go "bang", too) *If your trailer weighs more than your towcar, it will have reduced stability compared to if the towcar was heavier than the trailer. I think we all agreed from the start that the "rules" were sensible; what some of us have pointed out is they are not sufficient. If pilots never towed over 60 mph, we'd have far fewer trailer towing discussions! And a lot fewer accidents, too. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#65
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I tow with a Toyota 4-Runner which is a mid sized SUV. While it would
appear to be a good choice for towing I found 60 to be the limit before sway would start. I believe the problem is that even though it has fairly heavy suspension you can still induce sideways movement by pushing with one finger on the rear of the vehicle. After trying every solution I could think of I finally changed the trailer connector to Al-Ko AKS 1300 Stabilizer, which works by pad pressure to the ball. http://tinyurl.com/yvjhve Towing is now stable up to the max speed of the vehicle, which with a 6 cylinder engine and trailer in tow is 85. While pricey at $250 for the connector and special ball coupler it is cheaper than unwrapping the car/trailer from a tree. |
#67
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You guys are leaving out a very important part of the equation when it
comes to stability and the ability to prevent sway. That would be tires and the stiffness of their sidewalls. This makes a huge difference. This can have as much of an impact as suspension. Case in point; My brother and I at one time both had Dodge Ram trucks. I had "E" rated tires, and he had really low rated tires (can't remember which load designation). One of my trailers is a large 4- place enclosed snowmobile trailer. We hitched it up to his truck to head north for some snowmobiling and that rig was all over the place. Glad the trailer had electric brakes because he had to apply them a number of times to get the sway under control. Well, it wasn't very many miles of this adventure before we turned back to switch to my truck. When we got back from the trip, he replaced all of his tires with a higher load range (don't remember if he went all the way to "E") and we took a test drive with the trailer. The difference was night and day. Problem solved! Some of you guys with sway issues should see your tire dealer and inquire about stiffer tires. Granted, the ride is not quite as soft, but it's a lot safer. Even when you're not towing. Cheers, Dave |
#68
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On Oct 17, 3:02 pm, wrote:
You guys are leaving out a very important part of the equation when it comes to stability and the ability to prevent sway. That would be tires and the stiffness of their sidewalls. This makes a huge difference. This can have as much of an impact as suspension. Case in point; My brother and I at one time both had Dodge Ram trucks. I had "E" rated tires, and he had really low rated tires (can't remember which load designation). One of my trailers is a large 4- place enclosed snowmobile trailer. We hitched it up to his truck to head north for some snowmobiling and that rig was all over the place. Glad the trailer had electric brakes because he had to apply them a number of times to get the sway under control. Well, it wasn't very many miles of this adventure before we turned back to switch to my truck. When we got back from the trip, he replaced all of his tires with a higher load range (don't remember if he went all the way to "E") and we took a test drive with the trailer. The difference was night and day. Problem solved! Some of you guys with sway issues should see your tire dealer and inquire about stiffer tires. Granted, the ride is not quite as soft, but it's a lot safer. Even when you're not towing. Cheers, Dave Absolutely. Look back to an earlier post on towing. When I switched to a cheaper, lower speed rated tire to save some money on my tow vehicle (VW Passat wagon), the tow stability was noticably worse. Upgrading to better tires (similar to the OEM values) immediately got me back to where I used to be, which was a stable tow at up to about 70 mph. P3 |
#69
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I agree with Dave. Heavier sidewalls, which are higher load rated not
higher speed rated, will help since they are more resistant to lateral movement. Problem is that after an expensive tire change you may still end up with some sway but in addition a car that rides like a gravel truck. |
#70
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I agree with Dave. Heavier sidewalls, which are higher load rated not
higher speed rated, will help since they are more resistant to lateral movement. Problem is that after an expensive tire change you may still end up with some sway but in addition a car that rides like a gravel truck. |
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