Quote:
Originally Posted by MeteorGray
Traffic lights on roads with highway speeds should be outlawed. I pull a travel trailer with an F250 pickup, and the most terrifying part of the trip is on such highways. I'm a nervous wreck when doing highway speeds knowing a red light can pop up anytime at close range, and me not having the ability to stop as quickly as might be needed.
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Hitch rigging is as important as both vehicles. An equation where each is 1/3 the final product. In this case,
total stopping distance.
By itself (including reaction time) the solo truck ought to be around 325’-350’ from a little above sixty mph.
Correctly hitched the distance should be reduced.
It’s data you’re after. Then, tests.
The “reason” so many pickup & trailer combos have bad braking is:
1). Pickup FF/RR weight balance still skewed towards Steer Axle as the load in the bed wasn’t significantly high enough to justify the (increased accident risk design) of a pickup.
2). Tandem-axle trailers ALSO need FF/RR weight balance optimized. AND to travel “level” according to an instrument.
3). Where a weight distribution hitch is called for (more than 350# of trailer tongue weight) it must work to design. It doesn’t in more than 90% of what’s seen on the road. A trailer with a 1,200-lb TW will — when set correctly— via leverage restore the Steer Axle to the solo weight value, and set several hundred pounds atop the Trailer axles (Cat Scale conformation).
4). Trailer tire pressures to cold maximum. Tow vehicle tire pressure
according to Load.
5). Trailer bearing pre-set to spec. Drum brakes adjusted to spec.
6). A higher quality brake controller. The TUSON unit is that item. Trailer brake application MUST lead the tow vehicle in degree of relative application pressure. An algorithm-controlled trailer brake control is a wonder (as ABS and vehicle computer requirements keep us from using the old KELSEY-HAYES controller of yesteryear, or the JORDAN of the late 90’s-early 20’s).
The biggest (best) change to make is to convert the trailer to replacement DEXTER Tor-Flex axles with disc brakes. And all TUSON control components.
A). Independent suspension has far greater wheel travel. Each wheel is no longer affected by the one next to it or across the axle. It STAYS on the road where leaf won’t. Brakes won’t help when the tire is airborne. Then, it regains contact and locks (flat spotting). Rough roads, road surface camber, wet conditions all worsen this. IS just does a better job. Disc handles problems better.
B). Disc brakes have MORE THAN one application in them. In a full-on emergency stop, the drums aren’t working before the stop is completed given an initial high rate and even a road mildly descending. With disc, the heat shed is far better.
When I read that owners are concerned, I can take for granted:
— the pickup is relying on Steer Axle braking (insufficient bed load)
— the trailer is likely nose-down when cruising, and in a hard stop is reliant on two of four tires & brakes as the trailing axle has no purchase.
— one is using only two braked axles of four. Four tires with purchase versus eight. (This is before we get into relative braking ability of one tire design versus another).
MG, I have to remind myself when the trailer isn’t back there that I now have to anticipate
longer stopping distances solo, though I’ve gone from 17,000-lbs to 9,000.
There’s a solution.
I haven’t gotten into using the transmission to also decrease distance. Design, type and operator confidence are factors.
Just a few years ago in order to stop a tractor trailer rig with drum brakes all around and manual transmission, one was going to plant that size 13 steel toe with everything one could put behind it while simultaneously double-clutch downshifting that 13-speed while taking engine rpm to maximum with the clutch out. Say a prayer, as the brake pedal NEVER felt the same way twice.
Today, it’s (yawn) use my big toe on the brake pedal with a fully disc brake equipped tractor and trailer while moving the engine brake selector to the maximum needed. And let the 12-AMT do its computer-controller downshifts.
The brake design is the biggest factor. The
consistent performance of discs make them mandatory, IMO. Degree and duration is predictable. Never so with drums.
For a combination rig, the trailer tongue weight MUST be adequately distributed on the tow vehicle (which itself is best with about a 50/50 weight balance while solo). A fifth wheel or gooseneck hitch is mounted where the Steer Axke weight won’t change or barely increases. A conventional hitch must distribute in a 1/3-1/3-1/3 pattern (approx).
For EM purposes, the glide is much easier to maintain. Operator confidence is higher. Lower stress, thus fatigue pushed farther forward in time & miles for the day’s drive. Fine muscle control deteriorates under stress. Adrenaline murders it.
So, as with accurate shot placement, fine muscle control is the game throughout the day.
Additionally, there are other changes (not expensive) to tow vehicle handling which reduce the need for braking, as well as in degree & duration.
For a conventionally hitched trailer, a Hensley-patent WD hitch (guaranteed no sway) is the other big improvement past disc. The rig is MUCH more predictable as the trailer is no longer CONSTANTLY hunting from side to side (and they all do). It’s described as an
oscillation to help in seeing it.
I can tell a hitch of this type is in use from well more than a mile back as I overtake. Once one knows what to look for, it’s obvious.
Given the high rollover propensity of a pickup, I consider it mandatory for that tow vehicle.
The direct EM benefit is lower HP demand at highway speed. The trailer is LOCKED to the tow vehicle. They stay in constant alignment with one another. Passing big trucks or wind gusts doesn’t change this. Far fewer steering corrections are needed (which both Kenworth and Cummins cite as measurable effects on FE per 100-miles).
In short, that which reduces or eliminates Vehicle Control Input Degree and Duration (steering or handling or braking) is a direct FE benefit, not just reduced risk operation.
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