Fifth wheel placement on a long WB tractor
Discussion in 'Heavy Haul Trucking Forum' started by Macneil, Aug 27, 2019.
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Only thing I would be concerned about is the difference in ride it might make.
Best ride should occur, (but not on all trucks), when the pivot point on the 5th wheel is centred between the tandems or load bearing points where suspension joins the frame.
You get a little too much weight ahead of the pivot on the 5th wheel and it will ride a bit rougher, slams the front of the truck when the tandems or trailer wheels hit a bump.
Too far forward can also cause steering problems in winter conditions, has a tendency to not want to pivot around the pin, particularly when the 5th plate is dry or the grease is near frozen, more so with short WB than long..
(most of them folks down south and mainstream Europeans can't fully comprehend Canadian winters)
Too far back during winter is not good either, but you know that already.
You need to find your happy place, sometimes it just takes a little fiddling around.
Hope you find your happy place before the snow fly's.Last edited: Aug 28, 2019
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What you said about the pivot point makes sense in my head. Like I said most tandem tractors I’ve ever driven I’ve placed it between the drives and never had issues -
Even just a 100psi air gauge in the rear bags will help give you a reference point. You need to scale a lot at first and figure out where your redline is. For me 70 psi on the spread is 850 over and 60 is always fine so when im in the 65 psi zone i have the loader scooch something forward before i even throw a strap. My drives are always fine below 45psi. I figure i try to get a 40/60 reading with my hitch basically in the middle of its range for wiggle room to get the tractor axles legal. So far 48k and under i can always get legal with $20 of gauges.
Knoxville scale has segmented readout and is always on even when the coop is closed. I weighed myself there every time it was locked up for a few months just to correlate the PSI. -
I have an idea of what I have on the drives going off my load gauge. My trailer doesn’t have one and we don’t own any trailer that has one either for some reason. When I hauled US deck work we had them on every tractor and trailer which was immensely helpful.
However, this is not what I’m asking. I’m asking 5th wheel placement on a long tractor. I’ve got to scale now that I’ve moved it forward a few notches. -
Longer the wheel base you will have trouble getting weight on the steer. On a KW 8 bag start with the pivot of fifth wheel over the back bag of the front drive. It's close and scale it and adjust it from there. If your talking trailer. If your talking quickswap good luck ever getting weight up there loaded.
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I’ve got new way suspension. Quickswap I’m not overly concerned. Unless you’re ridiculously over loaded they don’t usually bug you at the scales.
jamespmack Thanks this. -
I'd say still at or just ahead of the bag on the front drive axle is were I set anything unknown. Normally only need to adjust a few notches eitherway. However different loads, different kin pin depth. There is no one answer. But that should have you close.Macneil Thanks this. -
I’ve got a 320 shovel on right now. Drives facing the back of wagon and tracks are centrées over signal light on the trailer. About 70 psi on my drives. Pulling nice and no complaints ride wise however there’s no scale around!
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