I always wanted to ask this and finally remembered - are speed limits always correct?

I tried to explain this theory to another driver one day as we were rolling west past the TN welcome center on I-40. There's a curve posted at 45 for trucks.

Long story short....he laughed it off and summarily told me I didn't know what I was talking about.

If you just remember that your trailer tandems are always pointing straight, it makes the understanding come much more clearly. But you just can't tell some people anything....

 

I've always wondered about this myself; how are the speeds determined? Do the engineers take into account the exceptional case of a high COG truckload such as swinging beef for example? And then there's 'too fast for conditions'. A benign stiff tailwind would become a quartering crosswind that could cause problems in the curve.

 

Sometimes it seems like a game. You come rushing down a hill with a pack of trucks and see who can take the curve fastest. Sometimes I am surprised how fast some take these curves. It does depend on your load and weight a lot, but I've never pushed the envelope. Don't want to find out what the tipping point is.

 

that's another thing I try to avoid....."packs of trucks"....I prefer to keep ample distance from other motorists....just in case!

Not to mention the fact.....why rush? With 75-80k rolling up and down the road, is there any reason to be in a hurry? Shouldn't be! Schedule planning is the biggest part of being safe!

 

Steady throttle through a corner allows a vehicle to turn better because the suspension is returned to a more neutral position as opposed to being compressed. Compressing a suspension sometimes causes bump steer.

Race suspensions are amazing in controlling what happens to the tire contact patch as suspensions are worked entering, going through and leaving the corner. There are millions of combinations that all work for or against the fastest speed in any one corner. Of course the fastest speed possible may also wear out the tire too fast.

Getting back on subject

Our company policy is 10 MPH under the posted corner speed. We had eleven roll overs last year. Most, if not all, were NOT rookies. They were experienced drivers that got caught out and got themselves in trouble. One of the drivers will not have to worry about making that decision ever again. He did not survive.

So ask yourself. How much time will you lose knocking off 10 MPH for a 1/4 or 1/2 mile? Especially if it is a downhill and you don't have to burn so much fuel to get back up to speed.

Another situation, I was taking the turn at an acceptable speed. It was a ramp from one expressway to another. Just as I got to the end where my merge was, the pavement looked like a WWII runway that was barraged with bombs!! It was a right hand turn and the truck was bouncing so much that it was not turning right, when I still needed it to! Luckily quick braking did get it back under control. Probably because the tandems were still on smooth pavement.

So, unknown pavement conditions is another factor for corner speed.

Another is sight lines. Can you stop if you suddenly see a stopped vehicle at the limit of your sight?

Sheesh! Long post!

Mikeeee

 

He's kidding right?

 

Racing rule.

Do all your braking, then all your cornering, then do your accelerating.

Mikeeee

 

When I have a load of hay stacked to the Roof of my 53' Dry Van. I feel the sharp curves much more. When I have a load of steel sitting on the bottom. I feel like I can go any speed. Lot depends on that load you are on.

 

Your truck can only do 65. If you go faster than that you are no longer pulling the trailer, the trailer is pushing you ... the sensation of leaning you are feeling is the trailer trying to push you straight through the turn, since you are no longer pulling it.

 

I'm not sure of the specifics, but I'm sure they use the worst case scenario plus some. Probably some funky g-force equation with a certain standard? Just like they build race track banks.

I doubt it's the extent of a top heavy load. That's on a driver I would say. I'm not listening to no one but me and the truck then. I use to haul suits when I first started. About 10,000 of them hanging from the ceiling. Those loads I had to be extra careful. I could imagine swinging beef.