Nitty-nitty pick- those aren’t for engine speed control but to increase EGR draw 
Two variants on basically the same theory for why some trucks are faster than others:
The fast trucks had time to build up speed as they approached the hill, so that even as they lose speed due to the hill they’re still going decently fast.
The slow trucks didn’t have that chance. The most obvious reason for that would be having just gotten on at an entrance, especially one of the ones with a big 35mph curve.
But a surprisingly common cause is some clown in a car.
A poster suggested that trucks are confined to the right two lanes there. Given the need to build momentum before the hill, one could easily find a truck doing 70 in one of those right lanes in the approach to that hill. When some car is moving at the usually well posted “minimum speed” of 45mph in one of those lanes, oblivious to the fact that trucks cannot legally move left to go around him, the trucker is going to have to hit the brakes. And then he’s doing 45 at the bottom of the hill, and does not have the power to maintain that speed, so he moves right and turns on his blinkers to signify that he is moving far slower than he ought to be.
I’ve never driven a truck, but I was taught to always think about the problems other drivers face. For instance, if trucks are limited to the right lane and a truck is coming up behind you, move left and let him pass.
And to both bicyclists and truckers momentum is precious, so you shouldn’t make them waste it.
Another related question.
Several times during some Biblical-level downpours-I’m talking 50 foot visibility, deep standing puddles in the main lanes, everything-I’ve noticed that semis hardly ever slow down significantly. Here I will be going along say at 45 in a 65, because I have no idea if a long line of stopped cars is 200 feet ahead of me, or not. And these buggers will go FLYING past me, still doing 65.
Rain stops, puddles disperse, and I’m back up to 70, and then pass them again in turn, still doing 65. 
As was stated in another post, the picking up of speed going downhill is to get more momentum to get to the top of the next hill. Even if the truck is governed at 105km/h (the norm around here), hitting the bottom of the hill at 120km/h will go a long way toward getting to the top of some hills without having to drop into the basement (bottom 4 gears). In a situation where for some reason, I have to keep my speed below 105 to the bottom of a hill, I’ll be down into the basement before I get halfway up a hill (say, one where it’s steeper near the bottom than past the halfway mark) and can’t get the speed to pick up until I’m near the crest. If I can get a run at the hill, I can often get past the steeper part before too much speed has been scrubbed off.
For full disclosure, I’m usually pulling 66k lbs of drywall on a triaxle flat deck, with an occasional 80k+ lb load on b-trains. Those really do not like hills. My regular tractor is an International 9400i with a Cummins. I really miss the CAT engines from my previous job. You could lug those things down to 1100rpm, and they’ll still pull you up a hill faster than Cummins and Detroits running (in a necessarily lower gear) at around 1700rpm.
Instead of getting pissed because you are caught behind a truck you should realize that most truckers spend months and a time away from home to keep this could try moving. We would love to go home everyday and see our families bit then store shelves would be empty. Be thankful guys like us are doing this it is because of us that you can go to a store and buy what you want or need without us us no industry in this country would have work.so the next time it takes you a few extra minutes to get home put your self in the driver’s place and then start respecting him for what he does. Trucks climb or decend grades at different speeds because of different weights. And realize that if all the Trucker were to decide to stop and not run for 2 full days the store shelves would be empty so thank us instead of thinking you are above us
If you’re talking about the grade east on the Moreno Valley Freeway (CA 60) out of the Moreno Valley, then, yah, there’s a reason they go slow. It’s not exactly flat.
I’d think it would be apparent to anyone who wasn’t completely self-absorbed that there are some grades that heavily loaded trucks cannot handle at max speed. Not far from there is the Cajon Pass on northbound Interstate 15, and the same thing happens there. Since the trucks are going from almost Sea Level to 4000’ elevation in the space of 15 miles, it’s not exactly a Bonneville Flats for them. :rolleyes:
joe, if you read this thread again, I think you’ll find that nobody is claiming to be “above” truckers. They’re saying it’s frustrating to be stuck behind a semi that’s moving slowly. And it is.
But as a guy who used to drive a truck that was severely underpowered, it’s also frustrating to be trying to push that pedal through the floorboard and still feel like you’re stuck in quicksand for hours on end.
At least the OP can get out of his predicament after a little suffering.
That’s awesome. From now on, whenever I see an Albertson’s truck I’m gonna imagine it’s actually carrying alien spawning vats or something.
Actually, alien spawning vats are sent FedEx.
ok, that’s great for the spawning vats, but what about the incubators?
I just hope they’re asleep/hibernating. Can you imagine some alien getting carsick?
One of my pet peeves is the geniuses who change lanes seven times to get ahead two car lengths.
Yep, yo really ARE going faster then I - why, just in the last 2 minutes, you’ve passed me THREE Times!
Here’s little time/speed/distance problem for you to solve: How far do you go “30-40 mph” when you are “stuck” behind one of these rude truckers who can’t go any faster: What is the time difference between the 35 mph you are forced to drive vs. the 70 mph you would drive if the road was clear?
I’m going to guess <30 seconds.
Is your blood pressure worth spiking over 30 seconds?
I also like the ones who run the red light (“It was still a Little yellow when I entered!”) just to joining the group already stopped at the red in the next block.
Why yes, I AM the asshole who stops short of a car trying to find an opening just back of a light during rush hour. Imagine deliberately allowing someone to get AHEAD of you!