Yes, they can see the shoes and the amount of material left. Providing they get UNDER the trailer or truck.
It is also possible for them to adjust their brakes if there is too much travel.
Hope this helps.
Life is not a journey to the grave with the intention of arriving
safely in one pretty and well preserved piece, but to skid in broadside, thoroughly used up, worn out and defiantly shouting "Wow, what a ride!".
2002 3500 6 Speed
Just 72 feet!
Can't vouch for the truckers, but I check the toad and all connections. I also do a walk around, checking compartment doors, tires, make sure the tow bar is tight, look at the toad tires and the brake cables from the ReadyBrake....walk the dog, use the bathroom and I'm good to go..last place I want surprises is half way down a hill....just sayin...Dennis
Among the above mentioned, they also have other things to do, like take a hammer, and check the tire, if it bounces back the tire is good, Also if you see them on the road side edge too long, don't look.
2005 gmc 3/4 hd, sb, 4x4, 8.1 gas/allison 17,000 and climbing.
2005 Lakota, by Monaco, 3 slds, 29f.
They are supposed to do a complete air brake check. Tractor service brakes, trailer service brakes, tractor spring brakes. Compressor load and unload test,low pressure warning devices and more. If a trucker has to stop to build up air he has some serious problems. The drums and shoes should have been checked in the morning when he did a complete pre trip and air brake test. If the truck brakes have been performing well they often will just do the tug test. Some do almost nothing!
Yes, on Class 8 trucks you can see the brake shoes.
They are also checking adjustment. It's not such a big deal on adjustment anymore, but until about the mid 90's, you had to manually adjust the brakes, now they auto-adjust (or are supposed to anyway).
I find on my own rig that I can just drop down to second gear, take my foot off the go pedal and let engine braking and gravity do the work, while I'm maintaining a 55-60 mph speed. To me it's 4 miles of downhill fun.
but it doesn't work in a semi-truck.
The weight is simply too much, you can actually over-speed the engine thru the mechanical forces working on it.
Diesel engines don't engine brake like gas engines do, that's why they invented engine brakes ( Jake Brakes is the common one) which forces engine back pressure. You can still over-speed it even with the engine brakes full on if you are heavy enough (or the brake is weak enough).
Comparing a pickup truck with a trailer to even an empty semi-truck is silly. Until you drive a semi, you simply cannot understand the forces working on it. The weight is overwhelming. Even a unloaded light semi and trailer weighs more than your entire rig. Then they add another 50,000 pounds of weight.