I think it’s fast enough. I think that the realisation is that it is not down to speed but driving skill when having to deal with the everyday motorist that will pull in front of you without warning etc etc. To me its a safety issue 
steve_24v:
56 ? I know you’re not going to like this but got my fully loaded 53 reg 18t (?) MAN off the clock last night going down the M5. Couldn’t belive my eyes !!
Dont say things like that on here steve all the part time coppers will crucify you mate 
simon
malcn:
i used to drive before speed limiters were introduced, (yes i am that old) the only limiter was your right foot and your road sense, even though i drove at about 100kph which seemed to be the norm,you only had an handfull of lunatics who drove over that speed. less bunching of trucks, quicker overtaking, i dont think you will get rid of speed limiters now but feel they should be set about 100kph
Yep, the above goes for me too.
56 60 65, doesn’t matter what speed the limiter is set to, somebody will want to go faster and we’ll still get bunching and vehicles taking miles to overtake.
So stop worring, relax a bit and enjoy 56mph, you’re at work just get the job done, you don’t get production line workers asking for the line to be speeded up so they can do more for their boss for the same money.
I think I am right in saying that turbo’s don’t come into action at the lower speed of 56 ■■? If you are poodling along at 56and hit a hill, it is the engine torque that takes you up… the turbo won’t operate properly at this speed. I have noticed on a few of our SSC480’s, the difference. Two of them are running at 58 and you can hear the turbo come in as soon as you hit a hill … no loss of speed. One of the others is running at 55 and you never hear the turbo. My motor is 4 years old, a 430 and runs at just under 58… it will pull 24 tons straight up hills and only loses momentum on steep climbs when it will drop to maybe 50. Last night I ran across the M27 from Southampton Docks to Portsmouth with 26 pallets of toms on and was on the limit in top gear all the way … and there are a few steep hills across that section
It all depends on how your gearing is set up. One truck magazine was showing how a unit had the wrong final gear ratio (designed for a more powerful truck) and thus needed to drop out of top on the slightest incline. When this was rectified the revs were right in the middle of the green band ( at 1500 rpm at 56 mph)
To everyone else : the subject of raising speed limits for trucks is to me not one to do with increased productivity or solving the overtaking problem, its simply this - in this 21st century where trucks (and all vehicles) are safer than ever with ABS brakes, ESP etc, we have a speed limit set that is lower than it was 20 years ago, at a time when there are calls to raise the motorway speed limit for cars to 80 mph in line with many other European countries.
If you sit a little below the limiter then when you approach a hill you can hit the pedal and get the turbo upto full power as you need it.
Vehicles have improved, but their are loads more vehicles on the roads and I think that driving standards have dropped. But mainly what the point in wanting another 4mph?
Definately a problem of overgearing leaving the turbo idling just when you need it. My last motor was a DAF 85 400 with a twin splitter - just at the bottom of the hill flick the switch , hit the throttle - what hill? and that was at ‘40’ tonnes! To my mind the big problem these days is the computer drives the wagon not the driver and a computer can’t see a hill coming up.
The turbo is powered by engine RPM, not road speed.
So, if your turbo doesn’t kick in on hills, drop a half gear just before the hill. That’ll get your turbo spinning and you’ll barely notice the hill. As soon as the road levels out enough for top gear to hold you on the limiter knock it back up that half gear.
There is a good reason for your engine spinning at revs just below when the turbo kicks in fully, in top, at full chat, on the limiter, its know as Fuel Economy 
.
As you know, a turbo increases the amount of air pulled into the engine. It will therefore burn an increased amount of fuel, giving more power in comparison to a non-turboed engine of the same capacity.
As, in most cases, we spend about half of our time on motorways (or at motorway speeds anyway ). Your engine doesn’t need the extra power from the turbo, to hold you at full chat on a fairly level road, it produces enough power without it. So if the turbo is spinning, it is pulling in extra air and so using extra fuel to no purpose. (There is a fairly precise ratio for the fuel to air mixture, for full and efficient burning of fuel. To much air is called running weak, to little is running rich. Both are inefficient and will damage the engine eventually)
Tsk, I must remember not to join sensible and serious debates!!
All I get is a lecture on how my turbo works
TheBear:
Tsk, I must remember not to join sensible and serious debates!!
All I get is a lecture on how my turbo works
It looked like a serious question to me, so it got a serious answer.
Simon:
As you know, a turbo increases the amount of air pulled into the engine. It will therefore burn an increased amount of fuel, quote]
In that case, if an engine burns an increased amount of fuel as it draws more air in, why does’nt it go into self destruct mode, as happens when the bearing seals go on a turbo and the engine starts to burn engine oil and over revs itself to into oblivion
No mate, its your right foot that controls the amount of fuel burnt, and the more fuel that gets burnt increases the compression produced, and that in turn spins the turbo faster forcing more air into the engine to burn the extra fuel more efficientlySimon:
As, in most cases, we spend about half of our time on motorways (or at motorway speeds anywayAny engine with a turbo uses turbo boost at all times, just different levels of boost depending on the amount of fuel being used, governed by the pump governer/electronic engine managemnt system
speed limiters are no longer necessary as the engine management system can now do the same job and every truck now has an engine management unit fitted to ensure maximum fuel efficiency and engine performance or whatever the customer wants.
on board telematics built into trucks allow operators and manufacturers to view the performance of each truck or to download the performance at a later date, some even have the technology to be altered whilst out on the road via telephone uplink or satellite technology, bhp can be altered, if trucks are running on flat ground they don’t need as much power so bhp can be reduced or increased if running in hills etc.
at the moment what happens with new trucks is that the onboard systems that work in conjunction with the vehicle are often hindered by this old mechanical design speed limiter that has to be fitted by law, with all it’s rods and cables and 1980’s design to slow trucks down, it’s now out of date and surplus to requirements.
as for the speed limit being raised i am sort of in favour.
i believe that the limit for hgv’s should be left at 60 mph in this country and what ever it is in any other country, speed limiters should be reset by the companies but new trucks with engine management systems should be allowed to use those systems for speed settings instead of limiters, each company can set the speed of it’s trucks to anything up to the limit of it’s own country.
hazardous goods transport should be set at lower speeds, ie 54mph and a lower speed limit for vehicles carrying hazardous goods should be made law to enforce this.
Fair coment, I also think hazardous should be down to 50mph as some of those tanker drivers act like idiots. If I had a bomb on the back I’d take it easy, no doubt. Was it the M25 j5-j6 recently, tanker driver spilled the lot, it’s probably still shut now, might not have been his fault but…
Well personally I think that coaches/buses and hgvs should be both set the same, even though the authorities are hypocrites saying that speed kills, if thats the case why arent coaches with 50 people or more on doing less speed? Bad drivers kill, not speed, muppets doing 40 in the nearside lane kill, muppets hogging the middle lane at 50 kill. The limits should be more realistic, and if they are thinking of upping the limit for lighter vehicles then they should consider the same for the heavy ones so there isnt such a big gap, and more room for disaster. I think 65 on motorways would be a reasonable speed and 80 for cars.
Take it easy out there
Allrighty
increase the speed limit? sound,but who’s gona buy me a new truck?
my old daf75 fully loaded will spend no more than 50% of it’s time on the limiter when on the motorway if that! talkin about modern trucks with abs and the like is a good arguement if you take every wagon off the road that’s more than a couple of years old,i passed a “b” reg tipper yesterday on the m5,i think thats an 1985, i wonder if it was fitted with abs?
Probably not mate, but just cos the the limit is ■■ doesnt mean you have to do that or can do that. Look at the trucks on the road, most are pretty new, not many old ones about really, doesnt help if the unit has ABS and the trailer doesnt, i mean whats the point in that?
take it easy
Allrighty
I’m all in favour of upping the speed limiters to that of the highway code or a bit higher, but whilst on the subject of speed limits the limit on ‘A’ roads should be adjusted aswell.
The 40 mph limit is just so far out dated it’s ridiculous, it only leads to irrate drivers behind us which then leads to silly overtaking manouveres. Those drivers who do 50 mph on an ‘A’ road and get stuck behind a fasttrack tractor or some old dear doing 40 mph and can’t overtake - annoying isn’t it? If we we’re legally allowed to do 50 mph on ‘A’ roads most car drivers would sit behind quite happily as that’s the sort of speed they do anyway, or they would at least wait for a good decent stretch of straight road before overtaking therefore taking less risks and causing less accidents.
Drive Safe.
i don’t know about that, certainly some stetches of road would be suitable for fifty but others may not be,take the A57 near me,it runs from the m1 j31 through to the A1 most of this road is good wide and straight, you good quite safely do fifty no bother but there are two sections either side of todwick and south anston traffic lights that are a bit twisty,these have become accident blackspots with the majority of crashes involving hgv’s,there was one about 18 months ago,a local driver running for a landfill nearby hit an on coming car in his fully loaded eight wheeler just after turning off the A57 the female car driver was killed and he got five years as it was proven he was doing 50mph i don’t know how he would of stood had the limit been fifty but the woman would still be dead.
I agree that there are some streches of road that need to be slower, but this can be achieved with good road planning of speed limits and warning signs and perhaps dare I say it, traffic calming measures. Ok we don’t have the best road planning people at the moment but if they were to get together with the people that mattered (transport groups for people who actually drive on the roads and not sit behind a desk thinking up ways to wreck them) then we may have a decent road network for all.
I would say the majority of ‘A’ roads in this country can sustain a 50 mph speed limit for trucks without a problem, there will allways be accidents on the roads despite of speed it mainly comes down to where common sense prevails and where it stops - and that goes to all road users, we are all responsible for our own driving standards in what ever we drive.
There is an article being run in this weeks Commercial Motor (11 Nov) about raising the speed limit to 50 mph, check it out.
Drive Safe.