Where do these skid marks come from?

[fjord]

As an example, these:



Is it a HGV? I assume so, but they go on forever. The picture probably starts a good 20-30 yards into the skid. I cant imagine the wagon was going 100mph, so why are they so long?

I know HGV's and stopping distances arent that great, but do they really lock up and slide so easily?

[simon1987]

making progress

[buggalugs]

Sometimes their brakes are faulty or not well adjusted, so one wheel locks instantly while the rest brake gently which leaves trails like this.

[Baryonyx]

Probably an HGV with one wheel locked whilst the rest are still braking fine. It wouldn't look dramatic whilst it was leaving the skid.

[sc0tt]

Trailer airbrake locked on.

[Speed addicted]

Lorries with empty trailers. They lock up easily

[GC8]

Unladen trailers can lock wheels quite easily and it can be unavoidable in some circumstances, or where the load sensing valve isnt correctly adjusted.

Also, people dont always realise that HGV brakes are held off by air, not applied; so in the event of an air or cylinder failure the brake or brakes affected will lock on, which is the cause of most of the random long skid marks that you see away from junctions.

[Petrolhead_Rich]

fjord said:

As an example, these:



Is it a HGV? I assume so, but they go on forever. The picture probably starts a good 20-30 yards into the skid. I cant imagine the wagon was going 100mph, so why are they so long?

I know HGV's and stopping distances arent that great, but do they really lock up and slide so easily?

As above, with a HGV with three axles on the trailer, when empty the trailer axles will take weight from one another resulting in one locking as it's barely in contact with the road surface, so as the lorry slows down gently for 3-400yds that wheel is locked and just touching with enough contact to leave a mark.

[Stoatman]

I wondered this for a long while. But then I saw a truck doing exactly as is described, plumes of smoke but no issues braking for the roundabout . All other wheels were turning fine.

[talksthetalk]

Its a Lamborghini Gallardo LP550-2 Valentino Balboni doing a burnout start.

Do I win the least boring post?

[Slow]

fjord said:

As an example, these:



Is it a HGV? I assume so, but they go on forever. The picture probably starts a good 20-30 yards into the skid. I cant imagine the wagon was going 100mph, so why are they so long?

I know HGV's and stopping distances arent that great, but do they really lock up and slide so easily?

Thats a wierd position for the skid if its a HGV in my opinion, its either been off the left of the road or in the middle of both lanes?

[Matt Harper]

Air brakes work by using compressed air to hold the brakes off, rather than to assist braking action. They are designed this way so that a failure in the braking system applies brake force, rather than negating it.
That tyre mark is a result of an axle brake reservoir failure - a leak which has resulted in full brake force being applied to a single brake drum.

[MajorProblem]

Red Ford Mustang woz ere.

[Bear Phils]

I took a big risk clicking on this thread while eating dinner...

[Smiler.]

Bear Phils said:

I took a big risk clicking on this thread while eating dinner...

Why, were you driving at the time?

[philmots]

Shouldn't happen on a modern trailer with abs present.

[cerb4.5lee]

talksthetalk said:

Its a Lamborghini Gallardo LP550-2 Valentino Balboni doing a burnout start.

Do I win the least boring post?

This! Plus it's my favourite Lamborghini!

[philmots]

GC8 said:

Also, people dont always realise that HGV brakes are held off by air, not applied; so in the event of an air or cylinder failure the brake or brakes affected will lock on, which is the cause of most of the random long skid marks that you see away from junctions.

and this... More commonly the cause is snapping an airline.

Easy to do if you're screwing it round, can get caught then when its stretched it pops.

[tubbystu]

Slow said:

fjord said:

As an example, these:



Is it a HGV? I assume so, but they go on forever. The picture probably starts a good 20-30 yards into the skid. I cant imagine the wagon was going 100mph, so why are they so long?

I know HGV's and stopping distances arent that great, but do they really lock up and slide so easily?

Thats a wierd position for the skid if its a HGV in my opinion, its either been off the left of the road or in the middle of both lanes?

Really ? Not just caused by the driver positioning the truck for the approaching roundabout ? Taking the first exit would be easier from the right hand lane after all.

[fjord]

MajorProblem said:

Red Ford Mustang woz ere.

No trees in sight!