Running without an under-tray?

[The Mirror Man]

Mine became detached just behind the middle section while driving slowly through 6-8" of water last week and got properly mangled and broken up as it was rolled round under the car. It's now in about 6 pieces and it will be a while before I can find a replacement of repair the damaged one with fibreglass.

Any thoughts on running the car without the rear (largest) section of the under-tray?

 

[markjay]

The undertray improves the car's aerodynamics... don't think its very important TBH.

 

[alabbasi]

Leaving the 1mm thick plastic under tray off the car could be disastrous. While it may seem unimportant. It's the only thing protecting the sump from being rippled clean off in the event that you accidentally drive over large debris on the road.

 

[toolman1954]

Following some MOT repair work I lost the centre section of my under tray on the M6 a couple of months ago on my way up to Scotland . Good job there was little traffic following because I thought I had blown a tyre and only later discovered the under tray had made a sharp exit. ( Apologies to anyone who had been following me ) This needed a breakdown call out as the front part of the back section was scraping on the floor.
First time I have broken down on the motorway, and it is quite scary, the dog and I standing on the grass verge, waiting for assistance, in the end I gave up waiting, got back in the car, raised the car up an inch on the air suspension, and slowly went up the hard shoulder at 20 mph ( over 20 mph the air pressure forced the under tray back onto the floor) and got off at Penrith. Where I met my call out mechanic who jacked up the car and removed the rear under tray, allowing me to carry on up to Scotland.
Good job it was a Saturday and so not much heavy traffic. The Police had already been to see me at this point, surprised at seeing a Mercedes broken down ! " Don't see many of these at the side of the road " he said .
I bought a new middle section for £45 off of Ebay, which came from Poland in 4 days and a bag of new screws and fittings for holding up the complete 3 sections for £6 odd It seems that the fittings were old and weak and after being disturbed by the recent MOT work just failed to grip and fell out. So now they have all been replaced. ( My top tip for the week !) and the rear tray repaired with some P40. ( you cannot make these stories up !! )
I did query the need for the under trays and was told it was all to do with aerodynamics and protecting the underside. Who am I to argue with aerodynamics !

Steve.

 

[190]

I thought they weren't permitted to remove under trays during the MOT inspection.

 

[The Mirror Man]

Following some MOT repair work I lost the centre section of my under tray on the M6 a couple of months ago on my way up to Scotland . Good job there was little traffic following because I thought I had blown a tyre and only later discovered the under tray had made a sharp exit. ( Apologies to anyone who had been following me ) This needed a breakdown call out as the front part of the back section was scraping on the floor.
First time I have broken down on the motorway, and it is quite scary, the dog and I standing on the grass verge, waiting for assistance, in the end I gave up waiting, got back in the car, raised the car up an inch on the air suspension, and slowly went up the hard shoulder at 20 mph ( over 20 mph the air pressure forced the under tray back onto the floor) and got off at Penrith. Where I met my call out mechanic who jacked up the car and removed the rear under tray, allowing me to carry on up to Scotland.
Good job it was a Saturday and so not much heavy traffic. The Police had already been to see me at this point, surprised at seeing a Mercedes broken down ! " Don't see many of these at the side of the road " he said .
I bought a new middle section for £45 off of Ebay, which came from Poland in 4 days and a bag of new screws and fittings for holding up the complete 3 sections for £6 odd It seems that the fittings were old and weak and after being disturbed by the recent MOT work just failed to grip and fell out. So now they have all been replaced. ( My top tip for the week !) and the rear tray repaired with some P40. ( you cannot make these stories up !! )
I did query the need for the under trays and was told it was all to do with aerodynamics and protecting the underside. Who am I to argue with aerodynamics !

Steve.

Pretty much what has happened to mine: old weak fittings allowed the front of the rear section to act as an water brake. Grabbed by the water it simply broke up under the passing car. Mine's in 6 pieces so I think Ill order the fibre glass. A new set of fixings is already on its way.

 

[clk320x]

I thought they weren't permitted to remove under trays during the MOT inspection.

They aren't. Almost every MOT has had an advisory 'undertrays fitted not allowing inspection of contain component etc' same for any child seats in the car

 

[markjay]

I thought they weren't permitted to remove under trays during the MOT inspection.

I think he meant to say that the car was being worked on by a garage mechanic to repair faults found during the MOT (or perhaps repairing known faults priour to the MOT?).

 

[markjay]

Leaving the 1mm thick plastic under tray off the car could be disastrous. While it may seem unimportant. It's the only thing protecting the sump from being rippled clean off in the event that you accidentally drive over large debris on the road.

This makes sense.

Said that... undertrays are 'news' to me... they started cropping-up some 20 yeards ago.

Up to then, undertrays were unheard off, and you could always see the ground when looking at either side (or front) of the engine.

Their usefulness for us DIY fans became apparent however when bits fall off while driving... and are being collected at the undertray.

 

[John]

The undertray improves the car's aerodynamics...

Definitely.

I lost mine travelling at 179mph once. 171mph was the most I could manage after that within the same distance.

Nightmare.

 

[clk320x]

Definitely.

I lost mine travelling at 179mph once. 171mph was the most I could manage after that within the same distance.

Nightmare.

Haha 'on a private road' I bet

 

[brucemillar]

My C55, does not like running at speed without the under tray. The car tends to lift and drift from side to side, you can also see the bonnet moving at the catches!! It also upset the guy who was following me on the M25 when it decided to take a holiday from it's home under my car and go flying, free as a bird above the M25, shedding a shower of plastic as it went. £98 for a new (front) tray from MB.

My 30 year old 4 Matic didn't like puddles when I was waiting for a new tray for that. It would flood the power steering belt(s) making them slip and killing any power steering. Strangely that was also £98 from MB Germany, and I bagged that last 1 of 2 left in MB.

The Under Tray / Bash Plates on my Pajero are used as a tool store for a variety of spanners/sockets/screwdrivers etc. If I ever drop it from the truck, I need an umbrella to protect me from the steel rain of tools that will come down on my head.

 

[John]

Haha 'on a private road' I bet

Yeah... RAF Woodbridge. That's why I only got to 179mph. I'm confident it could have surpassed the magic 200 had it been a longer runway.

@Bruce - my car seemed sturdy and stable without it though - maybe because of the weight.

 

[clk320x]

Yeah... RAF Woodbridge. That's why I only got to 179mph. I'm confident it could have surpassed the magic 200 had it been a longer runway.

@Bruce - my car seemed sturdy and stable without it though - maybe because of the weight.

haha