In my pothole adventure with our MG4 Pothole gives MG4 concussion. I mentioned the undertray was displaced downward and full of rocks. I removed it after devising a way to safely place the rear of the car on stands. The tray is held in with 9 6mm hex head bolts with large washers and 4 Phillips head screws, plus two plastic "speed nut" pre-positioners at the far outer corners. I undid these first as they are the most delicate. Careful use of a 10mm socket using very light pressure gets them out. Then take out the 4 Phillips head screws, then the bolts, rear first, then inner, then down to two. Hold up the tray with hand and prop as you take out the last couple to prevent the tray holes becoming overstressed. Out came the rocks and I cleaned the tray down. Yes the tray hole for the center bolt, the one into the Electrical Distribution Module (EDM) that hangs off the back of the battery pack, had started to tear.
OK so now what to do? I had the article in Electrifying Everything outlining AS-TEC-02112023-01 - MG's warranty fix for this issue. It involves a warranty claim via the dealer, then if successful a booking and the dealer applying a metal reinforcement to the undertray front lip using the center bolt and the two either side. I thought about the hassle and the 20 questions, the form, the approval wait, the booking and the wait for that to come up when the part becomes available (I ordered a tire pressure sensor in February and it arrived at the dealership on the 17th of July). By then the tray will be dragging along the ground.
Looking at the EE article photos I decided I could do better using aluminium. Although I had some 3mm aly plate it wasn't long enough and I would need 35mm round bar for the angle standoffs that go in the large indentations in the tray at the mounting points either side of the center bolt. $86 later I had what I needed. I used about $40 worth of this for this job. I'll let the pictures do the talking, the construction simply patterned off the holes in the plastic tray.
The angle washers are necessary because the tray sits at an 8° angle from the horizontal. The two outer holes are vertical and inset, so the alloy standoffs compensate for both, allowing the alloy stiffener to sit against the tray without stressing the tray. The EDM is already at the 8° angle and the tray screws flat onto it so the center bolt needs no standoff. I decided to use 3mm countersunk screws either side of the main hole in the standoffs to hold them in place on the stiffener as one unit and make the stiffener captive to the tray with rivets. That way the tray is removed as a single whole with no parts to get lost at the next "service". I added a bed of clear Liquid Nails glue between the alloy and the plastic as I assembled it too, reducing the chance that debris will find a way to wedge their way in between the two. The only change I made to the standard parts is to substitute longer 6mm bolts at the outer holes that go through the standoffs. I swapped the big washers from the original bolts across to the new bolts that are a gold colour rather than black. Hopefully that will be noted by the service person.
The result is very solid and hopefully serviceable. It is no heavier than the steel MG part but covers more area and won't get lost when the tray is next removed.
Glued tear and the parts produced to make a reinforcement. The big holes are just weight reduction.
The parts assembled on the tray, front (ground facing), and back (motor facing).
Tray back on car.
OK so now what to do? I had the article in Electrifying Everything outlining AS-TEC-02112023-01 - MG's warranty fix for this issue. It involves a warranty claim via the dealer, then if successful a booking and the dealer applying a metal reinforcement to the undertray front lip using the center bolt and the two either side. I thought about the hassle and the 20 questions, the form, the approval wait, the booking and the wait for that to come up when the part becomes available (I ordered a tire pressure sensor in February and it arrived at the dealership on the 17th of July). By then the tray will be dragging along the ground.
Looking at the EE article photos I decided I could do better using aluminium. Although I had some 3mm aly plate it wasn't long enough and I would need 35mm round bar for the angle standoffs that go in the large indentations in the tray at the mounting points either side of the center bolt. $86 later I had what I needed. I used about $40 worth of this for this job. I'll let the pictures do the talking, the construction simply patterned off the holes in the plastic tray.
The angle washers are necessary because the tray sits at an 8° angle from the horizontal. The two outer holes are vertical and inset, so the alloy standoffs compensate for both, allowing the alloy stiffener to sit against the tray without stressing the tray. The EDM is already at the 8° angle and the tray screws flat onto it so the center bolt needs no standoff. I decided to use 3mm countersunk screws either side of the main hole in the standoffs to hold them in place on the stiffener as one unit and make the stiffener captive to the tray with rivets. That way the tray is removed as a single whole with no parts to get lost at the next "service". I added a bed of clear Liquid Nails glue between the alloy and the plastic as I assembled it too, reducing the chance that debris will find a way to wedge their way in between the two. The only change I made to the standard parts is to substitute longer 6mm bolts at the outer holes that go through the standoffs. I swapped the big washers from the original bolts across to the new bolts that are a gold colour rather than black. Hopefully that will be noted by the service person.
The result is very solid and hopefully serviceable. It is no heavier than the steel MG part but covers more area and won't get lost when the tray is next removed.
Glued tear and the parts produced to make a reinforcement. The big holes are just weight reduction.
The parts assembled on the tray, front (ground facing), and back (motor facing).
Tray back on car.
