1997 M3 sedan underbody covers

[christospap]

Car is a '97 M3 sedan, manual, had it since 2006. When I bought the car it did not have any underbody covers, but I would like to buy and install the correct parts.

Can anyone help me determine what I need? Looking at FCPEuro I see the following:

https://www.fcpeuro.com/products?key...20250%20643%09

https://www.fcpeuro.com/products?key...20227%20690%09

https://www.fcpeuro.com/products?key...20209%20093%09

RealOEM also shows these parts.

https://www.realoem.com/bmw/enUS/sho...diagId=51_2048

Can someone confirm that I need all these? If you have a picture or a diagram to help me see how these are installed it would be wonderful!

Thanks!

[82bmw633]

.......

[blckstrm]

I'd do a little more homework. The main duct
(51712250643) is notorious for blowing out at high speed. Most guys use some kind of aftermarket undertray that also helps tie all those plastic parts together.

Something to think about...

[sirhodjibob]

I'm in a similar boat as you and am in the process of replacing my covers as well so I will be following your thread closely. While there are a multitude of aftermarket ones available I want to stick with OEM.

Someone correct me if I'm wrong, but you can run the aluminum belly pan 51718209093 only if you have not added the Lightweight/convertible X brace.

I ended up ordering 51712268673 which is the air duct for the Lightweight models and should work if you intend to run the OE front splitter set up. 51712250643 is the standard version of that.

Worth noting are 51712491567 and 51712489775. These were, as far as I can tell, never offered on US spec cars but were on the European models. These cover the transmission tunnel and the chassis X-brace if you have one. I believe the Z3Ms got similar versions of these parts.

The part numbers for the hardware for all this is something I'm still trying to track down. It's hard to decipher RealOEM sometimes for that. I'm sure a competent parts employee at a dealer could help though.

[pizzaman09]

I really should do this myself. I have most of the panels on but I have a significant number of self tapping screws and aluminum house siding brackets holding it all together. I manage to knock chucks free pretty often when I autocross and cream a cone.

[nalasivad]

I just replaced the main duct on my 95M3. While under the car I noticed a rubber piece hanging down off each side of the radiator. Each one had two of the captive metal clips for something to attach. Anyone know the part that attaches to these rubber pieces? Here is a link to a photo, yellow circles showing clips: http://nalasivad.com/part
Wondering if it is the part the op mentions: 17112227690. ???

[sirhodjibob]

I believe that is part of the air duct: 51712256543 & 51712256544

Item #6: https://www.realoem.com/bmw/enUS/sho...diagId=51_2112

Edit: nvm, you are asking what attaches to the air ducts.

[shogun]

I just repaired my original one with alu brackets, found this write up: "Inventive Repair for the Blasted E36 M3 Undertray", there are four points where it connects, and the tabs are usually broken off.
repair of original one, this is the easiest and fastest repair if you want to keep the original design and it is a solid repair unless one wants to switch to aftermarket Aluminum Under Panel https://www.m3pilot.com/repair-plast...e36-undertray/
some smaller cracks on the larger area I repaired with a fiberglass repair kit.
p/n is probably 21 Air duct M TECHNIC 51712250643 ,only in conjunction with Covering Lower L=708MM 17112227690 https://www.turnermotorsport.com/p-1...t-51712250643/

[NeilM]

I just repaired my original one with alu brackets, found this write up: "Inventive Repair for the Blasted E36 M3 Undertray", there are four points where it connects, and the tabs are usually broken off.
repair of original one, this is the easiest and fastest repair if you want to keep the original design and it is a solid repair unless one wants to switch to aftermarket Aluminum Under Panel https://www.m3pilot.com/repair-plast...e36-undertray/
some smaller cracks on the larger area I repaired with a fiberglass repair kit.

I cut and wrapped hardware store aluminum sheet metal reinforcements around all the mounting points, including pork chops and wheel arch liners, and pop-riveted these reinforcing parts in place. I've also replaced many of the original sheet metal screw/Tinnerman nut fasteners originally used on these plastic bits with rivnuts and machine screws. You can see these reinforcements at the top of the plastic sides here:

LTW-Undertray.jpg

This is a different undertray model, but you get the idea. Did this many years ago, everything is still solid.

Neil

[shogun]

I got another undertray 51712250643 from a parts car which I intend to repair as spare part, 2 plastic brackets on left side/driver side are broken, that is no problem, will make aluminium mounting point enforcements similar to above pic.
At the bottom the belly also has a half circle crack of about 8 inches length/diameter, nothing missing from the material, but just a crack.

On the undertray below the BMW part number there is the material mentioned <GM-20-PP>, what I found in the net is material PP is Polypropylene.
Does somebody have experience with repairing this crack in PP material with a glasfiber repair kit with resin + hardener?
In case FRP/resin+ hardener does not stick well to PP, another option is to use aluminium sheet metal and cover the cracked area and pop-rivet these reinforcements in place. I am not in a hurry with this one as it is for spare, so I have time to wait for replies of members with actual experience with FRP on PP. Thanks

Edit:
Checked more, Polypropylene is a difficult product to fix with fiberglass kits, the resin does not stick good and will get lose. The best is apparently a strong cyanoacrylate adhesive , Loctite says:
Loctite® Plastics Bonding System is a two-part cyanoacrylate adhesive that sets in seconds and develops tremendous strength with just one drop.The activator primes hard-to-bond surfaces such as polypropylene and polyethylene. Loctite® Super Glue Plastics Bonding System dries clear and sets without clamping. It is resistant to water, most chemicals and freezing temperatures.Invisible repairs.Bonds difficult-to-bond plastics such as polyethylene, polypropylene and Teflon.
https://www.ellsworth.com/globalasse...ic-bonding.pdf