BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > DIY Guides/ Discussions
 
BPM
Post Reply
 
Thread Tools Search this Thread
      01-13-2020, 10:22 AM   #1
LakeSurfer
First Lieutenant
United_States
272
Rep
319
Posts

Drives: bicycle
Join Date: May 2019
Location: Florida

iTrader: (0)

Repair the M3 Undertrays DIY

Im a DIYer who enjoys the challenge of taking care of things myself.

A while ago i asked the forum about a way to fix the under trays on my M3 that where pretty much destroyed. The majority of responses that I received were that they cannot be fixed and to just toss them and purchase new ones. I have no idea why i listened, moreover, why did i listen to people who haven't tried and wouldn't try to figure this type of stuff out for themselves.

Enough complaining.

The undertrays are made up of some type of plastic/composite and a layer of felt type fabric on the outside. To repair cracks, holes, delaminations and so on requires the use of a plastic welder. I used the soldering iron type of "welder". I failed a few times using the plastic that came with the kit so i ended up shaving small chunks of the actual undertrays themselves and using it like a skin graft. If you can do this, it is the best practice because chances are that it will be very difficult to find the exact plastic that they used to initially build the part. manufactures ABS might have a different compositions from one to the next.

1. clean, sand with sandpaper the damaged area.
2. heat up the damaged area with a heat gun or the welder.
3. when the damaged area is almost melted, lay down the clean grafted pieces of plastic and use the welder to melt them into the damaged area until they are completely mixed in.
4. sand and clean up the area as you desire.

Remember to use a caul, clamps or whatever else you might need while working on the part as you want to work on it in its final shape because the heat can change its shape.

For my repairs i built them up with new plastic much larger and thicker then the factory and melted some medal screen into a few of the more damaged areas. And if the damage area was 1 inch I would repair about a 2 inch area.


Stop listening to the masses.

-Mark
Appreciate 2
      01-13-2020, 11:55 AM   #2
SAMM3Y
Lieutenant Colonel
SAMM3Y's Avatar
1750
Rep
1,935
Posts

Drives: 2008 m3
Join Date: Feb 2018
Location: NorCal

iTrader: (2)

Great now they can get destroyed again...

The original felt piece is suspended and made to withstand a few bumps and damage from parking curbs. It's also an integral part of the oil cooling system. The reason the majority of people in the thread your referencing said toss it and start with an aluminum one is because it's a far more robust design that doesn't hang so low and resistant to damage. It's a solution to the problem.. I guess it's tough to recognize that though up there on your soap box.. 😂
__________________
9ers
Appreciate 0
      01-13-2020, 12:30 PM   #3
pbonsalb
Major General
2763
Rep
7,275
Posts

Drives: 08 E90 M3, 99 E36 M3 Turbo
Join Date: Feb 2011
Location: Concord, NH

iTrader: (3)

Pictures of repairs? I did some patching and zip tying on mine to get more life, but eventually bought the aluminum flat plate that deansbimmer sells and have not had any scrapes since. My car is lowered so that made the scraping and damage worse than on a stock car.
Appreciate 1
      01-14-2020, 06:58 AM   #4
LakeSurfer
First Lieutenant
United_States
272
Rep
319
Posts

Drives: bicycle
Join Date: May 2019
Location: Florida

iTrader: (0)

Quote:
Originally Posted by SAMM3Y View Post
Great now they can get destroyed again...

The original felt piece is suspended and made to withstand a few bumps and damage from parking curbs. It's also an integral part of the oil cooling system. The reason the majority of people in the thread your referencing said toss it and start with an aluminum one is because it's a far more robust design that doesn't hang so low and resistant to damage. It's a solution to the problem.. I guess it's tough to recognize that though up there on your soap box.. 😂
Ya mean to tell me that I have other options? Ground breaking stuff here, thanks for your input.

Again buying new panels sort of defeats the purpose of fixing the old ones doesn't it? Which is the entire point of this post. You can fix them without paying $700 for a piece of aluminum that has a slight bend in it and some holes cut out. Its not about the money though its the principal.

"But you'll just break it again" My car is a 2011 and the panel has lasted 9 years so I fixed it like new and it will last another 9 years.

Yes the aluminum panel sits up higher but what would happen if you hit a curb or a parking block with it installed? you'd surely do more damage opposed to the OEM. the OEM part is sacrificial and will break, bend or twist long before anything else. yet again not the point.

I also disagree with the importance that this part plays in oil cooling. It to me appears to simply help the air escape after smashing into the radiator. The from bumper cover is far more important then these plastic pieces. But again not the point. I would bet you can run your car as usual without the panels and not notice any difference.

-Mark
Appreciate 1
      01-14-2020, 07:05 AM   #5
LakeSurfer
First Lieutenant
United_States
272
Rep
319
Posts

Drives: bicycle
Join Date: May 2019
Location: Florida

iTrader: (0)

Quote:
Originally Posted by pbonsalb View Post
Pictures of repairs? I did some patching and zip tying on mine to get more life, but eventually bought the aluminum flat plate that deansbimmer sells and have not had any scrapes since. My car is lowered so that made the scraping and damage worse than on a stock car.
Unfortunately I did not take any pictures. It turned out OK looking. You can definitely see where and what was repaired, with time and patience you could get it looking factory for sure.

mine lasted 9 years so i took it off to see how bad it was and just started messing with it. I was actually planning on ordering from Deansbimmer and perhaps still will at some point but the repairs turned out so much better than I thought, i might wait on it for a while.

-Mark
Appreciate 0
      01-14-2020, 07:37 PM   #6
Pig Farmer
Major
306
Rep
1,280
Posts

Drives: E92M
Join Date: May 2010
Location: Florida

iTrader: (0)

A few months ago, I decided to laminate all three pieces in Kevlar and carbon fiber. I had previously done the same on the outside pieces, but the bottom leading edge eventually wore threw. On the new pieces, I made what looks like a horse shoe for the bottom leading edge out of 1/8” sheet aluminum, and fastened it with low profile sidewalk bolts. I’d post a picture if I could figure out how to post with a iPhone. In any case, this “horse shoe” has been holding up extremely well. I suspect you could use this horse shoe approach without laminating the pieces with carbon fiber and it would fend off 99% of the wear.
Appreciate 1
      01-15-2020, 02:19 AM   #7
sdbmwcoding
Lieutenant
112
Rep
597
Posts

Drives: BMW M3
Join Date: May 2019
Location: San Diego

iTrader: (0)

Badass, cool write up and nice option for anyone not wanting to fork up the replacement cost of one
Appreciate 1
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 06:55 PM.




m3post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST