1998 BMW M3 sedan (aluminum roof)

I was curious if anyone has replaced their stock roof with a aluminum piece and how best to go about having it done ie cheapest way.

I have heard that the stock piece with the moon roof runs about 200lbs Is this correct?

If so it seems to me a pour place on a vehicle to place so much weight and even more so on a car like the M3 which is why I would like to have this done

Look into getting just a carbon fiber sunroof. It will be a lot cheaper

Originally Posted by TRaV MaNN

Look into getting just a carbon fiber sunroof. It will be a lot cheaper

Yea that would help but I'm sure most of the weight is coming from the driving gears and motors plus there is probably at least an additional 20 lbs of savings with aluminum over the sheet metal. The carbon might save 30-40lbs but your still stuck with all that extra weight up top. That's just giving away performance

Thanks for the suggestion but I was looking more in the lines of wether anyone has attempted this and or how they could or would go about it

I don't think it is 200 pounds. I have heard the sunroof adds about 40 pounds.

The steel roof panel it self is not that heavy. But lighter up high is good.

Originally Posted by Pinecone

I don't think it is 200 pounds. I have heard the sunroof adds about 40 pounds.

The steel roof panel it self is not that heavy. But lighter up high is good.

Just what I read so you may be right but the sunroof panel alone Im sure weighs 40lbs but not everything combined I'm sure its easily within a 100lbs at a min. it's true the metal isnt all that heavy but if it was to go there is still some savings is all I was trying to say.

Ive thought about it with cf. I did a quick sunroof delete, the cartridge with everything attached prob weighed 40lb-60lb. Put I ended up reusing the panel instead of making a new one. I suppose you could cut the roof out and leave a small section of the original roof.

I would sandwich the inch or two of the roofline left with cf, that way theres no mounting points and its smooth. the roof has alot of extra sheet metal and layers that serve no purpose so its got to be pretty hefty.

Sent from my thumb to your eyes

Originally Posted by rooster1986

Ive thought about it with cf. I did a quick sunroof delete, the cartridge with everything attached prob weighed 40lb-60lb. Put I ended up reusing the panel instead of making a new one. I suppose you could cut the roof out and leave a small section of the original roof.

I would sandwich the inch or two of the roofline left with cf, that way theres no mounting points and its smooth. the roof has alot of extra sheet metal and layers that serve no purpose so its got to be pretty hefty.

Sent from my thumb to your eyes

Sounds about right. So in total probably looking more around 120? Including sheet metal etc. Good info thanks. Carbon would be great but it takes alot of knowhow to make it strong and also extreamly expensive if it is to be done right. I'm not in the market for a 2k roof although it would be sweet. I'm thinking I would only be a couple pounds off that with aluminum and all It would take is 3 brace bars for keeping any flex from happening and for welding points and a sheet of 5052. It would take some work but if I do it myself I could probably stay under 300 bucks and would be a sweet (as far as I can tell) one off.

Thanks everyone for the suggestions and insight to other Ideas

But remember, it needs to be engineered to take the stresses of the body twisting. Otherwise you will lose more by the loss of torsional rigidity than you gain my losing the weight up high.

Do you not think three braces would be enough?

I think an engineer should take look at it.

Braces are side to side. Torsional loads are diagonal on the roof panel.

Good point I will do further research into it

I've done it.
I'm a metallurgical engineer.
Take a look at my blog.
http://egebhardt.posterous.com/sunroof-removed

If you re-use the metal panel (13lbs) to plug the hole, you are only saving 19 lbs. Yes. 19 lbs.
For the amount of work involved, it is not worth it to de-value the car that much to shave 19 lbs.
You are better off carrying a cell phone and ditching the 50 lb spare tire in the trunk.
Then ditch the rear seats for 35 lbs more. Those things can all be put back in easily.

Originally Posted by egebhardt

I've done it.
I'm a metallurgical engineer.
Take a look at my blog.
http://egebhardt.posterous.com/sunroof-removed

If you re-use the metal panel (13lbs) to plug the hole, you are only saving 19 lbs. Yes. 19 lbs.
For the amount of work involved, it is not worth it to de-value the car that much to shave 19 lbs.
You are better off carrying a cell phone and ditching the 50 lb spare tire in the trunk.
Then ditch the rear seats for 35 lbs more. Those things can all be put back in easily.

I read your page and I thank you for the information. I actually had not taken into account de-valuing the car but you are right its not worth the savings. I had originaly read that the whole setup was 200lbs which of course I thought was insane but you never really know with these cars... To bad would have been a great way to save seriouse weight.

Thanks again!!!

If it really would have shaved 200 pounds from up high, BMW would have done it on the LightWeight.

Originally Posted by Pinecone

If it really would have shaved 200 pounds from up high, BMW would have done it on the LightWeight.

I'm sure you saying that means you know they didn't but I don't have a list handy for what all they did on it.

No they did not. Notice my Sig.

Aluminum door skins, but not aluminum roof. But NO sunroof.

Originally Posted by Pinecone

No they did not. Notice my Sig.

Aluminum door skins, but not aluminum roof. But NO sunroof.

So the sunroof was removed? And just to point out one quick thing just because something makes a car better doesn't mean a manufacture will do it. The light weight m3 was made using a car already made and striping out some weight to make it more agile. An aluminum roof would have made the car handle even better then I'm sure it already does but it would not have been cost effective for them to re stamp the roof with aluminum. Case an point 2010 viper did just that and save something like 60 lbs over the steel roof (those cars have tiny roofs) so I know if I where to be able to do the entire roof plus loosing the sun roof would be amazing. The other gentlemen was referring to just the moonroof.

Thanks guys for keeping this topic alive

1) The sunroof was not removed, it was not put in at all.

2) The Lightweight was built for RACING. So if it would have saved that much weight, they would have done it. It is only due to homologation rules that any were sold to normal people.

3) As for cost effective, how cost effective was it to make the doors of aluminum? How cost effective to have a special lighter weight carpet? How cost effective to make a thinner underbody insulation? How cost effective to develop a dual oil pump and special sump? Or splitter? Or any of the other special parts for the Lightweight?

Originally Posted by Pinecone

1) The sunroof was not removed, it was not put in at all.

2) The Lightweight was built for RACING. So if it would have saved that much weight, they would have done it. It is only due to homologation rules that any were sold to normal people.

3) As for cost effective, how cost effective was it to make the doors of aluminum? How cost effective to have a special lighter weight carpet? How cost effective to make a thinner underbody insulation? How cost effective to develop a dual oil pump and special sump? Or splitter? Or any of the other special parts for the Lightweight?

I see you point you got me. I don't have an answer winner winner chicken dinner!
Although some make since. But sump and oil pump would most def not be cost effective. Maybe they wanted to keep it do to keep the balance.

They wanted to win races to sell cars.

Heck, the early M6 had double injectors. Because they needed higher fuel flow for racing, but had to use the stock setup, so the street cars had two injectors for each cylinder, but only one was hooked up.

Originally Posted by Pinecone

They wanted to win races to sell cars.

Heck, the early M6 had double injectors. Because they needed higher fuel flow for racing, but had to use the stock setup, so the street cars had two injectors for each cylinder, but only one was hooked up.

Ha ha that's good stuff well at least the owners were well supplied for charged applications lol