Sunroof delete or other diet advice.

[dewme5]

I'd really like to find a Carbon Fibre sunroof delete panel. Anybody know of a maker of such an item for the E24?

Second, is diet advice. I'm removing my comfort seats, and they'll be replaced with something tasteful, but much much lighter. Rims and tires are on the chopping block as well. Add in the sunroof to that weight loss plan, and what's left? I'm not worried about the last 1/2 ounce, and this isn't a track car. I want to keep it decent, but do not plan on keeping it stock (I bought mine in rough shape, so as to not mess up a nice original). I see no reason to lug around the extra weight, and would rather put the car on a diet. Any suggestions?

From http://bigcoupegroup.com/archives/14


1985 US 635Csi
5 speed
3375 lbs.
Car & Driver



Bathroom scale measurements for my 85 635csi
Stock from comfort seats 68lbs each
Stock hood 52lbs

[Shipper]

maybe these guys have one or, can make one. Do the bonnet at the same time. Would love to know how much weight their bonnet saves!

http://dtmfiberwerkz.com/access/style-carbon-fiber-hood-cfrp-p-517.html

[dewme5]

Oh nice. Wasn't looking for that, but what has been seen, cannot be unseen! That's gotta be good for 70 pounds or so. Add that to the 60 for getting rid of all the sunroof stuff, and about another 100 for the seats, and that's a pretty good diet!

[eric1ono]

Another idea would be carbon fiber or maybe fiberglass front fenders. They are bolt on so pretty easy to swap out.

If we are just brainstorming right now, what about the same materials for the door skin and trunk lid?

Since you are not worried about keeping it stock, and I don't know what your budget is, could you come up with a lighter weight dash? The stock item looks like it weighs a ton. Has anyone out there who has removed there's ever weighed it?

Hope I'm not being to ridiculous. If so, please let me know, and I'll reel it in.

I like this thread. I've wondered about this before.

[dewme5]

My budget certainly has reasonable limits, but a few hundred pounds, is a few hundred pounds. Starting off with an E30 would have been the smarter thing to do in the weight category, but I can't get past the look of the Shark.

Shamefully, I did not get before weights. But I will be able to do the home scale method to get a good idea.

With the dash, I'm not sure how much of that I would get rid of. I have a full set of Autometer Gauges from a different project, new in box still, but I'm just not sure I like the looks of that, in this car. I am going with a Megasquirt, so the stock dash won't be as useful as it was. All the check lights are going, the trip computer is going. When I get to that point, it's going to take some serious contemplation.

Any idea how much weight savings is on the fenders? The sheetmetal doesn't seem like it would be very heavy.

Checked with DTMFibrewerks, and they do not make a sunroof delete at this time.

[FernandoBunster]

Check this out:

http://www.xmoorcars.co.uk/GRPwings.htm

[alpinacsi]

Oh nice. Wasn't looking for that, but what has been seen, cannot be unseen! That's gotta be good for 70 pounds or so. Add that to the 60 for getting rid of all the sunroof stuff, and about another 100 for the seats, and that's a pretty good diet!

230#s Really? This sounds like the old HotRod HP diet. Keep adding parts and you will have 1000hp. Your method and the car will have zero weight.

The CF parts will reduce weight but those are some really steep numbers. You still have to have a hood and seats. Also look at changing the battery to a small lightweight one. Replace the factory exhaust with lighter parts. Remove the carpet and underlayment including the tar pads (put carpet back if you wish). Remove all AC parts. Remove spare tire and associated tools. And forget about installing aftermarket sound system as it just adds weight and will sound like crap in the car now. No need for big brakes as they add weight and you are putting the car on a diet. Forget about large wheels as they add weight. Lots of things under the hood can go. Who needs bumpers?

Cheapest thing to do is loose or maintain weight of the driver and do not allow passengers.

[dewme5]

Google the difference the sunroof delete makes. I'm not pulling numbers from the sky.

Yes, I know I will still need seats. Have you picked up a set of comfort seats? Over 50 pounds each, easy. Depending on which replacement seats I like, the difference can be huge.

As i said before, I'm not making it a race car, but I also don't care if anyone else likes it.

Go try to pee on someone else parade. I'm not 15, and I don't need your permission. I did come ask for suggestions to move in the direction of my choice. I did not ask for you to give me opinions on why you think it's a bad idea. Stay in your lane.

[alpinacsi]

Go try to pee on someone else parade. I'm not 15, and I don't need your permission. I did come ask for suggestions to move in the direction of my choice. I did not ask for you to give me opinions on why you think it's a bad idea. Stay in your lane.


Never said it was a bad idea and actually gave some good advice. But now I will give you my opinion: if you want to be a boy racer and drive a wanabe BMW race car...get an e36.

I would like to see some numbers on the sunroof delete. Real numbers for our cars. Wait: you probably will not find any. So I will give them to you. 35-40 pounds but you still have to fill the hole. The actual sunroof panel weighs about 12-14#s. The mechanism with the motor and drive weight about 20-25 except for the very early e24s that had the motor in the trunk with long cables. You will have to cut out spot welds and do considerable cutting and grinding to remove the assembly. The headliner will most likely be destroyed in the process and will definitely not fit back after the parts are removed. So that leaves you with just pulling the motor and swapping the panel with CF if you wish to retain the headliner. So net gain (loss) would be what? 12#s

You mention a hood replacement would net 70#. Well the hood is actually less than 50 but with the grills, lights and small bits we can say it is 50 pounds. The CFRP hood is about 25# so that gives a net of about 25#

The seats are heavy; and the power comfort seats are about 55# each. No idea how much the seats and tracks weigh that you want to reinstall but weight can be saved there.

Removing the carpet underlayment and pad can save 20-25 and you can reinstall the carpet.


Replace the control arms with alum ones. Replace the flywheel with the earlier lighter one or an alum one (5-10 # savings). Maybe a lighter clutch.

And the list goes on. But I guess you know better than I because you have googled the differences.

[eric1ono]

Hopefully everyone has let off some steam and can just focus on the topic and move on from the personal stuff.

Alpinacsi, you've listed some good ideas. Your numbers are pretty accurate, I had inquired about the hood weights in the past and they were what you listed above. I still think this is an interesting exercise. As dewme5 said above, another car would have been a better choice for maximum lightness, but I think we are all on this forum because we love the 6er. Everyone has different priorities with what they want out of their 6er, but I think taking a look at adding lightness is worth pursuing for some.

Fernando, I had never seen those before. Interesting. I emailed them asking a few questions, including weights. So we'll see what they come back with.

Besides adding lightness in general, I especially like the idea of focusing on the front end since the car is forward weight biased in stock form.

While this idea doesn't make the car lighter, I would love to be able to move the drivetrain backwards a few inches (the idea being to get closer to a 50/50 balance), but I don't see how that is possible without hacking up the body and encroaching on other components behind the engine. I think I have heard of at least one person doing this, but I don't know any details about what they had to modify to make it work.

Later,

Eric

[dewme5]

Sorry alpinacsi. When I read your post earlier, it struck me much differently then when I read it again. Although, your boy racer comment still shows the angle at which you wish to look down your nose at my choice. That's fine. If I need a nice comfortable cruiser, I have an E60 535i.

As for the 1000hp. it'll only be 500ish. Yes, it will be turbo'd, sequential injection, and CNP ignition.

I've seen listings of various bmw sunroof deletes from #31 to #60. Various models, and various materials, so before buying anything, or removing anything, I started to ask about it.

Just weighted the comfort seats. 68lbs each. So, say 70+lbs saved with aftermarket seats. Carpet and sound deadening stay. Stripped dash is a possibility, but we'll see.

And the driver doesn't need a weight loss plan.

Also, nowhere did I state I plan to remove every last ounce possible. Yes, bigger brakes will weight more, for a good reason. A sunroof? I don't want one, so why carry one around? The body is pretty shameful, and rust riddled, which is getting fixed. But, if I have to buy parts, should I buy original, or what I want? I'll go with what I want.

[eric1ono]

dewme5,

Bigger brakes don't have to weigh more. Depends on which bigger brakes you get. The stock 635 brakes are not the lightest options out there, and again, depending on budget and how OCD you want to be, you could get something like machined calipers and 2 piece rotors that could be in the range of the stock ones, weight-wise. I am assuming you'd go no larger than a 17" rim since that seems to be the most common change made.

On the sunroof, you could just cut it out and have flat sheet welded back in. I would think a good body shop could do this with positive results in matching the contour of the roof. I realize the headliner would need to be replaced, as alpinacsi mentioned above, but I assumed that would happen anyway. I only suggest this because I was looking through a thread where a guy was setting up his e30 for track use and did this exact thing himself, and the results looked good. Something to think about.

Any other ideas on what could be tackled in the interest of less weight?

Take care,

Eric

[eric1ono]

I heard back from Xmoor today and they had some interesting feedback:

Hi Eric,
Many thanks for your interest. I will get some prices together for you for the front wings, a group purchase would probably be the best idea as the shipping costs are silly money. We are looking at bonnet, boot and rear spoiler being made in composites too, but may be late this year before we are able to produce it as we are so busy with various projects. We do have a slightly mad idea sitting on the back burner of nearly all the bodywork in carbon including the roof (including removing the sun hatch). The grp wings are half the weight of the steel items. Steel 7kg each, grp 3.5Kg each. Pre-preg carbon less than 3Kg. All the best and I will get back to you with more information as I get it.

So there's the weight difference on the front fenders. For the US market that would be steel: 15.43lbs/each, ~31lbs/pair; fiberglass: half the steel weight; carbon fiber: ~6lbs/each, ~12lbs/pair.

I thought it was very interesting that he talked about the roof idea. That is not something I inquired about at all so I was quite surprised. I have already asked him for more details as well as offering my services if I can be of any assistance. I've got ~15 years of design experience and am a mechanical engineer by trade.

We'll see where it goes.

Eric

[GarmaZabi]

Although this idea doesn't fill my cup of tea in the slightest, you're free to do what you want. I'm just confused about what you want as an end result. you want to do weight reduction and increase power but you don't want to track it? they're pretty heavy cars. minimum 3500 pounds but probably more. power window equipment and power seats would be my starting place though. then a lighter hood.

[dewme5]

This is not a track car. Maybe a few scca cone events, just for the fun of it at some point, but that has zero impact of building a car I enjoy. Also, to avoid any confusion, I do not street race.

BMW built a car for the masses. I'm just turning it into a car for me. Lighter weight is an easy performance upgrade. 100lbs is a pretty big deal.

The comfort seats, to me, feel horrible. Should I try to find something heavier? It just makes sense to go lighter. A performance upgrade.

Sunroofs. You may like yours, I have always thought they were a terrible idea, and I do not open them.

As for body weight, using http://bigcoupegroup.com/archives/14

1985 US 635Csi
5 speed
3375 lbs.
Car & Driver



What I don't understand, If my question was "what's the best folding chair, to sit on my but at a car show, next to my polished car", everyone would give suggestions.

Am I going to replace the hood with a carbon one? I don't know. Get rid of the sunroof. Yes. Get rid of those horrible seats. Yes. So, if I get rid of the sunroof, should I go old school, and lead in a new panel? Bolt on a few extra pounds, just for the heck of it, or seek ways to improve "The ultimate driving machine"? Lets say I do get 200lbs total. That's easier on the driveline, easier on the tires, better for gas mileage, it'll feel more nimble. easier on roll bars, easier on shocks, etc etc. I mentioned before, I have an E60 to cruise in luxury. My E24 is almost 30 years old, needs body work, and needs lots of stuff fixed. The brakes are toast, they need a complete replacement. Should I go with stock, or 30 year advance in options and technology? I would really like to hear the arguments and questions against putting better brakes on.

- - - Updated - - -


dewme5,

Bigger brakes don't have to weigh more. Depends on which bigger brakes you get. The stock 635 brakes are not the lightest options out there, and again, depending on budget and how OCD you want to be, you could get something like machined calipers and 2 piece rotors that could be in the range of the stock ones, weight-wise. I am assuming you'd go no larger than a 17" rim since that seems to be the most common change made.

On the sunroof, you could just cut it out and have flat sheet welded back in. I would think a good body shop could do this with positive results in matching the contour of the roof. I realize the headliner would need to be replaced, as alpinacsi mentioned above, but I assumed that would happen anyway. I only suggest this because I was looking through a thread where a guy was setting up his e30 for track use and did this exact thing himself, and the results looked good. Something to think about.

Any other ideas on what could be tackled in the interest of less weight?

Take care,

Eric

Brakes. Mine have to get replaced all the way around, so I'll start shopping pretty soon. Ireland Eng. has a kit based off of 750 fronts and 540 rears, calipers, rotors, and braided lines for $725. I know I can get an expensive race setup, but for the street that doesn't sound like the right deal. Usually to grabby, or require to much heat to qualify as a street brake. Some decent info here. http://bigcoupe.com/phpBB2/viewtopic.php?t=2137&highlight=brakes

Once I finish freshening up the engine, I'll pull my headliner down, and see what route to go. I have to do the seal, and chase drains at a bare minimum if it were to stay, so no point in waiting. I intend to take it down, and get a weight on it.