any reason not to go with fiberglass doors?

[kolosy]

doors are the last big ticket / low work weight reduction item i have available to me (plenty more actual weight to be saved elsewhere, but it gets into roastbeef territory with 5-10-20 lbs at a time at most).

i've been putting off getting a carbon set because.. it's all the dollars. i'm seeing something on the order of 5-6K before shipping and taxes. but it turns out that HGK will do a fiberglass set for ~$2K, and according to them it's 4.3kg for fiberglass and 3.4kg for cf. yes, carbon looks cooler but i'm ok without the cool factor if i get 99.99 percent of the weight savings and 1/3rd the cost.

i've obviously got a full cage so i don't think safety is a factor here, but thought i'd ask.

[jmeenach]

Carbon Microsystems makes our doors in carbon for far less than the quote you got:

https://carbon-microsystem.com/store...ber-p140285999

[kolosy]

Originally Posted by jmeenach

Carbon Microsystems makes our doors in carbon for far less than the quote you got:

https://carbon-microsystem.com/store/Doors-for-BMW-3series-E92-coupe-from-Carbon-Fiber-p140285999

You got me all excited. But alas they seem to be E92 only :/

[jmeenach]

Oh dang, you're e90. I forgot

[dogbone]

DTM Fiberwerkz in Northridge, CA made our E90 M3 carbon doors and molded them from the doors we gave them. They've been good for several years. These days, their website shows pricing of $4000 for carbon and $2700 for fiberglass.

There's a few things to consider with the DTM doors:

-We gave them fully gutted front OEM doors which means there's no structural support on the inside the of the front doors. This makes them a bit flexy. One of the people in our group was wishing for more structural stuff in the door to make it more rigid. Personally, I'm happy to have them as light as possible and they've been totally fine for me. The rear doors we gave them weren't quite as gutted, and as a result, they have more structural stuff and are more rigid. You can see what the inside of the doors look like on their website by clicking on the various pics.
-We put a rubber bumper at the bottom of the door frame to give the front door something to rest on to increase rigidity. Works well.
-There was some fabrication work necessary to make the front doors work with the OEM mirror assemblies. The shop had to add some fiberglass bridging to make that mirror area stiffer. The OEM mirrors are kinda heavy and see quite a bit of force at high speeds.
-The DTM doors don't really have any built in accommodation for an interior door pull. That will have to be figured out by whoever is installing. I actually don't have one. I just reach outside to the handle.
-The front doors were not designed with front windows in mind, for instance if you want transport windows or windows for rain racing, there's no built-in setup for that, and it would need to be sorted out once you got them. I do have plexy rear windows that are permanently screwed in.

I suspect all the brands probably need a fair amount of fabrication effort to make them work and fit properly. You hear that some brands' molds are aging and don't put out a great set anymore.....(I doubt the DTM molds have been used a ton.) My friend got some HGK carbon doors, and the carbon finish was not good---huge swirls, filmy. He had to hire a guy to sand them and re-finish them and then the finish looked very nice. Plus, if you get them from overseas, there's all the shipping and the import duties and (maybe tariffs?). DTM is domestic.

Anyway, DTM seems hit or miss at times. I mention their name and some people love them. Others don't. Can't quite figure that one out.

Here's DTM's site with their doors:

https://dtmfiberwerkz.com/shop/ols/p...C-DRS-CFR-CRB1

If you decide that DTM interests you, we can do a video chat. My car is here in the garage for the summer so I can show you the doors in detail. My build thread has plenty of photos of the car with the carbon doors. And to their credit, they've survived quite a few nasty off-track excursions with lots of rocks and dirt flying around. And they survived a front-end collision into a tire wall at VIR.

This one shows them pretty well:

[Nish90]

Dogbone, do you recall how much weight you were able to shed switching to carbon doors?

[dogbone]

Originally Posted by Nish90

Dogbone, do you recall how much weight you were able to shed switching to carbon doors?

On a sedan, if you went from a set of completely stock doors with door cards, glass, wiring, crash beams and everything, I'd say the loss is around 140-150lbs across the 4 doors.

In my specific case, I started with gutted doors, obviously no door cards, no wiring, no crash beams and no glass, and I still lost 70 lbs from the gutted doors.

It's some of the best bang for the buck in weight loss on the car. To lose 140lbs for $4000 plus install is a way better deal than paying $4000 for an installed carbon roof and losing 10 lbs (which I still have not done).

This post on my build thread digs in to the topic, but the conversation on carbon doors starts a couple pages earlier on page 67 of the build thread. I highly recommend you check it out:
https://www.m3post.com/forums/showpo...postcount=1518