bencpeters
Posts: 4
Joined: Fri Jan 01, 2016 8:36 pm
Location: Salt Lake City, UT

Install Thule roof rack tracks

Fri Jan 01, 2016 8:40 pm

I'm very interested in getting an I3, but need to be able to put a roof box on it for transporting skis in the winter. I was dismayed to learn that there are no roof rack options available "out of the box" for the car, but I was wondering if anyone knows whether aftermarket rails like these could be installed:

http://www.thule.com/en-us/us/products/ ... -_-6238999

The installation process involves drilling through the roof, is there anything about the carbon fiber body that makes that not feasible?

Thanks!

jadnashuanh
Posts: 4914
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Install Thule roof rack tracks

Fri Jan 01, 2016 10:00 pm

I would not drill any holes in the roof, or, for that matter, anywhere in the car! Cut a fiber in carbon fiber and you've changed the overall strength of it. Even a deep scratch can be problematic on CFRP. Metal's a bit different in that respect.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

brorob
Posts: 104
Joined: Sat Oct 31, 2015 5:53 am

Re: Install Thule roof rack tracks

Sat Jan 02, 2016 9:18 am

I wouldn't advise drilling any holes either. Even if you're able to drill clean holes without damaging the carbon fiber, you may damage the roof since it wasn't designed for those mounting feet.

I searched for any available roof rack option before leasing my i3 and couldn't find any. I was really disappointed about this and it almost broke the deal. I know the car was designed as a city commuter but it seems like a target market for an EV would be outdoor enthusiasts that would have a need for this. I would rather drive my EV to a trailhead than an SUV.

Maybe Thule or Yakima will come up with a foot pad design that will work with the i3. They make these for other vehicles so not sure why it's not possible for the i3. Wondering if it has anything to do with the load that the roof can accommodate. A few pair of skis or a bike would be fine but a carrier box full of gear might sag the roof if all 4 doors are open and the B pillars aren't supporting the roof.(?) Could just be there hasn't been a big enough demand yet.

I'm able to fit my 29er mountain bike in the back after taking the front wheel off but this isn't the most convenient option, especially since I put a tarp in first to protect the interior from dirt. If I want to drive to a bike trailhead with my wife or daughter, the i3 can't accommodate. I may check into rear mounted rack options for this as I've seen a few of these.

jadnashuanh
Posts: 4914
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Install Thule roof rack tracks

Sat Jan 02, 2016 6:42 pm

Two things come to mind...a metal roof doesn't have 'grain' and fibers, so drilling a hole isn't as radical as cutting CFRP; most of the exterior panels are plastic, so not perfectly rigid like metal, so the typical straps or clamps that hold the feet in place would take some considerable engineering, if it could be made to work at all. You might be able to epoxy some mounting feet in place - lots of the car is held together with adhesives, but those generally are not readily available to consumers that might be adequate. Keeping things neat looking and getting things exactly where you want and need them would be tricky as you'd only get one chance, and it would be permanent.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

Jeffj
Posts: 252
Joined: Mon Sep 15, 2014 12:32 pm
Location: Boulder, CO

Re: Install Thule roof rack tracks

Sun Jan 03, 2016 7:36 am

Other thing that would concern me about a "permanent" addition of a roof rack is the rather large negative impact they make on efficiency. I drove a Murano for years and noticed, over many months, that when I had a set of Yakima bars on the top, it would cut the mileage by 2+ mpg (on a car that struggled to get 20 mpg on my commute route). 10% hit is pretty huge for something that you don't use all that often.

I've seen a number of references to a rack system called SeaSucker (note, I don't have one, just seen references) that uses suction cups. Users of it seem really satisfied.

jadnashuanh
Posts: 4914
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Install Thule roof rack tracks

Mon Jan 04, 2016 3:29 pm

I wonder on the SeaSucker's vacuum cups, how often you need to repump them to maintain a good hold? MIght differ based on how hot or cold it was, and how clean the roof was at the time of installation. You wouldn't want to be moving down the interstate on a long haul and watch your bike crashing in the rear-view mirror! When pumped up, they certainly should have more than adequate hold, it's just how long will they stay that way.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

bencpeters
Posts: 4
Joined: Fri Jan 01, 2016 8:36 pm
Location: Salt Lake City, UT

Re: Install Thule roof rack tracks

Wed Jan 13, 2016 11:13 am

I talked to a ME (mechanical engineer) friend of mine who specializes in carbon fiber about this - he said if there was a bidirectional weave, he'd have no issues at all drilling, it shouldn't matter. However, after looking at some articles about the manufacturing process for the i3, he said it sounds like the weave they use for the roof is unidirectional, and thus not a good idea to drill into.

FWIW - he suggested stripping paint away on the surface and using Hysol epoxy with as close to flush-mount/rail mounts as available, then repaint around (and use removable feet so racks can be removed). Apparently the peel strength # for hysol is higher than the base laminate of the CF itself... I haven't tried it yet, but it's an idea!

The SeaSuckers seem like a great solution if you only occasionally need racks. For me, I drive into the mountains almost every day with skis in the winter, and my car spends much of its winter covered in all sorts of road salt, so I'm not sure it'd work very well, and I need a daily solution, not an occasional thing.

I33t
Posts: 894
Joined: Fri Dec 13, 2013 3:01 pm
Location: Australia

Re: Install Thule roof rack tracks

Wed Jan 13, 2016 3:52 pm

bencpeters wrote: FWIW - he suggested stripping paint away on the surface and using Hysol epoxy with as close to flush-mount/rail mounts as available, then repaint around (and use removable feet so racks can be removed). Apparently the peel strength # for hysol is higher than the base laminate of the CF itself... I haven't tried it yet, but it's an idea!
I'd get a second opinion on that suggestion.

We are not dealing with standard CF here that uses epoxy or similar resin. This is CFRP (Carbon Fibre Reinforced Plastic) I think you'd need to find a totalled i3 and get a roof section to test on for hysol peel strength and if it even adheres to CFRP.
2014 BMW i3 BEV deposit placed 19th Dec 2013
Delivered in Melbourne 4/12/2014. Arrived locally 11/12/14, with 24km on the clock.

S3RDP
Posts: 69
Joined: Wed Nov 05, 2014 9:35 am
Location: Tonbridge, Kent, UK

Re: Install Thule roof rack tracks

Wed Jan 13, 2016 4:03 pm

This may be of interest. I believe you can attach various carriers

http://torkliftcentral.com/rving-and-to ... ohitch-reg

There is also a YouTube video showing how to install
Richard

Rex, Andesit, Lodge, Driving Assist Plus, Prof Media Pack, Park Asst, Sunroof, 429 Wheels, DC Rapid Charge. Built and delivered March 2015.
Replaced MINI Cooper S. Partner for Porsche 997 Carrera 3.6 Coupe Gen2 PDK

imolazhp
Posts: 244
Joined: Sat Mar 28, 2015 8:02 pm

Re: Install Thule roof rack tracks

Wed Feb 10, 2016 1:16 pm

Subbing for a solution.

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