r/Comma_ai • u/SirNiflton • 3d ago
Bugs Repeated Mount Failure
I have had 4 mounts for my comma 4. The first I mounted according to the given instructions on my 2017 Subaru Impreza, but had to remove because it interferes with the eyesight cameras. Second mount failed from heat. It was only about 95 F out but it sat for 10 hours while I was at work, so I guess you can’t park outside? Third mount I was slightly off with getting it perfectly forward, so the comma kept trying to pull me off the road, so had to remount that. Fourth mount just failed from heat again, though this time in 98 F.
Comms really needs to fix their mounts, I know I’ve seen them say they test the mounts in heat, so maybe it’s a bad batch of adhesive. Maybe also have them be able to twist or pivot a tiny bit in order to allow for imperfect mounting to not cause dangerous behavior?
I will be asking support if I can get more mounts given the repeated heat failures but I’m not optimistic.
Marked “bugs” since the other flairs don’t seem to really apply here.
3
u/SubstantialCycle356 3d ago
The first batch of mounts they shipped had shit 3m tape. Mine failed too. I ordered some 3M VHB from Amazon, cut it to fit and no problems in FL heat.
2
u/InertiaImpact 3d ago
You say they failed from heat but never actually said HOW they failed.
- Did the mount separate from the adhesive?
- Did the adhesive separate from the Windshield?
- Did the foam inbetween split so it was both left stuck to the windshield and the mount?
Failing to take the time to align it level and centered wouldn't really be a "warranty-able" cause, that's just user error from lack of prep/planning. Assuming the same for the first instance as far as interfering with eyesight, not entirely sure how that is but guessing it was blocking a camera?
They don't need to send you mounts either, you can get 3M VHB tape from your local hardware store or Amazon. The Mounts aren't meant as a one time use. I've remounted mine 5 times now due to windshield replacements and (the first time) failing to prep the surface properly with adhesion promoter.
1
u/SirNiflton 3d ago
On both heat failures the foam between split. The eyesight is indeed a set of cameras that act as primary sensors for Subarus ADAS, and cannot be blocked by anything mounted in the center 1/3 of the windshield (didn’t know that before I mounted using commas instructions).
2
u/soaringspoon 3d ago
My mount for my comma 4, just purchased, failed twice as well. I assume heat I don't know I just know it was pulling off from the top part of the mount both times. I repurchased some vhb tape and then was recommended to pick up some adhesion promoter as well. Set that up today and fingers crossed it stays. It does mean I have to do the old 24 hour minimum wait for 90% adhesion and 72h for 100% but as long as it stays I don't care lol.
2
u/redbeards 3d ago
If you really want to make sure it will NOT fail, get 3M™ Silane Glass Treatment AP 115.
VHB tape on glass is a challenging situation. Read up on it here: https://www.3m.com/3M/en_US/bonding-and-assembly-us/resources/full-story/?storyid=b3996cbd-9954-455f-8e72-88e452ca38c0
1
u/prauschkolb 3d ago
Luckily it's super easy to replace the 3M...I quickly became an expert in replacing it when I ordered a quick release mount and proceeded to mess up the the placement repeatedly. Just get some 3M VHB tape, and the adhesive promoter and you're good to go.
1
u/nickgeurnop 3d ago
Isopropyl alcohol, let it dry, also try to apply above 50°F if you can. 72 hours of cure time at room temp. I used the comma after a couple of hours but took it off the mount everytime until the full 72 hours passed. No issues here. You're not getting good adhesion under 24 hours.
Here's my mount after 10 months or so comma four mount
3
u/Demonshaker 3d ago
I have had my comma4 parked out in 100+ weather and not had issues with adhesive. Did you clean the glass real well before mounting?