Subaru Outback Forums banner
21 - 40 of 60 Posts
Frontrunner is another quality platform rack option. It’s all aluminum and only 51lbs. The oem bars weigh about 6lbs.
There’s also a new offering called Spyder (I think) and unlike the Prinsu you do not have to drill holes your roof. It uses factory mounting points.
I emailed the owner of spiderroofrack.com this week. He said they will be coming out with a rack for the Gen 5 Outback 2014-2019 soon.
I’m holding out for it.
 
It's strange because in their installation video they show drilling and tapping of their aluminum blocks that are epoxied to the roof.

 
Yep you drill the blocks that expoxy to the roof not the roof. Should be easier to install than prinsu, drilling and tapping the blocks.
So your not making any new hole or hole bigger in the roof which should lesson the chance of a leak and it looks like they have a filler piece for the channel between the blocks. Makes it look nicer anyway.

I was worried about the epoxy holding but after watching some videos and reading reviews, seems really solid.
 
I have an aversion to doing things that aren't reversible and the epoxy bond to the paint in the channel will only be as strong as the bond of the paint to the channel - it's not mechanically fastened. These are concerns from ignorance on my part and for all I know this might be the most secure and permanent solution available. How many years have these been out?

If the rain channels were a block of solid steel I can imagine it holding but it's just sheet metal and if the epoxy loses grip I can imagine the thing popping out under certain conditions.

I was looking at the posts on Tundras.com and it wasn't confidence inspiring. It's been some time since he offered a group buy there and I'm not seeing the buzz about how wonderful it is.
 
  • Like
Reactions: ammcinnis
I was looking at the posts on Tundras.com and it wasn't confidence inspiring. It's been some time since he offered a group buy there and I'm not seeing the buzz about how wonderful it is.
That is discouraging!
The foundation must be of equal or greater strength that that that is built upon. Paint adhesion doesn’t factor well into this application. Welding...another story.
 
If you watch the video the blocks are engineered and designed to mechanically lock in to the channel and the adhesive is used as a secondary safety measure.

I’m certainly not going to be as harsee on the system than overland 4x4 tundras that I’ve seen with the rack loaded.

This was sent by someone in the tundra forum to spider and here is a spiders response.


“It was stated somewhere that the epoxy is not necessary for install and is a secondary safety measure. Is this still true?”
Spiders answer:
  • “ yes”
I agree adhesive alone is not a good idea. There are stock holes and other methods available.

We will see what they come up with to lock it to the roof on the gen 5 Outback.
 
They demonstrated that the front block is captured by the sheet metal of the roof rail, but that further back the blocks are loose and can be lifted straight up. It might be better if they had different sized blocks for each part of the roof rail that was secure, but instead they use the same blocks whether they are tight or loose.

Second, even if the sheet metal captures the block, if it were not for the glue it would pop out under stress. Sheet metal is flexible not rigid.

Compressive strength is one thing, but tensile strength is another. Sure you can jump up and down on it and it won't dent the roof but the failure mode of this device is when the rack is being pulled up, not held down. It can be pulled up by bouncing motions, air flow at high speed, or chassis flex.

A rhino roof rack held in with 14 aluminum rivets pulled itself out of a nissan:

 
I think, at minimum, the rivets have to be scaled up in size.
I went onto Rhino’s site, entered Outback info & boom, got rack products. Then I tap the Learn tab at the top of the webpage, & no boom! Meaning, for a brief moment, a drop down appears, then disappears. I did manage to see what options were in the drop down & saw load requirements. But before I could tap on it, it disappears. So I was unable to see, at least what Rhino declares, to be the load limits under various conditions.
I’m thinking that when Subaru states the limit for the roof rack, it’s in terms of dynamic...rolling down the road. But I was curious of it’s static limits, you know, with the car parked, rack fully geared up with tent, and a couple of people up there...rockin‘ away or not.
I’m wondering if Rhino said “Uh-Oh, we got to remove access to the load requirements & fully vet that info. out...”
 
Here's someone that has the Spider rack on a 2020 Outback:

 
  • Like
Reactions: Mutsuraboshi
Interesting. Rivnuts can be useful, but they are not intended for use as structural fasteners.
The Prinsu ships with 1/4-20 Plusnuts.

"A 1/4-20 Plusnut is rated for 1215 lbs of pull out force in sheet steel. That's probably as strong as a nut and washer from beneath."

There are four of these on each side. I would wager you could lift the car (for a moment) with the rack. A rooftop tent would need to see a lot of g's for it to be considered an issue. Shear strength is another story. I think things like fretting, creaking and loosening over time are definitely things to think about. But there has been a lot of engineering behind this type of fastening. I'm sure it will be ok for the life of the vehicle. Even the Eiffel tower is riveted together.
 
I’ve done architectural and custom sheetmetal work for a long time and used riv nuts, nut serts, rivets and epoxy on a lot of things.
I’ve also b.s’ed with my dad about this and he’s a Harvard grad retired structural engineer and he agrees with what I’ve come up with....I get lectures every time I build something with any weight involved lol.

I did the math and all these fasteners come out in the same ballpark of holding roughly 600 to 800 pounds per anchoring point.
With riv nuts and rivits the weak point is the thin sheet roof (probly 24 or 26 gauge steel there not for sure but may be even thinner) and pull out and would be much stronger if you put a plate inside the car under the headliner.

With epoxy the weak point would be the factory paint adhesion to the metal roof. Take that down to bare metal and epoxy and it would make a stronger hold but would likely introduce rust over a very short time.

Even if the paint adhesion factor is 1.0 Mpa , mega pascal of adhesion ,which is on the very low side (1.5 is average for factory paint) it equates to 150 pound per square inch on what look like about a 5 inch mounting bar for the spider rack. So again on the low end, 750 pounds per mounting block, x 8 blocks can withstand roughly 6000 pounds of pull.

So your right you could probly lift the car up by the rack on all these types of mounts.

I don’t think you can go wrong with any of these racks, they all have pros / cons and I’m glad to see options. In the end use common sense don’t overload the rack and they will be fine.
 
Discussion starter · #34 ·
Thank you everyone who contributed their knowledge and input.
I’ve ordered the Prinsu Rack and it’s gonna get shipped soon.
I don’t know about a rooftop tent yet, but who knows down the future..
Most of the cargo will be my climbing gear, camping, and snow gear during season.

Thanks everyone again. Next step to light bars and wheels/lift now.
 
Apples and oranges. Driven rivets are totally different from the blind fasteners being discussed here.
Yes I know. The Rivets in the Eiffel were installed by blacksmiths, and beat into place hot, so when they cooled it pulled the metal together. I do know that they would not have epoxied the Eiffel together if they were given the choice.
 
With epoxy the weak point would be the factory paint adhesion to the metal roof. Take that down to bare metal and epoxy and it would make a stronger hold but would likely introduce rust over a very short time.

Even if the paint adhesion factor is 1.0 Mpa , mega pascal of adhesion ,which is on the very low side (1.5 is average for factory paint) it equates to 150 pound per square inch on what look like about a 5 inch mounting bar for the spider rack. So again on the low end, 750 pounds per mounting block, x 8 blocks can withstand roughly 6000 pounds of pull.
What gives me pause about epoxy is not just that it's attached to paint - it's attached to clear coat that is attached to color coat that is attached to primer that is attached to the bare metal. A chain is as strong as its weakest link, and delamination can occur if there's a problem with any of those interfaces.

Maybe it's just me but epoxy garage floor coverings peeling off, differential rates of expansion from heat cycles, vibration, things like this can happen in the real world.

For the Tacoma, a mallet is used to secure the front aluminum blocks. Not sure what this does to paint layers, but it has epoxy. The middle blocks are literally loose in the track and are held only by the epoxy. The blocks at the rear I don't know if a mallet is used or if the blocks are loose. Not sure how it's done on a Subaru.


Maybe it's just an in-my-head issue but I'm not convinced that a glue-on roof rack is a proven mounting system.

The Spider guy went to the Tacoma forums and offered a group buy and it just kinda fell off the radar with no update since October 9, 2020.

 
Discussion starter · #38 ·
So, I’ve added the Prinsu rack today. Finished the install myself with help from friends.
Took us about 4-5 hours.
So far, there is a quite significant vibration between 50-70mph. I did some research and it sounds like I need to play around with the front wind deflector placement. Either much lower to almost flush or just raise it further up.
Currently there is about an inch of gap between the deflector and the roof. I will update after running some tests.
Installation wasn’t too difficult doing own with some help from friends.

510037
510038
 
So, I’ve added the Prinsu rack today. Finished the install myself with help from friends.
Took us about 4-5 hours.
So far, there is a quite significant vibration between 50-70mph. I did some research and it sounds like I need to play around with the front wind deflector placement. Either much lower to almost flush or just raise it further up.
Currently there is about an inch of gap between the deflector and the roof. I will update after running some tests.
Installation wasn’t too difficult doing own with some help from friends.

View attachment 510037 View attachment 510038
Lowest hole setting, that's how I have mine installed and it's flush with the roof. You may want to install some PPF where it contacts the roof to protect the paint. Drove the car up to 85mph-90mph, no sound or vibration on mines, don't even really notice any difference from stock, sound wise. Hopefully that fixes your issue. You will, from what I heard, get a lot of wind noise and a little vibration from the light cut out if you don't have a light bar installed.(I don't have the light bar cut out on mine, not planning on putting lights up there)

Sent from my SM-N950U using Tapatalk
 
Discussion starter · #40 ·
Lowered the deflector to lowest point flush with roof. = Problem Solved
Test drove upto 90mph.
No vibration but still some wind noise, but that’s given you have a roof rack.
Im ordering t-slot overs to cover up all the slots im not using to reduce noise and dust&water build in the channel.
Put up Roam Cargo Case today.
It’s turning out good so far.
510096
510097
 
21 - 40 of 60 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top