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Custom Bicycle rack - rear mount

12K views 17 replies 10 participants last post by  Abeg123 
#1 ·
I had a roof mounted bike rack system on my 6, but I thought it took away from the looks of the car. I decided to figure out a way to take advantage of the stock tow hook mounts in the rear. They are 28" apart.. very close to the 27" spacing of the roof mounted bar positions. There was absolutely no support online trying to figure out the bolt and thread spacing of the tow hooks.

I can definitively tell that they are 20mm bolts with 2.5mm thread pitch spacing.

After a ton of searching, I found a class 12.9 bolt with these specs in a 400mm length. About 16". With a clean 17mm Allen key head and the perfect amount of thread for this application. They were not cheap! About $74 for the two bolts shipped to my house, but worth every penny. I got them from a site called McMaster Carr. They have a great app for shopping and they bolts came in 1 day!

They fit perfectly inside 3/4" black polyethylene sprinkler pipe. Very strong, but flexible pipe. Feels very much like the plastic used in Yakima crossbars. I gave the bolts a couple coats of gloss black rustoleum to slow down the rust from the black oxide treated bolts. Hit the ends with a little anti seize so they would go in and out smoothly.

Once I figured that out it was simple. The bars will work with pretty much any roof mount bike rack. I opted for the Thule Big Mouth. I added some 3M reflective tape for increased visibility.

And before you ask, "why didn't you just get a hitch?" ... I did want to put a hitch on it. Don't like the looks. My setup can be removed in just few minutes, but is theft deterrent from the locked Thule rack. You can't take the Thule rack off when it is locked and you can't take out the bolts when the Thule rack is clamped down.

Now for a few pictures...
Automotive exterior Vehicle Bumper Automotive exhaust Exhaust system


I added some 3M reflective tape in the last picture


Sent from my iPhone using Tapatalk
 
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#5 ·
Here is a shot of when I had the roof rack.
I have nearly the same roof setup on my 2016 6. I agree, it's too busy, but ultimately I need the ability to haul a canoe and occasional lumber/etc on the roof.

I use the same Yakima setup with round bars, although I've ditched the fairing (didn't like it rubbing on the roof). I pull the bars off whenever I'm not using them. I don't love the four tower pads - they kinda spoil the roofline, but the bars are terribly loud and make a noticeable dent in gas mileage.

LOVE the rear bike rack you've whipped up. If I just needed to haul a bike or two, I'd definitely be looking at that.
 
#3 ·
Excellent Idea, I have been wanting to add a bike rack to mine as well.
I will have to try this.
 
#4 ·
This is brilliant. Coincidentally, I lost one of the covers for the tow eyes and I've been wondering if there's anything to do with the holes. Best idea I had was long bolts and a pipe or 2x4 in between to discourage those who 'park by feel.'

GTGTGT, if we ever meet, drinks are on me.
 
#8 · (Edited)
The notion of using the "shipping eye" locations to mount a bicycle rack is elegant... A very clean look. Now this is solely my opinion: for me it is not strong enough and I believe it could cause damage to the mounting points for those rods. YMMV...

I say this for the following reasons:

- Mazda expressly says (in the owner's manual, if memory serves) that those ports and the eyes that originally were shipped with the car (in fact, they have a form-fitting styrofoam spot in the trunk... and were supplied with the earliest Gen 3 cars) are NOT meant to be used as towing eyes (where the pull-direction will often be off-center)... (I know, I know... one of course would then question why were they initially supplied to customers, and why the cut-outs in the trunk?);

- The reason for those eyes was to allow the vehicles to be held-fast during overseas shipping, where the eyes were fitted and the pull-direction when lashed-in-place was directly along the long-axis of the car... no (lateral) sheer force or bending moment at all;

- When supporting a bicycle (and particularly when said bicycle bounces up and down as bumps on the road are encountered by the car) a "bending moment" and a sheer load is introduced at the mounting points. This IMHO is totally contrary to what I believe was their intended use and more importantly - their strength / design parameters;

- The bending moment is pretty darned considerable, as the "lever-arm" for the mass at the end is long;

- When using a trailer hitch for a bicycle rack mount the hitch manufacturers (almost all) indicate that an assist-strap, or a stabilizing strap is necessary to be used... 'cuz with their hitches, which generally are designed to be pretty stout, they are worried about the undulating / bouncing / moment-inducing weight of the bicycle(s) causing damage to the hitch and the vehicle.

These are my reasons for this opinion. Others may of course vary.

I may indeed be totally wrong; the empirical results may suggest all is fine.

I would suggest, in any case, a stabilizing strap, to (say) the leading edge of the trunk, maybe two of them... each anchored close to its respective (trunk) hinge-point?
 
#9 ·
I now have my second thoughts about this bike rack with what you said.

I've been on a car ship once. I didn't notice where they connect the lashings​ but surely, it is somewhere there.

Anyways, our bikes have been stolen so I need first to have a bike.
[emoji3]

Taking the opportunity, I think it is safe to use those "connections" for towing. Am I right?
 
#13 ·
Just a little update after all these postings. I have switched from the Yakima Frontloader Upright to the Thule Upride. It's a bit more stable and the bike doesn't shake as much as it did on the yakima. It also fits the bike better then the Yakima as it's now more centered.

I will say that I am a little nervous with this method. The right bar does tend to flex more then the left bar. It's mainly due to the weight. The bike is almost 31 lbs. I'm trying to see if I could get a strap and use it to help pull the bike more towards the car so it'll be more stable.
 

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#16 ·
It's a nice alternative to getting a hitch installed or a roof rack. While I do like it, it's not perfect. It does wobble a bit because the bars does not fit perfectly, it' tad smaller versus the tow hole. If I move the rack a bit closer to my car it is a bit more stable.
 
#18 ·
I had a roof mounted bike rack system on my 6, but I thought it took away from the looks of the car. I decided to figure out a way to take advantage of the stock tow hook mounts in the rear. They are 28" apart.. very close to the 27" spacing of the roof mounted bar positions. There was absolutely no support online trying to figure out the bolt and thread spacing of the tow hooks.

I can definitively tell that they are 20mm bolts with 2.5mm thread pitch spacing.

After a ton of searching, I found a class 12.9 bolt with these specs in a 400mm length. About 16". With a clean 17mm Allen key head and the perfect amount of thread for this application. They were not cheap! About $74 for the two bolts shipped to my house, but worth every penny. I got them from a site called McMaster Carr. They have a great app for shopping and they bolts came in 1 day!

They fit perfectly inside 3/4" black polyethylene sprinkler pipe. Very strong, but flexible pipe. Feels very much like the plastic used in Yakima crossbars. I gave the bolts a couple coats of gloss black rustoleum to slow down the rust from the black oxide treated bolts. Hit the ends with a little anti seize so they would go in and out smoothly.

Once I figured that out it was simple. The bars will work with pretty much any roof mount bike rack. I opted for the Thule Big Mouth. I added some 3M reflective tape for increased visibility.

And before you ask, "why didn't you just get a hitch?" ... I did want to put a hitch on it. Don't like the looks. My setup can be removed in just few minutes, but is theft deterrent from the locked Thule rack. You can't take the Thule rack off when it is locked and you can't take out the bolts when the Thule rack is clamped down.

Now for a few pictures...
View attachment 202433

I added some 3M reflective tape in the last picture


Sent from my iPhone using Tapatalk
I just want to say thank you so much. This helped me out!!
 

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