Need Help building bike rack from Fabricators and CAD guys

[Griff79]

Hi,
I need some help building a bike rack for two e-bikes to place over the bed in my Chevy Avalanche.

What I've initially done is put in my parameters and requests to Chat Gpt. After going back and forth a bit, It seems like this is a good basic plan.

Here's my ask, Would fabricators and CAD guys, take a look at this and help me refine this into a solid plan to build this bike rack, with schematics and any changes.

I haven't learned how to weld yet, so it's going to be a bolt together unit which is not wholly unacceptable.

I'd like to get some schematic drawings if that's not too hard to do. And advice on fabrication. I don't know if this is a ridiculous request or not. If it is, please let me know and accept my apologies. But if it's not too hard, to get some plans I think I can get this built by the end of July for a road trip.

I found some metal materials guys around me here in Denver so I can pick up the raw materials. I have the tools to cut, drill, measure, deburr, paint, assemble and install. Should be a fun project. I'll document this with photos so it could be used by others if they so choose.
Thanks,
Griff

 

[Griff79]

Deleted this message because the information was repititive.
Griff

 

[Griff79]

More info:

Chevy Avalanche Bolt-Together Overland E-Bike Rack Build Concept​

I’m designing a DIY bolt-together over-bed rack for a Chevy Avalanche that will carry heavy e-bikes above the factory tonneau covers while still allowing locked cargo storage underneath.

Goal is:

• no welding required
• modular construction
• strong enough for highway use and Colorado roads
• fabricated mostly with beginner/intermediate tools
• possible future expansion for overlanding accessories

I’d love feedback from fabricators on:

• tubing sizing
• bolt-together joint strength
• anti-wobble strategies
• Avalanche mounting points
• fatigue resistance
• improvements before I move into CAD drawings

---

Base Design Goals​

Truck: Chevy Avalanche with factory tonneau system.

Design targets:

• Carry 1–2 e-bikes
• 65–80 lb bikes each
• Preserve full tonneau functionality
• Keep bed usable underneath
• Medium-height over-bed rack
• No permanent welding required
• Modular bolt-together construction

Target rack height:

• 18–22 inches above bed rails
• Low profile preferred

---

Overall Rack Layout​

Concept is basically:

• two side ladder frames
• connected with removable crossbars
• diagonal braces for anti-wobble rigidity

Bike trays mount front-to-back on upper crossbars.

SIDE VIEW

2x2 upper side rails

Approx side length: 58–60 inches

Approx upright height: 18–20 inches

Diagonal braces: 12–18 inches

---

Rear View Concept​

2x3 crossbar

approx crossbar width: 62–66 inches depending on actual truck measurements.

Planning on:

• 3 removable crossbars
• bike trays mounted to top
• possible future cargo basket or recovery board mounts

---

Material Selection​

Main structure: 2x2x.120 wall square tubing

Crossbars: 2x3x.120 wall rectangular tubing

Diagonal braces: 1.5x1.5 or 2x2x.120 wall

Mounting feet: 1/4 inch steel plate

Gusset plates: 3/16 inch steel plate

Hardware: 3/8-16 Grade 8 bolts with Nylock nuts

Reasoning: Wanted to avoid thin tubing because of:

• heavy e-bikes
• highway wind loads
• dynamic loading over bumps
• fatigue concerns

---

Estimated Weight and Loading​

Estimated rack weight: 140–185 lb

Bike setup: 2 e-bikes @ 75 lb each Bike trays approx 25–40 lb total

Estimated static load: ~190 lb

Using roughly 3x dynamic factor: 500–600 lb effective design load

Trying to overbuild slightly for safety and stiffness.

---

Bolt-Together Joint Design​

Current idea is sandwich-plate joints using:

• 3/16 steel gusset plates
• 4 bolts per major corner
• through-bolted tubing

Example concept:

2x2 upper tube 3/16 plate outside, 3/16 plate inside upright tube

Hardware:

• 3/8 Grade 8 bolts
• large washers
• Nylock nuts

Possibly adding crush sleeves inside tubing if necessary.

Would love suggestions on:

• best anti-rotation joint design
• ways to reduce flex
• whether larger bolts are worthwhile
• whether slotted joints are a bad idea

---

Anti-Wobble Strategy​

I know bolt-together racks can rack/sway badly if not triangulated properly.

Current plan:

• diagonal braces on both side frames
• gussets at every major corner
• 3 crossbars instead of 2
• wide mounting feet
• removable but heavily reinforced crossbars

Would appreciate feedback from anyone who has built bolt-together overland racks before.

---

Avalanche Mounting Strategy​

Trying to avoid:

• drilling through tonneau panels
• weak sheet metal attachment points

Current thought:

Mount to strong bed rail / cladding support areas

• wide mounting feet
• rubber isolator pads
• backing plates where accessible

Foot concept:

Approx foot size: 4x6 inches minimum 1/4 inch plate

Would really appreciate Avalanche-specific advice here.

---

Fabrication Plan​

Trying to build this with beginner/intermediate tools.

Planned tool list:

• chop saw or portable bandsaw
• drill press
• angle grinder
• clamps
• squares
• step bits
• hand tools

Fabrication sequence:

1. Measure truck carefully
2. Create cardboard templates
3. Cut all tubing square
4. Drill all holes before assembly
5. Assemble side frames flat on garage floor
6. Install side frames on truck loosely
7. Measure exact crossbar width on truck
8. Install crossbars
9. Square structure
10. Tighten progressively
11. Add diagonal braces
12. Test drive empty
13. Retorque all hardware
14. Install bike trays
15. Test drive with one bike first

---

Possible Future Additions​

Potential future upgrades:

• recovery board mounts
• rear chase lights
• side scene lighting
• awning mounts
• rooftop cargo basket
• tie-down points
• integrated wiring channels

---

Questions for Fabricators​

1. Would you change tubing size or wall thickness?
2. Are there better bolt-together joint strategies?
3. Would aluminum crossbars make sense?
4. Any concern about fatigue cracking?
5. Best way to prevent wobble without welding?
6. Best mounting strategy for Avalanche bed structure?
7. Are crush sleeves worth adding?
8. Would rivnuts or backing plates be preferable?
9. Any obvious weak points in this concept?
10. Any recommendations before I move into CAD drawings?

Thanks in advance for any feedback. I’m hoping to refine this into a fully dimensioned fabrication drawing package next.

 

[Griff79]

This message was deleted because it was also repetitive.
Griff

 

[Bodj Built]

Does the tonneau cover go over the bed rails? Is it a fiberglass cap that hinges up, or is it a soft cover that folds in thirds/rolls up? If it hinges, I think you're going to want to drill through with sandwitch plates, covering a decently large surface area/using some aluminum extrusion bolted through in multiple places as your base rack, and then build off that.

Also, I'm assuming you're towing with the truck, but if not, why not use a hitch mount?

 

[Griff79]

Bodj,
Yes, I'll be towing the pop-up so I can't just do a simple hitch mount. Otherwise it would be bada boom, bada bing, Bob's your uncle with the rack.

The Avalanche has three separate sections that are removable and lockable, each section is independent of one another, so I'm able to access the bed without having to worry if there's clearance. The three individual sections sit flush with the top rails of the bed. So no they don't go over the bed rails. I think this is a good advantage.

 

[SusKatCas]

TLDR. Ask Chat GPT to make some drawings for you.

Why the welding restriction? I my opinion you are often better off welding the light HSS shapes together. They are to thin to behave nicely when compressed and if you only bolt to one side, the bolted joint is too thin to be effective.

Cheers, Alan

 

[Bodj Built]

Avalanches are awesome.

However, it seems like you're going to want some sort of bed rack like the overlanders use. They're abundantly available, though finding one that fits your bed may be a bit of a challenge. Then you can mount something like this off it

 

[Bodj Built]

TLDR. Ask Chat GPT to make some drawings for you.

Why the welding restriction? I my opinion you are often better off welding the light HSS shapes together. They are to thin to behave nicely when compressed and if you only bolt to one side, the bolted joint is too thin to be effective.

Cheers, Alan

I'm going to go out on a limb here and guess he doesn't own a welder, know how to weld, or know someone that owns a welder.

 

[bdbecker]

Have you seen this build?

Custom bed rack build

Hi All, I've been meaning to post this up for some time and finally got around to it. I made this bed rack using aluminum extrusion that I sourced primarily from 8020.net. It's great stuff and very modular. You can mount just about anything to the rack using t-slot hardware. The goals...

www.chevyavalanchefanclub.com

There are several floating around if do a search on the interwebs.

-----

Not to beat the DIY spirit out of you, but this sort of project can have real consequences if done incorrectly. Something breaks, a bike falls under the camper, throws you into a tank *******, and the next thing you know, you are in the ditch. It could go even more sideways from there, but you understand what I'm getting at.

I do not say this to offend you, but I suspect your metal fabrication skills and experience are limited given your reliance on AI to come up with a design and spec materials, along with the questions you have asked here on GJ. There is nothing wrong with that, everyone has to start somewhere, and it's good to use the resources you have to work your way through a project. However, this is not really an ideal project to learn on for the reason mentioned above.

 

[whateg01]

Have you seen this build?

Custom bed rack build

Hi All, I've been meaning to post this up for some time and finally got around to it. I made this bed rack using aluminum extrusion that I sourced primarily from 8020.net. It's great stuff and very modular. You can mount just about anything to the rack using t-slot hardware. The goals...

www.chevyavalanchefanclub.com

There are several floating around if do a search on the interwebs.

-----

I've not been a big fan of 8020, mainly because of the cost. But for bolt-together, minimal tooling, ease of assembly, and versatility, it's awfully hard to beat it!

 

[Old tool guy]

Even with the batteries removed they weigh 65~ lbs , going to be a chore to get them up that high. And the the lateral forces on the rack when turning corners needs to be considered.

 

[Griff79]

TLDR. Ask Chat GPT to make some drawings for you.

Why the welding restriction? I my opinion you are often better off welding the light HSS shapes together. They are to thin to behave nicely when compressed and if you only bolt to one side, the bolted joint is too thin to be effective.

Cheers, Alan

Alan,
Unfortunately, I haven't learned how to weld yet. It is a skill that is on my list to acquire.
Griff

 

[Griff79]

I'm going to go out on a limb here and guess he doesn't own a welder, know how to weld, or know someone that owns a welder.

Yup correct
Griff

 

[Griff79]

Have you seen this build?

Custom bed rack build

Hi All, I've been meaning to post this up for some time and finally got around to it. I made this bed rack using aluminum extrusion that I sourced primarily from 8020.net. It's great stuff and very modular. You can mount just about anything to the rack using t-slot hardware. The goals...

www.chevyavalanchefanclub.com

There are several floating around if do a search on the interwebs.

-----

Not to beat the DIY spirit out of you, but this sort of project can have real consequences if done incorrectly. Something breaks, a bike falls under the camper, throws you into a tank *******, and the next thing you know, you are in the ditch. It could go even more sideways from there, but you understand what I'm getting at.

I do not say this to offend you, but I suspect your metal fabrication skills and experience are limited given your reliance on AI to come up with a design and spec materials, along with the questions you have asked here on GJ. There is nothing wrong with that, everyone has to start somewhere, and it's good to use the resources you have to work your way through a project. However, this is not really an ideal project to learn on for the reason mentioned above.

I agree with you this is not something that I want to schlock together. It is something that if engineered correctly is within my skill set, I just don't know how to weld. My background in the trades stems from growing up on a farm where we had to basically do everything. As a young man, I built pre-engineered metal buildings from the ground up, then I transitioned into framing carpentry and then into a finish Carpenter. I realize these trades are not direct metal fabrication exclusively, there is carryover. I think your points are a valid concern. Thank you for your input.
Griff

 

[Griff79]

Even with the batteries removed they weigh 65~ lbs , going to be a chore to get them up that high. And the the lateral forces on the rack when turning corners needs to be considered.

Yes. This is duly noted and I think it is the aspect of this build that is most important.
Griff

 

[Bodj Built]

Griff, take the pop up to a local fabrication shop and have them replace the flimsy oem rear bumper with something more substantial (.120" wall 2x4 rect tube at minimum) and weld a hitch receiver to that. I did exactly that to my pop up camper in preparation for our road trip next weekend.




I am going to be using the hitch for the cargo rack to carry the generator and water, but I have no doubts about my bike rack hanging off the back instead. I may cobble together some mounts on the actual bumper so I can still put my bike back there, instead of it being one or the other. I might add some weight to the front. Might not. A drive around town before the trip will let me know if it's needed.

 

[whateg01]

Yes. This is duly noted and I think it is the aspect of this build that is most important.
Griff

At the risk of complicating things (it's what I do), I am thinking of an apparatus that swings down over the side to attach the bikes to.

 

[whateg01]

Griff, take the pop up to a local fabrication shop and have them replace the flimsy oem rear bumper with something more substantial (.120" wall 2x4 rect tube at minimum) and weld a hitch receiver to that. I did exactly that to my pop up camper in preparation for our road trip next weekend.




I am going to be using the hitch for the cargo rack to carry the generator and water, but I have no doubts about my bike rack hanging off the back instead. I may cobble together some mounts on the actual bumper so I can still put my bike back there, instead of it being one or the other. I might add some weight to the front. Might not. A drive around town before the trip will let me know if it's needed.

Once you start adding weight to the back, and counter weight to the front, you can get to the axle capacity on those little campers pretty fast

 

[Griff79]

Griff, take the pop up to a local fabrication shop and have them replace the flimsy oem rear bumper with something more substantial (.120" wall 2x4 rect tube at minimum) and weld a hitch receiver to that. I did exactly that to my pop up camper in preparation for our road trip next weekend.




I am going to be using the hitch for the cargo rack to carry the generator and water, but I have no doubts about my bike rack hanging off the back instead. I may cobble together some mounts on the actual bumper so I can still put my bike back there, instead of it being one or the other. I might add some weight to the front. Might not. A drive around town before the trip will let me know if it's needed.

This is a really good idea. I will do some exploring and let you know what I come up with. It would be so much easier if we could just do a receiver hitch.
Griff

 

[Bodj Built]

Once you start adding weight to the back, and counter weight to the front, you can get to the axle capacity on those little campers pretty fast

True, but axles are pretty cheap/easy to upgrade. That said, I'm not worried in the least bit.
1700# unloaded
85# water tank
50# generator
42# 5 gal water jug on the rear
Grand total of 1877#. Plenty of room to spare on the small 2200# axle.

 

[Griff79]

Once you start adding weight to the back, and counter weight to the front, you can get to the axle capacity on those little campers pretty fast

I just did a quick search for adding a hitch to the back of a pop-up. Several sources indicated that if you had too much weight on the back of the trailer it would deweight the tongue and cause sway and generally make the trailer x squirrely. I'm going to investigate this more. Maybe the solution is put the bikes to the front tongue and move the propane tanks to the back. I wonder what this type of weight distribution would do to the stability of the popup?
Griff

 

[whateg01]

I just did a quick search for adding a hitch to the back of a pop-up. Several sources indicated that if you had too much weight on the back of the trailer it would deweight the tongue and cause sway and generally make the trailer x squirrely. I'm going to investigate this more. Maybe the solution is put the bikes up front and move the propane tanks to the back.
Griff

Yes, not enough tongue weight will cause loss of stability. This isn't a pop-up camper issue; it's a trailer issue! But if the solution to that is just adding more weight to the tongue, the overall weight of the trailer just goes up. Overloading campers is apparently enough of a problem that I see warnings of it from time to time. I don't have a TT but have looked at building a little teardrop a few times. When you only start with a 2k axle, it doesn't take many "I'll just put this other 100#" in the trailer before you've hit the max weight. Relocating weight to the front is a better solution, imo, than just adding more weight.

 

[VR6ix]

Are you fully convinced that there isn't already a commonly-available solution?
Asking as an early 40's long-time mountain biker, pick-up truck owner, and fabrication estimator & designer at my day job... ... ...

 

[whateg01]

Are you fully convinced that there isn't already a commonly-available solution?
Asking as an early 40's long-time mountain biker, pick-up truck owner, and fabrication estimator & designer at my day job... ... ...

I tried that back before they had those fancy little blankets. Didn't like it. Can't open the tailgate without removing the bikes.

 

[strength_and_power]

Bolt together wouldn’t be my first option but reading your posts, welding isn’t an option. To keep tubing from crushing, you can drill the holes oversize and insert a piece of round tubing the length of the tubing so it can’t crush. You could also do a flat plate to distribute the force.

From a security standpoint, I like the bikes up high, make it harder for the bad guys and more obvious.

I used Send Cut Send for some parts recently. Not having a CAD drawing, I uploaded a rudimentary drawing my boss did and used their AI. It interpreted the part correctly and the finished product was exactly what we needed. Price was expensive for one part, about $36 for one part. They had free shipping at $35 so I started increasing the quantity, ended up getting 14 pieces for $37 shipped. A project like this I could see having a lot of repetitive parts so that may be an option.
A shop with a tube laser could make some nice tunes to match up with the flat parts.

You may look into the Fiver app to turn your rough sketch into a decent drawing on the cheap.

 

[K13]

Designed by ChatGP? Yeah I wouldn't be building anything that failure could result in me spilling e bikes onto the freeway that ChatGP designed. It can barely provide basic reliable information let alone engineer a bike rack.

 

[Griff79]

Are you fully convinced that there isn't already a commonly-available solution?
Asking as an early 40's long-time mountain biker, pick-up truck owner, and fabrication estimator & designer at my day job... ... ...

Yup thought of this style. Here's the thing though. When we hit the road for camping, the bed and gear is exposed to the elements I would rather have the items protected.. Also, how do I keep the contents of the bed secure from thieves? There's a solution somewhere. We just have to find it, Garage Journal
Griff

 

[Griff79]

Designed by ChatGP? Yeah I wouldn't be building anything that failure could result in me spilling e bikes onto the freeway that ChatGP designed. It can barely provide basic reliable information let alone engineer a bike rack.

It's a tool, you just need to know how to use it. it is not end all be all.

 

[JuncleJohn]

I recommend you buy a rack and modify it to suit your purpose. I’ve done this with a rack from agricover.com.

I bought an ADARAC series rack and built bolt on rails that I mounted on top out of square tubing. That allowed me to transport a kayak on the right and carry my canoe on the left. This is all mounted above the tonneau cover.

Why re-invent the wheel?

John

 

[Squashfest81]

Where do I put 4 bikes while the bed is full of camping stuff and I’m towing the camper? Here’s what I did.

 

[Squashfest81]

A rack on the roof of the pop-up is a good camping solution, but won’t help when you aren’t towing, and the weight of the e-bikes is a few pounds.
You need a raised rack. Just drill a few nice holes in those pristine bed rails, little extrusion risers, and crossbars.

 

[Griff79]

I recommend you buy a rack and modify it to suit your purpose. I’ve done this with a rack from agricover.com.

I bought an ADARAC series rack and built bolt on rails that I mounted on top out of square tubing. That allowed me to transport a kayak on the right and carry my canoe on the left. This is all mounted above the tonneau cover.

Why re-invent the wheel?

John

This is the route that seems to be the best tact to take. Time to scour more of the interwebs to see what is out there.
Griff

 

[RoninB4]

...

 

[Beerhippie]

Don't forget the davit crane to get the bikes up and down!

 

[Damon L.]

What about a dual hitch mount?

https://www.etrailer.com/Hitch-Adapters/Roadmaster/RM-077-6.html?feed=npn&gad_source=1&gad_campaignid=1338935271&gbraid=0AAAAAD_vMtlbykVirDUbl0UE4smpOzEmI&gclid=Cj0KCQjw2_TQBhCnARIsAF3-Xhy0YbMoIXlSxuIi0JaSHbc-k4sPL2ugSTg4BI3rU-00XMxe-hftcPsaAi_YEALw_wcB

 

[Griff79]

What about a dual hitch mount?

https://www.etrailer.com/Hitch-Adapters/Roadmaster/RM-077-6.html?feed=npn&gad_source=1&gad_campaignid=1338935271&gbraid=0AAAAAD_vMtlbykVirDUbl0UE4smpOzEmI&gclid=Cj0KCQjw2_TQBhCnARIsAF3-Xhy0YbMoIXlSxuIi0JaSHbc-k4sPL2ugSTg4BI3rU-00XMxe-hftcPsaAi_YEALw_wcB

Yes, as I've been searching the interwebs for solutions, I came across this. I thought this was the answer. We could put a bike rack in the top. Put the pop-up in the bottom receiver and off, we go.

However, after doing some research, the word that I found was that its dangerous to put the pop-up in this dual hitch receiver. It moves the camper too far away from the initial hitch receiver and the shear forces increase and could cause failure of the double hitch.

I'm not sure this is true and accurate or if it's over estimation. If anyone has some definitive information in this, please let us know.
Griff

 

[Beerhippie]

Yes, as I've been searching the interwebs for solutions, I came across this. I thought this was the answer. We could put a bike rack in the top. Put the pop-up in the bottom receiver and off, we go.

However, after doing some research, the word that I found was that its dangerous to put the pop-up in this dual hitch receiver. It moves the camper too far away from the initial hitch receiver and the shear forces increase and could cause failure of the double hitch.

I'm not sure this is true and accurate or if it's over estimation. If anyone has some definitive information in this, please let us know.
Griff

I'd be more worried about the bikes getting "pinched" if you make a tight turn while backing.

 

[Griff79]

I'd be more worried about the bikes getting "pinched" if you make a tight turn while backing.

Right. My wife and I were discussing this exact thing. Good call!
Griff

 

[whateg01]

I'd be more worried about the bikes getting "pinched" if you make a tight turn while backing.

Right. My wife and I were discussing this exact thing. Good call!
Griff

Problem solved!