Rear rack for my dropper post.

[303-biker]

Got out and did the first 50 of the Colorado trail route (Denver to Bailey) last week. I wanted to test my newly built rack and it worked great. I know that nobody likes racks but I like my dropper post and wanted to be able get behind the saddle. While I've never ridden with one of the monster seat-bags it seems like getting behind the saddle would be tough and they all seem to attach where the dropper post telescopes so.... I wanted a rack.
Why not just buy a seat post rack? I don't like all the leverage on my post, especially a dropper post and especially while jumping the bike. Additionally they are heavy and I’m not sure if they angle up enough to clear my six inches of travel.

[303-biker]

-I started off with eight feet of 1.5” aluminum strap.
-Cut two 18” strips leaving five feet for the body of the rack.
-Then I heated and bent the five feet into a U shape.
-I then notched the middle of the two 18” strips so that they could interlock.
-Then I bent the two interlocking strips so that they formed a X shape.
-Drilled a couple holes so that I could bolt it all together and then JB welded it before bolting everything to position.

[303-biker]

Drilling the holes allowed me to set the angle of the rack so that at max suspension compression the tire just barely cleared the rack and so the dropper post could be brought all the way down.

[303-biker]

To attach the rack I purchased a seat collar with attachment points for a traditional rack. To accommodate the side to side angle of the rack I used those little cup and cone spacers we all have on our post mounted brakes.
In the front I used the shock mount and some handy little aluminum spacers out of the parts bin. Naturally I needed to purchase a longer shoulder bolt for the extra width. Still I was unsure if the rack would contact the shock during suspension travel so I notched the rack to provide better clearance.

[303-biker]

After is was all said and done I drilled a bunch of large diameter holes all along the outside for weight reduction and then counter sunk the holes for that finished look. I really went back and forth on the topic of paint vs. raw aluminum but decided to paint it with an industrial KEM4000 white.

So how does it work? Well I'm totally happy; the bike is well balanced, it's easy to get behind the seat and I still feel confident doing drops and techy sections while loaded. Uphill of course it's heavy but it still climbs well and is capable of riding challenging terrain.

[bicyclehobo]

wow...good idea, nice design, kick ass follow through, and excellent documenting for the group to take part of your discovery.

The DIY abilities of the people on this board are commendable.

Let us know how it performs over the long haul.

[12wheels]

Very original and impressive.  Thanks for sharing

[Dr Galactus]

That, gets a  
Excellent work!

[303-biker]

thanks for all the feedback everyone. I figure why not share? I know for me designing and planning my setup has been just as much fun as using the thing.

[bicyclehobo]

This could actually be a product if you could design it in a way where the shock mount was adjustable.

[303-biker]

This could actually be a product if you could design it in a way where the shock mount was adjustable.

Thanks, you know you're actually not to first to suggest that, maybe I should send it to Blackburn or Topeka? I agree it would be interesting to see how universal it could be made while taking into account all the different frame sizes and designs.

[Area54]

Top marks. Very well thought out and executed. 

[jhl99]

I like racks.

Regarding making it universal--way back in the mid 1980s, Cannondale made a rear and maybe a front rack.  That racks where not welded, but bolted together....

Your rack could be made in a similar fashion to make it more universal...   Punch say 5.8 mm dia holes, say every 1/2" on center along the complete perimeter of the 'U' shaped piece.  Instead of using the X brace, use common spaces, tapped M5 at both ends, between the legs of the 'U'.  Put the spacers where you want (along the 1/2" spaced hole pattern ) and attach through the 'U' frame with M5 hardware.

An oversized hole might need to be added to accomodate the shocking mounting.

***
You could add a set of smaller holes along the bottom edge of the 'U' and cable tie a piece of plastic onto the rack... creating a fender.

[bicyclehobo]

My axiom rack [I still have not shed the racks yet] has a 'linkage' that allows some modulation for mounting on different sized frames.

You can see it in this photo at the bottom. I am referring to the 'arms' that are not mounted. They are at the bottom of the photo with a red aluminum part.

It allows some rotation to where dropouts are mounted and the ability to shorten or lengthen the arms to accomodate different size frames, angles, and mount points. They mount up next to the center mount that is currently attached to the frame. The mount was quite sturdy.

I am not saying use these, but you can see how they have solved a 'fit' problem here, and you could adapt this to your rack making it fit a wider variety of rear suspension frames.

[fotooutdoors]

Curious what it weighs.  Any idea?  Also, how much weight are you putting on it?  Look like a good idea and great execution!

[bicyclehobo]

How is production coming? When will I see this in a bike shop?

[303-biker]

Bicyclehobo, thanks for the vote of confidence, but no I haven't done a thing with it. Sadly, I've hardly even been riding. I've done three 70 hour weeks at work in a row, which is also why I haven't responded very promptly. I agree with idea of making it adjustable and I had actually started the project with two round tubes (very similar  to your picture) which telescoped. I got as far as mounting them, which was really easy as i just used a insulated conduit clamp and the existing bolts, but they just just seemed too week and I thought going with a bigger pipe would cause my thighs to rub so I scraped the idea and went to flat strap.

Fotooutdoors, I did put in on a scale and with all the bolts and the seat post clamp it came in just barely under two pounds. I tested it with somewhere around five to six pounds on it and if anything the rack is overkill, there was absolutely no movement or flex. Perhaps a slightly narrower strap would be strong enough, provided you could weld the x-shape together rather than notching it.

[Bob Loblaw]

I know this thread is ancient, but are there any updates on how this rack has performed?

[303-biker]

Hey Bob, thanks for the interest. I wish I could say it's been thoroughly tested over months of abuse but the reality is that I've done a couple trips with it but it has worked almost perfectly! Only down side so far is that it scuffs up the dry sack a bit, hasn't worn through or anything but some paint has rubbed off onto it...

[Bob Loblaw]

Understandable. Thanks for the update. I have a very similar bike (26", 5.5" travel, dropper). I don't need to use the lowest setting on my dropper, but being able to drop to the middle setting would be nice. I'm trying to figure out if I can fit a usable seat bag in the space or if I should build a rack similar to yours.