Hello people!
I'm building a Big Dummy for an upcoming cycling tour. However, I ordered a pair of P racks from Xtracycle and I'm clueless on how to install them. On the image below you can see my problem.



As far as I understand the rack should simply slide into the tubes 4 on the rear. However, for the longer tubes near the middle of the bike there is stuff blocking on the inside so the racks can not completely slide to the bottom. Whats blocking is a threaded hole on each side of these tubes (see the image red arrow, you can screw a bolt all the way through on this location) which is sticking out on the inside of the tube like 5mm for each hole.
So when you slide in the Xtracycle P or V rack it rests on these things sticking out (it does not drop lower than the red arrow), while surely it should slide all the way to the bottom?
Anyone know whats up with that?

The frame is correct. Slide the racks in as far as they go, thats it.

Are you saying its normal that there's like 15cm of thin air below the red arrow? I'm pretty sure either the aluminium will slowly rip or the holes that stick out will break off at some point

the rack will slide in on the front tube as far as the rear. Like John said, slide it in and you are good to go.

I sent an email to Xtracycle and Surly. Below you can see a better explanation of my problem.
Yellow marker shows where the rack is stopped by the threaded holes.
Blue marker shows where the rack is supposed to be stopped (in my opinion).



Here's the reply from Xtracycle (no reply from Surly yet, their support is sloooooow).

The racks on my BD stop at your yellow line.
I have had my BD since 2008 and have not had any trouble with the V-racks or the frame.

but.. it feels so clunky/amateur

Wait until you load your panniers on the P-racks and realize there is no place to attach the lower hooks of your bags like you would on a normal rear rack - so the bounce and flap around... I just stuck with the normal Freeloader setup when I toured with my BD and loaded them with dry bags.

hm. what annoys me even more is that the rack is not even a perfect fit, its slightly thinner than what it should be (and thus wobbles a bit..)

I'm still baffled by all the pictures I'm seeing from people riding with heavy adult passengers on the back; how do they secure the rack so well?? I can't imagine having so much weight on there with a simple snap deck that pushes the two racks apart. The downwards force is not so much of a problem, its the sideways force I'm worried about.
I guess what I can do is add those double seat clamps, maybe that'll improve things. And then tie the two racks together to get some inward tension going. I'm also tempted to push an extra aluminum tube inside the racks just to make them stiffer at the bottom (where all the side force will apply).
Do the bags they sell at xtracycle somehow add some strength too? I didn't get them.

I used two toe clip straps - one at the back and one at the front of the vertical racks that squeezed them together sandwiching the snap deck. I had freeloader bags on mine - which when properly installed - pull the whole shebang down tight onto the BD's frame. With that setup I can carry two adults on the back and lift the BD up by the rear [without any passengers] to move it around.

The quality/fit of the Xtracycle bits is not as good as it could be, but it works and nobody seems eager to pay higher prices for better stuff so it's what we have. I've used my Big Dummy for years and it has never let me down.

https://www.flickr.com/photos/vikappr...7604923671546/

The watchamacollars help, but I use two compression straps for inboard tension. The new superhooks should help as well.

I made my own rack frames from 3/4" EMT conduit. It's a nice snug fit in the mounting holes, so I don't have any wobbling and rattling going on, and I didn't have to do anything to secure the rack to the frame.
I'm surprized at Extracycle's response to your enquiry. Maybe the Extracycle kit doesn't have the threaded mounting hole like the BD frame does.
Oh yeah, and hauling an adult or two kids is no problem.

That's awesome Dan, great work :-)
I did a test drive on my dummy this weekend, quite nice! no big surprises so far, its as roomy, sturdy, big and heavy as i thought it would be, although it does handle a little easier and faster than expected
I'm still working on a custom snapdeck, ways to add grocery bags and attachments for the xtracycle rack
To be honest it doesn't feel like much thought went into the Xtracycle P rack, sure you can clip on panniers, but they pretty much slide left and right, there are only 3 vertical bars in the middle to stop the clips from sliding and these are in the wrong places to accommodate 2 panniers side by side (as advertised)
I'll make it work but for the price I expected more

Best thing you can do is email Xtracycle and let them know what you liked and didn't like about the P-racks. At least it gives them the chance to improve the design.