For those of you that use a BOB trailer, did you buy the BOB bag that fits in it? Did it perform well? Is it waterproofed well? Could I use a bigger bag instead?

Yes. Yes. Absolutely. Yes.

As to the fourth questions, you shouldn't need a larger bag unless you intend to carry a LOT of stuff. If you really feel the need for more cubic inches, consider pairing the trailer with front panniers, in part so you are not pulling all the weight.

I agree with indyfabz, however is I need more stuff, I put in a dry sack and bungee it on top of the BOB bag.

The Yak Sak is as a tough as any roll-top bag, and is waterproof when closed adequately. You need to roll the top at least twice to seal it well, and each additional roll diminishes the volume of the bag significantly. Bob claims a Yak Sak volume of 5600 cubic inches/92 liters (they evidently can't do unit conversions accurately), but every way I've ever measured it I get ~4500 ci with the top rolled only once (not a secure closure), and close to 4000ci with a proper double roll closure.

The Yak Sak weighs about 4.5 lbs (I've weighed it). BOB has never mentioned this in their specs all these years. They DO say the trailer weighs 13.5#, which is true, but when you add the bag (which most people use) it totals 18 lbs. This is a little trick they do to make their trailer sound comparable to their main competitor, the Burley Nomad. The Burley Nomad claims 105 liters space under the hood, with total weight of 14.8 lbs - it's lighter and holds more stuff. You can stack stuff on top of the Yak Sak for more capacity, but you can do the same with the Nomad if you add the accessory rack. Bob carries 70 lbs, Nomad carries 100 lbs (according to specs). Also worth noting Nomad isn't 100% waterproof under hood - you need to store electronics in another WP bag, but you'd probably do this also with the BOB Yak.

As an alternative to the Yak Sak, Ortlieb makes a bag that's larger, weighs less and and fits the BOB Yak very well - available in several colors, even the same yellow BOB Yak color. The Ortlieb Rack Pack XL weighs nearly 2 lbs less than the Yak Sak but costs $20 more, which may be a fair deal to many people. Plus it could color match your Ortlieb panniers. It's been discussed here before.

https://www.ortliebusa.com/CartGenie/prod-62.htm

https://www.ortlieb.com/_pdf_en/rackpack.pdf

https://www.bikebagshop.com/ortlieb-r...xl-p-1039.html

https://www.burley.com/home/bur/page_454/nomad.html

https://www.bobgear.com/yak

https://www.bobgear.com/trailers/drysak

G'day

I have sold my Ibex in the last week or so and will be replacing it with a Extrawheel but when I had the Ibex I did use the bag.

I found it okay, but it has as has been commented on less capacity than claimed. I also found it not easy to pack. I can pack my 90 L Macpac backpack better than I can the BoB sack and again I can do better with panniers.

I would also distribute my load with some on the front. I believe the ratio is something like 40:60. I am sure someone will have more accurate figures.

Regards
Andrew

A friend has a BOB trailer & bag that he lends out to others when he is not using them, so they have seen a lot of use. I’ve borrowed the trailer & bag for a couple of tours and found them easy to use, easy to pack and completely waterproof. (It always seems to rain when I go on a vacation.)
Unfortunately, the last time I used it, I went to pick the bag up by the handles and the fabric on one of the handles shredded where it was attached to the bag. I called the BOB Company a couple of times about warranty or repair options, and they could not help. I also took the bag to a luggage shop to ask about repairing it, and they also could not help. So, the only draw back is if the bag gets damaged, buying a replacement bag seems to be the only option.

The Bob bag carries alot and keeps stuff dry. I have tied a duffle bag on top of the bag in the trailer for extra room.

I have beaten my Bob bag up so much, the straps came off. Time for a new Bob or Ortlib bag.

1+

Dry sack on top of Bob bag. We use a stretchable cargo-net to hold it there (came in the trunk of our 89 Mercury Sable sedan (for stopping less than a full trunk-load from shifting around)).