Need suggestions on large seat post bag
 

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Check out carradice bags like:

SQR Trax $137.95 BG117
L37 X W18 X D20cm

Seen here at Harris Cyclery.

Not cheep, but very good.

get a rear rack and strap stuff to it

Wow...that's like the "Dork From Hell" bag, man.

huh? that will be kind of large. i have never seen a "seat post" bag this large. as others alluded to and you stated you didn't want, i would suggest a back pack style apparatus. why are you against this?

HAHAHA maybe he just needs a huge fanny pack

Check out a rack from Old man mountain. You're not going to get much more durable then that.

A good rack will hold up fine. I used a Tubus rack from Vienna Austria to Hue' city Vietnam. Although technicly not off road, after Saratov Russia most of the roads weren't even "nice" graded dirt roads. Kinda like what I'd imagine cycling on the moon might be...

adding: I broke a Jandd aluminum rack in France (of all places), and zip tied it untill I found a replacement. I supposedly had a model which was flawed, Jandd notes that new model racks have been corrected.

I give the rack more chance of holding up than the huge seatbag ... a hardtail is just begging for a rack. so where are you going to be riding that you need to take a days worth of food??

An unsupported bag hauling that much stuff cinched to a seatpost and rails would be uncomfortable and it probably wouldn't be so great for the rails, either. The suggestions to opt for quality racks are excellent and definitely would make for a more pleasant ride in highly-technical trail conditions.

...but have you tried some of the latest, most advanced hydration systems available that money can buy??

i have. it is a necessity for the way i ride.

are you worried about it bouncing around or making a sweaty area on your back? it is also nice to have all that dead weight as one with your body instead of making your HT feel like a 36 lb transition beast. :D

I don't doubt that you are...most "Dorks From Hell" are.:D

A few water bottles and a days worth of food...you said : "The carradice bags are interesting, and HUGE...." kinda like it was a bad thing. It sounds like you need a bag that's "HUGE" though...don't ya think? I'm also of the opinion that "expert trails" would necessitate getting down low behind the saddle. I think the "Dork From Hell" bag may get in your "expert" way.

Just something to ponder when plunking down such a large amount of cash for a bag. I think the rack idea is probably better for your case...though I think it's foolish to put the weight on your bike instead of on your M.U.L.E.


IMO

Then I'd recommend the tubus "cargo" model rack, in combination with a very good quality pannier. The rack and bag will likely cost you 200+$ total. You can sometimes luck out and find a good bag on e-bay/craigslist at a realy good price.

I'd recommend a smaller pannier, one which cycle tourists would normally use on a front rack. Something like an Ortlieb classic bag would suite your post requirements and have extra room. This bag also has a narrow profile, especially if not packed full. Another cost saving option would be to use a racktop trunk bag. some can be expanded to fit your size requirements as posted. Trunk bags are much cheaper than panniers, and a good quality one will stay on the rack no problems.

Mind that the rack mounting will depend on the bike having rack eyelets or not. If not then going with an Old Man Mountain rack might be better because they have work around systems for bikes w/o eyelets (and bikes running disc brakes). The work around system may not be as sturdy as direct mounting-but that's my opinion only. You can also cludge together works arounds by using hardware from your local hardware store/home depot.

CHeck out what folks have used for gear along the Great Divide Mountain Bike route, or the annual race

Wow, double black diamonds on a hard tail, props to you!

As suggestions for a bag, for the stuff you need, I would recommend:

http://www.homedepot.ca/wcsstore/Hom...b7b4e801_4.jpg

Ha! Florida.

Yeah, I don't know if there's any better recommendation than a backpack. If there were a better way to go about it, well, then we'd all be going that way, instead of with hydration packs. And riding "expert" trails with panniers sounds something less than fun.

Perhaps you need to try a newer, better pack. Depending on what pack you have now, a newer and better one may be more comfortable.