I'm having some balance issues with my heavy backpack falling off the cheap "clamp-onto-the seatpost" type rack that I used to have. I tried more bungy cords and that didn't work. The backpack kept falling off during my bumpy, twisty, urban commute ride.

Anybody know how to deal with this? Is there a extremly strong rack or tie-down method that I can get that would allow me to basically tie the backpack to the rack, get to my destination, and quickly get the backpack off the bike? Maybe, I should get something other than my old setpost quickrelease rack.

Using bungee cords to secure a backpack to a rear rack just plain doesn't work very well. If you want an actual backpack to carry around when you reach your destination, you might consider the Arkel Bug, although that might not work very well on a seatpost rack (it attaches to a rear rack like a pannier).

Try getting a Topeak clamp on seatpost rack and integrated bag that slides on and off the rack.Mine slides on and clicks into place securely and it has a shoulder strap to carry the bag also.
Here is the rack https://www.topeak.com/products/rack_008.html
and here is the bag https://www.topeak.com/products/bag_019.html
I routinely use it to carry 30 lbs of books and I also do my weekly shopping at the
grocery store 7 miles from the house with it.The side pockets zip out and fold down
into 2 large panniers when needed. I think I payed about 70 bucks for both at the LBS.
Good luck

I agree with the other posts. You aren't going to have an easy time making a generic backpack stick to a seat post rack. Upgrade your pack.

I use a regular MTB rack and a square, elastic motorcycle web type
thing and have no problems securing my backpack to the rack.

If you use zipties or hose clamps to secure some kind of ~12inch wide flat platform to your rack (i've used pieces of millk crate)

... you will have no worries about a bungee'd down backpack moving around.

Why don't you just carry it on your back? It can't be that heavy... isn't the max. weight limit of those clamp on racks around 20 lbs?

How large is this backpack (when compressed by bungee cords)? It sounds like the pack is wider than the rack will securely hold without the pack "rolling" off sideways. If you made a slightly curved cradle out of something attached to the rack, you could widen this support and probably make it harder for the bag to slide sideways off of the rack. Copper tubing or some kind of heavy guage wire mesh might work. I'm envisioning making something that runs the length of the rack, is about 8-12 inches across, and curves upwards as if shaped to securely hold a bucket or drum.

This backpack is quite a hefty thing when loaded down with all my gear. I don't know how big exactly, but imagine a 2-3 big books + some notebooks + sometimes a notebook PC. So, pretty heavy. Thanks to the other guy for the Arkel Bug bag suggestion. It's cool, but just got this nice and fancy Jansport backpack that even fits a notebook computer. So, I don't want to buy another bag. The Topeak rack looks nice. Are there any other really strong ones. Just wondering b/c my piece of crap seatpost one just isn't strong enough. I'd really like to see the motorcycle web bungy cord thing. That might do the trick.

So, if I get a new rack how do I mount a milkcrate or a bucket on it? Never seen anything like that, but sounds pretty strong. That would be awesome and I could just throw the backpack in the bucket. Any ideas?

Any auto / MC place has them....you can even get them in colors to match
your bike or backpack for added posuer factor



My pack weighs about 15lbs when Im done stuffing it with tools, clothes, lunch,
book, glasses, etc....Its never fallen off yet !

I have toured with a heavily packed 25l backpack bungied to a rack but it took 4 bungies and was not quick on/off.
Heavy looads need secure racks . If your bike can take a bolt-on rack use one of those.
The elasticated net looks good but I would suppliment it with a wide webbing strap.

I've attached a bright orange file crate ($10 from the local Business Depot) to my rack: not a standard Canadian milk crate as the milk crate is smaller and I'd guess 3 times heavier/stronger. I don't need the extra strength, it seems.

It's attached with rubber tie down straps, not bungee cords. I can take the crate off if I'm not commuting.

I have quite a big back pack (day pack) and it fits quite well, it didn't fit so well in a real milk crate (smaller). I use this crate combo instead of paniers on this particular bike: if I need to stop at a store on the way home and don't have enough room in my bag for watever I buy, it can go in the crate, the bag goes on my back. The crate also allows me to carry three locks at the bottom, under the bag. The bag inside of the crate is not tied down in any way: quick in and out for the bag plus quick access to all the pockets. If I need to loose a layer, the extra layer can temporarily go into the crate as well. I also carry a garbage bag to cover the crate contents in case of rain.

Definitely ditch the seatpost rack.

I've been carrying my bookbag like this for the last two years. Just a regular rack bolted to the frame and two bungee cords holding the bags on (one along the length, the other along the width). The bags weigh in at 22lbs or so (depending on which classes I have). Takes only a few seconds to undo the bungees and I have not had it come loose or anything despite having run into a tree, ditched into a field, and hit numerous potholes. That milk crate looks pretty cool, though. I'll have to try that out.

I'm in agreement with iBarna. Just carry it on your back. It's a back pack!! On the plus side your bike will handle alot better.

My first choice would be to wear the backpack; second would be trade in the pack for a set of panniers -- that much weight is better carried down low. Some bikes are more finicky about that than others; my old Motobecane gets goofy with only a two-liter bottle of soda on the rack.

I see carrying the backpack if it was a couple of miles. If the OP's commute is longer (mine is 16 miles), then carrying a backpack that heavy will not be a very good solution. I had to do it a couple of times and my shoulders were shot for days.

I got mine from Nashbar -- Delta cargo net, $7.99. It's helped me carry all sorts of weird things around.

I've done this and it works. Attach it with heavy duty zip ties from Home Depot. When you don't want it anymore, cut 'em off. Get rid of the seatpost rack - it's just bike candy. If you're commuting with that much of a load, you need to up-tool.

Consider the good advice about panniers.

Get a basket! (Wald is a good one) Bolt it to the top of your rack, toss in the backpack and tie it down with strip of an old tube. These things are cheap and unlike trunks or panniers, nobody is likely to steal it.

This rig is really popular with school kids in Europe. You can also toss your empty backback in the basket, ride to the supermarket and bring home a lot of stuff. Even more if you learn to ride with a pair of cloth shopping bags hanging off your handle bars

keep your nice pack, but get some panniers, too. They don't have to be expensive or fancy. Use them to distribute your gear, especially your books. Then carry the light stuff on your back.

This is why they sell quality racks that bolt to the frame and panniers. There are many kinds that don't cost a lot.

I agree, get a sturdy bolt-on rack, not the seatpost kind. Use bungee cords or that cool cargo net to hold the backpack onto the rack. Be sure to secure all the straps too, you don't want them getting caught in your wheel.

Don't forget to try eliminating as much of what you are carrying now as you can. Even if you start by tossing out one thing at a time, I'll bet you can cut way back and still have what you need to get by on.

I vote milkcrate- preferably one that you find. And attach it with 2- 8" long metal strips from any hardware store with bolts and wingnuts for easy removal. Then you can just toss in the backpack and off you go. Then if you pick up some groceries on the ride home you wear the back pack and put the groceries in the milkcrate- and mine fits two grocery bags side by side. and if you've got a fat butt like mine you may have to cut the milkcrate where it interferes with the gluteus maximus. Oh, yeah and get the beefiest, sturdiest rack you can get.

In my post above, I mentioned I was going to try the milk crate. Well, I got a hold of one and zip-tied it to my rack. I'm lovin' it! You can just jam all your crap in there and take off!