Earlier this year, walmart had a bell or schwinn rear bike rack on clearance for $5. Couldn’t pass it up. However, theres one problem with it. In order to get it on (mounts to seat stem/wtf u call it), I had to pry it apart, slip it over the stem with a rubber spacer, then use my vice to squeeze it back together and bolt it. A real PITA and it can’t be easily removed. Not a problem except I’m wanting to get another stem so I can mount a more comfortable seat for longer rides. This way I can switch out seats real easy depending on the type of riding I plan to do (mtn bike has quick release lever). But now I cant move the rack from one stem to the other. So my question is, are there any rear racks out there that has a quick release and won’t break the bank? Thanks.

I believe you are using the term 'stem' but you mean 'seatpost'. The stem is the piece that holds your handlebars to the top of your fork. The seat post is the piece that connects your saddle to your bicycles frame.

Stems look like this [quill and threadless styles]:


Seatposts look roughly like this:


I'm not sure I understand why you would swap out saddles between rides? Your best bet is to find a comfortable saddle and use it for all your rides. Swapping saddles every time you want to ride will be a huge PITA. Saddles are designed to be used with specific bicycle types based on riding position. Using a saddle designed for a different type of riding will probably not be very comfortable. (eg. using a narrow road racing saddle on an upright comfort bike) There is no reason you should need to swap out saddles once you find one that fits the style bike and your body.

My advice- Find one seat that fits you and ride it regardless of whether you ride on road or off with the bike, long ride or short.

I bought a seatpost rear rack and I removed the seat or saddle and slid the rack down on the post. mine has a quick release lever but it still has to slide up off the seatpost - and of course the seat has to be removed first. or conversely remove the seatpost and slide the rack down.

this is the one I have

https://www.walmart.com/ip/Schwinn-Se...e-Rack/9207799

what I didn't like was that when it was loaded it would sway back and forth and in turn would move my saddle left and right. so I had to makeshift a couple of vertical supports

I prefer racks that don't attach to the seatpost so that I can make minor adjustments from time to time. once you get the saddle you like and get the fit right everything should stay put though, unless you change a saddle.

this bike is gone now but I kept the rack. some pics also show that I extended the rail so that the rack sat further back from the saddle allowing me to load it up even more. eventually I would discover that having so much weight over the far end of the back wheels affected the front wheel quite a bit. I've learned to distribute my rack weight better now. now if only I can cut 1/2 the cr*p out that I carry!